Northern Trust (NTRS) 10-Q29 Oct 242024 Q3 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page	9 Months Ended
Cover Page	Sep. 30, 2024 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-36609
Entity Registrant Name	NORTHERN TRUST CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-2723087
Entity Address, Address Line One	50 South LaSalle Street
Entity Address, City or Town	Chicago,
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60603
City Area Code	312
Local Phone Number	630-6000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)	198,218,483
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Entity Central Index Key	0000073124
Current Fiscal Year End Date	--12-31
Common Stock, $1.66 2/3 Par Value
Entity Information [Line Items]
Title of 12(b) Security	Common Stock, $1.66 2/3 Par Value
Trading Symbol	NTRS
Security Exchange Name	NASDAQ
Depositary Shares, each representing 1/1,000th interest in a share of Series E Non-Cumulative Perpetual Preferred Stock
Entity Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing 1/1,000th interest in a share of Series E Non-Cumulative Perpetual Preferred Stock
Trading Symbol	NTRSO
Security Exchange Name	NASDAQ

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
ASSETS
Cash and Due from Banks	$ 6,871.7	$ 4,791.5
Federal Reserve and Other Central Bank Deposits	40,848.8	34,326.2
Interest-Bearing Deposits with Banks	1,606.8	1,939
Securities Purchased under Agreements to Resell	981.6	784.7
Debt Securities
Available for Sale	28,311.9	23,089.8
Held to Maturity	22,708.6	26,221.7
Total Debt Securities	51,020.5	49,311.5
Loans
Total Loans (Net of unearned income of $6.2 and $5.9)	41,950.3	47,617
Allowance for Credit Losses	(193.3)	(192.3)
Buildings and Equipment	480.3	502.2
Client Security Settlement Receivables	354.2	212.6
Goodwill	707.8	702.3
Other Assets	11,125.1	10,788.4
Total Assets	155,753.8	150,783.1
Deposits
Demand and Other Noninterest-Bearing	13,610.6	14,246.4
Savings, Money Market and Other Interest-Bearing	23,069	25,252.1
Savings Certificates and Other Time	6,255.2	4,109.7
Non U.S. Offices — Noninterest-Bearing	8,564.2	8,584.7
Non U.S. Offices — Interest-Bearing	69,684.3	63,971.1
Total Deposits	121,183.3	116,164
Federal Funds Purchased	2,761.9	3,045.4
Securities Sold Under Agreements to Repurchase	170.8	784.7
Other Borrowings	6,903.2	6,567.8
Senior Notes	2,820.9	2,773.2
Long-Term Debt	4,077.2	4,065
Other Liabilities	5,087.5	5,485.1
Total Liabilities	143,004.8	138,885.2
STOCKHOLDERS' EQUITY
Common Stock	408.6	408.6
Additional Paid-In Capital	1,008.1	1,009.6
Retained Earnings	15,313.1	14,233.8
Accumulated Other Comprehensive Loss	(779.5)	(1,137.9)
Treasury Stock	(4,086.2)	(3,501.1)
Total Stockholders’ Equity	12,749	11,897.9
Total Liabilities and Stockholders’ Equity	155,753.8	150,783.1
Series D Preferred Stock
STOCKHOLDERS' EQUITY
Preferred Stock	493.5	493.5
Series E Preferred Stock
STOCKHOLDERS' EQUITY
Preferred Stock	391.4	391.4
Commercial
Loans
Total Loans (Net of unearned income of $6.2 and $5.9)	20,833.8	25,412.8
Personal
Loans
Total Loans (Net of unearned income of $6.2 and $5.9)	$ 21,116.5	$ 22,204.2

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Available-for-sale securities, amortized cost	$ 28,513.1	$ 23,659
Held to maturity, fair value	21,372	24,473
Unearned income	$ 6.2	$ 5.9
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in usd per share)	$ 1.6667	$ 1.6667
Common stock, authorized (in shares)	560,000,000	560,000,000
Common stock, outstanding (in shares)	198,218,483	205,126,224
Treasury stock (in shares)	46,953,041	40,045,300
Series D Preferred Stock
Preferred stock, outstanding (in shares)	5,000	5,000
Series E Preferred Stock
Preferred stock, outstanding (in shares)	16,000	16,000

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Noninterest Income
Trust, Investment and Other Servicing Fees	$ 1,196.6	$ 1,111.9	$ 3,505.6	$ 3,271.8
Foreign Exchange Trading Income	54.1	51.8	169.5	154.9
Treasury Management Fees	8.2	7.5	26.5	23.8
Security Commissions and Trading Income	35.5	30.9	107.7	101.7
Other Operating Income	111.8	68.2	1,097.5	170.2
Investment Security Gains (Losses), net	0	0	(189.3)	6.9
Total Noninterest Income	1,406.2	1,270.3	4,717.5	3,729.3
Net Interest Income
Interest Income	2,530.2	1,935	7,482.3	5,125.4
Interest Expense	1,967.9	1,478.8	5,869	3,626.5
Net Interest Income	562.3	456.2	1,613.3	1,498.9
Provision for Credit Losses	8	14	7.5	13.5
Net Interest Income after Provision for Credit Losses	554.3	442.2	1,605.8	1,485.4
Noninterest Expense
Compensation	583.6	558.1	1,875.9	1,757.8
Employee Benefits	109.2	100.8	310.5	303.2
Outside Services	256.3	229.6	746.5	671.3
Equipment and Software	270.4	232.5	800.6	693.5
Occupancy	53.8	58.7	162.7	173.8
Other Operating Expense	86.1	98.5	361.8	296.1
Total Noninterest Expense	1,359.4	1,278.2	4,258	3,895.7
Income before Income Taxes	601.1	434.3	2,065.3	1,319
Provision for Income Taxes	136.2	106.5	489.6	324.8
Net Income	464.9	327.8	1,575.7	994.2
Preferred Stock Dividends	16.2	16.2	37.1	37.1
Net Income Applicable to Common Stock	$ 448.7	$ 311.6	$ 1,538.6	$ 957.1
Per Common Share
Net Income — Basic (in dollars per share)	$ 2.23	$ 1.49	$ 7.53	$ 4.56
Net Income - Diluted (in dollars per share)	$ 2.22	$ 1.49	$ 7.51	$ 4.56
Average Number of Common Shares Outstanding
Basic (in shares)	199,937,543	207,021,554	202,614,386	207,611,420
Diluted (in shares)	200,549,063	207,252,992	203,131,400	207,927,720

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 464.9	$ 327.8	$ 1,575.7	$ 994.2
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains (Losses) on Available for Sale Debt Securities	63.9	32.3	320.7	170.5
Net Unrealized Gains (Losses) on Cash Flow Hedges	0.3	(0.4)	(0.5)	(1.1)
Net Foreign Currency Adjustments	18.9	9.6	30.5	34.2
Net Pension and Other Postretirement Benefit Adjustments	2.4	1	7.7	2.2
Other Comprehensive Income (Loss)	85.5	42.5	358.4	205.8
Comprehensive Income (Loss)	$ 550.4	$ 370.3	$ 1,934.1	$ 1,200

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	PREFERRED STOCK	COMMON STOCK	ADDITIONAL PAID-IN CAPITAL	RETAINED EARNINGS	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	TREASURY STOCK
Beginning balance at Dec. 31, 2022	$ 11,259.5	$ 884.9	$ 408.6	$ 983.5	$ 13,798.5	$ (1,569.2)	$ (3,246.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	334.6				334.6
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	203					203
Dividends Declared:
Common Stock	(158.6)				(158.6)
Preferred Stock	(16.2)				(16.2)
Stock Awards and Options Exercised	66.4			(19)			85.4
Stock Purchased	(100.9)						(100.9)
Ending balance at Mar. 31, 2023	11,587.8	884.9	408.6	964.5	13,958.3	(1,366.2)	(3,262.3)
Beginning balance at Dec. 31, 2022	11,259.5	884.9	408.6	983.5	13,798.5	(1,569.2)	(3,246.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	994.2
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	205.8
Dividends Declared:
Stock Purchased	(201.3)
Ending balance at Sep. 30, 2023	11,847.2	884.9	408.6	993.1	14,281.6	(1,363.4)	(3,357.6)
Beginning balance at Mar. 31, 2023	11,587.8	884.9	408.6	964.5	13,958.3	(1,366.2)	(3,262.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	331.8				331.8
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	(39.7)					(39.7)
Dividends Declared:
Common Stock	(157.8)				(157.8)
Preferred Stock	(4.7)				(4.7)
Stock Awards and Options Exercised	17.6			15.5			2.1
Stock Purchased	(99.3)						(99.3)
Ending balance at Jun. 30, 2023	11,635.7	884.9	408.6	980	14,127.6	(1,405.9)	(3,359.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	327.8				327.8
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	42.5					42.5
Dividends Declared:
Common Stock	(157.6)				(157.6)
Preferred Stock	(16.2)				(16.2)
Stock Awards and Options Exercised	17.2			13.1			4.1
Stock Purchased	(1.1)						(1.1)
Excise Tax on Share Repurchases	(1.1)						(1.1)
Ending balance at Sep. 30, 2023	11,847.2	884.9	408.6	993.1	14,281.6	(1,363.4)	(3,357.6)
Beginning balance at Dec. 31, 2023	11,897.9	884.9	408.6	1,009.6	14,233.8	(1,137.9)	(3,501.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	214.7				214.7
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	220.3					220.3
Dividends Declared:
Common Stock	(153.4)				(153.4)
Preferred Stock	(16.2)				(16.2)
Stock Awards and Options Exercised	71			(26.1)			97.1
Stock Purchased	(132)						(132)
Excise Tax on Share Repurchases	(0.5)						(0.5)
Ending balance at Mar. 31, 2024	12,101.8	884.9	408.6	983.5	14,278.9	(917.6)	(3,536.5)
Beginning balance at Dec. 31, 2023	11,897.9	884.9	408.6	1,009.6	14,233.8	(1,137.9)	(3,501.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	1,575.7
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	358.4
Dividends Declared:
Stock Purchased	(684.2)
Ending balance at Sep. 30, 2024	12,749	884.9	408.6	1,008.1	15,313.1	(779.5)	(4,086.2)
Beginning balance at Mar. 31, 2024	12,101.8	884.9	408.6	983.5	14,278.9	(917.6)	(3,536.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	896.1				896.1
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	52.6					52.6
Dividends Declared:
Common Stock	(154.3)				(154.3)
Preferred Stock	(4.7)				(4.7)
Stock Awards and Options Exercised	17.5			13.4			4.1
Stock Purchased	(250.8)						(250.8)
Excise Tax on Share Repurchases	(2.4)						(2.4)
Ending balance at Jun. 30, 2024	12,655.8	884.9	408.6	996.9	15,016	(865)	(3,785.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	464.9				464.9
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)	85.5					85.5
Dividends Declared:
Common Stock	(151.6)				(151.6)
Preferred Stock	(16.2)				(16.2)
Stock Awards and Options Exercised	15			11.2			3.8
Stock Purchased	(301.4)						(301.4)
Excise Tax on Share Repurchases	(3)						(3)
Ending balance at Sep. 30, 2024	$ 12,749	$ 884.9	$ 408.6	$ 1,008.1	$ 15,313.1	$ (779.5)	$ (4,086.2)

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Statement of Stockholders' Equity [Abstract]
Common stock dividends (in usd per share)	$ 0.75	$ 0.75	$ 0.75	$ 0.75	$ 0.75	$ 0.75

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income		$ 1,575.7	$ 994.2
Adjustments to Reconcile Net Income to Net Cash Used in Operating Activities
Investment Security Losses/(Gains)		189.3	(6.9)
Amortization and Accretion of Securities and Unearned Income, net		(24.6)	5.8
Provision for Credit Losses		7.5	13.5
Depreciation and Amortization		533.9	465.6
Pension Plan Contributions		(208)	(16.5)
Change in Receivables		(278.6)	(200.3)
Change in Interest Payable		4.1	88.8
Change in Collateral With Derivative Counterparties, net		(7.4)	(1,857.5)
Other Operating Activities, net		356.9	335.7
Net Cash Provided by / (Used in) Operating Activities		2,148.8	(177.6)
CASH FLOWS FROM INVESTING ACTIVITIES
Change in Federal Funds Sold		0	(32)
Change in Securities Purchased under Agreements to Resell		(179.6)	717.5
Change in Interest-Bearing Deposits with Banks		294.8	(203)
Net Change in Federal Reserve and Other Central Bank Deposits		(6,116.4)	7,760.3
Purchases of Held to Maturity Debt Securities		(19,233.9)	(25,821.1)
Proceeds from the Maturity and Redemption of Held to Maturity Debt Securities		23,008.3	25,872.9
Purchases of Available for Sale Debt Securities		(10,075.5)	(4,412)
Proceeds from the Maturity and Sales of Available for Sale Debt Securities		5,218.9	6,912.5
Change in Loans		5,669.1	(681.6)
Purchases of Buildings and Equipment		(60.8)	(52.7)
Purchases and Development of Computer Software		(458.2)	(412.8)
Change in Client Security Settlement Receivables		(132.2)	1,555
Proceeds from the sale of Visa Shares		794.9	0
Other Investing Activities, net		914.7	(1,555.9)
Net Cash (Used in) Investing Activities		(355.9)	9,647.1
CASH FLOWS FROM FINANCING ACTIVITIES
Change in Deposits		2,112.4	(13,089.4)
Change in Federal Funds Purchased		(283.5)	3,642.4
Change in Securities Sold under Agreements to Repurchase		(613.9)	(21.3)
Change in Short-Term Other Borrowings		250.1	(717.4)
Proceeds from Long Term Debt		0	2,000
Treasury Stock Purchased		(684.2)	(201.3)
Net Proceeds from Stock Options		4.3	1.9
Cash Dividends Paid on Common Stock		(454.7)	(467.3)
Cash Dividends Paid on Preferred Stock		(37.1)	(37.1)
Other Financing Activities, net		(5.7)	(1.2)
Net Cash Provided by Financing Activities		287.7	(8,890.7)
Effect of Foreign Currency Exchange Rates on Cash		(0.4)	(277.3)
Change in Cash and Due from Banks		2,080.2	301.5
Cash and Due from Banks at Beginning of Period		4,791.5	4,654.2
Cash and Due from Banks at End of Period		6,871.7	4,955.7
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest Paid		5,852.4	3,536.9
Income Taxes Paid		185.3	211.1
Transfers from Loans to OREO		0	0.2
Reclassification of certain cash collateral received from Other Operating Activities to Deposits	[1]	$ 1,157.2	$ 0

[1]Beginning January 1, 2024, Northern Trust reclassified certain cash collateral received from Other Liabilities to Deposits on the consolidated statement of financial condition. Prior periods have not been restated.

Basis of Presentation

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of Northern Trust Corporation (Corporation) and its wholly-owned subsidiary, The Northern Trust Company (Bank), and various other wholly-owned subsidiaries of the Corporation and Bank. Throughout the notes to the consolidated financial statements, the term “Northern Trust” refers to the Corporation and its subsidiaries. Intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements, as of and for the periods ended September 30, 2024 and 2023, have not been audited by the Corporation’s independent registered public accounting firm. In the opinion of management, all accounting entries and adjustments, including normal recurring accruals, necessary for a fair presentation of the financial position and the results of operations for the interim periods have been made. The accounting and financial reporting policies of Northern Trust conform to U.S. generally accepted accounting principles (GAAP) and reporting practices prescribed for the banking industry. For a description of Northern Trust’s significant accounting policies, refer to Note 1—Summary of Significant Accounting Policies included under Item 8. Financial Statements and Supplementary Data in the Annual Report on Form 10-K for the year ended December 31, 2023.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
Recent Accounting Pronouncements	Sep. 30, 2024
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements On January 1, 2024, Northern Trust adopted Accounting Standards Update (ASU) No. 2023-02, “Investments—Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method—a consensus of the Emerging Issues Task Force” (ASU 2023-02). The amendments in ASU 2023-02 allow entities to elect the proportional amortization method to account for tax equity investments if certain conditions are met regardless of the tax credit program from which the income tax credits are received. Under the proportional amortization method, an entity amortizes the initial cost of the investment in proportion to the income tax credits and other income tax benefits received and recognizes the net amortization and income tax credits and other income tax benefits in the income statement as a component of income tax expense (benefit). In addition, ASU 2023-02 requires specific disclosures that must be applied to all investments that generate income tax credits and other income tax benefits for which the entity has elected to apply the proportional amortization method in accordance with Subtopic 323-740. Upon adoption of ASU 2023-02, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. Please refer to Note 19—Variable Interest Entities for further information. On January 1, 2024, Northern Trust adopted ASU No. 2022-03, “Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions” (ASU 2022-03). The amendments in ASU 2022-03 clarify that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. ASU 2022-03 also clarifies that an entity cannot, as a separate unit of account, recognize and measure a contractual sale restriction. Additionally, ASU 2022-03 introduces new disclosure requirements to provide investors with information about contractual sale restrictions including the nature and remaining duration of these restrictions. Upon adoption of ASU 2022-03, there was no impact to Northern Trust’s consolidated balance sheets or consolidated statements of income.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Fair Value Hierarchy. The following describes the hierarchy of valuation inputs (Levels 1, 2, and 3) used to measure fair value and the primary valuation methodologies used by Northern Trust for financial instruments measured at fair value on a recurring basis. Observable inputs reflect market data obtained from sources independent of the reporting entity; unobservable inputs reflect the entity’s own assumptions about how market participants would value an asset or liability based on the best information available. GAAP requires an entity measuring fair value to maximize the use of observable inputs and minimize the use of unobservable inputs and establishes a fair value hierarchy of inputs. Financial instruments are categorized within the hierarchy based on the lowest level input that is significant to their valuation. No transfers into or out of Level 3 occurred during the nine months ended September 30, 2024 or the year ended December 31, 2023. Level 1 — Quoted, active market prices for identical assets or liabilities. Northern Trust’s Level 1 assets are comprised primarily of available for sale (AFS) investments in U.S. Treasury securities. Level 2 — Observable inputs other than Level 1 prices, such as quoted active market prices for similar assets or liabilities, quoted prices for identical or similar assets in inactive markets, and model-derived valuations in which all significant inputs are observable in active markets. Northern Trust’s Level 2 assets include AFS debt securities, the fair values of which are determined predominantly by external pricing vendors. Prices received from vendors are compared to other vendor and third-party prices. If a security price obtained from a pricing vendor is determined to exceed predetermined tolerance levels that are assigned based on an asset type’s characteristics, the exception is researched and, if the price is not able to be validated, an alternate pricing vendor is utilized, consistent with Northern Trust’s pricing source hierarchy. As of September 30, 2024, Northern Trust’s AFS debt securities portfolio included 943 Level 2 debt securities with an aggregate market value of $21.8 billion. Substantially all were valued by external pricing vendors. As of December 31, 2023, Northern Trust’s AFS debt securities portfolio included 929 Level 2 debt securities with an aggregate market value of $19.5 billion. All 929 debt securities were valued by external pricing vendors. Level 2 assets and liabilities also include derivative contracts which are valued internally using widely accepted income-based models that incorporate inputs readily observable in actively quoted markets and reflect the contractual terms of the contracts. Observable inputs include foreign exchange rates and interest rates for foreign exchange contracts; interest rates for interest rate swap contracts and forward contracts; and interest rates and volatility inputs for interest rate option contracts. Northern Trust evaluates the impact of counterparty credit risk and its own credit risk on the valuation of its derivative instruments. Factors considered include the likelihood of default by Northern Trust and its counterparties, the remaining maturities of the instruments, net exposures after giving effect to master netting arrangements or similar agreements, available collateral, and other credit enhancements in determining the appropriate fair value of derivative instruments. The resulting valuation adjustments have not been considered material. Visa Class C common shares are also categorized as Level 2 assets and are valued using quoted active market prices for similar securities (Visa Class A common stock). See “Visa Class B Common Shares and Makewhole Agreement” under Note 20—Commitments and Contingent Liabilities for further information. Level 3 — Valuation techniques in which one or more significant inputs are unobservable in the marketplace. Northern Trust’s Level 3 liabilities consist of swaps that Northern Trust entered into with the purchaser of 1.1 million and 1.0 million shares of Visa Class B common shares previously held by Northern Trust and sold in June 2016 and 2015, respectively. Pursuant to the swaps, Northern Trust retains the risks associated with the ultimate conversion of the Visa Class B common shares into shares of Visa Class A common stock (Visa Class A common shares), such that the counterparty will be compensated for any dilutive adjustments to the conversion ratio and Northern Trust will be compensated for any anti-dilutive adjustments to the ratio. The swaps also require periodic payments from Northern Trust to the counterparty calculated by reference to the market price of Visa Class A common shares and a fixed rate of interest. The fair value of the swaps is determined using a discounted cash flow methodology. The significant unobservable inputs used in the fair value measurement are Northern Trust’s own assumptions about estimated changes in the conversion rate of the Visa Class B common shares into Visa Class A common shares, the date on which such conversion is expected to occur and the estimated growth rate of the Visa Class A common share price. See “Visa Class B Common Shares and Makewhole Agreement” under Note 20—Commitments and Contingent Liabilities for further information. Northern Trust believes its valuation methods for its assets and liabilities carried at fair value are appropriate; however, the use of different methodologies or assumptions, particularly as applied to Level 3 assets and liabilities, could have a material effect on the computation of their estimated fair values. The following table presents the fair values of Northern Trust’s Level 3 liabilities as of September 30, 2024 and December 31, 2023, as well as the valuation techniques, significant unobservable inputs, and quantitative information used to develop significant unobservable inputs for such liabilities as of such dates. TABLE 35: LEVEL 3 SIGNIFICANT UNOBSERVABLE INPUTS SEPTEMBER 30, 2024 FINANCIAL INSTRUMENT FAIR VALUE VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES (1) Swaps Related to Sale of Certain Visa Class B Common Shares $27.8 million Discounted Cash Flow Conversion Rate 1.54x 1.54x Visa Class A Appreciation 9.06% 9.06% Expected Duration 13 - 35.5 months 26.5 months (1) Weighted average of expected duration based on scenario probability. DECEMBER 31, 2023 FINANCIAL INSTRUMENT FAIR VALUE VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES (1) Swaps Related to Sale of Certain Visa Class B Common Shares $25.4 million Discounted Cash Flow Conversion Rate 1.59x 1.59x Visa Class A Appreciation 10.49% 10.49% Expected Duration 9 - 27 months 13 months (1) Weighted average of expected duration based on scenario probability. The following table presents assets and liabilities measured at fair value on a recurring basis as of September 30, 2024 and December 31, 2023, segregated by fair value hierarchy level. TABLE 36: RECURRING BASIS HIERARCHY LEVELING SEPTEMBER 30, 2024 (In Millions) LEVEL 1 LEVEL 2 LEVEL 3 NETTING ASSETS/LIABILITIES AT FAIR VALUE Debt Securities Available for Sale U.S. Government $ 6,481.7 $ — $ — $ — $ 6,481.7 Obligations of States and Political Subdivisions — 306.0 — — 306.0 Government Sponsored Agency — 13,653.7 — — 13,653.7 Non-U.S. Government — 327.1 — — 327.1 Corporate Debt — 201.1 — — 201.1 Covered Bonds — 239.7 — — 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 3,988.1 — — 3,988.1 Other Asset-Backed — 2,487.4 — — 2,487.4 Commercial Mortgage-Backed — 627.1 — — 627.1 Total Available for Sale Debt Securities 6,481.7 21,830.2 — — 28,311.9 Other Assets Equity Securities (1) 85.0 27.8 — — 112.8 Derivative Assets Foreign Exchange Contracts — 3,052.9 — (2,664.5) 388.4 Interest Rate Contracts — 466.1 — (108.6) 357.5 Total Derivative Assets — 3,519.0 — (2,773.1) 745.9 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,083.9 — (1,784.0) 1,299.9 Interest Rate Contracts — 504.1 — (9.1) 495.0 Other Financial Derivatives (2) — — 27.8 (26.8) 1.0 Total Derivative Liabilities $ — $ 3,588.0 $ 27.8 $ (1,819.9) $ 1,795.9 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of September 30, 2024, derivative assets and liabilities shown above also include reductions of $2.0 billion and $1.0 billion, respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) Equity securities consists of a money market investment and Visa Class C common shares with a fair value of $85.0 million and $27.8 million, respectively, as of September 30, 2024. (2) Consists of swaps related to the sale of certain Visa Class B common shares. DECEMBER 31, 2023 (In Millions) LEVEL 1 LEVEL 2 LEVEL 3 NETTING ASSETS/LIABILITIES AT FAIR VALUE Debt Securities Available for Sale U.S. Government $ 3,622.2 $ — $ — $ — $ 3,622.2 Obligations of States and Political Subdivisions — 295.8 — — 295.8 Government Sponsored Agency — 11,553.0 — — 11,553.0 Non-U.S. Government — 264.4 — — 264.4 Corporate Debt — 279.5 — — 279.5 Covered Bonds — 347.1 — — 347.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 2,899.9 — — 2,899.9 Other Asset-Backed — 2,962.6 — — 2,962.6 Commercial Mortgage-Backed — 865.3 — — 865.3 Total Available for Sale Debt Securities 3,622.2 19,467.6 — — 23,089.8 Other Assets Money Market Investment 95.0 — — — 95.0 Derivative Assets Foreign Exchange Contracts — 3,266.7 — (2,937.2) 329.5 Interest Rate Contracts — 301.5 — (189.5) 112.0 Total Derivative Assets — 3,568.2 — (3,126.7) 441.5 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,255.2 — (2,175.7) 1,079.5 Interest Rate Contracts — 369.2 — (6.0) 363.2 Other Financial Derivatives (1) — — 25.4 (23.7) 1.7 Total Derivative Liabilities $ — $ 3,624.4 $ 25.4 $ (2,205.4) $ 1,444.4 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of December 31, 2023, derivative assets and liabilities shown above also include reductions of $2.1 billion and $1.2 billion, respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) Consists of swaps related to the sale of certain Visa Class B common shares. The following table presents the changes in Level 3 liabilities for the three and nine months ended September 30, 2024 and 2023. TABLE 37: CHANGES IN LEVEL 3 LIABILITIES (In Millions) SWAPS RELATED TO SALE OF CERTAIN VISA CLASS B COMMON SHARES THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 Fair Value at July 1 $ 30.6 $ 36.4 Total (Gains) Losses: Included in Earnings (1) 13.8 (2.4) Purchases, Issues, Sales, and Settlements Settlements (16.6) (5.1) Fair Value at September 30 $ 27.8 $ 28.9 (1) (Gains) losses are recorded in Other Operating Income on the consolidated statements of income. NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 Fair Value at January 1 $ 25.4 $ 34.8 Total (Gains) Losses: Included in Earnings (1) 30.4 16.1 Purchases, Issues, Sales, and Settlements Settlements (28.0) (22.0) Fair Value at September 30 $ 27.8 $ 28.9 (1) (Gains) losses are recorded in Other Operating Income on the consolidated statements of income. Carrying values of assets and liabilities that are not measured at fair value on a recurring basis may be adjusted to fair value in periods subsequent to their initial recognition, for example, to record an impairment of an asset. GAAP requires entities to separately disclose these subsequent fair value measurements and to classify them under the fair value hierarchy. Assets measured at fair value on a nonrecurring basis at September 30, 2024 and December 31, 2023, all of which were categorized as Level 3 under the fair value hierarchy, were comprised of nonaccrual loans whose values were based on real estate and other available collateral. Assets measured at fair value on a nonrecurring basis at December 31, 2023 also includes other real estate owned (OREO) properties, categorized as Level 3 under the fair value hierarchy. Fair values of real estate loan collateral were estimated using a market approach typically supported by third-party valuations and property-specific fees and taxes. The fair values of real estate loan collateral were subject to adjustments to reflect management’s judgment as to realizable value and consisted of discount factors of 20.0% with a weighted average based on fair values of 20.0%, and a range of discount factors from 0% to 20.0% with a weighted average of 2.0%, as of September 30, 2024 and December 31, 2023, respectively. Other loan collateral, which typically consists of accounts receivable, inventory and equipment, is valued using a market approach adjusted for asset-specific characteristics and in limited instances third-party valuations are used. OREO assets are carried at the lower of cost or fair value less estimated costs to sell, with fair value typically based on third-party appraisals. Collateral-dependent nonaccrual loans that have been adjusted to fair value totaled $25.8 million and $43.3 million at September 30, 2024 and December 31, 2023, respectively. The following table presents the fair values of Northern Trust’s Level 3 assets that were measured at fair value on a nonrecurring basis as of September 30, 2024 and December 31, 2023, as well as the valuation technique, significant unobservable inputs and quantitative information used to develop the significant unobservable inputs for such assets as of such dates. TABLE 38: LEVEL 3 NONRECURRING BASIS SIGNIFICANT UNOBSERVABLE INPUTS SEPTEMBER 30, 2024 FINANCIAL INSTRUMENT FAIR VALUE (1) VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES Loans $25.8 million Market Approach Discount factor applied to real estate collateral-dependent loans to reflect realizable value 20.0% 20.0% (1) Includes real estate collateral-dependent loans and other collateral-dependent loans. DECEMBER 31, 2023 FINANCIAL INSTRUMENT FAIR VALUE (1) VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES Loans $43.3 million Market Approach Discount factor applied to real estate collateral-dependent loans to reflect realizable value 0.0 % - 20.0% 2.0% (1) Includes real estate collateral-dependent loans and other collateral-dependent loans. The following tables present the book value and estimated fair value, including the fair value hierarchy level, of Northern Trust’s financial instruments that are not measured at fair value on the consolidated balance sheets as of September 30, 2024 and December 31, 2023. The following tables exclude those items measured at fair value on a recurring basis. TABLE 39: FAIR VALUE OF FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 ESTIMATED FAIR VALUE (In Millions) BOOK VALUE TOTAL ESTIMATED FAIR VALUE LEVEL 1 LEVEL 2 LEVEL 3 FINANCIAL ASSETS Cash and Due from Banks $ 6,871.7 $ 6,871.7 $ 6,871.7 $ — $ — Federal Reserve and Other Central Bank Deposits 40,848.8 40,848.8 — 40,848.8 — Interest-Bearing Deposits with Banks 1,606.8 1,606.8 — 1,606.8 — Securities Purchased under Agreements to Resell 981.6 981.6 — 981.6 — Debt Securities - Held to Maturity 22,708.6 21,372.0 — 21,372.0 — Loans Held for Investment 41,765.5 41,488.7 — — 41,488.7 Other Assets 1,450.5 1,446.0 87.9 1,358.1 — FINANCIAL LIABILITIES Deposits 121,183.3 123,302.5 — 123,302.5 — Federal Funds Purchased 2,761.9 2,761.9 — 2,761.9 — Securities Sold Under Agreements to Repurchase 170.8 170.8 — 170.8 — Other Borrowings 6,903.2 6,940.0 — 6,940.0 — Senior Notes 2,820.9 2,869.1 — 2,869.1 — Long-Term Debt 4,077.2 4,248.1 — 4,248.1 — Unfunded Commitments 173.4 173.4 — 173.4 — Other Liabilities 47.9 47.9 — — 47.9 DECEMBER 31, 2023 ESTIMATED FAIR VALUE (In Millions) BOOK VALUE TOTAL ESTIMATED FAIR VALUE LEVEL 1 LEVEL 2 LEVEL 3 FINANCIAL ASSETS Cash and Due from Banks $ 4,791.5 $ 4,791.5 $ 4,791.5 $ — $ — Federal Reserve and Other Central Bank Deposits 34,326.2 34,326.2 — 34,326.2 — Interest-Bearing Deposits with Banks 1,939.0 1,939.0 — 1,939.0 — Securities Purchased under Agreements to Resell 784.7 784.7 — 784.7 — Debt Securities - Held to Maturity 26,221.7 24,473.0 — 24,473.0 — Loans Held for Investment 47,438.3 47,598.3 — — 47,598.3 Other Assets 1,476.6 1,458.0 86.1 1,371.9 — FINANCIAL LIABILITIES Deposits 116,164.0 116,207.6 — 116,207.6 — Federal Funds Purchased 3,045.4 3,045.4 — 3,045.4 — Securities Sold Under Agreements to Repurchase 784.7 784.7 — 784.7 — Other Borrowings 6,567.8 6,607.4 — 6,607.4 — Senior Notes 2,773.2 2,798.1 — 2,798.1 — Long-Term Debt 4,065.0 4,186.8 — 4,186.8 — Unfunded Commitments 178.8 178.8 — 178.8 — Other Liabilities 74.9 74.9 — — 74.9

Securities

Securities	9 Months Ended
Securities	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Securities	Securities Available for Sale Debt Securities. The following tables provide the amortized cost and fair values as of September 30, 2024 and December 31, 2023, and remaining maturities of AFS debt securities as of September 30, 2024. TABLE 40: RECONCILIATION OF AMORTIZED COST TO FAIR VALUE OF AVAILABLE FOR SALE DEBT SECURITIES SEPTEMBER 30, 2024 (In Millions) AMORTIZED COST GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR VALUE U.S. Government $ 6,497.4 $ 3.4 $ 19.1 $ 6,481.7 Obligations of States and Political Subdivisions 321.6 — 15.6 306.0 Government Sponsored Agency 13,749.0 19.0 114.3 13,653.7 Non-U.S. Government 341.5 — 14.4 327.1 Corporate Debt 205.0 0.1 4.0 201.1 Covered Bonds 242.2 0.6 3.1 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 4,019.7 14.0 45.6 3,988.1 Other Asset-Backed 2,494.5 7.1 14.2 2,487.4 Commercial Mortgage-Backed 642.2 0.1 15.2 627.1 Total $ 28,513.1 $ 44.3 $ 245.5 $ 28,311.9 DECEMBER 31, 2023 (In Millions) AMORTIZED COST GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR VALUE U.S. Government $ 3,681.5 $ 2.2 $ 61.5 $ 3,622.2 Obligations of States and Political Subdivisions 315.8 — 20.0 295.8 Government Sponsored Agency 11,744.3 9.0 200.3 11,553.0 Non-U.S. Government 284.8 — 20.4 264.4 Corporate Debt 287.5 0.1 8.1 279.5 Covered Bonds 356.8 — 9.7 347.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 3,013.8 0.1 114.0 2,899.9 Other Asset-Backed 3,061.0 1.6 100.0 2,962.6 Commercial Mortgage-Backed 913.5 0.2 48.4 865.3 Total $ 23,659.0 $ 13.2 $ 582.4 $ 23,089.8 TABLE 41: REMAINING MATURITY OF AVAILABLE FOR SALE DEBT SECURITIES SEPTEMBER 30, 2024 ONE YEAR OR LESS ONE TO FIVE YEARS FIVE TO TEN YEARS OVER TEN YEARS TOTAL (In Millions) AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE U.S. Government $ 496.2 $ 493.9 $ 3,862.0 $ 3,852.1 $ 2,139.2 $ 2,135.7 $ — $ — $ 6,497.4 $ 6,481.7 Obligations of States and Political Subdivisions — — 206.3 198.0 115.3 108.0 — — 321.6 306.0 Government Sponsored Agency 3,223.6 3,209.3 7,181.0 7,141.1 2,472.3 2,449.7 872.1 853.6 13,749.0 13,653.7 Non-U.S. Government 69.2 68.8 272.3 258.3 — — — — 341.5 327.1 Corporate Debt 114.6 114.1 90.4 87.0 — — — — 205.0 201.1 Covered Bonds — — 242.2 239.7 — — — — 242.2 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 192.8 190.9 3,520.1 3,501.1 306.8 296.1 — — 4,019.7 3,988.1 Other Asset-Backed 154.6 152.6 1,726.6 1,719.6 496.6 498.2 116.7 117.0 2,494.5 2,487.4 Commercial Mortgage-Backed 23.1 22.8 585.0 576.2 34.1 28.1 — — 642.2 627.1 Total $ 4,274.1 $ 4,252.4 $ 17,685.9 $ 17,573.1 $ 5,564.3 $ 5,515.8 $ 988.8 $ 970.6 $ 28,513.1 $ 28,311.9 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments. Available for Sale Debt Securities with Unrealized Losses. The following table provides information regarding AFS debt securities with no credit losses reported that had been in a continuous unrealized loss position for less than twelve months and for twelve months or longer as of September 30, 2024 and December 31, 2023. TABLE 42: AVAILABLE FOR SALE DEBT SECURITIES IN UNREALIZED LOSS POSITION WITH NO CREDIT LOSSES REPORTED SEPTEMBER 30, 2024 LESS THAN 12 MONTHS 12 MONTHS OR LONGER TOTAL (In Millions) FAIR UNREALIZED FAIR UNREALIZED FAIR UNREALIZED U.S. Government $ 5,293.0 $ 6.9 $ 630.9 $ 12.2 $ 5,923.9 $ 19.1 Obligations of States and Political Subdivisions — — 305.9 15.6 305.9 15.6 Government Sponsored Agency 2,028.2 3.6 6,676.9 110.7 8,705.1 114.3 Non-U.S. Government 55.3 — 271.9 14.4 327.2 14.4 Corporate Debt — — 104.5 2.4 104.5 2.4 Covered Bonds — — 126.7 3.1 126.7 3.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 645.3 0.7 917.6 44.9 1,562.9 45.6 Other Asset-Backed — — 476.3 14.2 476.3 14.2 Commercial Mortgage-Backed 12.5 — 587.8 15.2 600.3 15.2 Total $ 8,034.3 $ 11.2 $ 10,098.5 $ 232.7 $ 18,132.8 $ 243.9 Note: One corporate debt AFS security with a fair value of $43.1 million and unrealized losses of $1.6 million has been excluded from the table above as this AFS security had a $0.2 million allowance for credit losses reported as of September 30, 2024. Refer to the discussion further below and Note 6—Allowance for Credit Losses for further information. DECEMBER 31, 2023 LESS THAN 12 MONTHS 12 MONTHS OR LONGER TOTAL (In Millions) FAIR UNREALIZED FAIR UNREALIZED FAIR UNREALIZED U.S. Government $ — $ — $ 3,364.7 $ 61.5 $ 3,364.7 $ 61.5 Obligations of States and Political Subdivisions 87.8 5.9 208.0 14.1 295.8 20.0 Government Sponsored Agency 331.0 11.5 9,486.6 188.8 9,817.6 200.3 Non-U.S. Government — — 264.5 20.4 264.5 20.4 Corporate Debt 4.4 0.1 143.0 2.1 147.4 2.2 Covered Bonds — — 213.2 9.7 213.2 9.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — — 2,477.0 105.8 2,477.0 105.8 Other Asset-Backed 19.8 2.0 1,998.7 98.0 2,018.5 100.0 Commercial Mortgage-Backed 60.0 4.6 776.6 43.8 836.6 48.4 Total $ 503.0 $ 24.1 $ 18,932.3 $ 544.2 $ 19,435.3 $ 568.3 Note: Three corporate debt AFS securities with a fair value of $98.4 million and unrealized losses of $5.9 million and one sub-sovereign, supranational and non-U.S. agency bonds AFS security with a fair value of $71.0 million and unrealized loss of $8.2 million have been excluded from the table above as these AFS securities have a $1.2 million allowance for credit losses reported as of December 31, 2023. Refer to the discussion further below and Note 6—Allowance for Credit Losses for further information. As of September 30, 2024, 693 AFS debt securities with a combined fair value of $18.1 billion were in an unrealized loss position without an allowance for credit losses, with their unrealized losses totaling $243.9 million. As of September 30, 2024, unrealized losses related to AFS debt securities of $114.3 million, $45.6 million, and $19.1 million related to government-sponsored agency securities, sub-sovereign, supranational and non-U.S. agency bonds and U.S. Government, respectively, which are primarily attributable to higher average market interest rates as compared to the respective purchase dates of the securities. As of December 31, 2023, 898 AFS debt securities with a combined fair value of $19.4 billion were in an unrealized loss position without an allowance for credit losses, with their unrealized losses totaling $568.3 million. As of December 31, 2023, unrealized losses related to AFS debt securities of $200.3 million, $105.8 million, and $100.0 million related to government-sponsored agency, sub-sovereign, supranational and non-U.S. agency bonds, and other asset-backed, respectively, which are primarily attributable to lower yields and tighter spreads. AFS debt securities impairment reviews are conducted quarterly to identify and evaluate securities that have indications of possible credit losses. A determination as to whether a security’s decline in market value is related to credit impairment takes into consideration numerous factors and the relative significance of any single factor can vary by security. Factors Northern Trust considers in determining whether impairment is credit-related include, but are not limited to, the severity of the impairment; the cause of the impairment; the financial condition and near-term prospects of the issuer; activity in the market of the issuer, which may indicate adverse credit conditions; Northern Trust’s intent regarding the sale of the security as of the balance sheet date; and the likelihood that Northern Trust will not be required to sell the security for a period of time sufficient to allow for the recovery of the security’s amortized cost basis. For each security meeting the requirements of Northern Trust’s internal screening process, an extensive review is conducted to determine if a credit loss has occurred. In January 2024, the Corporation sold certain AFS debt securities that were in an unrealized loss position. The $189.4 million loss is recognized in Investment Security Gains (Losses), net on the consolidated statements of income for the nine months ended September 30, 2024. In November 2023, the Corporation sold certain AFS debt securities that were in an unrealized loss position. The $176.4 million loss is recognized in Investment Security Gains (Losses), net on the consolidated statements of income for the period ended December 31, 2023. There was a negative provision for credit losses of $0.4 million and a negative provision for credit losses of $1.0 million for AFS securities for the three and nine months ended September 30, 2024, respectively. There was a negative provision for credit losses of $0.6 million for AFS securities for both the three and nine months ended September 30, 2023. There was a $0.2 million allowance for credit losses for AFS securities as of September 30, 2024, which was related to corporate debt securities and $1.2 million allowance for credit losses for AFS securities as of December 31, 2023, which was related to corporate debt securities and non-U.S. agency bonds. The process for identifying credit losses for AFS securities is based on the best estimate of cash flows to be collected from the security, discounted using the security’s effective interest rate. If the present value of the expected cash flows is found to be less than the current amortized cost of the security, an allowance for credit losses is generally recorded equal to the difference between the two amounts, limited to the amount the amortized cost basis exceeds the fair value of the security. For additional information, please refer to Note 6— Allowance for Credit Losses. Held to Maturity Debt Securities. Held to maturity (HTM) debt securities consist of securities that management intends to, and Northern Trust has the ability to, hold until maturity. The following tables provide the amortized cost and fair values as of September 30, 2024 and December 31, 2023, and remaining maturities of HTM debt securities as of September 30, 2024. TABLE 43: RECONCILIATION OF AMORTIZED COST TO FAIR VALUE OF HELD TO MATURITY DEBT SECURITIES SEPTEMBER 30, 2024 (In Millions) AMORTIZED GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR Obligations of States and Political Subdivisions $ 2,549.9 $ 4.4 $ 14.8 $ 2,539.5 Government Sponsored Agency 8,826.8 2.6 823.8 8,005.6 Non-U.S. Government 2,361.3 0.2 65.2 2,296.3 Corporate Debt 491.1 — 14.7 476.4 Covered Bonds 2,124.8 0.3 72.7 2,052.4 Certificates of Deposit 542.6 — 0.3 542.3 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 5,062.1 2.6 197.6 4,867.1 Other Asset-Backed 111.6 0.5 0.2 111.9 Commercial Mortgage-Backed 37.6 — 1.0 36.6 Other 600.8 — 156.9 443.9 Total $ 22,708.6 $ 10.6 $ 1,347.2 $ 21,372.0 DECEMBER 31, 2023 (In Millions) AMORTIZED GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR Obligations of States and Political Subdivisions 2,563.9 0.5 72.4 2,492.0 Government Sponsored Agency 9,355.3 2.3 1,012.4 8,345.2 Non-U.S. Government 4,789.1 0.2 90.7 4,698.6 Corporate Debt 646.1 — 28.2 617.9 Covered Bonds 2,208.6 0.3 108.3 2,100.6 Certificates of Deposit 585.1 — 0.7 584.4 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 5,245.5 3.2 294.9 4,953.8 Other Asset-Backed 214.2 0.4 0.2 214.4 Commercial Mortgage-Backed 37.6 — 0.8 36.8 Other 576.3 — 147.0 429.3 Total $ 26,221.7 $ 6.9 $ 1,755.6 $ 24,473.0 As of September 30, 2024, the $22.7 billion HTM debt securities portfolio had unrealized losses of $823.8 million, $197.6 million and $156.9 million related to government-sponsored agency, sub-sovereign, supranational and non-U.S. agency bonds and other, respectively, which are primarily attributable to higher average market interest rates as compared to the respective purchase dates of the securities . As of December 31, 2023, the $26.2 billion HTM debt securities portfolio had unrealized losses of $1.0 billion and $294.9 million related to government-sponsored agency and sub-sovereign, supranational and non-U.S. agency bonds, respectively, which are primarily attributable to lower yields and tighter spreads. TABLE 44: REMAINING MATURITY OF HELD TO MATURITY DEBT SECURITIES SEPTEMBER 30, 2024 ONE YEAR OR LESS ONE TO FIVE YEARS FIVE TO TEN YEARS OVER TEN YEARS TOTAL (In Millions) Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Obligations of States and Political Subdivisions $ 106.8 $ 106.3 $ 1,302.2 $ 1,298.7 $ 935.6 $ 931.9 $ 205.3 $ 202.6 $ 2,549.9 $ 2,539.5 Government Sponsored Agency 917.4 843.7 3,345.6 3,056.6 2,874.6 2,617.6 1,689.2 1,487.7 8,826.8 8,005.6 Non-U.S. Government 1,254.9 1,252.6 1,072.4 1,013.1 34.0 30.6 — — 2,361.3 2,296.3 Corporate Debt 249.3 245.5 226.1 217.2 15.7 13.7 — — 491.1 476.4 Covered Bonds 660.6 656.9 1,254.4 1,200.5 209.8 195.0 — — 2,124.8 2,052.4 Certificates of Deposit 542.6 542.3 — — — — — — 542.6 542.3 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,723.9 1,705.6 3,332.5 3,156.7 5.7 4.8 — — 5,062.1 4,867.1 Other Asset-Backed 4.7 4.5 69.2 69.7 37.7 37.7 — — 111.6 111.9 Commercial Mortgage-Backed — — 37.6 36.6 — — — — 37.6 36.6 Other 71.0 69.3 293.3 267.6 50.7 42.5 185.8 64.5 600.8 443.9 Total $ 5,531.2 $ 5,426.7 $ 10,933.3 $ 10,316.7 $ 4,163.8 $ 3,873.8 $ 2,080.3 $ 1,754.8 $ 22,708.6 $ 21,372.0 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments. Credit Quality Indicators. The following table provides the amortized cost of HTM debt securities by credit rating. TABLE 45: AMORTIZED COST OF HELD TO MATURITY DEBT SECURITIES BY CREDIT RATING SEPTEMBER 30, 2024 ($ In Millions) AAA AA A BBB NOT RATED TOTAL Obligations of States and Political Subdivisions $ 980.8 $ 1,569.1 $ — $ — $ — $ 2,549.9 Government Sponsored Agency 8,826.8 — — — — 8,826.8 Non-U.S. Government 456.4 816.2 752.7 336.0 — 2,361.3 Corporate Debt — 290.4 200.7 — — 491.1 Covered Bonds 2,124.8 — — — — 2,124.8 Certificates of Deposit 513.2 — — — 29.4 542.6 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 3,825.8 1,204.5 30.7 1.1 — 5,062.1 Other Asset-Backed 111.6 — — — — 111.6 Commercial Mortgage-Backed 37.6 — — — — 37.6 Other 54.7 — — — 546.1 600.8 Total $ 16,931.7 $ 3,880.2 $ 984.1 $ 337.1 $ 575.5 $ 22,708.6 Percent of Total 75 % 17 % 4 % 1 % 3 % 100 % DECEMBER 31, 2023 ($ In Millions) AAA AA A BBB NOT RATED TOTAL Obligations of States and Political Subdivisions $ 954.7 $ 1,609.0 $ — $ — $ 0.2 $ 2,563.9 Government Sponsored Agency 9,355.3 — — — — 9,355.3 Non-U.S. Government 813.3 1,179.6 2,463.3 332.9 — 4,789.1 Corporate Debt 2.1 302.6 341.4 — — 646.1 Covered Bonds 2,208.6 — — — — 2,208.6 Certificates of Deposit 545.9 — — — 39.2 585.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 4,047.9 1,166.5 30.0 1.1 — 5,245.5 Other Asset-Backed 214.2 — — — — 214.2 Commercial Mortgage-Backed 37.6 — — — — 37.6 Other 54.8 — — — 521.5 576.3 Total $ 18,234.4 $ 4,257.7 $ 2,834.7 $ 334.0 $ 560.9 $ 26,221.7 Percent of Total 70 % 16 % 11 % 1 % 2 % 100 % Credit quality indicators are metrics that provide information regarding the relative credit risk of debt securities. Northern Trust maintains a high quality debt securities portfolio, with 96% and 97% of the HTM portfolio at September 30, 2024 and December 31, 2023, respectively, comprised of securities rated A or higher. The remaining HTM debt securities portfolio was comprised of 1% rated BBB at both September 30, 2024 and December 31, 2023 and 3% and 2% which were not rated by Moody’s, S&P Global, or Fitch Ratings at September 30, 2024 and December 31, 2023, respectively. Securities not explicitly rated were grouped where possible under the credit rating of the issuer of the security. Investment Security Gains and Losses. There were no sales of debt securities and no net investment security gains (losses) for the three months ended September 30, 2024. Proceeds of $17.1 million from the sale of debt securities resulted in an investment security gain of less than $0.1 million for the three months ended September 30, 2023. Proceeds of $2.0 billion from the sale of debt securities resulted in investment security loss of $189.3 million for the nine months ended September 30, 2024. Proceeds of $2.2 billion from the sale of debt securities resulted in investment security gains of $6.9 million for the nine months ended September 30, 2023. TABLE 46: INVESTMENT SECURITY GAINS AND LOSSES THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Gross Realized Debt Securities Gains $ — $ — $ 185.2 $ 213.0 Gross Realized Debt Securities Losses — — (374.5) (206.1) Investment Security Gains (Losses), net $ — $ — $ (189.3) $ 6.9 TABLE 47: INVESTMENT SECURITY GAINS AND LOSSES BY SECURITY TYPE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 U.S. Government $ — $ — $ (34.8) $ — Obligations of States and Political Subdivisions — — — 9.8 Government Sponsored Agency — — (23.0) — Corporate Debt — — — (1.2) Covered Bonds — — (4.2) — Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — — (48.2) — Other Asset-Backed — — (56.5) (0.8) Commercial Mortgage-Backed — — (22.6) (0.9) Investment Security Gains (Losses), net $ — $ — $ (189.3) $ 6.9

Loans

Loans	9 Months Ended
Loans	Sep. 30, 2024
Receivables [Abstract]
Loans	Loans Amounts outstanding for Loans, by segment and class, are shown in the following table. TABLE 48: LOANS (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Commercial Commercial and Institutional (1) $ 10,391.3 $ 11,555.3 Commercial Real Estate 5,251.0 5,134.2 Non-U.S. (1) 2,742.6 2,778.5 Other 2,448.9 5,944.8 Total Commercial 20,833.8 25,412.8 Personal Private Client 14,195.5 14,360.0 Residential Real Estate 6,141.2 6,327.1 Non-U.S. 457.2 428.8 Other 322.6 1,088.3 Total Personal 21,116.5 22,204.2 Total Loans $ 41,950.3 $ 47,617.0 (1) Commercial and institutional and commercial-non-U.S. combined include $3.8 billion and $4.5 billion of private equity capital call finance loans at September 30, 2024 and December 31, 2023, respectively. Residential real estate loans consist of traditional first lien mortgages and equity credit lines that generally require a loan-to-collateral value of no more than 65% to 80% at inception. Northern Trust’s equity credit line products generally have draw periods of up to 10 years and a balloon payment of any outstanding balance is due at maturity. Payments are interest-only with variable interest rates. In general, Northern Trust does not offer equity credit lines that include an option to convert the outstanding balance to an amortizing payment loan. As of September 30, 2024 and December 31, 2023, equity credit lines totaled $221.1 million and $228.7 million, respectively, and equity credit lines for which first liens were held by Northern Trust represented 98% and 96% of the total equity credit lines, respectively. Included within the commercial-other, commercial-non-U.S., and personal-other classes are short-duration advances primarily related to the processing of custodied client investments, totaling $4.5 billion and $8.4 billion at September 30, 2024 and December 31, 2023, respectively. Demand deposit overdrafts reclassified as loan balances, primarily in personal-other, totaled $19.0 million and $12.1 million at September 30, 2024 and December 31, 2023, respectively. Loans classified as held for sale are recorded at the lower of cost or fair value. There were no loans classified as held for sale at September 30, 2024 or December 31, 2023. There were no loans sold for the three and nine months ended September 30, 2024 and September 30, 2023. Credit Quality Indicators. Credit quality indicators are statistics, measurements or other metrics that provide information regarding the relative credit risk of loans. Northern Trust uses a variety of credit quality indicators to assess the credit risk of loans at the segment, class, and individual credit exposure levels. As part of its credit process, Northern Trust utilizes an internal borrower risk rating system to support identification, approval, and monitoring of credit risk. Borrower risk ratings are used in credit underwriting and management reporting. Risk ratings are used for ranking the credit risk of borrowers and their probability of default. Each borrower is rated using one of a number of ratings models, which consider both quantitative and qualitative factors. The ratings models vary among classes of loans in order to capture the unique risk characteristics inherent within each particular type of credit exposure. Provided below are the more significant performance indicator attributes considered within Northern Trust’s borrower rating models, by loan class. • Commercial and Institutional: leverage, profit margin, liquidity, asset size and capital levels; • Commercial Real Estate: debt service coverage, loan-to-value ratio, leasing status and guarantor support; • Commercial-Other: leverage, profit margin, liquidity, asset size and capital levels; • Non-U.S.: leverage, profit margin, liquidity, return on assets and capital levels; • Residential Real Estate: payment history, credit bureau scores and loan-to-value ratio; • Private Client: cash-flow-to-debt and net worth ratios, leverage and liquidity; and • Personal-Other: cash-flow-to-debt and net worth ratios. While the criteria vary by model, the objective is for the borrower ratings to be consistent in both the measurement and ranking of risk. Each model is calibrated to a master rating scale to support this consistency. Ratings for borrowers not in default range from “1” for the strongest credits to “7” for the weakest non-defaulted credits. Ratings of “8” or “9” are used for defaulted borrowers. Borrower risk ratings are monitored and are revised when events or circumstances indicate a change is required. Risk ratings are generally validated at least annually. Loan segment and class balances as of September 30, 2024 and December 31, 2023 are provided in the following table, segregated by borrower ratings into “1 to 3,” “4 to 5” and “6 to 9” (watch list and nonaccrual status) categories by year of origination at amortized cost basis. Loans that are held for investment are reported at the principal amount outstanding, net of unearned income. TABLE 49: CREDIT QUALITY INDICATOR AT AMORTIZED COST BASIS BY ORIGINATION YEAR TERM LOANS REVOLVING LOANS REVOLVING LOANS CONVERTED TO TERM LOANS September 30, 2024 2024 2023 2022 2021 2020 PRIOR TOTAL Commercial Commercial and Institutional Risk Rating: 1 to 3 Category $ 322.6 $ 247.5 $ 371.2 $ 588.1 $ 66.1 $ 381.0 $ 4,222.0 $ 21.3 $ 6,219.8 4 to 5 Category 544.9 538.1 458.1 494.4 103.8 141.9 1,513.4 56.3 3,850.9 6 to 9 Category 34.9 81.4 63.0 81.5 2.3 2.3 48.2 7.0 320.6 Total Commercial and Institutional 902.4 867.0 892.3 1,164.0 172.2 525.2 5,783.6 84.6 10,391.3 C&I Gross Charge-offs — (7.3) (1.3) — — — — — (8.6) Commercial Real Estate Risk Rating: 1 to 3 Category 97.3 339.5 289.1 219.5 18.8 68.5 53.7 — 1,086.4 4 to 5 Category 274.1 1,669.7 1,048.1 436.2 193.2 200.1 159.6 5.3 3,986.3 6 to 9 Category 14.1 16.0 126.4 17.1 4.3 0.4 — — 178.3 Total Commercial Real Estate 385.5 2,025.2 1,463.6 672.8 216.3 269.0 213.3 5.3 5,251.0 Commercial Real Estate Gross Charge-offs — — (2.4) — — — — — (2.4) Non-U.S. Risk Rating: 1 to 3 Category 1,215.8 24.2 — — 117.7 30.2 577.0 — 1,964.9 4 to 5 Category 606.0 16.5 0.8 1.2 — 69.3 69.6 — 763.4 6 to 9 Category 0.5 — 13.8 — — — — — 14.3 Total Non-U.S. 1,822.3 40.7 14.6 1.2 117.7 99.5 646.6 — 2,742.6 Other Risk Rating: 1 to 3 Category 1,183.9 — — — — — — — 1,183.9 4 to 5 Category 1,264.9 — — — — — — — 1,264.9 6 to 9 Category 0.1 — — — — — — — 0.1 Total Other 2,448.9 — — — — — — — 2,448.9 Other Gross Charge-offs — — — — — — — — — Total Commercial 5,559.1 2,932.9 2,370.5 1,838.0 506.2 893.7 6,643.5 89.9 20,833.8 Commercial Gross Charge-offs — (7.3) (3.7) — — — — — (11.0) Personal Private Client Risk Rating: 1 to 3 Category 206.7 80.0 39.5 38.3 19.1 39.8 4,503.2 144.1 5,070.7 4 to 5 Category 141.8 635.2 423.2 424.4 124.1 188.0 6,688.7 474.7 9,100.1 6 to 9 Category 0.1 16.3 — — — — 8.3 — 24.7 Total Private Client 348.6 731.5 462.7 462.7 143.2 227.8 11,200.2 618.8 14,195.5 Private Client Gross Charge-offs — — — — — (0.3) — — (0.3) Residential Real Estate Risk Rating: 1 to 3 Category 138.5 231.3 433.6 407.3 332.0 816.6 189.9 — 2,549.2 4 to 5 Category 134.6 224.0 664.6 706.2 678.4 940.4 165.6 2.1 3,515.9 6 to 9 Category — — 7.5 3.9 0.4 37.0 27.3 — 76.1 Total Residential Real Estate 273.1 455.3 1,105.7 1,117.4 1,010.8 1,794.0 382.8 2.1 6,141.2 Residential Real Estate Gross Charge-offs — — — — — (0.1) — — (0.1) Non-U.S. Risk Rating: 1 to 3 Category 3.2 1.0 — — — 6.8 158.0 — 169.0 4 to 5 Category 19.6 16.0 15.3 39.3 — 19.2 163.6 7.3 280.3 6 to 9 Category 7.9 — — — — — — — 7.9 Total Non-U.S. 30.7 17.0 15.3 39.3 — 26.0 321.6 7.3 457.2 Other Risk Rating: 1 to 3 Category 199.4 — — — — — — — 199.4 4 to 5 Category 123.1 — — — — — — — 123.1 6 to 9 Category 0.1 — — — — — — — 0.1 Total Other 322.6 — — — — — — — 322.6 Total Personal 975.0 1,203.8 1,583.7 1,619.4 1,154.0 2,047.8 11,904.6 628.2 21,116.5 Personal Gross Charge-offs — — — — — (0.4) — — (0.4) Total Loans $ 6,534.1 $ 4,136.7 $ 3,954.2 $ 3,457.4 $ 1,660.2 $ 2,941.5 $ 18,548.1 $ 718.1 $ 41,950.3 Total Loans Gross Charge-offs $ — $ (7.3) $ (3.7) $ — $ — $ (0.4) $ — $ — $ (11.4) December 31, 2023 TERM LOANS REVOLVING LOANS REVOLVING LOANS CONVERTED TO TERM LOANS (In Millions) 2023 2022 2021 2020 2019 PRIOR TOTAL Commercial Commercial and Institutional Risk Rating: 1 to 3 Category $ 443.9 $ 534.1 $ 668.3 $ 78.1 $ 137.2 $ 409.9 $ 4,909.8 $ 15.0 $ 7,196.3 4 to 5 Category 801.4 790.9 729.5 138.7 120.5 178.7 1,332.4 72.0 4,164.1 6 to 9 Category 13.8 70.0 60.8 12.0 0.1 1.7 34.7 1.8 194.9 Total Commercial and Institutional 1,259.1 1,395.0 1,458.6 228.8 257.8 590.3 6,276.9 88.8 11,555.3 Commercial Real Estate Risk Rating: 1 to 3 Category 403.6 389.9 159.1 23.9 37.8 44.8 51.0 — 1,110.1 4 to 5 Category 1,513.5 1,208.8 521.0 218.4 252.8 96.0 136.3 7.9 3,954.7 6 to 9 Category 16.1 — 30.5 — 8.2 14.6 — — 69.4 Total Commercial Real Estate 1,933.2 1,598.7 710.6 242.3 298.8 155.4 187.3 7.9 5,134.2 CRE Gross Charge-offs (0.7) (4.4) — — — — — — (5.1) Non-U.S. Risk Rating: 1 to 3 Category 487.9 — 43.2 65.2 34.2 3.3 760.0 — 1,393.8 4 to 5 Category 974.7 0.8 — — — 150.0 243.4 — 1,368.9 6 to 9 Category 1.5 14.3 — — — — — — 15.8 Total Non-U.S. 1,464.1 15.1 43.2 65.2 34.2 153.3 1,003.4 — 2,778.5 Other Risk Rating: 1 to 3 Category 4,313.2 — — — — — — — 4,313.2 4 to 5 Category 1,631.6 — — — — — — — 1,631.6 Total Other 5,944.8 — — — — — — — 5,944.8 Other Gross Charge-offs (0.6) — — — — — — — (0.6) Total Commercial 10,601.2 3,008.8 2,212.4 536.3 590.8 899.0 7,467.6 96.7 25,412.8 Commercial Gross Charge-offs (1.3) (4.4) — — — — — — (5.7) Personal Private Client Risk Rating: 1 to 3 Category 504.7 140.8 52.3 67.5 8.7 134.7 5,320.9 168.1 6,397.7 4 to 5 Category 290.1 488.2 655.1 100.9 158.8 44.7 5,721.5 447.8 7,907.1 6 to 9 Category 23.6 0.3 — — — 18.3 13.0 — 55.2 Total Private Client 818.4 629.3 707.4 168.4 167.5 197.7 11,055.4 615.9 14,360.0 Residential Real Estate Risk Rating: 1 to 3 Category 278.7 464.0 500.6 373.3 142.4 722.4 219.8 — 2,701.2 4 to 5 Category 191.6 694.9 717.4 686.7 290.0 805.3 170.3 — 3,556.2 6 to 9 Category — 10.9 — 0.7 1.6 43.6 12.9 — 69.7 Total Residential Real Estate 470.3 1,169.8 1,218.0 1,060.7 434.0 1,571.3 403.0 — 6,327.1 RRE Gross Charge-offs (0.8) — — — — (1.0) — — (1.8) Non-U.S. Risk Rating: 1 to 3 Category 15.5 — 0.6 — — 4.6 71.4 — 92.1 4 to 5 Category 12.7 16.0 39.2 — 16.4 8.9 236.1 7.4 336.7 6 to 9 Category — — — — — — — — — Total Non-U.S. 28.2 16.0 39.8 — 16.4 13.5 307.5 7.4 428.8 Other Risk Rating: 1 to 3 Category 461.7 — — — — — — — 461.7 4 to 5 Category 626.6 — — — — — — — 626.6 Total Other 1,088.3 — — — — — — — 1,088.3 Total Personal 2,405.2 1,815.1 1,965.2 1,229.1 617.9 1,782.5 11,765.9 623.3 22,204.2 Personal Gross Charge-Offs $ (0.8) $ — $ — $ — $ — $ (1.0) $ — $ — $ (1.8) Total Loans 13,006.4 4,823.9 4,177.6 1,765.4 1,208.7 2,681.5 19,233.5 720.0 47,617.0 Total Loans Gross Charge-Offs $ (2.1) $ (4.4) $ — $ — $ — $ (1.0) $ — $ — $ (7.5) Past Due Status. Past due status is based on the length of time from the contractual due date a principal or interest payment has been past due. For disclosure purposes, loans that are 29 days past due or less are reported as current. The following table provides balances and delinquency status of accrual and nonaccrual loans by segment and class, as well as the other real estate owned and nonaccrual asset balances, as of September 30, 2024 and December 31, 2023. TABLE 50: DELINQUENCY STATUS ACCRUAL NONACCRUAL WITH NO ALLOWANCE (In Millions) CURRENT 30 – 59 DAYS 60 – 89 DAYS 90 DAYS TOTAL ACCRUAL NONACCRUAL TOTAL LOANS September 30, 2024 Commercial Commercial and Institutional $ 10,246.1 $ 65.3 $ 16.4 $ 55.4 $ 10,383.2 $ 8.1 $ 10,391.3 $ 8.1 Commercial Real Estate 5,220.6 19.8 5.0 — 5,245.4 5.6 5,251.0 5.6 Non-U.S. 2,691.6 46.9 — 3.6 2,742.1 0.5 2,742.6 — Other 2,448.9 — — — 2,448.9 — 2,448.9 — Total Commercial 20,607.2 132.0 21.4 59.0 20,819.6 14.2 20,833.8 13.7 Personal Private Client 14,015.9 131.1 18.3 28.2 14,193.5 2.0 14,195.5 — Residential Real Estate 6,086.6 8.5 23.0 — 6,118.1 23.1 6,141.2 23.1 Non-U.S. 457.1 0.1 — — 457.2 — 457.2 — Other 322.6 — — — 322.6 — 322.6 — Total Personal 20,882.2 139.7 41.3 28.2 21,091.4 25.1 21,116.5 23.1 Total Loans $ 41,489.4 $ 271.7 $ 62.7 $ 87.2 $ 41,911.0 $ 39.3 $ 41,950.3 $ 36.8 Other Real Estate Owned $ — Total Nonaccrual Assets $ 39.3 ACCRUAL NONACCRUAL WITH NO ALLOWANCE (In Millions) CURRENT 30 – 59 DAYS 60 – 89 DAYS 90 DAYS TOTAL ACCRUAL NONACCRUAL TOTAL LOANS December 31, 2023 Commercial Commercial and Institutional $ 11,374.6 $ 163.7 $ 0.7 $ — $ 11,539.0 $ 16.3 $ 11,555.3 $ 4.1 Commercial Real Estate 5,123.7 4.4 6.1 — 5,134.2 — 5,134.2 — Non-U.S. 2,778.5 — — — 2,778.5 — 2,778.5 — Other 5,944.8 — — — 5,944.8 — 5,944.8 — Total Commercial 25,221.6 168.1 6.8 — 25,396.5 16.3 25,412.8 4.1 Personal Private Client 14,240.0 63.9 24.8 11.0 14,339.7 20.3 14,360.0 18.3 Residential Real Estate 6,283.0 7.5 0.5 9.1 6,300.1 27.0 6,327.1 27.0 Non-U.S 428.2 — 0.6 — 428.8 — 428.8 — Other 1,088.3 — — — 1,088.3 — 1,088.3 — Total Personal 22,039.5 71.4 25.9 20.1 22,156.9 47.3 22,204.2 45.3 Total Loans $ 47,261.1 $ 239.5 $ 32.7 $ 20.1 $ 47,553.4 $ 63.6 $ 47,617.0 $ 49.4 Other Real Estate Owned $ 1.5 Total Nonaccrual Assets $ 65.1 Interest income that would have been recorded for nonaccrual loans in accordance with their original terms was $0.5 million and $1.7 million for the three and nine months ended September 30, 2024, respectively, and $0.9 million and $2.3 million for the three and nine months ended September 30, 2023, respectively. Northern Trust may obtain physical possession of real estate via foreclosure or an in-substance repossession. As of September 30, 2024 and December 31, 2023, Northern Trust held foreclosed real estate properties with an immaterial carrying value as a result of obtaining physical possession. In addition, as of September 30, 2024 and December 31, 2023, Northern Trust had loans with a carrying value of $5.2 million and $3.5 million, respectively, for which formal foreclosure proceedings were in process. Loan Modifications to Borrowers Experiencing Financial Difficulty For borrowers experiencing financial difficulties, Northern Trust may provide payment relief by modifying the terms of the original loan. Loan modifications to borrowers experiencing financial difficulty involve primarily extensions of term, deferrals of principal and interest, interest rate concessions, and other modifications or a combination thereof. Northern Trust considers payment deferrals of less than 90 days as insignificant, absent any material modifications to other loan terms. Loan modifications were immaterial for both the three and nine months ended September 30, 2024 and September 30, 2023, respectively. The effectiveness of Northern Trust’s modification efforts is measured by the loans’ respective past due status under the modified terms as of the end of the period. At September 30, 2024, loans that were modified in the previous 12 months and that are now past due by more than 90 days totaled less than $1 million. No modified loans were considered past-due for purposes of these disclosures as of September 30, 2023. As of the three months ended September 30, 2024, Northern Trust had no charge offs related to modifications to borrowers experiencing financial difficulty that had been modified in the last 12 months. As of the nine months ended September 30, 2024, Northern Trust had $8.5 million charged off related to modifications to borrowers experiencing financial difficulty that had been modified in the last 12 months. As of the three and nine months ended September 30, 2023, Northern Trust had charge offs of less than $1 million related to modifications to borrowers experiencing financial difficulty that had been modified in the last 12 months. There were no undrawn loan commitments or standby letters of credit issued to financially distressed borrowers for which Northern Trust has modified the payment terms of the loans as of September 30, 2024 and December 31, 2023, respectively. The expected credit loss for nonaccrual loans including loan modifications to borrowers experiencing financial difficulty is measured based on either the expected future cash flows, the value of collateral, or other factors that may impact the borrower’s ability to pay. If the discounted cash flow method is utilized, the credit loss is measured based upon the present value of expected future cash flows, discounted at the effective interest rate based on the post-modification contractual rate. If a loan’s contractual interest rate varies based on subsequent changes in an independent factor, such as an index or rate, the loan’s effective interest rate is calculated based on the factor as it changes over the life of the loan. Northern Trust elected not to project changes in the factor for purposes of estimating expected future cash flows. Further, Northern Trust elected not to adjust the effective interest rate for prepayments. If the loan is collateral dependent, the expected loss is measured based on the fair value of the collateral at the reporting date. If the loan valuation is less than the recorded value of the loan, either an allowance is established or a charge-off is recorded for the difference. The nature and extent of further deterioration in credit quality, including a subsequent default, is considered in the determination of an appropriate level of allowance for credit losses for all loan modifications to borrowers experiencing financial difficulty.

Allowance for Credit Losses

Allowance for Credit Losses	9 Months Ended
Allowance for Credit Losses	Sep. 30, 2024
Receivables [Abstract]
Allowance for Credit Losses	Allowance for Credit Losses Allowance and Provision for Credit Losses. The allowance for credit losses—which represents management’s best estimate of lifetime expected credit losses related to various portfolios subject to credit risk, off-balance-sheet credit exposures, and specific borrower relationships—is determined by management through a disciplined credit review process. Northern Trust measures expected credit losses of financial assets with similar risk characteristics on a collective basis. A financial asset is measured individually if it does not share similar risk characteristics with other financial assets and the related allowance is determined through an individual evaluation. Management’s estimates utilized in establishing an appropriate level of allowance for credit losses are not dependent on any single assumption. In determining an appropriate allowance level, management evaluates numerous variables and takes into consideration past events, current conditions, and reasonable and supportable forecasts. The results of the credit reserve estimation methodology are reviewed quarterly by Northern Trust’s Credit Loss Reserve Committee, which receives input from Financial Risk Management, Treasury, Corporate Finance, the Economic Research Department, and each of Northern Trust’s reporting business units. The Credit Loss Reserve Committee determines the probability weights applied to each forecast approved by Northern Trust’s Macroeconomic Scenario Development Committee, and also reviews and approves qualitative adjustments to the collective allowance in line with Northern Trust’s qualitative adjustment framework. The Provision for Credit Losses on the consolidated statements of income represents the change in the Allowance for Credit Losses on the consolidated balance sheets after accounting for net charge-offs or recoveries and is the charge to current period earnings. It represents the amount needed to maintain the Allowance for Credit Losses on the consolidated balance sheets at an appropriate level to absorb lifetime expected credit losses related to financial assets in scope. Actual losses may vary from current estimates and the amount of the Provision for Credit Losses may be either greater or less than actual net charge-offs. The following table provides information regarding changes in the total Allowance for Credit Losses during the three and nine months ended September 30, 2024 and 2023. TABLE 51: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 167.7 $ 29.5 $ 10.9 $ 0.9 $ 209.0 Charge-Offs — — — — — Recoveries 2.4 — — — 2.4 Net Recoveries (Charge-Offs) 2.4 — — — 2.4 Provision for Credit Losses (1) 14.7 (3.0) (3.4) 0.1 8.4 Balance at End of Period $ 184.8 $ 26.5 $ 7.5 $ 1.0 $ 219.8 (1) The table excludes a negative provision for credit losses of $0.4 million for the three months ended September 30, 2024 for AFS debt securities. See further detail in Note 4—Securities. NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT DEBT SECURITIES HELD TO MATURITY OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 178.7 $ 26.9 $ 12.7 $ 0.9 $ 219.2 Charge-Offs (11.4) — — — (11.4) Recoveries 3.5 — — — 3.5 Net Recoveries (Charge-Offs) (7.9) — — — (7.9) Provision for Credit Losses (1) 14.0 (0.4) (5.2) 0.1 8.5 Balance at End of Period $ 184.8 $ 26.5 $ 7.5 $ 1.0 $ 219.8 (1) The table excludes a negative provision for credit losses of $1.0 million for the nine months ended September 30, 2024 for AFS debt securities. See further detail in Note 4—Securities. THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 152.5 $ 26.0 $ 16.7 $ 1.0 $ 196.2 Charge-Offs (0.8) — — — (0.8) Recoveries 1.1 — — — 1.1 Net Recoveries (Charge-Offs) 0.3 — — — 0.3 Provision for Credit Losses (1) 14.0 2.3 (1.8) 0.1 14.6 Balance at End of Period $ 166.8 $ 28.3 $ 14.9 $ 1.1 $ 211.1 (1) The table excludes a negative provision for credit losses of $0.6 million for the three months ended September 30, 2023 for AFS debt securities. See further detail in Note 4—Securitie s. NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 144.3 $ 38.5 $ 16.0 $ 0.8 $ 199.6 Charge-Offs (5.6) — — — (5.6) Recoveries 3.0 — — — 3.0 Net Recoveries (Charge-Offs) (2.6) — — — (2.6) Provision for Credit Losses (1) 25.1 (10.2) (1.1) 0.3 14.1 Balance at End of Period $ 166.8 $ 28.3 $ 14.9 $ 1.1 $ 211.1 (1) The table excludes a negative provision for credit losses of $0.6 million for the nine months ended September 30, 2023 for AFS debt securities. See further detail in Note 4—Securities. Excluding the impact of the negative provision for AFS debt securities, there was a Provision for Credit Losses of $8.4 million in the current quarter, as compared to a provision of $14.6 million in the prior-year quarter. The provision resulted from an increase in both the collective and individual reserves. The increase in collective reserves was primarily driven by a small number of downgrades and extensions in the Commercial and Institutional (C&I) portfolio. The reserve evaluated on a collective basis relates to pooled financial assets sharing similar risk characteristics. The increase in individual reserves was driven by the default of one C&I loan. There were net recoveries of $2.4 million during the three months ended September 30, 2024, while there were $0.3 million net recoveries for the three months ended September 30, 2023. For further detail, please see the Allowance for the Loan Portfolio and the Allowance for Held to Maturity Debt Securities Portfolio sections below. Excluding the impact of the negative provision for AFS debt securities, there was a Provision for Credit Losses of $8.5 million for the nine months ended September 30, 2024, as compared to a $14.1 million provision in the prior-year period. The provision was primarily due to an increase in collective reserves, partially offset by a decrease in individual reserves. The increase in collective reserves was primarily driven by a small number of downgrades and extensions in the C&I portfolio and by expectations for weaker prices in the CRE portfolio. The decrease in individual reserves was driven by one C&I loan charge-off in the first quarter, partially offset by the default of one C&I loan in the current quarter. There were net charge-offs of $7.9 million during the nine months ended September 30, 2024, as compared to net charge-offs of $2.6 million during the nine months ended September 30, 2023. For further detail, please see the Allowance for the Loan Portfolio and the Allowance for Held to Maturity Debt Securities Portfolio sections below. The portion of the allowance assigned to loans, HTM debt securities, and other financial assets is presented as a contra asset in Allowance for Credit Losses on the consolidated balance sheets. The portion of the allowance assigned to undrawn loan commitments and standby letters of credit is reported in Other Liabilities on the consolidated balance sheets. For credit exposure and the associated allowance related to fee receivables, please refer to Note 13—Revenue from Contracts with Clients. For information related to the allowance for AFS debt securities, please refer to Note 4—Securities. For all other financial assets recognized at amortized cost, which includes Cash and Due from Banks, Other Central Bank Deposits, Interest Bearing Deposits with Banks, and Other Assets, please refer to the Allowance for Other Financial Assets section within this footnote. Forecasting and Reversion. Estimating expected lifetime credit losses requires the consideration of the effect of future economic conditions. Northern Trust employs multiple scenarios over a reasonable and supportable period (currently two years) to project future conditions. Key variables determined to be relevant for projecting credit losses on the portfolios in scope include macroeconomic factors, such as corporate profits, unemployment, disposable income, and real estate price indices, as well as financial market factors such as market volatility and credit spreads. For periods beyond the reasonable and supportable period, Northern Trust reverts to its own historical loss experiences on a straight-line basis over four quarters. The primary forecast in the current quarter reflects an outlook of steady growth, despite modest deterioration within the Commercial Real Estate industry, with inflation and labor markets stabilizing and interest rates falling. Recognizing the uncertainty in the primary forecast, an alternative scenario is also considered, which reflects a recession that incorporates the experiences of a wider set of historical economic cycles. Contractual Term. Northern Trust estimates expected credit losses over the contractual term of the financial assets adjusted for prepayments, unless prepayments are not relevant to specific portfolios or sub-portfolios. Extension and renewal options are typically not considered since it is not Northern Trust’s practice to enter into arrangements where the borrower has the unconditional option to renew, or a conditional extension option whereby the conditions are beyond Northern Trust’s control. Allowance for the Loan Portfolio. The following table provides information regarding changes in the total Allowance for Credit Losses related to loans, including undrawn loan commitments and standby letters of credit, by segment during the three and nine months ended September 30, 2024 and 2023. TABLE 52: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES RELATED TO LOANS THREE MONTHS ENDED SEPTEMBER 30, 2024 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 136.9 $ 30.8 $ 167.7 $ 27.2 $ 2.3 $ 29.5 Charge-Offs — — — — — — Recoveries — 2.4 2.4 — — — Net Recoveries (Charge-Offs) — 2.4 2.4 — — — Provision for Credit Losses 15.7 (1.0) 14.7 (2.7) (0.3) (3.0) Balance at End of Period $ 152.6 $ 32.2 $ 184.8 $ 24.5 $ 2.0 $ 26.5 NINE MONTHS ENDED SEPTEMBER 30, 2024 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 146.8 $ 31.9 $ 178.7 $ 24.9 $ 2.0 $ 26.9 Charge-Offs (11.0) (0.4) (11.4) — — — Recoveries — 3.5 3.5 — — — Net Recoveries (Charge-Offs) (11.0) 3.1 (7.9) — — — Provision for (Release of) Credit Losses 16.8 (2.8) 14.0 (0.4) — (0.4) Balance at End of Period $ 152.6 $ 32.2 $ 184.8 $ 24.5 $ 2.0 $ 26.5 THREE MONTHS ENDED SEPTEMBER 30, 2023 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 124.0 $ 28.5 $ 152.5 $ 23.3 $ 2.7 $ 26.0 Charge-Offs (0.5) (0.3) (0.8) — — — Recoveries — 1.1 1.1 — — — Net Recoveries (Charge-Offs) (0.5) 0.8 0.3 — — — Provision for Credit Losses 13.9 0.1 14.0 2.2 0.1 2.3 Balance at End of Period $ 137.4 $ 29.4 $ 166.8 $ 25.5 $ 2.8 $ 28.3 NINE MONTHS ENDED SEPTEMBER 30, 2023 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 116.2 $ 28.1 $ 144.3 $ 36.3 $ 2.2 $ 38.5 Charge-Offs (4.5) (1.1) (5.6) — — — Recoveries 0.1 2.9 3.0 — — — Net Recoveries (Charge-Offs) (4.4) 1.8 (2.6) — — — Provision for (Release of) Credit Losses 25.6 (0.5) 25.1 (10.8) 0.6 (10.2) Balance at End of Period $ 137.4 $ 29.4 $ 166.8 $ 25.5 $ 2.8 $ 28.3 Allowance Related to Credit Exposure Evaluated on a Collective Basis. Expected credit losses are measured on a collective basis as long as the financial assets included in the respective pool share similar risk characteristics. If financial assets are deemed to not share similar risk characteristics, an individual assessment is warranted. The allowance estimation methodology for the collective assessment is based on data representative of the Corporation’s financial asset portfolio from a historical observation period that includes both expansionary and recessionary periods. The estimation methodology and the related qualitative adjustment framework segregate the loan portfolio into homogeneous segments based on similar risk characteristics or risk monitoring methods. Northern Trust utilizes a quantitative probability of default/loss given default approach for the calculation of its credit allowance on a collective basis. For each of the different parameters, specific credit models or qualitative estimation methodologies for the individual loan segments were developed. For each segment, the probability of default and the loss given default are applied to the exposure at default for each projected quarter to determine the quantitative component of the allowance. The quantitative allowance is then reviewed within the qualitative adjustment framework, through which management applies judgment by assessing internal risk factors, potential limitations in the quantitative methodology, and environmental factors that are not fully contemplated in the forecast to compute an adjustment to the quantitative allowance for each segment and class of the loan portfolio. Allowance Related to Credit Exposure Evaluated on an Individual Basis. The individual allowance is determined through individual evaluation of loans and lending-related commitments that have defaulted, generally those with borrower ratings of 8 and 9, that are based on expected future cash flows, the value of collateral, and other factors that may impact the borrower’s ability to pay. For defaulted loans for which the amount of allowance, if any, is determined based on the value of the underlying real estate collateral, third-party appraisals are typically obtained and utilized by management. These appraisals are generally less than twelve months old and are subject to adjustments to reflect management’s judgment as to the realizable value of the collateral. The following table provides information regarding the recorded investments in loans and the Allowance for Credit Losses for loans and undrawn loan commitments and standby letters of credit by segment as of September 30, 2024 and December 31, 2023. TABLE 53: RECORDED INVESTMENTS IN LOANS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Loans Evaluated on an Individual Basis $ 38.1 $ 35.3 $ 73.4 $ 33.7 $ 62.6 $ 96.3 Evaluated on a Collective Basis 20,795.7 21,081.2 41,876.9 25,379.1 22,141.6 47,520.7 Total Loans 20,833.8 21,116.5 41,950.3 25,412.8 22,204.2 47,617.0 Allowance for Credit Losses on Loans Evaluated on an Individual Basis 3.3 2.2 5.5 11.4 2.0 13.4 Evaluated on a Collective Basis 149.3 30.0 179.3 135.4 29.9 165.3 Allowance Assigned to Loans 152.6 32.2 184.8 146.8 31.9 178.7 Allowance Assigned to Undrawn Loan Commitments and Standby Letters of Credit - Evaluated on a Collective Basis 24.5 2.0 26.5 24.9 2.0 26.9 Total Allowance Assigned to Loans and Undrawn Loan Commitments and Standby Letters of Credit $ 177.1 $ 34.2 $ 211.3 $ 171.7 $ 33.9 $ 205.6 Northern Trust analyzes its exposure to credit losses from both on-balance-sheet and off-balance-sheet activity using a consistent methodology for the quantitative framework as well as the qualitative framework. For purposes of estimating the allowance for credit losses for undrawn loan commitments and standby letters of credit, the exposure at default includes an estimated drawdown of unused credit based on credit utilization factors, resulting in a proportionate amount of expected credit losses. Allowance for Held to Maturity Debt Securities Portfolio. The following table provides information regarding changes in the total allowance for credit losses for HTM debt securities during the three and nine months ended September 30, 2024 and 2023. TABLE 54: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES RELATED TO HELD TO MATURITY DEBT SECURITIES THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS (1) COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 0.5 $ 2.6 $ 1.7 $ 1.0 $ 0.1 $ 5.0 $ 10.9 Provision for Credit Losses — (0.1) (0.1) — (0.1) (3.1) (3.4) Balance at End of Period $ 0.5 $ 2.5 $ 1.6 $ 1.0 $ — $ 1.9 $ 7.5 (1) The allowance for Obligations of States and Political Subdivisions is related to (non pre-refunded) municipal securities that do not fall under Northern Trust’s zero-loss assumption. NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS (1) COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 0.9 $ 3.5 $ 2.2 $ 1.2 $ 0.1 $ 4.8 $ 12.7 Provision for (Release of) Credit Losses (0.4) (1.0) (0.6) (0.2) (0.1) (2.9) (5.2) Balance at End of Period $ 0.5 $ 2.5 $ 1.6 $ 1.0 $ — $ 1.9 $ 7.5 (1) The allowance for Obligations of States and Political Subdivisions is related to (non pre-refunded) municipal securities that do not fall under Northern Trust’s zero-loss assumption. THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 1.4 $ 5.4 $ 3.4 $ 1.3 $ 0.1 $ 5.1 $ 16.7 Provision for Credit Losses (0.1) (0.8) (0.5) (0.1) — (0.3) (1.8) Balance at End of Period $ 1.3 $ 4.6 $ 2.9 $ 1.2 $ 0.1 $ 4.8 $ 14.9 NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 1.9 $ 3.6 $ 4.0 $ 1.5 $ 0.1 $ 4.9 $ 16.0 Provision for (Release of) Credit Losses (0.6) 1.0 (1.1) (0.3) — (0.1) (1.1) Balance at End of Period $ 1.3 $ 4.6 $ 2.9 $ 1.2 $ 0.1 $ 4.8 $ 14.9 HTM debt securities classified as U.S. government, government sponsored agency, and certain securities classified as obligations of states and political subdivisions are considered to be guarantees of the U.S. government or an agency of the U.S. government and, therefore, an allowance for credit losses is not estimated for such investments as the expected probability of non-payment of the amortized cost basis is zero. HTM debt securities classified as “other asset-backed securities” represent pools of underlying receivables from which the cash flows are used to pay the bonds that vary in seniority. Utilizing a qualitative estimation approach, the allowance for other asset-backed securities is assessed by evaluating underlying pool performance based on delinquency rates and available credit support. HTM debt securities classified as “other” relate to investments purchased by Northern Trust to fulfill its obligations under the Community Reinvestment Act (CRA). Northern Trust fulfills its obligations under the CRA by making qualified investments for purposes of supporting institutions and programs that benefit low-to-moderate income communities within Northern Trust’s market area. The allowance for CRA investments is assessed using a qualitative estimation approach primarily based on internal historical performance experience and default history of the underlying CRA portfolios to determine a quantitative component of the allowance. The allowance estimation methodology for all other HTM debt securities is developed using a combination of external and internal data. The estimation methodology groups securities with shared characteristics for which the probability of default and the loss given default are applied to the total exposure at default to determine a quantitative component of the allowance. Allowance for Other Financial Assets. The allowance for Other Financial Assets consists of the allowance for Due from Banks, Other Central Bank Deposits, Interest Bearing Deposits with Banks, and Other Assets. The Other Assets category includes other miscellaneous credit exposures reported in Other Assets on the consolidated balance sheets. The allowance estimation methodology for Other Financial Assets primarily utilizes a similar approach as the one used for the HTM debt securities portfolio. It consists of a combination of externally and internally developed loss data, adjusted for the appropriate contractual term. Northern Trust’s portfolio of Other Financial Assets is composed mostly of institutions within the “1 to 2” internal borrower rating category and is expected to exhibit minimal to modest likelihood of loss. The Allowance for Credit Losses related to Other Financial Assets was $1.0 million and $0.9 million as of September 30, 2024 and December 31, 2023, respectively. Accrued Interest. Accrued interest balances are reported within Other Assets on the consolidated balance sheets. Northern Trust elected not to measure an allowance for credit losses for accrued interest receivables related to its loan and securities portfolio as its policy is to write-off uncollectible accrued interest receivable balances in a timely manner. Accrued interest is written off by reversing interest income during the period the financial asset is moved from an accrual to a nonaccrual status. The following table provides the amount of accrued interest excluded from the amortized cost basis of the following portfolios. TABLE 55: ACCRUED INTEREST (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Loans $ 220.2 $ 241.7 Debt Securities Held to Maturity 75.1 72.0 Available for Sale 177.2 129.2 Other Financial Assets 79.2 86.0 Total $ 551.7 $ 528.9 The amount of accrued interest reversed through interest income for loans was immaterial for the three and nine months ended September 30, 2024 and 2023, and there was no accrued interest reversed through interest income related to any other financial assets for the three and nine months ended September 30, 2024 and 2023.

Pledged Assets, Accepted Collat

Pledged Assets, Accepted Collateral and Restricted Assets	9 Months Ended
Pledged Assets, Accepted Collateral and Restricted Assets	Sep. 30, 2024
Transfers and Servicing [Abstract]
Pledged Assets, Accepted Collateral and Restricted Assets	Pledged Assets, Accepted Collateral and Restricted Assets Pledged Assets . As part of its liquidity management strategy, Northern Trust may pledge loans and/or securities to various financial market utilities to allow for client payment, clearing and settlement processing as part of our custody services. Northern Trust may also pledge loans or securities to Central Banks, Federal Home Loan Bank (FHLB) of Chicago and third parties for various purposes, for example: securing public and trust deposits, repurchase agreements, borrowings and derivative contracts. The following table presents the carrying value of Northern Trust's pledged assets by type. TABLE 56: TYPE OF PLEDGED ASSETS (In Billions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Debt Securities (1) $ 31.1 $ 33.0 Loans (2) 10.0 10.3 Total Pledged Assets $ 41.1 $ 43.3 (1) Debt securities are comprised of held to maturity and available for sale securities. (2) Loans pledged at the FHLB of Chicago and the Federal Reserve Bank of Chicago. As of September 30, 2024 and December 31, 2023, respectively, $1.2 billion and $1.1 billion of collateral pledged, related to loans and/or securities, is eligible to be repledged or sold by the secured party. Accepted Collateral. Northern Trust accepts financial assets as collateral that it may, in some instances, be permitted to repledge or sell. The collateral is generally obtained under certain reverse repurchase agreements and derivative contracts. The following table presents the fair value of securities accepted as collateral. TABLE 57: ACCEPTED COLLATERAL (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Collateral that may be repledged or sold Reverse repurchase agreements (1)(2) $ 66,367.0 $ 62,767.8 Derivative contracts 10.3 12.2 Collateral that may not be repledged or sold Reverse repurchase agreements — — Total Collateral Accepted $ 66,377.3 $ 62,780.0 (1) The fair value of securities collateral that was repledged or sold totaled $65.3 billion and $62.0 billion at September 30, 2024 and December 31, 2023, respectively. (2) This includes collateral accepted as related to the sponsored member program. Refer to Note 20—Commitments and Contingent Liabilities for further information. Restricted Assets . Certain cash may be restricted in terms of usage or withdrawal. As a result of the continuing military conflict involving Ukraine and the Russian Federation and related sanctions and legal restrictions in place, cash balances denominated in Russian rubles received for the benefit of certain clients in our Asset Servicing business are subject to distribution restrictions. As of September 30, 2024 and December 31, 2023, these balances totaled $1.0 billion and $722.2 million, respectively, and are reported in Cash and Due from Banks on the consolidated balance sheets. At September 30, 2024 and December 31, 2023, Northern Trust held cash of $519.8 million and $575.2 million, respectively, to meet non-U.S. reserve requirements. As a result of the economic environment arising from the COVID-19 pandemic, the Federal Reserve reduced the U.S. reserve requirement to zero percent on March 26, 2020. There were no average deposits required to meet Federal Reserve Bank reserve requirements for the three and nine months ended September 30, 2024 and 2023, respectively.

Goodwill and Other Intangibles

Goodwill and Other Intangibles	9 Months Ended
Goodwill and Other Intangibles	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangibles	Goodwill and Other Intangibles Goodwill. Changes by reporting segment in the carrying amount of Goodwill for the nine months ended September 30, 2024, including the effect of foreign exchange rates on non-U.S. dollar denominated balances, were as follows. TABLE 58: GOODWILL (In Millions) ASSET WEALTH MANAGEMENT TOTAL Balance at December 31, 2023 $ 621.9 $ 80.4 $ 702.3 Foreign Exchange Rates 5.5 — 5.5 Balance at September 30, 2024 $ 627.4 $ 80.4 $ 707.8 Other Intangible Assets Subject to Amortization . The gross carrying amount and accumulated amortization of other intangible assets subject to amortization as of September 30, 2024 and December 31, 2023 were as follows. TABLE 59: OTHER INTANGIBLE ASSETS (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Gross Carrying Amount $ 136.0 $ 135.0 Less: Accumulated Amortization 71.1 63.4 Net Book Value $ 64.9 $ 71.6 Other intangible assets consist primarily of the value of acquired client relationships and are included within Other Assets on the consolidated balance sheets. Amortization expense related to other intangible assets totaled $2.4 million and $7.1 million for the three and nine months ended September 30, 2024 and $2.3 million and $7.0 million for the three and nine months ended September 30, 2023, respectively. Amortization for the remainder of 2024 and for the years 2025, 2026, 2027, and 2028 is estimated to be $2.3 million, $9.0 million, $8.6 million, $8.4 million, and $7.7 million, respectively. Capitalized Software. The gross carrying amount and accumulated amortization of capitalized software as of September 30, 2024 and December 31, 2023 were as follows. TABLE 60: CAPITALIZED SOFTWARE (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Gross Carrying Amount $ 4,256.2 $ 3,781.7 Less: Accumulated Amortization 2,197.4 1,754.2 Net Book Value $ 2,058.8 $ 2,027.5 Capitalized software, which is included in Other Assets on the consolidated balance sheets, consists primarily of purchased software, software licenses, and allowable internal costs, including compensation relating to software developed for internal use. Fees paid for the use of software licenses that are not hosted by Northern Trust are expensed as incurred. Amortization expense, which is included in Equipment and Software expense on the consolidated statements of income, totaled $153.1 million and $444.1 million for the three and nine months ended September 30, 2024, respectively, and $126.7 million and $370.8 million for the three and nine months ended September 30, 2023, respectively.

Reporting Segments

Reporting Segments	9 Months Ended
Reporting Segments	Sep. 30, 2024
Segment Reporting [Abstract]
Reporting Segments	Reporting Segments Northern Trust is organized around its two client-focused reporting segments: Asset Servicing and Wealth Management. Asset management and related services are provided to Asset Servicing and Wealth Management clients primarily by the Asset Management business. The revenue and expenses of Asset Management and certain other support functions are allocated fully to Asset Servicing and Wealth Management. Reporting segment financial information, presented on an internal management-reporting basis, is determined by accounting systems used to allocate revenue and expense to each segment, and incorporates processes for allocating assets, liabilities, equity and the applicable interest income and expense utilizing a funds transfer pricing (FTP) methodology. Under the methodology, assets and liabilities receive a funding charge or credit that considers interest rate risk, liquidity risk, and other product characteristics on an instrument level. Additionally, segment information is presented on an FTE basis as management believes an FTE presentation provides a clearer indication of net interest income. The adjustment to an FTE basis has no impact on Net Income. Revenues, expenses and average assets are allocated to Asset Servicing and Wealth Management, with the exception of non-recurring activities such as certain corporate transactions and costs incurred associated with acquisitions, divestitures, litigation, restructuring, and tax adjustments not directly attributable to a specific reporting segment, which are reported within Other. Effective January 2024, Northern Trust implemented certain enhancements to its FTP methodology, impacting the allocation of Net Interest Income to the Asset Servicing and Wealth Management segments. As a result, the approximate impact on the Asset Servicing and Wealth Management segments was a $36 million decrease and a $36 million increase in Net Interest Income, respectively, for the three months ended September 30, 2024. The approximate impact on the Asset Servicing and Wealth Management segments was a $99 million decrease and a $99 million increase in Net Interest Income, respectively, for the nine months ended September 30, 2024. Prior-period segment results have not been revised to reflect this methodology change. Reporting segment results are subject to reclassification when organizational changes are made. The results are also subject to refinements in revenue and expense allocation methodologies, which are typically reflected on a prospective basis. The following table presents the earnings contributions and average assets of Northern Trust’s reporting segments for the three- and nine-month periods ended September 30, 2024 and 2023. TABLE 61: RESULTS OF REPORTING SEGMENTS ($ In Millions) ASSET SERVICING WEALTH MANAGEMENT OTHER (1) RECONCILING ITEMS TOTAL CONSOLIDATED THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees $ 667.1 $ 626.0 $ 529.5 $ 485.9 $ — $ — $ — $ — $ 1,196.6 $ 1,111.9 Foreign Exchange Trading Income (Loss) 59.5 54.3 (5.4) (2.5) — — — — 54.1 51.8 Other Noninterest Income (Loss) 67.3 66.1 35.7 38.1 52.5 2.4 — — 155.5 106.6 Total Noninterest Income (Loss) 793.9 746.4 559.8 521.5 52.5 2.4 — — 1,406.2 1,270.3 Net Interest Income 321.4 281.2 248.0 188.2 — — (7.1) (13.2) 562.3 456.2 Revenue 1,115.3 1,027.6 807.8 709.7 52.5 2.4 (7.1) (13.2) 1,968.5 1,726.5 Provision for Credit Losses (0.6) 3.1 12.4 10.9 (3.8) — — — 8.0 14.0 Noninterest Expense 860.7 809.3 491.3 456.9 7.4 12.0 — — 1,359.4 1,278.2 Income before Income Taxes 255.2 215.2 304.1 241.9 48.9 (9.6) (7.1) (13.2) 601.1 434.3 Provision for Income Taxes 57.1 54.3 75.1 67.7 11.1 (2.3) (7.1) (13.2) 136.2 106.5 Net Income $ 198.1 $ 160.9 $ 229.0 $ 174.2 $ 37.8 $ (7.3) $ — $ — $ 464.9 $ 327.8 Percentage of Consolidated Net Income 43 % 49 % 49 % 53 % 8 % (2) % N/A N/A 100 % 100 % Average Assets $ 108,108.0 $ 108,656.7 $ 38,734.9 $ 31,544.9 $ — $ — N/A N/A $ 146,842.9 $ 140,201.6 (1) Includes the current quarter gain related to the sale of an equity investment. (In Millions) ASSET SERVICING WEALTH MANAGEMENT OTHER (1) RECONCILING ITEMS TOTAL CONSOLIDATED NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees $ 1,957.3 $ 1,850.2 $ 1,548.3 $ 1,421.6 $ — $ — $ — $ — $ 3,505.6 $ 3,271.8 Foreign Exchange Trading Income (Loss) 181.6 161.2 (12.1) (6.3) — — — — 169.5 154.9 Other Noninterest Income (Loss) 199.2 199.0 105.3 112.8 737.9 (9.2) — — 1,042.4 302.6 Total Noninterest Income (Loss) 2,338.1 2,210.4 1,641.5 1,528.1 737.9 (9.2) — — 4,717.5 3,729.3 Net Interest Income 900.5 902.6 734.1 635.8 — — (21.3) (39.5) 1,613.3 1,498.9 Revenue 3,238.6 3,113.0 2,375.6 2,163.9 737.9 (9.2) (21.3) (39.5) 6,330.8 5,228.2 Provision for Credit Losses (1.9) (3.3) 15.7 16.8 (6.3) — — — 7.5 13.5 Noninterest Expense 2,634.0 2,459.7 1,504.9 1,402.4 119.1 33.6 — — 4,258.0 3,895.7 Income before Income Taxes 606.5 656.6 855.0 744.7 625.1 (42.8) (21.3) (39.5) 2,065.3 1,319.0 Provision for Income Taxes 146.1 167.4 223.0 207.5 141.8 (10.6) (21.3) (39.5) 489.6 324.8 Net Income $ 460.4 $ 489.2 $ 632.0 $ 537.2 $ 483.3 $ (32.2) $ — $ — $ 1,575.7 $ 994.2 Percentage of Consolidated Net Income 29 % 49 % 40 % 54 % 31 % (3) % N/A N/A 100 % 100 % Average Assets $ 108,025.6 $ 110,380.4 $ 38,629.2 $ 34,311.2 $ — $ — N/A N/A $ 146,654.8 $ 144,691.6 (1) Includes the current quarter gain related to the sale of an equity investment. Includes the gain related to the net impact from the Visa transactions in the second quarter of 2024, refer to Note 20—Commitments and Contingent Liabilities for further information. Note: Segment results are stated on an FTE basis. The FTE adjustments are eliminated in the reconciling items column with the Corporation’s total consolidated financial results stated on a GAAP basis. The adjustment to an FTE basis has no impact on Net Income.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2024
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock. The Corporation is authorized to issue 10 million shares of preferred stock without par value. The Board of Directors is authorized to fix the particular designations, preferences and relative, participating, optional and other special rights and qualifications, limitations or restrictions for each series of preferred stock issued. As of September 30, 2024, 5,000 shares of Series D Non-Cumulative Perpetual Preferred Stock (Series D Preferred Stock) and 16,000 shares of Series E Non-Cumulative Perpetual Preferred Stock (Series E Preferred Stock) were outstanding. Series D Preferred Stock. As of September 30, 2024, the Corporation had issued and outstanding 500,000 depositary shares, each representing a 1/100th ownership interest in a share of Series D Preferred Stock, issued in August 2016. Equity related to Series D Preferred Stock as of both September 30, 2024 and December 31, 2023 was $493.5 million. Shares of the Series D Preferred Stock have no par value and a liquidation preference of $100,000 (equivalent to $1,000 per depositary share). Dividends on the Series D Preferred Stock, which are not mandatory, accrue and are payable on the liquidation preference amount, on a non-cumulative basis, at a rate per annum equal to (i) 4.60% from the original issue date of the Series D Preferred Stock to but excluding October 1, 2026; and (ii) a floating rate equal to the three-month CME Term Secured Overnight Finance Rate (SOFR), as administered by CME Group Benchmark Administration, Ltd., plus a statutory spread adjustment of 0.26161% (as set forth in the final rule to implement the LIBOR Act) plus 3.202% from and including October 1, 2026. Fixed rate dividends are payable in arrears on the first day of April and October of each year, through and including October 1, 2026, and floating rate dividends will be payable in arrears on the first day of January, April, July and October of each year, commencing on January 1, 2027. On July 16, 2024, the Corporation declared a cash dividend of $2,300.00 per share of Series D Preferred Stock payable on October 1, 2024, to stockholders of record as of September 15, 2024. Series E Preferred Stock. As of September 30, 2024, the Corporation had issued and outstanding 16 million depositary shares, each representing 1/1,000th ownership interest in a share of Series E Preferred Stock, issued in November 2019. Equity related to Series E Preferred Stock as of September 30, 2024 and December 31, 2023 was $391.4 million. Shares of the Series E Preferred Stock have no par value and a liquidation preference of $25,000 (equivalent to $25 per depositary share). Dividends on the Series E Preferred Stock, which are not mandatory, will accrue and be payable on the liquidation preference amount, on a non-cumulative basis, quarterly in arrears on the first day of January, April, July and October of each year, at a rate per annum equal to 4.70%. On July 16, 2024, the Corporation declared a cash dividend of $293.75 per share of Series E Preferred Stock payable on October 1, 2024, to stockholders of record as of September 15, 2024. Common Stock. The Corporation’s current stock repurchase authorization to repurchase up to 25 million shares was approved by the Board of Directors in October 2021. Shares are repurchased by the Corporation to, among other things, manage the Corporation’s capital levels. Repurchased shares are used for general purposes, including the issuance of shares under stock option and other incentive plans. The repurchase authorization approved by the Board of Directors has no expiration date. For the three and nine months ended September 30, 2024, the Corporation repurchased 3,463,546 and 8,112,288 shares of common stock, respectively, at a total cost of $301.4 million ($87.01 average price per share) and $684.2 million ($84.34 average price per share), respectively, including 15,629 and 398,646 shares, withheld to satisfy tax withholding obligations related to share-based compensation, respectively. For the three and nine months ended September 30, 2023, the Corporation repurchased 14,738 and 2,426,793 shares of common stock, respectively, at a total cost of $1.1 million ($77.39 average price per share) and $201.3 million ($82.95 average price per share), respectively, including 14,738 and 356,145 shares withheld to satisfy tax withholding obligations related to share-based compensation, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
Accumulated Other Comprehensive Income (Loss)	Sep. 30, 2024
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The following tables summarize the components of Accumulated Other Comprehensive Income (Loss) (AOCI) at September 30, 2024 and 2023, and changes during the three and nine months then ended. TABLE 62: SUMMARY OF CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at June 30, 2024 $ (667.1) $ — $ 215.2 $ (413.1) $ (865.0) Net Change 63.9 0.3 18.9 2.4 85.5 Balance at September 30, 2024 $ (603.2) $ 0.3 $ 234.1 $ (410.7) $ (779.5) NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at December 31, 2023 $ (923.9) $ 0.8 $ 203.6 $ (418.4) $ (1,137.9) Net Change 320.7 (0.5) 30.5 7.7 358.4 Balance at September 30, 2024 $ (603.2) $ 0.3 $ 234.1 $ (410.7) $ (779.5) THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at June 30, 2023 $ (1,229.4) $ 0.5 $ 189.2 $ (366.2) $ (1,405.9) Net Change 32.3 (0.4) 9.6 1.0 42.5 Balance at September 30, 2023 $ (1,197.1) $ 0.1 $ 198.8 $ (365.2) $ (1,363.4) NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at December 31, 2022 $ (1,367.6) $ 1.2 $ 164.6 $ (367.4) $ (1,569.2) Net Change 170.5 (1.1) 34.2 2.2 205.8 Balance at September 30, 2023 $ (1,197.1) $ 0.1 $ 198.8 $ (365.2) $ (1,363.4) TABLE 63: DETAILS OF CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 (In Millions) PRE-TAX TAX AFTER TAX PRE-TAX TAX AFTER TAX Unrealized Gains (Losses) on Available for Sale Debt Securities Unrealized Gains (Losses) on Available for Sale Debt Securities $ 63.7 $ (18.6) $ 45.1 $ 18.0 $ (5.6) $ 12.4 Reclassification Adjustments for (Gains) Losses Included in Net Income: Interest Income on Debt Securities (1) 24.9 (6.1) 18.8 26.7 (6.8) 19.9 Net (Gains) Losses on Debt Securities (2) — — — — — — Net Change $ 88.6 $ (24.7) $ 63.9 $ 44.7 $ (12.4) $ 32.3 Unrealized Gains (Losses) on Cash Flow Hedges Foreign Exchange Contracts $ 1.0 $ (0.2) $ 0.8 $ 14.3 $ (3.6) $ 10.7 Reclassification Adjustment for (Gains) Losses Included in Net Income (3) (0.6) 0.1 (0.5) (14.9) 3.8 (11.1) Net Change $ 0.4 $ (0.1) $ 0.3 $ (0.6) $ 0.2 $ (0.4) Foreign Currency Adjustments Foreign Currency Translation Adjustments $ 122.9 $ (2.4) $ 120.5 $ (89.2) $ 1.7 $ (87.5) Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) 1.0 (0.3) 0.7 (0.2) 0.1 (0.1) Net Investment Hedge Gains (Losses) (135.6) 33.3 (102.3) 129.9 (32.7) 97.2 Net Change $ (11.7) $ 30.6 $ 18.9 $ 40.5 $ (30.9) $ 9.6 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gains (Losses) $ (0.1) $ — $ (0.1) $ (0.2) $ — $ (0.2) Reclassification Adjustment for (Gains) Losses Included in Net Income (4) Amortization of Net Actuarial Loss 3.2 (0.7) 2.5 1.6 (0.4) 1.2 Net Change $ 3.1 $ (0.7) $ 2.4 $ 1.4 $ (0.4) $ 1.0 Total Net Change $ 80.4 $ 5.1 $ 85.5 $ 86.0 $ (43.5) $ 42.5 NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 (In Millions) PRE-TAX TAX AFTER TAX PRE-TAX TAX AFTER TAX Unrealized Gains (Losses) on Available for Sale Debt Securities Unrealized Gains (Losses) on Available for Sale Debt Securities $ 176.9 $ (55.1) $ 121.8 $ 158.6 $ (42.0) $ 116.6 Reclassification Adjustments for (Gains) Losses Included in Net Income: Interest Income on Debt Securities (1) 76.5 (19.0) 57.5 79.0 (19.9) 59.1 Net (Gains) Losses on Debt Securities (2) 189.3 (47.9) 141.4 (6.9) 1.7 (5.2) Net Change $ 442.7 $ (122.0) $ 320.7 $ 230.7 $ (60.2) $ 170.5 Unrealized Gains (Losses) on Cash Flow Hedges Foreign Exchange Contracts $ 6.4 $ (1.5) $ 4.9 $ 16.2 $ (4.1) $ 12.1 Reclassification Adjustment for (Gains) Losses Included in Net Income (3) (7.1) 1.7 (5.4) (17.7) 4.5 (13.2) Net Change $ (0.7) $ 0.2 $ (0.5) $ (1.5) $ 0.4 $ (1.1) Foreign Currency Adjustments Foreign Currency Translation Adjustments $ 52.5 $ (1.2) $ 51.3 $ (15.7) $ 1.2 $ (14.5) Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) 0.2 (0.1) 0.1 (1.8) 0.5 (1.3) Net Investment Hedge Gains (Losses) (36.3) 15.4 (20.9) 66.8 (16.8) 50.0 Net Change $ 16.4 $ 14.1 $ 30.5 $ 49.3 $ (15.1) $ 34.2 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gains (Losses) $ 0.9 $ (0.5) $ 0.4 $ (1.5) $ 0.1 $ (1.4) Reclassification Adjustment for (Gains) Losses Included in Net Income (4) Amortization of Net Actuarial Loss 9.6 (2.3) 7.3 4.8 (1.2) 3.6 Net Change $ 10.5 $ (2.8) $ 7.7 $ 3.3 $ (1.1) $ 2.2 Total Net Change $ 468.9 $ (110.5) $ 358.4 $ 281.8 $ (76.0) $ 205.8 (1) The before-tax reclassification adjustment is related to the unrealized gains (losses) amortization on AFS debt securities that were transferred to HTM debt securities during the second quarter of 2021 and third quarter of 2022. (2) The net gains (losses) on AFS debt securities before-tax reclassification adjustment is recorded in Investment Security Gains (Losses), net on the consolidated statements of income. (3) See Note 21—Derivative Financial Instruments for the location of the reclassification adjustment related to cash flow hedges. (4) The pension and other postretirement benefit before-tax reclassification adjustment is recorded in Employee Benefits expense on the consolidated statements of income.

Net Income Per Common Share

Net Income Per Common Share	9 Months Ended
Net Income Per Common Share	Sep. 30, 2024
Earnings Per Share [Abstract]
Net Income Per Common Share	Net Income Per Common Share The computations of net income per common share are presented in the following table. TABLE 64: NET INCOME PER COMMON SHARE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, ($ In Millions Except Per Common Share Information) 2024 2023 2024 2023 Basic Net Income Per Common Share Average Number of Common Shares Outstanding 199,937,543 207,021,554 202,614,386 207,611,420 Net Income $ 464.9 $ 327.8 $ 1,575.7 $ 994.2 Less: Dividends on Preferred Stock 16.2 16.2 37.1 37.1 Net Income Applicable to Common Stock 448.7 311.6 1,538.6 957.1 Less: Earnings Allocated to Participating Securities 3.6 3.1 13.2 9.7 Earnings Allocated to Common Shares Outstanding 445.1 308.5 1,525.4 947.4 Basic Net Income Per Common Share $ 2.23 $ 1.49 $ 7.53 $ 4.56 Diluted Net Income Per Common Share Average Number of Common Shares Outstanding 199,937,543 207,021,554 202,614,386 207,611,420 Plus: Dilutive Effect of Share-based Compensation 611,520 231,438 517,014 316,300 Average Common and Potential Common Shares 200,549,063 207,252,992 203,131,400 207,927,720 Earnings Allocated to Common and Potential Common Shares $ 445.1 $ 308.5 $ 1,525.4 $ 947.3 Diluted Net Income Per Common Share 2.22 1.49 7.51 4.56

Revenue from Contracts with Cli

Revenue from Contracts with Clients	9 Months Ended
Revenue from Contracts with Clients	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Clients	Revenue from Contracts with Clients Trust, Investment, and Other Servicing Fees. Custody and Fund Administration income is comprised of revenues received from our core asset servicing business for providing custody, fund administration, and middle-office-related services, primarily to Asset Servicing clients. Investment Management and Advisory income contains revenue received from providing asset management and related services to Wealth Management and Asset Servicing clients and to Northern Trust sponsored funds. Securities Lending income represents revenues generated from securities lending arrangements that Northern Trust enters into as agent, mainly with Asset Servicing clients. Other income largely consists of revenues received from providing employee benefit, investment risk and analytic and other services to Asset Servicing and Wealth Management clients. Other Noninterest Income. Treasury Management income represents revenues received from providing cash and liquidity management services to Asset Servicing and Wealth Management clients. The portion of Security Commissions and Trading Income that relates to revenue from contracts with clients is primarily comprised of commissions earned from providing securities brokerage services to Wealth Management and Asset Servicing clients. The portion of Other Operating Income that relates to revenue from contracts with clients is mainly comprised of service fees for banking-related services provided to Wealth Management and Asset Servicing clients. Performance Obligations. Clients are typically charged monthly or quarterly in arrears based on the fee arrangement agreed to with each client; payment terms will vary depending on the client and services offered. Substantially all revenues generated from contracts with clients for asset servicing, asset management, securities lending, treasury management and banking-related services are recognized on an accrual basis, over the period in which services are provided. The nature of Northern Trust’s performance obligations is to provide a series of distinct services in which the customer simultaneously receives and consumes the benefits of the promised services as they are performed. Fee arrangements are mainly comprised of variable amounts based on market value of client assets managed and serviced, transaction volumes, number of accounts, and securities lending volume and spreads. Revenue is recognized using the output method in an amount that reflects the consideration to which Northern Trust expects to be entitled in exchange for providing each month or quarter of service. For contracts with multiple performance obligations, revenue is allocated to each performance obligation based on the price agreed to with the client, representing its relative standalone selling price. Security brokerage revenue is primarily represented by securities commissions received in exchange for providing trade execution related services. Control is transferred at a point in time, on the trade date of the transaction, and fees are typically variable based on transaction volumes and security types. Northern Trust’s contracts with its clients are typically open-ended arrangements and are therefore considered to have an original duration of less than one year. Northern Trust has elected the practical expedient to not disclose the value of remaining performance obligations for contracts with an original expected duration of one year or less. The following table presents revenues disaggregated by major revenue source. TABLE 65: REVENUE DISAGGREGATION THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees Custody and Fund Administration $ 482.5 $ 459.0 $ 1,427.1 $ 1,358.7 Investment Management and Advisory 634.8 574.1 1,838.3 1,673.4 Securities Lending 17.7 20.7 53.2 61.3 Other 61.6 58.1 187.0 178.4 Total Trust, Investment and Other Servicing Fees $ 1,196.6 $ 1,111.9 $ 3,505.6 $ 3,271.8 Other Noninterest Income Foreign Exchange Trading Income $ 54.1 $ 51.8 $ 169.5 $ 154.9 Treasury Management Fees 8.2 7.5 26.5 23.8 Security Commissions and Trading Income 35.5 30.9 107.7 101.7 Other Operating Income 111.8 68.2 1,097.5 170.2 Investment Security Gains (Losses), net — — (189.3) 6.9 Total Other Noninterest Income $ 209.6 $ 158.4 $ 1,211.9 $ 457.5 Total Noninterest Income $ 1,406.2 $ 1,270.3 $ 4,717.5 $ 3,729.3 On the consolidated statements of income, Trust, Investment and Other Servicing Fees and Treasury Management Fees represent revenue from contracts with clients. For the three months ended September 30, 2024, revenue from contracts with clients also includes $31.0 million of the $35.5 million total Security Commissions and Trading Income and $9.7 million of the $111.8 million total Other Operating Income. For the nine months ended September 30, 2024, revenue from contracts with clients also includes $95.7 million of the $107.7 million total Security Commissions and Trading Income and $29.0 million of the $1,097.5 million total Other Operating Income For the three months ended September 30, 2023, revenue from contracts with clients also includes $27.4 million of the $30.9 million total Security Commissions and Trading Income and $11.2 million of the $68.2 million total Other Operating Income. For the nine months ended September 30, 2023, revenue from contracts with clients also includes $86.3 million of the $101.7 million total Security Commissions and Trading Income and $30.5 million of the $170.2 million total Other Operating Income. Receivables Balances. The table below represents receivables balances from contracts with clients, which are included in Other Assets on the consolidated balance sheets, at September 30, 2024 and December 31, 2023. TABLE 66: CLIENT RECEIVABLES (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Trust Fees Receivable, net (1) $ 973.6 $ 863.5 Other 57.1 64.9 Total Client Receivables $ 1,030.7 $ 928.4 (1) Trust Fees Receivable is net of a $13.5 million and $15.9 million fee receivable allowance as of September 30, 2024 and December 31, 2023, respectively.

Net Interest Income

Net Interest Income	9 Months Ended
Net Interest Income	Sep. 30, 2024
Banking and Thrift, Interest [Abstract]
Net Interest Income	Net Interest Income The components of Net Interest Income were as follows. TABLE 67: NET INTEREST INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Interest Income Federal Reserve and Other Central Bank Deposits $ 451.7 $ 352.1 $ 1,369.0 $ 1,128.0 Interest-Bearing Due from and Deposits with Banks (1) 28.5 34.9 94.5 95.2 Federal Funds Sold — — — 0.3 Securities Purchased under Agreements to Resell 890.8 463.9 2,578.2 874.1 Securities — Taxable 486.3 402.4 1,409.0 1,106.5 — Nontaxable (2) 0.2 0.3 0.8 1.0 Loans 644.5 664.2 1,946.4 1,881.6 Other Interest-Earning Assets (3) 28.2 17.2 84.4 38.7 Total Interest Income $ 2,530.2 $ 1,935.0 $ 7,482.3 $ 5,125.4 Interest Expense Deposits $ 873.5 $ 716.6 $ 2,653.5 $ 1,914.7 Federal Funds Purchased 29.6 77.5 101.9 205.2 Securities Sold Under Agreements to Repurchase 869.7 454.0 2,535.1 843.5 Other Borrowings 94.8 154.8 278.7 446.3 Senior Notes 44.2 44.1 132.4 125.4 Long-Term Debt 56.1 31.8 167.4 91.4 Total Interest Expense $ 1,967.9 $ 1,478.8 $ 5,869.0 $ 3,626.5 Net Interest Income $ 562.3 $ 456.2 $ 1,613.3 $ 1,498.9 (1) Interest-Bearing Due from and Deposits with Banks includes the interest-bearing component of Cash and Due from Banks and Interest-Bearing Deposits with Banks as presented on the consolidated balance sheets. (2) Non-taxable Securities represent securities that are exempt from U.S. federal income taxes. (3) Other Interest-Earning Assets include certain community development investments, collateral deposits with certain securities depositories and clearing houses, Federal Home Loan Bank and Federal Reserve stock, and money market investments which are classified in Other Assets on the consolidated balance sheets.

Other Operating Income

Other Operating Income	9 Months Ended
Other Operating Income	Sep. 30, 2024
Other Income and Expenses [Abstract]
Other Operating Income	Other Operating Income The components of Other Operating Income were as follows. TABLE 68: OTHER OPERATING INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Loan Service Fees $ 14.0 $ 21.2 $ 43.4 $ 61.3 Banking Service Fees 14.2 15.0 40.8 40.8 Bank Owned Life Insurance 18.4 17.3 60.4 51.0 Other Income (1) (2) 65.2 14.7 952.9 17.1 Total Other Operating Income $ 111.8 $ 68.2 $ 1,097.5 $ 170.2 (1) Other Income for three months ended September 30, 2024 includes a $68.1 million pre-tax gain related to the sale of an equity investment. (2) Other Income for the three and nine months ended September 30, 2024 includes the mark-to-market loss on derivative swap activity primarily related to the sale of certain Visa Class B common shares. For the nine months ended September 30, 2024, Other Income includes the mark-to-market gain related to Visa Class C common shares. Refer to Note 20—Commitments and Contingent Liabilities for further information. The components of Other Operating Expense were as follows. TABLE 69: OTHER OPERATING EXPENSE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, In Millions) 2024 2023 2024 2023 Business Promotion $ 19.1 $ 16.2 $ 56.6 $ 53.5 Staff Related 12.4 11.0 34.8 27.7 FDIC Insurance Premiums (1) 7.1 8.3 35.6 21.1 Charitable Contributions (2) 3.3 3.8 79.3 11.3 Other Expenses 44.2 59.2 155.5 182.5 Total Other Operating Expense $ 86.1 $ 98.5 $ 361.8 $ 296.1 (1) FDIC Insurance Premiums for the nine months ended September 30, 2024 includes $14.7 million related to the FDIC Insurance Premium Special Assessment. Refer to Note 20—Commitments and Contingent Liabilities for further information. (2) Charitable Contributions includes a $70 million charitable contribution to the Northern Trust Foundation for the nine months ended September 30, 2024.

Other Operating Expense

Other Operating Expense	9 Months Ended
Other Operating Expense	Sep. 30, 2024
Other Income and Expenses [Abstract]
Other Operating Expense	Other Operating Income The components of Other Operating Income were as follows. TABLE 68: OTHER OPERATING INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Loan Service Fees $ 14.0 $ 21.2 $ 43.4 $ 61.3 Banking Service Fees 14.2 15.0 40.8 40.8 Bank Owned Life Insurance 18.4 17.3 60.4 51.0 Other Income (1) (2) 65.2 14.7 952.9 17.1 Total Other Operating Income $ 111.8 $ 68.2 $ 1,097.5 $ 170.2 (1) Other Income for three months ended September 30, 2024 includes a $68.1 million pre-tax gain related to the sale of an equity investment. (2) Other Income for the three and nine months ended September 30, 2024 includes the mark-to-market loss on derivative swap activity primarily related to the sale of certain Visa Class B common shares. For the nine months ended September 30, 2024, Other Income includes the mark-to-market gain related to Visa Class C common shares. Refer to Note 20—Commitments and Contingent Liabilities for further information. The components of Other Operating Expense were as follows. TABLE 69: OTHER OPERATING EXPENSE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, In Millions) 2024 2023 2024 2023 Business Promotion $ 19.1 $ 16.2 $ 56.6 $ 53.5 Staff Related 12.4 11.0 34.8 27.7 FDIC Insurance Premiums (1) 7.1 8.3 35.6 21.1 Charitable Contributions (2) 3.3 3.8 79.3 11.3 Other Expenses 44.2 59.2 155.5 182.5 Total Other Operating Expense $ 86.1 $ 98.5 $ 361.8 $ 296.1 (1) FDIC Insurance Premiums for the nine months ended September 30, 2024 includes $14.7 million related to the FDIC Insurance Premium Special Assessment. Refer to Note 20—Commitments and Contingent Liabilities for further information. (2) Charitable Contributions includes a $70 million charitable contribution to the Northern Trust Foundation for the nine months ended September 30, 2024.

Pension

Pension	9 Months Ended
Pension	Sep. 30, 2024
Retirement Benefits [Abstract]
Pension	Pension The following table sets forth the net periodic pension expense for Northern Trust’s U.S. Qualified Plan, Non-U.S. Pension Plans, and U.S. Non-Qualified Plan for the three and nine months ended September 30, 2024 and 2023. TABLE 70: NET PERIODIC PENSION EXPENSE (BENEFIT) U.S. QUALIFIED PLAN THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 13.4 $ 11.5 $ 40.2 $ 34.5 Interest Cost 13.9 13.5 41.7 40.5 Expected Return on Plan Assets (28.9) (25.3) (86.7) (75.9) Amortization Net Actuarial Loss 1.9 0.4 5.7 1.2 Net Periodic Pension Expense $ 0.3 $ 0.1 $ 0.9 $ 0.3 NON-U.S. PENSION PLANS THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 0.5 $ 0.4 $ 1.5 $ 1.1 Interest Cost 1.1 1.2 3.3 3.6 Expected Return on Plan Assets (1.6) (1.6) (4.8) (4.7) Amortization Net Actuarial (Gain) — (0.1) — (0.3) Net Periodic Pension (Benefit) $ — $ (0.1) $ — $ (0.3) U.S. NON-QUALIFIED PLAN THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 1.2 $ 1.2 $ 3.6 $ 3.6 Interest Cost 1.2 1.3 3.6 3.9 Amortization Net Actuarial Loss 1.3 1.3 3.9 3.9 Net Periodic Pension Expense $ 3.7 $ 3.8 $ 11.1 $ 11.4 The components of net periodic pension expense are recorded in Employee Benefits expense on the consolidated statements of income. There were $200.0 million of contributions to the U.S. Qualified Plan during the nine months ended September 30, 2024. There were no contributions to the U.S. Qualified Plan during the nine months ended September 30, 2023. There were $8.0 million and $16.5 million of contributions to the U.S. Non-Qualified Plan during the nine months ended September 30, 2024 and 2023, respectively.

Share-Based Compensation Plans

Share-Based Compensation Plans	9 Months Ended
Share-Based Compensation Plans	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation Plans	Share-Based Compensation Plans The Northern Trust Corporation 2017 Long-Term Incentive Plan provides for the grant of non-qualified and incentive stock options; tandem and free-standing stock appreciation rights; stock awards in the form of restricted stock, restricted stock units and other stock awards; and performance awards. Restricted stock unit and performance stock unit grants continue to vest in accordance with the original terms of the award if the applicable employee retires after satisfying applicable age and service requirements. Total compensation expense for share-based payment arrangements and the associated tax impacts were as follows for the three and nine months ended September 30, 2024 and 2023. TABLE 71: TOTAL COMPENSATION EXPENSE FOR SHARE-BASED PAYMENT ARRANGEMENTS THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Restricted Stock Unit Awards $ 13.4 $ 14.7 $ 78.3 $ 80.5 Performance Stock Units 1.3 1.8 19.8 17.8 Total Share-Based Compensation Expense 14.7 16.5 98.1 98.3 Tax Benefits Recognized $ 3.6 $ 4.2 $ 24.0 $ 24.7

Variable Interest Entities

Variable Interest Entities	9 Months Ended
Variable Interest Entities	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	Variable Interest Entities Northern Trust is involved with various entities in the normal course of business that are deemed to be variable interest entities (VIEs). VIEs are defined within GAAP as entities which either (1) lack sufficient equity at risk to permit the entity to finance its activities without additional subordinated financial support, (2) have equity investors that lack attributes typical of an equity investor, such as the ability to make significant decisions through voting rights affecting the entity’s operations, or the obligation to absorb expected losses or the right to receive residual returns of the entity, or (3) are structured with voting rights that are disproportionate to the equity investor’s obligation to absorb losses or right to receive returns, and substantially all of the activities are conducted on behalf of the holder of the equity investment at risk with disproportionately few voting rights. Investors that finance a VIE through debt or equity interests are variable interest holders in the entity and the variable interest holder, if any, that has both the power to direct the activities that most significantly impact the entity’s economic performance and, through its variable interest, the obligation to absorb losses or the right to receive returns that could potentially be significant to the entity is deemed to be the VIE’s primary beneficiary and is required to consolidate the VIE. Tax credit structures. Northern Trust holds tax-advantaged investments in unconsolidated entities that own and operate affordable housing and projects through the new markets tax credit program. These entities, which are limited partnerships and similar entities, are primarily VIEs and are designed to generate a return primarily through the realization of tax credits and other tax benefits, such as tax deductions from operating losses of the investments. Northern Trust invests as a limited partner/investor member and lacks both the power to direct the entities’ most significant activities and the obligation to absorb losses or right to receive benefits that could potentially be significant to the entities. Northern Trust is not required to consolidate these entities as it does not have a controlling financial interest and thus is not the primary beneficiary. Northern Trust’s maximum exposure to loss as a result of its involvement with these entities is limited to the carrying amounts of its investments, including any undrawn commitments. Northern Trust’s funding requirements are limited to its invested capital and undrawn commitments for future equity contributions. Northern Trust has no exposure to loss from liquidity arrangements and no obligation to purchase assets of these entities. Northern Trust’s investments in these unconsolidated entities and related unfunded commitments are reported in Other Assets and Other Liabilities, respectively, on the consolidated balance sheets. TABLE 72: SUMMARY OF UNCONSOLIDATED TAX CREDIT STRUCTURES (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Investment Carrying Amount Affordable Housing $ 599.3 $ 622.8 New Markets 223.9 266.3 Total Investment Carrying Amount (1) $ 823.2 $ 889.1 Unfunded Commitments Affordable Housing $ 173.4 $ 178.8 New Markets — — Total Unfunded Commitments (2) $ 173.4 $ 178.8 (1) As of September 30, 2024 and December 31, 2023, $795.0 million and $857.0 million are VIEs, respectively. (2) As of September 30, 2024 and December 31, 2023, $167.3 million and $172.0 million relate to undrawn commitments on VIEs, respectively. Upon adoption of ASU 2023-02 on January 1, 2024, Northern Trust elected to account for qualifying new markets tax credit investments under the proportional amortization method. Prior to the adoption of ASU 2023-02, Northern Trust accounted for qualifying affordable housing investments under the proportional amortization method and continues to do so subsequent to the adoption of ASU 2023-02. Under the proportional amortization method, the carrying amount of the investment is amortized in proportion to the income tax credits and other income tax benefits received in the current period as compared to the total income tax credits and income tax benefits expected to be received over the life of the investment. Income tax credits and other income tax benefits and amortization expense associated with unconsolidated tax credit structures are primarily reported in the Provision for Income Tax on the consolidated statement of income. Northern Trust adopted ASU 2023-02 on a modified retrospective basis. As a result, amortization expense related to new markets tax credit investments is reported in the Provision for Income Tax beginning January 1, 2024. Prior to January 1, 2024, amortization expense related to new markets tax credit investments was previously reported in Other Operating Expense. Refer to Note 2—Recent Accounting Pronouncements for additional information. TABLE 73: INCOME TAX CREDITS AND OTHER TAX BENEFITS AND AMORTIZATION EXPENSE ASSOCIATED WITH TAX CREDIT STRUCTURES THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Income Tax Credits and Other Income Tax Benefits Affordable Housing $ 21.9 $ 22.5 $ 65.5 $ 67.3 New Markets 5.1 5.9 15.1 17.8 Total Income Tax Credits and Other Income Tax Benefits $ 27.0 $ 28.4 $ 80.6 $ 85.1 Amortization Expense Affordable Housing $ 19.6 $ 19.9 $ 58.5 $ 59.5 New Markets 4.4 4.7 13.3 14.1 Total Amortization Expense $ 24.0 $ 24.6 $ 71.8 $ 73.6 Investment funds. Northern Trust acts as asset manager for various funds in which clients of Northern Trust are investors. As an asset manager of funds, Northern Trust earns a competitively priced fee that is based on assets managed and varies with each fund’s investment objective. Based on its analysis, Northern Trust has determined that it is not the primary beneficiary of these VIEs under GAAP. Some of the funds for which Northern Trust acts as asset manager comply or operate in accordance with requirements that are similar to those in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds and, therefore, the funds are exempt from the consolidation requirements in ASC 810-10. Northern Trust does not have any contractual obligations to provide financial support to the funds. Any potential future support of the funds will be at the discretion of Northern Trust after an evaluation of the specific facts and circumstances.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	9 Months Ended
Commitments and Contingent Liabilities	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities Off-Balance Sheet Financial Instruments, Guarantees and Other Commitments. Northern Trust, in the normal course of business, enters into various types of commitments and issues letters of credit to meet the liquidity and credit enhancement needs of its clients. The contractual amounts of these instruments represent the maximum potential credit exposure should the instrument be fully drawn upon and the client default. To control the credit risk associated with entering into commitments and issuing letters of credit, Northern Trust subjects such activities to the same credit quality and monitoring controls as its lending activities. Northern Trust does not believe the total contractual amount of these instruments to be representative of its future credit exposure or funding requirements. The following table provides details of Northern Trust's off-balance sheet financial instruments as of September 30, 2024 and December 31, 2023. TABLE 74: SUMMARY OF OFF-BALANCE SHEET FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) ONE YEAR AND LESS OVER ONE YEAR TOTAL ONE YEAR AND LESS OVER ONE YEAR TOTAL Undrawn Commitments (1) $ 11,202.5 $ 18,982.6 $ 30,185.1 $ 11,849.5 $ 18,909.6 $ 30,759.1 Standby Letters of Credit and Financial Guarantees (2)(3) 113,405.2 493.7 113,898.9 85,752.0 639.0 86,391.0 Commercial Letters of Credit 34.8 0.3 35.1 29.2 1.3 30.5 Securities Lent with Indemnification 146,058.1 — 146,058.1 140,539.1 — 140,539.1 Unsettled Reverse Repurchase Agreements 11,544.1 — 11,544.1 27,667.7 — 27,667.7 Total Off-Balance Sheet Financial Instruments $ 282,244.7 $ 19,476.6 $ 301,721.3 $ 265,837.5 $ 19,549.9 $ 285,387.4 (1) These amounts exclude $203.1 million and $222.2 million of commitments participated to others at September 30, 2024 and December 31, 2023, respectively. (2) These amounts include $101.8 million and $39.1 million of standby letters of credit secured by cash deposits or participated to others as of September 30, 2024 and December 31, 2023, respectively. (3) These amounts include a $112.0 billion and $84.6 billion guarantee to the Fixed Income Clearing Corporation (FICC) under the sponsored member program, without taking into consideration the related collateral, as of September 30, 2024 and December 31, 2023, respectively. Undrawn Commitments generally have fixed expiration dates or other termination clauses. Since a significant portion of the commitments are expected to expire without being drawn upon, the total commitment amount does not necessarily represent future loans or liquidity requirements. Standby Letters of Credit obligate Northern Trust to meet certain financial obligations of its clients, if, under the contractual terms of the agreement, the clients are unable to do so. These instruments are primarily issued to support public and private financial commitments, including commercial paper, bond financing, initial margin requirements on futures exchanges and similar transactions. Northern Trust is obligated to meet the entire financial obligation of these agreements and in certain cases is able to recover the amounts paid through recourse against collateral received or other participants. Since the vast majority of the standby letters of credit are never drawn, the total standby letters of credit amount does not necessarily represent future loans or liquidity requirements. Financial Guarantees are issued by Northern Trust to guarantee the performance of a client to a third party under certain arrangements. Commercial Letters of Credit are instruments issued by Northern Trust on behalf of its clients that authorize a third party (the beneficiary) to draw drafts up to a stipulated amount under the specified terms and conditions of the agreement and other similar instruments. Commercial letters of credit are issued primarily to facilitate international trade. Securities Lent with Indemnification involves Northern Trust lending securities owned by clients to borrowers who are reviewed and approved by the Northern Trust Capital Markets Credit Committee, as part of its securities custody activities and at the direction of its clients. In connection with these activities, Northern Trust has issued indemnifications to certain clients against certain losses that are a direct result of a borrower’s failure to return securities when due, should the value of such securities exceed the value of the collateral required to be posted. Borrowers are required to collateralize fully securities received with cash or marketable securities. As securities are loaned, collateral is maintained at a minimum of 100% of the fair value of the securities plus accrued interest. The collateral is revalued on a daily basis. The amount of securities loaned as of September 30, 2024 and December 31, 2023 subject to indemnification was $146.1 billion and $140.5 billion, respectively. Because of the credit quality of the borrowers and the requirement to fully collateralize securities borrowed, management believes that the exposure to credit loss from this activity is not significant and no liability was recorded as of September 30, 2024 or December 31, 2023, related to these indemnifications. Unsettled Repurchase and Reverse Repurchase Agreements. Northern Trust enters into repurchase agreements and reverse repurchase agreements which may settle at a future date. In repurchase agreements, Northern Trust receives cash from and provides securities as collateral to a counterparty. In reverse repurchase agreements, Northern Trust advances cash to and receives securities as collateral from a counterparty. These transactions are recorded on the consolidated balance sheets on the settlement date. As of September 30, 2024 and December 31, 2023, there were $11.5 billion and $27.7 billion unsettled reverse repurchase agreements, respectively, and no unsettled repurchase agreements. Sponsored Member Program . Northern Trust is an approved Government Securities Division (GSD) netting and sponsoring member in the FICC sponsored member program, through which Northern Trust submits eligible repurchase and reverse repurchase transactions in U.S. government securities between Northern Trust and its sponsored member clients for novation and clearing. Northern Trust may sponsor clients to clear their eligible repurchase transactions with the FICC. As a sponsoring member, Northern Trust guarantees to the FICC the prompt and full payment and performance of its sponsored member clients’ respective obligations under the FICC GSD’s rules. To mitigate Northern Trust’s credit exposure under this guarantee, Northern Trust obtains a security interest in its sponsored member clients’ collateral. See Note 23—Offsetting of Assets and Liabilities for additional information on Northern Trust’s repurchase and reverse repurchase agreements. Clearing and Settlement Organizations . The Bank is a participating member of various cash, securities and foreign exchange clearing and settlement organizations. It participates in these organizations on behalf of its clients and on its own behalf as a result of its own activities. A wide variety of cash and securities transactions are settled through these organizations, including those involving U.S. Treasuries, obligations of states and political subdivisions, asset-backed securities, commercial paper, dollar placements, and securities issued by the Government National Mortgage Association. Certain of these industry clearing and settlement exchanges require their members to guarantee their obligations and liabilities and/or to provide liquidity support in the event other members do not honor their obligations as stipulated in each clearing organization’s membership agreement. Exposure related to these agreements varies, primarily as a result of fluctuations in the volume of transactions cleared through the organizations. At September 30, 2024 and December 31, 2023, Northern Trust has not recorded any material liabilities under these arrangements as Northern Trust believes the likelihood that a clearing or settlement exchange (of which Northern Trust is a member) would become insolvent is remote. Controls related to these clearing transactions are closely monitored by management to protect the assets of Northern Trust and its clients. FDIC Special Assessment . In November 2023, the Federal Deposit Insurance Corporation (FDIC) issued a final rule to implement a special assessment to recoup losses to the deposit insurance fund associated with bank failures in the first half of 2023. In conjunction with the special assessment, $84.6 million was recognized as an accrued liability and related expense in the fourth quarter of 2023. During the first half of 2024, the FDIC published revised estimated losses as well as estimated recoveries from the related bank failures. As a result, Northern Trust recognized an additional accrued liability and related expense of $14.7 million for the nine months ended September 30, 2024, recorded to Other Operating Expense. As of September 30, 2024 , Northern Trust estimates its total liability related to the special assessment to be $99.3 million. Legal Proceedings. In the normal course of business, the Corporation and its subsidiaries are routinely defendants in or parties to pending and threatened legal actions, and are subject to regulatory examinations, information-gathering requests, investigations, and proceedings, both formal and informal. In certain legal actions, claims for substantial monetary damages are asserted. In regulatory matters, claims for disgorgement, restitution, penalties and/or other remedial actions or sanctions may be sought. Based on current knowledge, after consultation with legal counsel and after taking into account current accruals, management does not believe that losses, fines or penalties, if any, arising from pending litigation or threatened legal actions or regulatory matters either individually or in the aggregate, after giving effect to applicable reserves and insurance coverage will have a material adverse effect on the consolidated financial position or liquidity of the Corporation, although such matters could have a material adverse effect on the Corporation’s operating results for a particular period. Under GAAP, (i) an event is “probable” if the “future event or events are likely to occur”; (ii) an event is “reasonably possible” if “the chance of the future event or events occurring is more than remote but less than likely”; and (iii) an event is “remote” if “the chance of the future event or events occurring is slight.” The outcome of litigation and regulatory matters is inherently difficult to predict and/or the range of loss often cannot be reasonably estimated, particularly for matters that (i) will be decided by a jury, (ii) are in early stages, (iii) involve uncertainty as to the likelihood of a class being certified or the ultimate size of the class, (iv) are subject to appeals or motions, (v) involve significant factual issues to be resolved, including with respect to the amount of damages, (vi) do not specify the amount of damages sought or (vii) seek very large damages based on novel and complex damage and liability legal theories. Accordingly, the Corporation cannot reasonably estimate the eventual outcome of these pending matters, the timing of their ultimate resolution or what the eventual loss, fines or penalties, if any, related to each pending matter will be. In accordance with applicable accounting guidance, the Corporation records accruals for litigation and regulatory matters when those matters present loss contingencies that are both probable and reasonably estimable. When loss contingencies are not both probable and reasonably estimable, the Corporation does not record accruals. No material accruals have been recorded for pending litigation or threatened legal actions or regulatory matters. For a limited number of matters for which a loss is reasonably possible in future periods, whether in excess of an accrued liability or where there is no accrued liability, the Corporation is able to estimate a range of possible loss. As of September 30, 2024, the Corporation has estimated the range of reasonably possible loss for these matters to be from zero to approximately $20 million in the aggregate. The Corporation’s estimate with respect to the aggregate range of reasonably possible loss is based upon currently available information and is subject to significant judgment and a variety of assumptions and known and unknown uncertainties. The matters underlying the estimated range will change from time to time, and actual results may vary significantly from the current estimate. In certain other pending matters, there may be a range of reasonably possible loss (including reasonably possible loss in excess of amounts accrued) that cannot be reasonably estimated for the reasons described above. Such matters are not included in the estimated range of reasonably possible loss discussed above. In 2015, Northern Trust Fiduciary Services (Guernsey) Limited (NTFS), an indirect subsidiary of the Corporation, was charged by a French investigating magistrate judge with complicity in estate tax fraud in connection with the administration of two trusts for which it serves as trustee. Charges also were brought against a number of other persons and entities related to this matter. In 2017, a French court found no estate tax fraud had occurred and NTFS and all other persons and entities charged were acquitted. The Public Prosecutor’s Office of France appealed the court decision and in June 2018 a French appellate court issued its opinion on the matter, acquitting all persons and entities charged, including NTFS. In January 2021, the Cour de Cassation, the highest court in France, reversed the June 2018 appellate court ruling, requiring a re-trial at the appellate court level. This re-trial concluded in October 2023. On March 5, 2024 the appellate court rendered a judgment against all defendants, including NTFS. NTFS was ordered to pay a fine of €187,500 in conjunction with the judgment. In addition, the court ordered that certain of those convicted in relation to tax fraud or aiding and abetting tax fraud, including NTFS, are jointly and severally liable for any allegedly unpaid estate taxes owing, plus penalties and interest. NTFS provided no tax advice and was not involved in the preparation or filing of the challenged estate tax filings in this case. Further, NTFS believes it acted in accordance with all applicable laws and fully complied with its fiduciary duties. Accordingly, NTFS filed an appeal of the judgment on March 5, 2024. Under applicable law, upon the filing by NTFS of its appeal, the judgment, as well as its effects (including the fine and joint and several liability) will be stayed pending the outcome of the appeal. Visa Class B Common Shares and Makewhole Agreement. Northern Trust, as a member of Visa U.S.A. Inc. (Visa U.S.A.) and in connection with the 2007 restructuring of Visa U.S.A. and its affiliates and the 2008 initial public offering of Visa Inc. (Visa), received certain Visa Class B common shares. The Visa Class B common shares are subject to certain transfer restrictions until the final resolution of certain litigation related to interchange fees involving Visa (the covered litigation), at which time the shares are convertible into Visa Class A common shares based on a conversion rate dependent upon the ultimate cost of resolving the covered litigation. Since 2018, Visa has deposited an additional $4.3 billion into an escrow account previously established with respect to the covered litigation. As a result of the additional contributions to the escrow account, the rate at which Visa Class B common shares will convert into Visa Class A common shares was reduced to 1.5430 as of September 30, 2024. In September 2018, Visa reached a proposed class settlement agreement covering damage claims but not injunctive relief claims regarding the covered litigation. In December 2019, the district court granted final approval for the proposed class settlement agreement. In March 2023, the Second Circuit Court of Appeals affirmed the district court’s approval of the class settlement agreement. Certain merchants have opted out of the class settlement and are pursuing claims separately. The ultimate resolution of the covered litigation, the timing for removal of the selling restrictions on the Visa Class B common shares and the rate at which such shares will ultimately convert into Visa Class A common shares are uncertain. In May 2024, Northern Trust received 2.1 million Visa Class B-2 common shares and 819.5 thousand Visa Class C common shares via its full participation in an offer to exchange outstanding shares of Visa’s Class B common stock (Exchange Offer). The newly issued series of Visa Class B common shares are subject to the same transfer and convertibility restrictions as the previously outstanding Visa Class B common shares. The Visa Class C common shares will automatically be converted at the then applicable conversion rate into shares of Visa Class A common stock if transferred to a person other than a Visa member or an affiliate of a Visa member. After the initial exchange offer, Visa can, at its discretion, conduct up to three successive potential exchange offers, in each case, if more than 12 months have passed since the previous exchange offer and after a further 50% reduction of interchange fees at issue in the unresolved claims for damages in the covered litigation. Northern Trust holds the Visa Class B-2 common shares received in the Exchange Offer at their carryover basis of zero as of September 30, 2024. Based upon the September 30, 2024, closing price of $274.95 for a Visa Class A common share, the estimated value of Northern Trust’s Visa Class B-2 common shares was approximately $876.0 million at the current conversion rate of Visa Class B to Visa Class A common shares. The estimated value does not represent fair value given the shares’ limited transferability. Northern Trust sold 794.2 thousand Visa Class C common shares as of September 30, 2024 and recorded a realized gain of $864.8 million on the sales through Other Operating Income for the nine months ended September 30, 2024. The remaining Visa Class C common shares are recorded at their fair value of $27.8 million in Other Assets on the consolidated balance sheets with changes in fair value recorded in Other Operating Income on the consolidated statement of income.

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
Derivative Financial Instruments	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Northern Trust is a party to various derivative financial instruments that are used in the normal course of business to meet the needs of its clients, as part of its trading activity for its own account and as part of its risk management activities. These instruments may include foreign exchange contracts, interest rate contracts, total return swap contracts, and swaps related to the sales of certain Visa Class B common shares. Foreign exchange contracts are agreements to exchange specific amounts of currencies at a future date, at a specified rate of exchange. Foreign exchange contracts are entered into primarily to meet the foreign exchange needs of clients. Foreign exchange contracts are also used for trading and risk management purposes. For risk management purposes, Northern Trust uses foreign exchange contracts to reduce its exposure to changes in foreign exchange rates relating to certain forecasted non-functional-currency-denominated revenue and expenditure transactions, foreign-currency-denominated assets and liabilities, including debt securities, and net investments in non-U.S. affiliates. Interest rate contracts include swap and option contracts. Interest rate swap contracts involve the exchange of fixed and floating rate interest payment obligations without the exchange of the underlying principal amounts. Northern Trust enters into interest rate swap contracts with its clients and also may utilize such contracts to reduce or eliminate the exposure to changes in the cash flows or fair value of hedged assets or liabilities due to changes in interest rates. Interest rate option contracts may include caps, floors, collars and swaptions, and provide for the transfer or reduction of interest rate risk, typically in exchange for a fee. Northern Trust enters into option contracts primarily as a seller of interest rate protection to clients. Northern Trust receives a fee at the outset of the agreement for the assumption of the risk of an unfavorable change in interest rates. This assumed interest rate risk is then mitigated by entering into an offsetting position with an outside counterparty. Northern Trust may also purchase or enter into option contracts for risk management purposes including to reduce the exposure to changes in the cash flows of hedged assets due to changes in interest rates. The following table shows the notional and fair values of all derivative financial instruments as of September 30, 2024 and December 31, 2023. TABLE 75: NOTIONAL AND FAIR VALUES OF DERIVATIVE FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 NOTIONAL VALUE FAIR VALUE NOTIONAL VALUE FAIR VALUE (In Millions) ASSET (1) LIABILITY (2) ASSET (1) LIABILITY (2) Derivatives Designated as Hedging under GAAP Interest Rate Contracts Fair Value Hedges $ 9,706.3 $ 308.9 $ 289.7 $ 7,042.7 $ 94.7 $ 71.0 Foreign Exchange Contracts Cash Flow Hedges 454.6 1.5 0.5 1,453.6 15.0 42.2 Net Investment Hedges 4,650.7 6.7 103.9 4,077.4 13.3 31.9 Total Derivatives Designated as Hedging under GAAP $ 14,811.6 $ 317.1 $ 394.1 $ 12,573.7 $ 123.0 $ 145.1 Derivatives Not Designated as Hedging under GAAP Non-Designated Risk Management Derivatives Foreign Exchange Contracts $ 1.7 $ — $ — $ 20.7 $ — $ 0.1 Other Financial Derivatives (3) 458.3 — 27.8 867.9 — 25.4 Total Non-Designated Risk Management Derivatives $ 460.0 $ — $ 27.8 $ 888.6 $ — $ 25.5 Client-Related and Trading Derivatives Foreign Exchange Contracts $ 367,149.3 $ 3,044.7 $ 2,979.5 $ 313,336.9 $ 3,238.4 $ 3,181.0 Interest Rate Contracts 15,378.0 157.2 214.4 13,584.1 206.8 298.2 Total Client-Related and Trading Derivatives $ 382,527.3 $ 3,201.9 $ 3,193.9 $ 326,921.0 $ 3,445.2 $ 3,479.2 Total Derivatives Not Designated as Hedging under GAAP $ 382,987.3 $ 3,201.9 $ 3,221.7 $ 327,809.6 $ 3,445.2 $ 3,504.7 Total Gross Derivatives $ 397,798.9 $ 3,519.0 $ 3,615.8 $ 340,383.3 $ 3,568.2 $ 3,649.8 Less: Netting (4) 2,773.1 1,819.9 3,126.7 2,205.4 Total Derivative Financial Instruments $ 745.9 $ 1,795.9 $ 441.5 $ 1,444.4 (1) Derivative assets are reported in Other Assets on the consolidated balance sheets. (2) Derivative liabilities are reported in Other Liabilities on the consolidated balance sheets. (3) Includes swaps related to sales of certain Visa Class B common shares. (4) See further detail in Note 23—Offsetting of Assets and Liabilities. Notional amounts of derivative financial instruments do not represent credit risk and are not recorded in the consolidated balance sheets. They are used merely to express the volume of this activity. Northern Trust’s credit-related risk of loss is limited to the positive fair value of the derivative instrument, net of any collateral received, which is significantly less than the notional amount. All derivative financial instruments, whether designated as hedges or not, are recorded on the consolidated balance sheets at fair value within Other Assets or Other Liabilities. Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. Hedging Derivative Instruments Designated under GAAP. Northern Trust uses derivative instruments to hedge its exposure to foreign currency and interest rate risk. Certain hedging relationships are formally designated and qualify for hedge accounting under GAAP as fair value, cash flow or net investment hedges. In order to qualify for hedge accounting, a formal assessment is performed on a calendar-quarter basis to verify that derivatives used in designated hedging transactions continue to be highly effective in offsetting the changes in fair value or cash flows of the hedged item. If a derivative ceases to be highly effective, matures, is sold or is terminated, or if a hedged forecasted transaction is no longer probable of occurring, hedge accounting is terminated and the derivative is treated as a trading instrument. Fair Value Hedges. Derivatives are designated as fair value hedges to limit Northern Trust’s exposure to changes in the fair value of assets and liabilities due to movements in interest rates. Northern Trust may enter into interest rate swaps to hedge changes in fair value of AFS debt securities and long-term subordinated debt and senior notes. Northern Trust applied the “shortcut” method of accounting, available under GAAP, which assumes there is perfect effectiveness in a hedge, for all of its fair value hedges during the three- and nine-month periods ended September 30, 2024 and 2023. Changes in the fair value of the derivative instrument and changes in the fair value of the hedged asset or liability attributable to the hedged risk are recognized currently in earnings within the same income statement line item. Cash Flow Hedges. Derivatives are also d esignated as cash flow hedges in order to minimize the variability in cash flows of earning assets or forecasted transactions caused by movements in interest or foreign exchange rates. Northern Trust may enter into foreign exchange contracts to hedge changes in cash flows due to movements in foreign exchange rates of forecasted foreign-currency-denominated transactions and foreign-currency-denominated debt securities. Northern Trust may also enter into interest rate contracts to hedge changes in cash flows due to movements in interest rates of AFS debt securities. The change in fair value of cash flow hedging derivative instruments are recorded in AOCI and reclassified to earnings when the hedged forecasted transaction impacts earnings within the same income statement line item. There were no material gains or losses reclassified into earnings during the three- and nine-month periods ended September 30, 2024 and 2023, as a result of the discontinuance of forecasted transactions that were no longer probable of occurring. It is estimated that net gains of $2.7 million will be reclassified into Net Income within the next twelve months relating to cash flow hedges of foreign-currency-denominated debt securities. As of September 30, 2024, three months was the maximum length of time over which the exposure to variability in future cash flows of forecasted foreign-currency-denominated debt securities was being hedged. The following tables provide fair value and cash flow hedge derivative gains and losses recognized in income during the three- and nine-month periods ended September 30, 2024 and 2023. TABLE 76: LOCATION AND AMOUNT OF FAIR VALUE AND CASH FLOW HEDGE DERIVATIVE GAINS AND LOSSES RECORDED IN INCOME (In Millions) INTEREST INCOME INTEREST EXPENSE OTHER OPERATING INCOME THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 Total amounts on the consolidated statements of income $ 2,530.2 $ 1,935.0 $ 1,967.9 $ 1,478.8 $ 111.8 $ 68.2 Gains (Losses) on fair value hedges recognized on Interest Rate Contracts Recognized on derivatives (251.6) 14.1 76.5 (41.8) — — Recognized on hedged items 251.6 (14.1) (76.5) 41.8 — — Amounts related to interest settlements on derivatives 29.3 11.1 (20.1) (24.9) — — Total gains (losses) recognized on fair value hedges $ 29.3 $ 11.1 $ (20.1) $ (24.9) $ — $ — Gains (Losses) on cash flow hedges recognized on Foreign Exchange Contracts Net gains (losses) reclassified from AOCI to net income $ 0.6 $ 14.6 $ — $ — $ — $ 0.3 Total gains (losses) reclassified from AOCI to net income on cash flow hedges $ 0.6 $ 14.6 $ — $ — $ — $ 0.3 (In Millions) INTEREST INCOME INTEREST EXPENSE OTHER OPERATING INCOME NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 Total amounts on the consolidated statements of income $ 7,482.3 $ 5,125.4 $ 5,869.0 $ 3,626.5 $ 1,097.5 $ 170.2 Gains (Losses) on fair value hedges recognized on Interest Rate Contracts Recognized on derivatives (94.1) 0.6 46.5 (42.5) — — Recognized on hedged items 94.1 (0.6) (46.5) 42.5 — — Amounts related to interest settlements on derivatives 79.9 34.7 (59.9) (65.9) — — Total gains (losses) recognized on fair value hedges $ 79.9 $ 34.7 $ (59.9) $ (65.9) $ — $ — Gains (Losses) on cash flow hedges recognized on Foreign Exchange Contracts Net gains (losses) reclassified from AOCI to net income $ 7.1 $ 15.8 $ — $ — $ — $ 1.9 Total gains (losses) reclassified from AOCI to net income on cash flow hedges $ 7.1 $ 15.8 $ — $ — $ — $ 1.9 The following table provides the impact of fair value hedge accounting on the carrying value of the designated hedged items as of September 30, 2024 and December 31, 2023. TABLE 77: HEDGED ITEMS IN FAIR VALUE HEDGES SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) CARRYING VALUE OF THE HEDGED ITEMS CUMULATIVE HEDGE ACCOUNTING BASIS ADJUSTMENT (1)(3) CARRYING VALUE OF THE HEDGED ITEMS CUMULATIVE HEDGE ACCOUNTING BASIS ADJUSTMENT (2)(3) Available for Sale Debt Securities (4) $ 7,779.7 $ 171.9 $ 5,048.8 $ 77.5 Senior Notes and Long-Term Subordinated Debt 2,554.9 (190.3) 2,495.9 (248.7) (1) The cumulative hedge accounting basis adjustment includes $1.9 million related to discontinued hedging relationships of AFS debt securities and $17.7 million related to discontinued hedging relationships in the cumulative hedge accounting basis adjustment of senior notes and long-term debt as of September 30, 2024. (2) The cumulative hedge accounting basis adjustment includes $2.2 million related to discontinued hedging relationships of AFS debt securities and $29.6 million related to discontinued hedging relationships in the cumulative hedge accounting basis adjustment of senior notes and long-term debt as of December 31, 2023. (3) Positive (negative) amounts related to AFS securities represent cumulative fair value hedge basis adjustments that will reduce (increase) net interest income in future periods. Positive (negative) amounts related to Senior Notes and Long-Term Subordinated Debt represent cumulative fair value hedge basis adjustments that will increase (reduce) net interest income in future periods. (4) Carrying value represents amortized cost. Net Investment Hedges. Certain foreign exchange contracts are designated as net investment hedges to minimize Northern Trust’s exposure to variability in the foreign currency translation of net investments in non-U.S. branches and subsidiaries. Net investment hedge losses of $135.6 million and gains of $129.9 million were recognized in AOCI related to foreign exchange contracts for the three months ended September 30, 2024 and 2023, respectively. Net investment hedge losses of $36.3 million and gains of $66.8 million were recognized in AOCI related to foreign exchange contracts for the nine months ended September 30, 2024 and 2023, respectively. Derivative Instruments Not Designated as Hedging under GAAP. Northern Trust’s derivative instruments that are not designated as hedging under GAAP include derivatives for purposes of client-related and trading activities, as well as other risk management purposes. These activities consist principally of providing foreign exchange services to clients in connection with Northern Trust’s global custody business. However, in the normal course of business, Northern Trust also engages in trading of currencies for its own account. Non-designated risk management derivatives may include foreign exchange contracts entered into to manage the foreign currency risk of non-U.S.-dollar-denominated assets and liabilities, the net investment in certain non-U.S. affiliates, commercial loans and forecasted foreign-currency-denominated transactions. Swaps related to sales of certain Visa Class B common shares were entered into pursuant to which Northern Trust retains the risks associated with the ultimate conversion of the Visa Class B common shares into Visa Class A common shares. Total return swaps are entered into to manage the equity price risk associated with certain investments. Changes in the fair value of derivative instruments not designated as hedges under GAAP are recognized currently in income. The following table provides the location and amount of gains and losses recorded in the consolidated statements of income for the three and nine months ended September 30, 2024 and 2023 for derivative instruments not designated as hedges under GAAP. TABLE 78: LOCATION AND AMOUNT OF GAINS AND LOSSES RECORDED IN INCOME FOR DERIVATIVES NOT DESIGNATED AS HEDGING UNDER GAAP (In Millions) DERIVATIVE GAINS (LOSSES) LOCATION RECOGNIZED IN INCOME AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 Non-designated risk management derivatives Foreign Exchange Contracts Other Operating Income $ — $ 1.4 $ (0.2) $ 2.9 Other Financial Derivatives (1) Other Operating Income (13.8) 2.4 (30.4) (18.3) Gains (Losses) from non-designated risk management derivatives $ (13.8) $ 3.8 $ (30.6) $ (15.4) Client-related and trading derivatives Foreign Exchange Contracts Foreign Exchange Trading Income $ 54.1 $ 51.8 $ 169.5 $ 154.9 Interest Rate Contracts Security Commissions and Trading Income 0.9 1.2 2.8 8.1 Gains from client-related and trading derivatives $ 55.0 $ 53.0 $ 172.3 $ 163.0 Total gains from derivatives not designated as hedging under GAAP $ 41.2 $ 56.8 $ 141.7 $ 147.6 (1) Includes swaps related to the sale of certain Visa Class B common shares.

Securities Sold Under Agreement

Securities Sold Under Agreements to Repurchase	9 Months Ended
Securities Sold Under Agreements to Repurchase	Sep. 30, 2024
Banking and Thrift, Other Disclosure [Abstract]
Securities Sold Under Agreements to Repurchase	Securities Sold Under Agreements to Repurchase Securities sold under agreements to repurchase are accounted for as collateralized financings and recorded at the amounts at which the securities were sold plus accrued interest. To minimize any potential credit risk associated with these transactions, the fair value of the securities sold is monitored, limits are set on exposure with counterparties, and the financial condition of counterparties is regularly assessed. Securities sold under agreements to repurchase are either directly held by, or pledged to the counterparty until the repurchase. Northern Trust nets securities sold under repurchase agreements against those purchased under resale agreements when there is a legally enforceable master netting arrangement and the other conditions to net are met. The following table provides information regarding repurchase agreements that are accounted for as secured borrowings as of September 30, 2024 and December 31, 2023. TABLE 79: REPURCHASE AGREEMENTS ACCOUNTED FOR AS SECURED BORROWINGS REMAINING CONTRACTUAL MATURITY OF THE AGREEMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) OVERNIGHT AND CONTINUOUS U.S. Treasury and Agency Securities $ 170.8 $ 784.7 Total Borrowings 170.8 784.7 Net Amount of Recognized Liabilities for Repurchase Agreements in Note 23 170.8 784.7

Offsetting of Assets and Liabil

Offsetting of Assets and Liabilities	9 Months Ended
Offsetting of Assets and Liabilities	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Offsetting of Assets and Liabilities	Offsetting of Assets and Liabilities The following table provides information regarding the offsetting of derivative assets and securities purchased under agreements to resell within the consolidated balance sheets as of September 30, 2024 and December 31, 2023. TABLE 80: OFFSETTING OF DERIVATIVE ASSETS AND SECURITIES PURCHASED UNDER AGREEMENTS TO RESELL SEPTEMBER 30, 2024 (In Millions) GROSS RECOGNIZED ASSETS GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Assets (1) Foreign Exchange Contracts Over the Counter (OTC) $ 2,814.6 $ 2,664.5 $ 150.1 $ 10.3 $ 139.8 Interest Rate Swaps OTC 466.1 108.6 357.5 — 357.5 Total Derivatives Subject to a Master Netting Arrangement 3,280.7 2,773.1 507.6 10.3 497.3 Total Derivatives Not Subject to a Master Netting Arrangement 238.3 — 238.3 — 238.3 Total Derivatives 3,519.0 2,773.1 745.9 10.3 735.6 Securities Purchased under Agreements to Resell (2) $ 66,358.2 $ 65,376.6 $ 981.6 $ 981.6 $ — DECEMBER 31, 2023 (In Millions) GROSS RECOGNIZED ASSETS GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Assets (1) Foreign Exchange Contracts OTC $ 3,006.3 $ 2,937.2 $ 69.1 $ 12.2 $ 56.9 Interest Rate Swaps OTC 301.4 189.5 111.9 — 111.9 Interest Rate Swaps Exchange Cleared 0.1 — 0.1 — 0.1 Total Derivatives Subject to a Master Netting Arrangement 3,307.8 3,126.7 181.1 12.2 168.9 Total Derivatives Not Subject to a Master Netting Arrangement 260.4 — 260.4 — 260.4 Total Derivatives 3,568.2 3,126.7 441.5 12.2 429.3 Securities Purchased under Agreements to Resell (2) $ 62,860.2 $ 62,075.5 $ 784.7 $ 784.7 $ — (1) Derivative assets are reported in Other Assets on the consolidated balance sheets. Other Assets (excluding derivative assets) totaled $10.4 billion and $10.3 billion as of September 30, 2024 and December 31, 2023, respectively. (2) Offsetting of Securities Purchased under Agreements to Resell primarily relates to our involvement in the FICC. (3) Including cash collateral received from counterparties. (4) Including financial assets accepted as collateral which are received from counterparties. (5) Northern Trust did not possess any cash collateral that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of September 30, 2024 and December 31, 2023. The following table provides information regarding the offsetting of derivative liabilities and securities sold under agreements to repurchase within the consolidated balance sheets as of September 30, 2024 and December 31, 2023. TABLE 81: OFFSETTING OF DERIVATIVE LIABILITIES AND SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE SEPTEMBER 30, 2024 (In Millions) GROSS RECOGNIZED LIABILITIES GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,226.4 $ 1,784.0 $ 442.4 $ — $ 442.4 Interest Rate Swaps OTC 504.1 9.1 495.0 — 495.0 Other Financial Derivatives 27.8 26.8 1.0 — 1.0 Total Derivatives Subject to a Master Netting Arrangement 2,758.3 1,819.9 938.4 — 938.4 Total Derivatives Not Subject to a Master Netting Arrangement 857.5 — 857.5 — 857.5 Total Derivatives 3,615.8 1,819.9 1,795.9 — 1,795.9 Securities Sold under Agreements to Repurchase (2) $ 65,547.4 $ 65,376.6 $ 170.8 $ 170.8 $ — DECEMBER 31, 2023 (In Millions) GROSS RECOGNIZED LIABILITIES GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,411.7 $ 2,175.7 $ 236.0 $ — $ 236.0 Interest Rate Swaps OTC 368.3 6.0 362.3 — 362.3 Interest Rate Swaps Exchange Cleared 0.9 — 0.9 — 0.9 Other Financial Derivatives 25.4 23.7 1.7 — 1.7 Total Derivatives Subject to a Master Netting Arrangement 2,806.3 2,205.4 600.9 — 600.9 Total Derivatives Not Subject to a Master Netting Arrangement 843.5 — 843.5 — 843.5 Total Derivatives 3,649.8 2,205.4 1,444.4 — 1,444.4 Securities Sold under Agreements to Repurchase (2) $ 62,860.2 $ 62,075.5 $ 784.7 $ 784.7 $ — (1) Derivative liabilities are reported in Other Liabilities on the consolidated balance sheets. Other Liabilities (excluding derivative liabilities) totaled $3.3 billion and $4.0 billion as of September 30, 2024 and December 31, 2023, respectively. (2) Offsetting of Securities Sold under Agreements to Repurchase primarily relates to our involvement in the FICC. (3) Including cash collateral deposited with counterparties. (4) Including financial assets accepted as collateral which are deposited with counterparties. (5) Northern Trust did not place any cash collateral with counterparties that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of September 30, 2024 and December 31, 2023. All of Northern Trust’s securities sold under agreements to repurchase (repurchase agreements) and securities purchased under agreements to resell (reverse repurchase agreements) involve the transfer of financial assets in exchange for cash subject to a right and obligation to repurchase those assets for an agreed upon amount. In the event of a repurchase failure, the cash or financial assets are available for offset. Certain repurchase agreements and reverse repurchase agreements are subject to a master netting arrangement, which sets forth the rights and obligations for repurchase and offset. Under the master netting arrangement, Northern Trust is entitled to offset receivables from and collateral placed with a single counterparty against obligations owed to that counterparty. In addition, collateral held by Northern Trust can be offset against receivables from that counterparty. Northern Trust has elected to net securities sold under repurchase agreements against those purchased under resale agreements when the GAAP requirements to net are met. Derivative asset and liability positions with a single counterparty can be offset against each other in cases where legally enforceable master netting arrangements or similar agreements exist. Derivative assets and liabilities can be further offset by cash collateral received from, and deposited with, the transacting counterparty. The basis for this view is that, upon termination of transactions subject to a master netting arrangement or similar agreement, the individual derivative receivables do not represent resources to which general creditors have rights and individual derivative payables do not represent claims that are equivalent to the claims of general creditors. Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. Credit risk associated with derivative instruments relates to the failure of the counterparty and the failure of Northern Trust to pay based on the contractual terms of the agreement, and is generally limited to the unrealized fair value gains and losses on these instruments, net of any collateral received or deposited. The amount of credit risk will increase or decrease during the lives of the instruments as interest rates, foreign exchange rates, or equity prices fluctuate. Northern Trust’s risk is controlled by limiting such activity to an approved list of counterparties and by subjecting such activity to the same credit and quality controls as are followed in lending and investment activities. Credit support annexes and other similar agreements are currently in place with a number of Northern Trust’s counterparties which mitigate the aforementioned credit risk associated with derivative activity conducted with those counterparties by requiring that significant net unrealized fair value gains be supported by collateral placed with Northern Trust. Additional cash collateral received from and deposited with derivative counterparties totaling $140.3 million and $10.0 million, respectively, as of September 30, 2024, and $373.1 million and $21.3 million, respectively, as of December 31, 2023, was not offset against derivative assets and liabilities in the consolidated balance sheets as the amounts exceeded the net derivative positions with those counterparties. Certain master netting arrangements Northern Trust enters into with derivative counterparties contain credit-risk-related contingent features in which the counterparty has the option to declare Northern Trust in default and accelerate cash settlement of net derivative liabilities with the counterparty in the event Northern Trust’s credit rating falls below specified levels. The aggregate fair value of all derivative instruments with credit-risk-related contingent features that were in a liability position was $1.2 billion at September 30, 2024 and December 31, 2023. Cash collateral amounts deposited with derivative counterparties on those dates included $929.3 million and $1.1 billion, respectively, posted against these liabilities, resulting in a net maximum amount of termination payments that could have been required at September 30, 2024 and December 31, 2023, of $270.9 million and $52.2 million, respectively. Accelerated settlement of these liabilities would not have a material effect on the consolidated financial position or liquidity of Northern Trust.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Millions	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income	$ 464.9	$ 896.1	$ 214.7	$ 327.8	$ 331.8	$ 334.6	$ 1,575.7	$ 994.2

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Policies)	9 Months Ended
Recent Accounting Pronouncements (Policies)	Sep. 30, 2024
Accounting Changes and Error Corrections [Abstract]
Basis of Presentation	The consolidated financial statements include the accounts of Northern Trust Corporation (Corporation) and its wholly-owned subsidiary, The Northern Trust Company (Bank), and various other wholly-owned subsidiaries of the Corporation and Bank. Throughout the notes to the consolidated financial statements, the term “Northern Trust” refers to the Corporation and its subsidiaries. Intercompany balances and transactions have been eliminated in consolidation. The consolidated financial statements, as of and for the periods ended September 30, 2024 and 2023, have not been audited by the Corporation’s independent registered public accounting firm. In the opinion of management, all accounting entries and adjustments, including normal recurring accruals, necessary for a fair presentation of the financial position and the results of operations for the interim periods have been made. The accounting and financial reporting policies of Northern Trust conform to U.S. generally accepted accounting principles (GAAP) and reporting practices prescribed for the banking industry.
Recent Accounting Pronouncements	On January 1, 2024, Northern Trust adopted Accounting Standards Update (ASU) No. 2023-02, “Investments—Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method—a consensus of the Emerging Issues Task Force” (ASU 2023-02). The amendments in ASU 2023-02 allow entities to elect the proportional amortization method to account for tax equity investments if certain conditions are met regardless of the tax credit program from which the income tax credits are received. Under the proportional amortization method, an entity amortizes the initial cost of the investment in proportion to the income tax credits and other income tax benefits received and recognizes the net amortization and income tax credits and other income tax benefits in the income statement as a component of income tax expense (benefit). In addition, ASU 2023-02 requires specific disclosures that must be applied to all investments that generate income tax credits and other income tax benefits for which the entity has elected to apply the proportional amortization method in accordance with Subtopic 323-740. Upon adoption of ASU 2023-02, there was no significant impact to Northern Trust’s consolidated balance sheets or consolidated statements of income. Please refer to Note 19—Variable Interest Entities for further information. On January 1, 2024, Northern Trust adopted ASU No. 2022-03, “Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions” (ASU 2022-03). The amendments in ASU 2022-03 clarify that a contractual restriction on the sale of an equity security is not considered part of the unit of account of the equity security and, therefore, is not considered in measuring fair value. ASU 2022-03 also clarifies that an entity cannot, as a separate unit of account, recognize and measure a contractual sale restriction. Additionally, ASU 2022-03 introduces new disclosure requirements to provide investors with information about contractual sale restrictions including the nature and remaining duration of these restrictions. Upon adoption of ASU 2022-03, there was no impact to Northern Trust’s consolidated balance sheets or consolidated statements of income.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurement Inputs and Valuation Techniques	The following table presents the fair values of Northern Trust’s Level 3 liabilities as of September 30, 2024 and December 31, 2023, as well as the valuation techniques, significant unobservable inputs, and quantitative information used to develop significant unobservable inputs for such liabilities as of such dates. TABLE 35: LEVEL 3 SIGNIFICANT UNOBSERVABLE INPUTS SEPTEMBER 30, 2024 FINANCIAL INSTRUMENT FAIR VALUE VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES (1) Swaps Related to Sale of Certain Visa Class B Common Shares $27.8 million Discounted Cash Flow Conversion Rate 1.54x 1.54x Visa Class A Appreciation 9.06% 9.06% Expected Duration 13 - 35.5 months 26.5 months (1) Weighted average of expected duration based on scenario probability. DECEMBER 31, 2023 FINANCIAL INSTRUMENT FAIR VALUE VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES (1) Swaps Related to Sale of Certain Visa Class B Common Shares $25.4 million Discounted Cash Flow Conversion Rate 1.59x 1.59x Visa Class A Appreciation 10.49% 10.49% Expected Duration 9 - 27 months 13 months (1) Weighted average of expected duration based on scenario probability. The following table presents the fair values of Northern Trust’s Level 3 assets that were measured at fair value on a nonrecurring basis as of September 30, 2024 and December 31, 2023, as well as the valuation technique, significant unobservable inputs and quantitative information used to develop the significant unobservable inputs for such assets as of such dates. TABLE 38: LEVEL 3 NONRECURRING BASIS SIGNIFICANT UNOBSERVABLE INPUTS SEPTEMBER 30, 2024 FINANCIAL INSTRUMENT FAIR VALUE (1) VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES Loans $25.8 million Market Approach Discount factor applied to real estate collateral-dependent loans to reflect realizable value 20.0% 20.0% (1) Includes real estate collateral-dependent loans and other collateral-dependent loans. DECEMBER 31, 2023 FINANCIAL INSTRUMENT FAIR VALUE (1) VALUATION TECHNIQUE UNOBSERVABLE INPUTS INPUT VALUES WEIGHTED-AVERAGE INPUT VALUES Loans $43.3 million Market Approach Discount factor applied to real estate collateral-dependent loans to reflect realizable value 0.0 % - 20.0% 2.0% (1) Includes real estate collateral-dependent loans and other collateral-dependent loans.
Recurring Basis Hierarchy Leveling	The following table presents assets and liabilities measured at fair value on a recurring basis as of September 30, 2024 and December 31, 2023, segregated by fair value hierarchy level. TABLE 36: RECURRING BASIS HIERARCHY LEVELING SEPTEMBER 30, 2024 (In Millions) LEVEL 1 LEVEL 2 LEVEL 3 NETTING ASSETS/LIABILITIES AT FAIR VALUE Debt Securities Available for Sale U.S. Government $ 6,481.7 $ — $ — $ — $ 6,481.7 Obligations of States and Political Subdivisions — 306.0 — — 306.0 Government Sponsored Agency — 13,653.7 — — 13,653.7 Non-U.S. Government — 327.1 — — 327.1 Corporate Debt — 201.1 — — 201.1 Covered Bonds — 239.7 — — 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 3,988.1 — — 3,988.1 Other Asset-Backed — 2,487.4 — — 2,487.4 Commercial Mortgage-Backed — 627.1 — — 627.1 Total Available for Sale Debt Securities 6,481.7 21,830.2 — — 28,311.9 Other Assets Equity Securities (1) 85.0 27.8 — — 112.8 Derivative Assets Foreign Exchange Contracts — 3,052.9 — (2,664.5) 388.4 Interest Rate Contracts — 466.1 — (108.6) 357.5 Total Derivative Assets — 3,519.0 — (2,773.1) 745.9 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,083.9 — (1,784.0) 1,299.9 Interest Rate Contracts — 504.1 — (9.1) 495.0 Other Financial Derivatives (2) — — 27.8 (26.8) 1.0 Total Derivative Liabilities $ — $ 3,588.0 $ 27.8 $ (1,819.9) $ 1,795.9 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of September 30, 2024, derivative assets and liabilities shown above also include reductions of $2.0 billion and $1.0 billion, respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1) Equity securities consists of a money market investment and Visa Class C common shares with a fair value of $85.0 million and $27.8 million, respectively, as of September 30, 2024. (2) Consists of swaps related to the sale of certain Visa Class B common shares. DECEMBER 31, 2023 (In Millions) LEVEL 1 LEVEL 2 LEVEL 3 NETTING ASSETS/LIABILITIES AT FAIR VALUE Debt Securities Available for Sale U.S. Government $ 3,622.2 $ — $ — $ — $ 3,622.2 Obligations of States and Political Subdivisions — 295.8 — — 295.8 Government Sponsored Agency — 11,553.0 — — 11,553.0 Non-U.S. Government — 264.4 — — 264.4 Corporate Debt — 279.5 — — 279.5 Covered Bonds — 347.1 — — 347.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — 2,899.9 — — 2,899.9 Other Asset-Backed — 2,962.6 — — 2,962.6 Commercial Mortgage-Backed — 865.3 — — 865.3 Total Available for Sale Debt Securities 3,622.2 19,467.6 — — 23,089.8 Other Assets Money Market Investment 95.0 — — — 95.0 Derivative Assets Foreign Exchange Contracts — 3,266.7 — (2,937.2) 329.5 Interest Rate Contracts — 301.5 — (189.5) 112.0 Total Derivative Assets — 3,568.2 — (3,126.7) 441.5 Other Liabilities Derivative Liabilities Foreign Exchange Contracts — 3,255.2 — (2,175.7) 1,079.5 Interest Rate Contracts — 369.2 — (6.0) 363.2 Other Financial Derivatives (1) — — 25.4 (23.7) 1.7 Total Derivative Liabilities $ — $ 3,624.4 $ 25.4 $ (2,205.4) $ 1,444.4 Note: Northern Trust has elected to net derivative assets and liabilities when legally enforceable master netting arrangements or similar agreements exist between Northern Trust and the counterparty. As of December 31, 2023, derivative assets and liabilities shown above also include reductions of $2.1 billion and $1.2 billion, respectively, as a result of cash collateral received from and deposited with derivative counterparties. (1)
Changes in Level 3 Liabilities	The following table presents the changes in Level 3 liabilities for the three and nine months ended September 30, 2024 and 2023. TABLE 37: CHANGES IN LEVEL 3 LIABILITIES (In Millions) SWAPS RELATED TO SALE OF CERTAIN VISA CLASS B COMMON SHARES THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 Fair Value at July 1 $ 30.6 $ 36.4 Total (Gains) Losses: Included in Earnings (1) 13.8 (2.4) Purchases, Issues, Sales, and Settlements Settlements (16.6) (5.1) Fair Value at September 30 $ 27.8 $ 28.9 (1) (Gains) losses are recorded in Other Operating Income on the consolidated statements of income. NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 Fair Value at January 1 $ 25.4 $ 34.8 Total (Gains) Losses: Included in Earnings (1) 30.4 16.1 Purchases, Issues, Sales, and Settlements Settlements (28.0) (22.0) Fair Value at September 30 $ 27.8 $ 28.9 (1) (Gains) losses are recorded in Other Operating Income on the consolidated statements of income.
Fair Value of Financial Instruments	The following tables present the book value and estimated fair value, including the fair value hierarchy level, of Northern Trust’s financial instruments that are not measured at fair value on the consolidated balance sheets as of September 30, 2024 and December 31, 2023. The following tables exclude those items measured at fair value on a recurring basis. TABLE 39: FAIR VALUE OF FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 ESTIMATED FAIR VALUE (In Millions) BOOK VALUE TOTAL ESTIMATED FAIR VALUE LEVEL 1 LEVEL 2 LEVEL 3 FINANCIAL ASSETS Cash and Due from Banks $ 6,871.7 $ 6,871.7 $ 6,871.7 $ — $ — Federal Reserve and Other Central Bank Deposits 40,848.8 40,848.8 — 40,848.8 — Interest-Bearing Deposits with Banks 1,606.8 1,606.8 — 1,606.8 — Securities Purchased under Agreements to Resell 981.6 981.6 — 981.6 — Debt Securities - Held to Maturity 22,708.6 21,372.0 — 21,372.0 — Loans Held for Investment 41,765.5 41,488.7 — — 41,488.7 Other Assets 1,450.5 1,446.0 87.9 1,358.1 — FINANCIAL LIABILITIES Deposits 121,183.3 123,302.5 — 123,302.5 — Federal Funds Purchased 2,761.9 2,761.9 — 2,761.9 — Securities Sold Under Agreements to Repurchase 170.8 170.8 — 170.8 — Other Borrowings 6,903.2 6,940.0 — 6,940.0 — Senior Notes 2,820.9 2,869.1 — 2,869.1 — Long-Term Debt 4,077.2 4,248.1 — 4,248.1 — Unfunded Commitments 173.4 173.4 — 173.4 — Other Liabilities 47.9 47.9 — — 47.9 DECEMBER 31, 2023 ESTIMATED FAIR VALUE (In Millions) BOOK VALUE TOTAL ESTIMATED FAIR VALUE LEVEL 1 LEVEL 2 LEVEL 3 FINANCIAL ASSETS Cash and Due from Banks $ 4,791.5 $ 4,791.5 $ 4,791.5 $ — $ — Federal Reserve and Other Central Bank Deposits 34,326.2 34,326.2 — 34,326.2 — Interest-Bearing Deposits with Banks 1,939.0 1,939.0 — 1,939.0 — Securities Purchased under Agreements to Resell 784.7 784.7 — 784.7 — Debt Securities - Held to Maturity 26,221.7 24,473.0 — 24,473.0 — Loans Held for Investment 47,438.3 47,598.3 — — 47,598.3 Other Assets 1,476.6 1,458.0 86.1 1,371.9 — FINANCIAL LIABILITIES Deposits 116,164.0 116,207.6 — 116,207.6 — Federal Funds Purchased 3,045.4 3,045.4 — 3,045.4 — Securities Sold Under Agreements to Repurchase 784.7 784.7 — 784.7 — Other Borrowings 6,567.8 6,607.4 — 6,607.4 — Senior Notes 2,773.2 2,798.1 — 2,798.1 — Long-Term Debt 4,065.0 4,186.8 — 4,186.8 — Unfunded Commitments 178.8 178.8 — 178.8 — Other Liabilities 74.9 74.9 — — 74.9

Securities (Tables)

Securities (Tables)	9 Months Ended
Securities (Tables)	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale	The following tables provide the amortized cost and fair values as of September 30, 2024 and December 31, 2023, and remaining maturities of AFS debt securities as of September 30, 2024. TABLE 40: RECONCILIATION OF AMORTIZED COST TO FAIR VALUE OF AVAILABLE FOR SALE DEBT SECURITIES SEPTEMBER 30, 2024 (In Millions) AMORTIZED COST GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR VALUE U.S. Government $ 6,497.4 $ 3.4 $ 19.1 $ 6,481.7 Obligations of States and Political Subdivisions 321.6 — 15.6 306.0 Government Sponsored Agency 13,749.0 19.0 114.3 13,653.7 Non-U.S. Government 341.5 — 14.4 327.1 Corporate Debt 205.0 0.1 4.0 201.1 Covered Bonds 242.2 0.6 3.1 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 4,019.7 14.0 45.6 3,988.1 Other Asset-Backed 2,494.5 7.1 14.2 2,487.4 Commercial Mortgage-Backed 642.2 0.1 15.2 627.1 Total $ 28,513.1 $ 44.3 $ 245.5 $ 28,311.9 DECEMBER 31, 2023 (In Millions) AMORTIZED COST GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR VALUE U.S. Government $ 3,681.5 $ 2.2 $ 61.5 $ 3,622.2 Obligations of States and Political Subdivisions 315.8 — 20.0 295.8 Government Sponsored Agency 11,744.3 9.0 200.3 11,553.0 Non-U.S. Government 284.8 — 20.4 264.4 Corporate Debt 287.5 0.1 8.1 279.5 Covered Bonds 356.8 — 9.7 347.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 3,013.8 0.1 114.0 2,899.9 Other Asset-Backed 3,061.0 1.6 100.0 2,962.6 Commercial Mortgage-Backed 913.5 0.2 48.4 865.3 Total $ 23,659.0 $ 13.2 $ 582.4 $ 23,089.8
Remaining Maturity of Securities Available for Sale and Held to Maturity	TABLE 41: REMAINING MATURITY OF AVAILABLE FOR SALE DEBT SECURITIES SEPTEMBER 30, 2024 ONE YEAR OR LESS ONE TO FIVE YEARS FIVE TO TEN YEARS OVER TEN YEARS TOTAL (In Millions) AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE AMORTIZED COST FAIR VALUE U.S. Government $ 496.2 $ 493.9 $ 3,862.0 $ 3,852.1 $ 2,139.2 $ 2,135.7 $ — $ — $ 6,497.4 $ 6,481.7 Obligations of States and Political Subdivisions — — 206.3 198.0 115.3 108.0 — — 321.6 306.0 Government Sponsored Agency 3,223.6 3,209.3 7,181.0 7,141.1 2,472.3 2,449.7 872.1 853.6 13,749.0 13,653.7 Non-U.S. Government 69.2 68.8 272.3 258.3 — — — — 341.5 327.1 Corporate Debt 114.6 114.1 90.4 87.0 — — — — 205.0 201.1 Covered Bonds — — 242.2 239.7 — — — — 242.2 239.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 192.8 190.9 3,520.1 3,501.1 306.8 296.1 — — 4,019.7 3,988.1 Other Asset-Backed 154.6 152.6 1,726.6 1,719.6 496.6 498.2 116.7 117.0 2,494.5 2,487.4 Commercial Mortgage-Backed 23.1 22.8 585.0 576.2 34.1 28.1 — — 642.2 627.1 Total $ 4,274.1 $ 4,252.4 $ 17,685.9 $ 17,573.1 $ 5,564.3 $ 5,515.8 $ 988.8 $ 970.6 $ 28,513.1 $ 28,311.9 Note: Mortgage-backed and asset-backed securities are included in the above table taking into account anticipated future prepayments. TABLE 44: REMAINING MATURITY OF HELD TO MATURITY DEBT SECURITIES SEPTEMBER 30, 2024 ONE YEAR OR LESS ONE TO FIVE YEARS FIVE TO TEN YEARS OVER TEN YEARS TOTAL (In Millions) Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Amortized Cost Fair Value Obligations of States and Political Subdivisions $ 106.8 $ 106.3 $ 1,302.2 $ 1,298.7 $ 935.6 $ 931.9 $ 205.3 $ 202.6 $ 2,549.9 $ 2,539.5 Government Sponsored Agency 917.4 843.7 3,345.6 3,056.6 2,874.6 2,617.6 1,689.2 1,487.7 8,826.8 8,005.6 Non-U.S. Government 1,254.9 1,252.6 1,072.4 1,013.1 34.0 30.6 — — 2,361.3 2,296.3 Corporate Debt 249.3 245.5 226.1 217.2 15.7 13.7 — — 491.1 476.4 Covered Bonds 660.6 656.9 1,254.4 1,200.5 209.8 195.0 — — 2,124.8 2,052.4 Certificates of Deposit 542.6 542.3 — — — — — — 542.6 542.3 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 1,723.9 1,705.6 3,332.5 3,156.7 5.7 4.8 — — 5,062.1 4,867.1 Other Asset-Backed 4.7 4.5 69.2 69.7 37.7 37.7 — — 111.6 111.9 Commercial Mortgage-Backed — — 37.6 36.6 — — — — 37.6 36.6 Other 71.0 69.3 293.3 267.6 50.7 42.5 185.8 64.5 600.8 443.9 Total $ 5,531.2 $ 5,426.7 $ 10,933.3 $ 10,316.7 $ 4,163.8 $ 3,873.8 $ 2,080.3 $ 1,754.8 $ 22,708.6 $ 21,372.0
Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value	The following table provides information regarding AFS debt securities with no credit losses reported that had been in a continuous unrealized loss position for less than twelve months and for twelve months or longer as of September 30, 2024 and December 31, 2023. TABLE 42: AVAILABLE FOR SALE DEBT SECURITIES IN UNREALIZED LOSS POSITION WITH NO CREDIT LOSSES REPORTED SEPTEMBER 30, 2024 LESS THAN 12 MONTHS 12 MONTHS OR LONGER TOTAL (In Millions) FAIR UNREALIZED FAIR UNREALIZED FAIR UNREALIZED U.S. Government $ 5,293.0 $ 6.9 $ 630.9 $ 12.2 $ 5,923.9 $ 19.1 Obligations of States and Political Subdivisions — — 305.9 15.6 305.9 15.6 Government Sponsored Agency 2,028.2 3.6 6,676.9 110.7 8,705.1 114.3 Non-U.S. Government 55.3 — 271.9 14.4 327.2 14.4 Corporate Debt — — 104.5 2.4 104.5 2.4 Covered Bonds — — 126.7 3.1 126.7 3.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 645.3 0.7 917.6 44.9 1,562.9 45.6 Other Asset-Backed — — 476.3 14.2 476.3 14.2 Commercial Mortgage-Backed 12.5 — 587.8 15.2 600.3 15.2 Total $ 8,034.3 $ 11.2 $ 10,098.5 $ 232.7 $ 18,132.8 $ 243.9 Note: One corporate debt AFS security with a fair value of $43.1 million and unrealized losses of $1.6 million has been excluded from the table above as this AFS security had a $0.2 million allowance for credit losses reported as of September 30, 2024. Refer to the discussion further below and Note 6—Allowance for Credit Losses for further information. DECEMBER 31, 2023 LESS THAN 12 MONTHS 12 MONTHS OR LONGER TOTAL (In Millions) FAIR UNREALIZED FAIR UNREALIZED FAIR UNREALIZED U.S. Government $ — $ — $ 3,364.7 $ 61.5 $ 3,364.7 $ 61.5 Obligations of States and Political Subdivisions 87.8 5.9 208.0 14.1 295.8 20.0 Government Sponsored Agency 331.0 11.5 9,486.6 188.8 9,817.6 200.3 Non-U.S. Government — — 264.5 20.4 264.5 20.4 Corporate Debt 4.4 0.1 143.0 2.1 147.4 2.2 Covered Bonds — — 213.2 9.7 213.2 9.7 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — — 2,477.0 105.8 2,477.0 105.8 Other Asset-Backed 19.8 2.0 1,998.7 98.0 2,018.5 100.0 Commercial Mortgage-Backed 60.0 4.6 776.6 43.8 836.6 48.4 Total $ 503.0 $ 24.1 $ 18,932.3 $ 544.2 $ 19,435.3 $ 568.3 Note: Three corporate debt AFS securities with a fair value of $98.4 million and unrealized losses of $5.9 million and one sub-sovereign, supranational and non-U.S. agency bonds AFS security with a fair value of $71.0 million and unrealized loss of $8.2 million have been excluded from the table above as these AFS securities have a $1.2 million allowance for credit losses reported as of December 31, 2023. Refer to the discussion further below and Note 6—Allowance for Credit Losses for further information.
Debt Securities, Held-to-maturity	The following tables provide the amortized cost and fair values as of September 30, 2024 and December 31, 2023, and remaining maturities of HTM debt securities as of September 30, 2024. TABLE 43: RECONCILIATION OF AMORTIZED COST TO FAIR VALUE OF HELD TO MATURITY DEBT SECURITIES SEPTEMBER 30, 2024 (In Millions) AMORTIZED GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR Obligations of States and Political Subdivisions $ 2,549.9 $ 4.4 $ 14.8 $ 2,539.5 Government Sponsored Agency 8,826.8 2.6 823.8 8,005.6 Non-U.S. Government 2,361.3 0.2 65.2 2,296.3 Corporate Debt 491.1 — 14.7 476.4 Covered Bonds 2,124.8 0.3 72.7 2,052.4 Certificates of Deposit 542.6 — 0.3 542.3 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 5,062.1 2.6 197.6 4,867.1 Other Asset-Backed 111.6 0.5 0.2 111.9 Commercial Mortgage-Backed 37.6 — 1.0 36.6 Other 600.8 — 156.9 443.9 Total $ 22,708.6 $ 10.6 $ 1,347.2 $ 21,372.0 DECEMBER 31, 2023 (In Millions) AMORTIZED GROSS UNREALIZED GAINS GROSS UNREALIZED LOSSES FAIR Obligations of States and Political Subdivisions 2,563.9 0.5 72.4 2,492.0 Government Sponsored Agency 9,355.3 2.3 1,012.4 8,345.2 Non-U.S. Government 4,789.1 0.2 90.7 4,698.6 Corporate Debt 646.1 — 28.2 617.9 Covered Bonds 2,208.6 0.3 108.3 2,100.6 Certificates of Deposit 585.1 — 0.7 584.4 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 5,245.5 3.2 294.9 4,953.8 Other Asset-Backed 214.2 0.4 0.2 214.4 Commercial Mortgage-Backed 37.6 — 0.8 36.8 Other 576.3 — 147.0 429.3 Total $ 26,221.7 $ 6.9 $ 1,755.6 $ 24,473.0
Debt Securities, Held-to-maturity, Credit Quality Indicator	The following table provides the amortized cost of HTM debt securities by credit rating. TABLE 45: AMORTIZED COST OF HELD TO MATURITY DEBT SECURITIES BY CREDIT RATING SEPTEMBER 30, 2024 ($ In Millions) AAA AA A BBB NOT RATED TOTAL Obligations of States and Political Subdivisions $ 980.8 $ 1,569.1 $ — $ — $ — $ 2,549.9 Government Sponsored Agency 8,826.8 — — — — 8,826.8 Non-U.S. Government 456.4 816.2 752.7 336.0 — 2,361.3 Corporate Debt — 290.4 200.7 — — 491.1 Covered Bonds 2,124.8 — — — — 2,124.8 Certificates of Deposit 513.2 — — — 29.4 542.6 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 3,825.8 1,204.5 30.7 1.1 — 5,062.1 Other Asset-Backed 111.6 — — — — 111.6 Commercial Mortgage-Backed 37.6 — — — — 37.6 Other 54.7 — — — 546.1 600.8 Total $ 16,931.7 $ 3,880.2 $ 984.1 $ 337.1 $ 575.5 $ 22,708.6 Percent of Total 75 % 17 % 4 % 1 % 3 % 100 % DECEMBER 31, 2023 ($ In Millions) AAA AA A BBB NOT RATED TOTAL Obligations of States and Political Subdivisions $ 954.7 $ 1,609.0 $ — $ — $ 0.2 $ 2,563.9 Government Sponsored Agency 9,355.3 — — — — 9,355.3 Non-U.S. Government 813.3 1,179.6 2,463.3 332.9 — 4,789.1 Corporate Debt 2.1 302.6 341.4 — — 646.1 Covered Bonds 2,208.6 — — — — 2,208.6 Certificates of Deposit 545.9 — — — 39.2 585.1 Sub-Sovereign, Supranational and Non-U.S. Agency Bonds 4,047.9 1,166.5 30.0 1.1 — 5,245.5 Other Asset-Backed 214.2 — — — — 214.2 Commercial Mortgage-Backed 37.6 — — — — 37.6 Other 54.8 — — — 521.5 576.3 Total $ 18,234.4 $ 4,257.7 $ 2,834.7 $ 334.0 $ 560.9 $ 26,221.7 Percent of Total 70 % 16 % 11 % 1 % 2 % 100 %
Investment Security Gains and Losses	TABLE 46: INVESTMENT SECURITY GAINS AND LOSSES THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Gross Realized Debt Securities Gains $ — $ — $ 185.2 $ 213.0 Gross Realized Debt Securities Losses — — (374.5) (206.1) Investment Security Gains (Losses), net $ — $ — $ (189.3) $ 6.9 TABLE 47: INVESTMENT SECURITY GAINS AND LOSSES BY SECURITY TYPE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 U.S. Government $ — $ — $ (34.8) $ — Obligations of States and Political Subdivisions — — — 9.8 Government Sponsored Agency — — (23.0) — Corporate Debt — — — (1.2) Covered Bonds — — (4.2) — Sub-Sovereign, Supranational and Non-U.S. Agency Bonds — — (48.2) — Other Asset-Backed — — (56.5) (0.8) Commercial Mortgage-Backed — — (22.6) (0.9) Investment Security Gains (Losses), net $ — $ — $ (189.3) $ 6.9

Loans (Tables)

Loans (Tables)	9 Months Ended
Loans (Tables)	Sep. 30, 2024
Receivables [Abstract]
Loans	Amounts outstanding for Loans, by segment and class, are shown in the following table. TABLE 48: LOANS (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Commercial Commercial and Institutional (1) $ 10,391.3 $ 11,555.3 Commercial Real Estate 5,251.0 5,134.2 Non-U.S. (1) 2,742.6 2,778.5 Other 2,448.9 5,944.8 Total Commercial 20,833.8 25,412.8 Personal Private Client 14,195.5 14,360.0 Residential Real Estate 6,141.2 6,327.1 Non-U.S. 457.2 428.8 Other 322.6 1,088.3 Total Personal 21,116.5 22,204.2 Total Loans $ 41,950.3 $ 47,617.0 (1)
Borrower Ratings	Loan segment and class balances as of September 30, 2024 and December 31, 2023 are provided in the following table, segregated by borrower ratings into “1 to 3,” “4 to 5” and “6 to 9” (watch list and nonaccrual status) categories by year of origination at amortized cost basis. Loans that are held for investment are reported at the principal amount outstanding, net of unearned income. TABLE 49: CREDIT QUALITY INDICATOR AT AMORTIZED COST BASIS BY ORIGINATION YEAR TERM LOANS REVOLVING LOANS REVOLVING LOANS CONVERTED TO TERM LOANS September 30, 2024 2024 2023 2022 2021 2020 PRIOR TOTAL Commercial Commercial and Institutional Risk Rating: 1 to 3 Category $ 322.6 $ 247.5 $ 371.2 $ 588.1 $ 66.1 $ 381.0 $ 4,222.0 $ 21.3 $ 6,219.8 4 to 5 Category 544.9 538.1 458.1 494.4 103.8 141.9 1,513.4 56.3 3,850.9 6 to 9 Category 34.9 81.4 63.0 81.5 2.3 2.3 48.2 7.0 320.6 Total Commercial and Institutional 902.4 867.0 892.3 1,164.0 172.2 525.2 5,783.6 84.6 10,391.3 C&I Gross Charge-offs — (7.3) (1.3) — — — — — (8.6) Commercial Real Estate Risk Rating: 1 to 3 Category 97.3 339.5 289.1 219.5 18.8 68.5 53.7 — 1,086.4 4 to 5 Category 274.1 1,669.7 1,048.1 436.2 193.2 200.1 159.6 5.3 3,986.3 6 to 9 Category 14.1 16.0 126.4 17.1 4.3 0.4 — — 178.3 Total Commercial Real Estate 385.5 2,025.2 1,463.6 672.8 216.3 269.0 213.3 5.3 5,251.0 Commercial Real Estate Gross Charge-offs — — (2.4) — — — — — (2.4) Non-U.S. Risk Rating: 1 to 3 Category 1,215.8 24.2 — — 117.7 30.2 577.0 — 1,964.9 4 to 5 Category 606.0 16.5 0.8 1.2 — 69.3 69.6 — 763.4 6 to 9 Category 0.5 — 13.8 — — — — — 14.3 Total Non-U.S. 1,822.3 40.7 14.6 1.2 117.7 99.5 646.6 — 2,742.6 Other Risk Rating: 1 to 3 Category 1,183.9 — — — — — — — 1,183.9 4 to 5 Category 1,264.9 — — — — — — — 1,264.9 6 to 9 Category 0.1 — — — — — — — 0.1 Total Other 2,448.9 — — — — — — — 2,448.9 Other Gross Charge-offs — — — — — — — — — Total Commercial 5,559.1 2,932.9 2,370.5 1,838.0 506.2 893.7 6,643.5 89.9 20,833.8 Commercial Gross Charge-offs — (7.3) (3.7) — — — — — (11.0) Personal Private Client Risk Rating: 1 to 3 Category 206.7 80.0 39.5 38.3 19.1 39.8 4,503.2 144.1 5,070.7 4 to 5 Category 141.8 635.2 423.2 424.4 124.1 188.0 6,688.7 474.7 9,100.1 6 to 9 Category 0.1 16.3 — — — — 8.3 — 24.7 Total Private Client 348.6 731.5 462.7 462.7 143.2 227.8 11,200.2 618.8 14,195.5 Private Client Gross Charge-offs — — — — — (0.3) — — (0.3) Residential Real Estate Risk Rating: 1 to 3 Category 138.5 231.3 433.6 407.3 332.0 816.6 189.9 — 2,549.2 4 to 5 Category 134.6 224.0 664.6 706.2 678.4 940.4 165.6 2.1 3,515.9 6 to 9 Category — — 7.5 3.9 0.4 37.0 27.3 — 76.1 Total Residential Real Estate 273.1 455.3 1,105.7 1,117.4 1,010.8 1,794.0 382.8 2.1 6,141.2 Residential Real Estate Gross Charge-offs — — — — — (0.1) — — (0.1) Non-U.S. Risk Rating: 1 to 3 Category 3.2 1.0 — — — 6.8 158.0 — 169.0 4 to 5 Category 19.6 16.0 15.3 39.3 — 19.2 163.6 7.3 280.3 6 to 9 Category 7.9 — — — — — — — 7.9 Total Non-U.S. 30.7 17.0 15.3 39.3 — 26.0 321.6 7.3 457.2 Other Risk Rating: 1 to 3 Category 199.4 — — — — — — — 199.4 4 to 5 Category 123.1 — — — — — — — 123.1 6 to 9 Category 0.1 — — — — — — — 0.1 Total Other 322.6 — — — — — — — 322.6 Total Personal 975.0 1,203.8 1,583.7 1,619.4 1,154.0 2,047.8 11,904.6 628.2 21,116.5 Personal Gross Charge-offs — — — — — (0.4) — — (0.4) Total Loans $ 6,534.1 $ 4,136.7 $ 3,954.2 $ 3,457.4 $ 1,660.2 $ 2,941.5 $ 18,548.1 $ 718.1 $ 41,950.3 Total Loans Gross Charge-offs $ — $ (7.3) $ (3.7) $ — $ — $ (0.4) $ — $ — $ (11.4) December 31, 2023 TERM LOANS REVOLVING LOANS REVOLVING LOANS CONVERTED TO TERM LOANS (In Millions) 2023 2022 2021 2020 2019 PRIOR TOTAL Commercial Commercial and Institutional Risk Rating: 1 to 3 Category $ 443.9 $ 534.1 $ 668.3 $ 78.1 $ 137.2 $ 409.9 $ 4,909.8 $ 15.0 $ 7,196.3 4 to 5 Category 801.4 790.9 729.5 138.7 120.5 178.7 1,332.4 72.0 4,164.1 6 to 9 Category 13.8 70.0 60.8 12.0 0.1 1.7 34.7 1.8 194.9 Total Commercial and Institutional 1,259.1 1,395.0 1,458.6 228.8 257.8 590.3 6,276.9 88.8 11,555.3 Commercial Real Estate Risk Rating: 1 to 3 Category 403.6 389.9 159.1 23.9 37.8 44.8 51.0 — 1,110.1 4 to 5 Category 1,513.5 1,208.8 521.0 218.4 252.8 96.0 136.3 7.9 3,954.7 6 to 9 Category 16.1 — 30.5 — 8.2 14.6 — — 69.4 Total Commercial Real Estate 1,933.2 1,598.7 710.6 242.3 298.8 155.4 187.3 7.9 5,134.2 CRE Gross Charge-offs (0.7) (4.4) — — — — — — (5.1) Non-U.S. Risk Rating: 1 to 3 Category 487.9 — 43.2 65.2 34.2 3.3 760.0 — 1,393.8 4 to 5 Category 974.7 0.8 — — — 150.0 243.4 — 1,368.9 6 to 9 Category 1.5 14.3 — — — — — — 15.8 Total Non-U.S. 1,464.1 15.1 43.2 65.2 34.2 153.3 1,003.4 — 2,778.5 Other Risk Rating: 1 to 3 Category 4,313.2 — — — — — — — 4,313.2 4 to 5 Category 1,631.6 — — — — — — — 1,631.6 Total Other 5,944.8 — — — — — — — 5,944.8 Other Gross Charge-offs (0.6) — — — — — — — (0.6) Total Commercial 10,601.2 3,008.8 2,212.4 536.3 590.8 899.0 7,467.6 96.7 25,412.8 Commercial Gross Charge-offs (1.3) (4.4) — — — — — — (5.7) Personal Private Client Risk Rating: 1 to 3 Category 504.7 140.8 52.3 67.5 8.7 134.7 5,320.9 168.1 6,397.7 4 to 5 Category 290.1 488.2 655.1 100.9 158.8 44.7 5,721.5 447.8 7,907.1 6 to 9 Category 23.6 0.3 — — — 18.3 13.0 — 55.2 Total Private Client 818.4 629.3 707.4 168.4 167.5 197.7 11,055.4 615.9 14,360.0 Residential Real Estate Risk Rating: 1 to 3 Category 278.7 464.0 500.6 373.3 142.4 722.4 219.8 — 2,701.2 4 to 5 Category 191.6 694.9 717.4 686.7 290.0 805.3 170.3 — 3,556.2 6 to 9 Category — 10.9 — 0.7 1.6 43.6 12.9 — 69.7 Total Residential Real Estate 470.3 1,169.8 1,218.0 1,060.7 434.0 1,571.3 403.0 — 6,327.1 RRE Gross Charge-offs (0.8) — — — — (1.0) — — (1.8) Non-U.S. Risk Rating: 1 to 3 Category 15.5 — 0.6 — — 4.6 71.4 — 92.1 4 to 5 Category 12.7 16.0 39.2 — 16.4 8.9 236.1 7.4 336.7 6 to 9 Category — — — — — — — — — Total Non-U.S. 28.2 16.0 39.8 — 16.4 13.5 307.5 7.4 428.8 Other Risk Rating: 1 to 3 Category 461.7 — — — — — — — 461.7 4 to 5 Category 626.6 — — — — — — — 626.6 Total Other 1,088.3 — — — — — — — 1,088.3 Total Personal 2,405.2 1,815.1 1,965.2 1,229.1 617.9 1,782.5 11,765.9 623.3 22,204.2 Personal Gross Charge-Offs $ (0.8) $ — $ — $ — $ — $ (1.0) $ — $ — $ (1.8) Total Loans 13,006.4 4,823.9 4,177.6 1,765.4 1,208.7 2,681.5 19,233.5 720.0 47,617.0 Total Loans Gross Charge-Offs $ (2.1) $ (4.4) $ — $ — $ — $ (1.0) $ — $ — $ (7.5)
Delinquency Status	The following table provides balances and delinquency status of accrual and nonaccrual loans by segment and class, as well as the other real estate owned and nonaccrual asset balances, as of September 30, 2024 and December 31, 2023. TABLE 50: DELINQUENCY STATUS ACCRUAL NONACCRUAL WITH NO ALLOWANCE (In Millions) CURRENT 30 – 59 DAYS 60 – 89 DAYS 90 DAYS TOTAL ACCRUAL NONACCRUAL TOTAL LOANS September 30, 2024 Commercial Commercial and Institutional $ 10,246.1 $ 65.3 $ 16.4 $ 55.4 $ 10,383.2 $ 8.1 $ 10,391.3 $ 8.1 Commercial Real Estate 5,220.6 19.8 5.0 — 5,245.4 5.6 5,251.0 5.6 Non-U.S. 2,691.6 46.9 — 3.6 2,742.1 0.5 2,742.6 — Other 2,448.9 — — — 2,448.9 — 2,448.9 — Total Commercial 20,607.2 132.0 21.4 59.0 20,819.6 14.2 20,833.8 13.7 Personal Private Client 14,015.9 131.1 18.3 28.2 14,193.5 2.0 14,195.5 — Residential Real Estate 6,086.6 8.5 23.0 — 6,118.1 23.1 6,141.2 23.1 Non-U.S. 457.1 0.1 — — 457.2 — 457.2 — Other 322.6 — — — 322.6 — 322.6 — Total Personal 20,882.2 139.7 41.3 28.2 21,091.4 25.1 21,116.5 23.1 Total Loans $ 41,489.4 $ 271.7 $ 62.7 $ 87.2 $ 41,911.0 $ 39.3 $ 41,950.3 $ 36.8 Other Real Estate Owned $ — Total Nonaccrual Assets $ 39.3 ACCRUAL NONACCRUAL WITH NO ALLOWANCE (In Millions) CURRENT 30 – 59 DAYS 60 – 89 DAYS 90 DAYS TOTAL ACCRUAL NONACCRUAL TOTAL LOANS December 31, 2023 Commercial Commercial and Institutional $ 11,374.6 $ 163.7 $ 0.7 $ — $ 11,539.0 $ 16.3 $ 11,555.3 $ 4.1 Commercial Real Estate 5,123.7 4.4 6.1 — 5,134.2 — 5,134.2 — Non-U.S. 2,778.5 — — — 2,778.5 — 2,778.5 — Other 5,944.8 — — — 5,944.8 — 5,944.8 — Total Commercial 25,221.6 168.1 6.8 — 25,396.5 16.3 25,412.8 4.1 Personal Private Client 14,240.0 63.9 24.8 11.0 14,339.7 20.3 14,360.0 18.3 Residential Real Estate 6,283.0 7.5 0.5 9.1 6,300.1 27.0 6,327.1 27.0 Non-U.S 428.2 — 0.6 — 428.8 — 428.8 — Other 1,088.3 — — — 1,088.3 — 1,088.3 — Total Personal 22,039.5 71.4 25.9 20.1 22,156.9 47.3 22,204.2 45.3 Total Loans $ 47,261.1 $ 239.5 $ 32.7 $ 20.1 $ 47,553.4 $ 63.6 $ 47,617.0 $ 49.4 Other Real Estate Owned $ 1.5 Total Nonaccrual Assets $ 65.1

Allowance for Credit Losses (Ta

Allowance for Credit Losses (Tables)	9 Months Ended
Allowance for Credit Losses (Tables)	Sep. 30, 2024
Receivables [Abstract]
Allowance for Credit Loss	The following table provides information regarding changes in the total Allowance for Credit Losses during the three and nine months ended September 30, 2024 and 2023. TABLE 51: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 167.7 $ 29.5 $ 10.9 $ 0.9 $ 209.0 Charge-Offs — — — — — Recoveries 2.4 — — — 2.4 Net Recoveries (Charge-Offs) 2.4 — — — 2.4 Provision for Credit Losses (1) 14.7 (3.0) (3.4) 0.1 8.4 Balance at End of Period $ 184.8 $ 26.5 $ 7.5 $ 1.0 $ 219.8 (1) The table excludes a negative provision for credit losses of $0.4 million for the three months ended September 30, 2024 for AFS debt securities. See further detail in Note 4—Securities. NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT DEBT SECURITIES HELD TO MATURITY OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 178.7 $ 26.9 $ 12.7 $ 0.9 $ 219.2 Charge-Offs (11.4) — — — (11.4) Recoveries 3.5 — — — 3.5 Net Recoveries (Charge-Offs) (7.9) — — — (7.9) Provision for Credit Losses (1) 14.0 (0.4) (5.2) 0.1 8.5 Balance at End of Period $ 184.8 $ 26.5 $ 7.5 $ 1.0 $ 219.8 (1) The table excludes a negative provision for credit losses of $1.0 million for the nine months ended September 30, 2024 for AFS debt securities. See further detail in Note 4—Securities. THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 152.5 $ 26.0 $ 16.7 $ 1.0 $ 196.2 Charge-Offs (0.8) — — — (0.8) Recoveries 1.1 — — — 1.1 Net Recoveries (Charge-Offs) 0.3 — — — 0.3 Provision for Credit Losses (1) 14.0 2.3 (1.8) 0.1 14.6 Balance at End of Period $ 166.8 $ 28.3 $ 14.9 $ 1.1 $ 211.1 (1) The table excludes a negative provision for credit losses of $0.6 million for the three months ended September 30, 2023 for AFS debt securities. See further detail in Note 4—Securitie s. NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT HELD TO MATURITY DEBT SECURITIES OTHER FINANCIAL ASSETS TOTAL Balance at Beginning of Period $ 144.3 $ 38.5 $ 16.0 $ 0.8 $ 199.6 Charge-Offs (5.6) — — — (5.6) Recoveries 3.0 — — — 3.0 Net Recoveries (Charge-Offs) (2.6) — — — (2.6) Provision for Credit Losses (1) 25.1 (10.2) (1.1) 0.3 14.1 Balance at End of Period $ 166.8 $ 28.3 $ 14.9 $ 1.1 $ 211.1 (1) The table excludes a negative provision for credit losses of $0.6 million for the nine months ended September 30, 2023 for AFS debt securities. See further detail in Note 4—Securities. The following table provides information regarding changes in the total Allowance for Credit Losses related to loans, including undrawn loan commitments and standby letters of credit, by segment during the three and nine months ended September 30, 2024 and 2023. TABLE 52: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES RELATED TO LOANS THREE MONTHS ENDED SEPTEMBER 30, 2024 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 136.9 $ 30.8 $ 167.7 $ 27.2 $ 2.3 $ 29.5 Charge-Offs — — — — — — Recoveries — 2.4 2.4 — — — Net Recoveries (Charge-Offs) — 2.4 2.4 — — — Provision for Credit Losses 15.7 (1.0) 14.7 (2.7) (0.3) (3.0) Balance at End of Period $ 152.6 $ 32.2 $ 184.8 $ 24.5 $ 2.0 $ 26.5 NINE MONTHS ENDED SEPTEMBER 30, 2024 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 146.8 $ 31.9 $ 178.7 $ 24.9 $ 2.0 $ 26.9 Charge-Offs (11.0) (0.4) (11.4) — — — Recoveries — 3.5 3.5 — — — Net Recoveries (Charge-Offs) (11.0) 3.1 (7.9) — — — Provision for (Release of) Credit Losses 16.8 (2.8) 14.0 (0.4) — (0.4) Balance at End of Period $ 152.6 $ 32.2 $ 184.8 $ 24.5 $ 2.0 $ 26.5 THREE MONTHS ENDED SEPTEMBER 30, 2023 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 124.0 $ 28.5 $ 152.5 $ 23.3 $ 2.7 $ 26.0 Charge-Offs (0.5) (0.3) (0.8) — — — Recoveries — 1.1 1.1 — — — Net Recoveries (Charge-Offs) (0.5) 0.8 0.3 — — — Provision for Credit Losses 13.9 0.1 14.0 2.2 0.1 2.3 Balance at End of Period $ 137.4 $ 29.4 $ 166.8 $ 25.5 $ 2.8 $ 28.3 NINE MONTHS ENDED SEPTEMBER 30, 2023 LOANS UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Balance at Beginning of Period $ 116.2 $ 28.1 $ 144.3 $ 36.3 $ 2.2 $ 38.5 Charge-Offs (4.5) (1.1) (5.6) — — — Recoveries 0.1 2.9 3.0 — — — Net Recoveries (Charge-Offs) (4.4) 1.8 (2.6) — — — Provision for (Release of) Credit Losses 25.6 (0.5) 25.1 (10.8) 0.6 (10.2) Balance at End of Period $ 137.4 $ 29.4 $ 166.8 $ 25.5 $ 2.8 $ 28.3 The following table provides information regarding the recorded investments in loans and the Allowance for Credit Losses for loans and undrawn loan commitments and standby letters of credit by segment as of September 30, 2024 and December 31, 2023. TABLE 53: RECORDED INVESTMENTS IN LOANS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) COMMERCIAL PERSONAL TOTAL COMMERCIAL PERSONAL TOTAL Loans Evaluated on an Individual Basis $ 38.1 $ 35.3 $ 73.4 $ 33.7 $ 62.6 $ 96.3 Evaluated on a Collective Basis 20,795.7 21,081.2 41,876.9 25,379.1 22,141.6 47,520.7 Total Loans 20,833.8 21,116.5 41,950.3 25,412.8 22,204.2 47,617.0 Allowance for Credit Losses on Loans Evaluated on an Individual Basis 3.3 2.2 5.5 11.4 2.0 13.4 Evaluated on a Collective Basis 149.3 30.0 179.3 135.4 29.9 165.3 Allowance Assigned to Loans 152.6 32.2 184.8 146.8 31.9 178.7 Allowance Assigned to Undrawn Loan Commitments and Standby Letters of Credit - Evaluated on a Collective Basis 24.5 2.0 26.5 24.9 2.0 26.9 Total Allowance Assigned to Loans and Undrawn Loan Commitments and Standby Letters of Credit $ 177.1 $ 34.2 $ 211.3 $ 171.7 $ 33.9 $ 205.6
Debt Securities, Held-to-maturity, Allowance for Credit Loss	The following table provides information regarding changes in the total allowance for credit losses for HTM debt securities during the three and nine months ended September 30, 2024 and 2023. TABLE 54: CHANGES IN THE ALLOWANCE FOR CREDIT LOSSES RELATED TO HELD TO MATURITY DEBT SECURITIES THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS (1) COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 0.5 $ 2.6 $ 1.7 $ 1.0 $ 0.1 $ 5.0 $ 10.9 Provision for Credit Losses — (0.1) (0.1) — (0.1) (3.1) (3.4) Balance at End of Period $ 0.5 $ 2.5 $ 1.6 $ 1.0 $ — $ 1.9 $ 7.5 (1) The allowance for Obligations of States and Political Subdivisions is related to (non pre-refunded) municipal securities that do not fall under Northern Trust’s zero-loss assumption. NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS (1) COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 0.9 $ 3.5 $ 2.2 $ 1.2 $ 0.1 $ 4.8 $ 12.7 Provision for (Release of) Credit Losses (0.4) (1.0) (0.6) (0.2) (0.1) (2.9) (5.2) Balance at End of Period $ 0.5 $ 2.5 $ 1.6 $ 1.0 $ — $ 1.9 $ 7.5 (1) The allowance for Obligations of States and Political Subdivisions is related to (non pre-refunded) municipal securities that do not fall under Northern Trust’s zero-loss assumption. THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 1.4 $ 5.4 $ 3.4 $ 1.3 $ 0.1 $ 5.1 $ 16.7 Provision for Credit Losses (0.1) (0.8) (0.5) (0.1) — (0.3) (1.8) Balance at End of Period $ 1.3 $ 4.6 $ 2.9 $ 1.2 $ 0.1 $ 4.8 $ 14.9 NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) CORPORATE DEBT NON-U.S. GOVERNMENT SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS OBLIGATIONS OF STATES AND POLITICAL SUBDIVISIONS COVERED BONDS OTHER TOTAL Balance at Beginning of Period $ 1.9 $ 3.6 $ 4.0 $ 1.5 $ 0.1 $ 4.9 $ 16.0 Provision for (Release of) Credit Losses (0.6) 1.0 (1.1) (0.3) — (0.1) (1.1) Balance at End of Period $ 1.3 $ 4.6 $ 2.9 $ 1.2 $ 0.1 $ 4.8 $ 14.9
Schedule of Accrued Liabilities	The following table provides the amount of accrued interest excluded from the amortized cost basis of the following portfolios. TABLE 55: ACCRUED INTEREST (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Loans $ 220.2 $ 241.7 Debt Securities Held to Maturity 75.1 72.0 Available for Sale 177.2 129.2 Other Financial Assets 79.2 86.0 Total $ 551.7 $ 528.9

Pledged Assets, Accepted Coll_2

Pledged Assets, Accepted Collateral and Restricted Assets (Tables)	9 Months Ended
	Sep. 30, 2024
Transfers and Servicing [Abstract]
Schedule of Financial Instruments Owned and Pledged as Collateral	The following table presents the carrying value of Northern Trust's pledged assets by type. TABLE 56: TYPE OF PLEDGED ASSETS (In Billions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Debt Securities (1) $ 31.1 $ 33.0 Loans (2) 10.0 10.3 Total Pledged Assets $ 41.1 $ 43.3 (1) Debt securities are comprised of held to maturity and available for sale securities. (2) Loans pledged at the FHLB of Chicago and the Federal Reserve Bank of Chicago.
Schedule of Customer Securities for which Entity has Right to Sell or Repledge	The following table presents the fair value of securities accepted as collateral. TABLE 57: ACCEPTED COLLATERAL (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Collateral that may be repledged or sold Reverse repurchase agreements (1)(2) $ 66,367.0 $ 62,767.8 Derivative contracts 10.3 12.2 Collateral that may not be repledged or sold Reverse repurchase agreements — — Total Collateral Accepted $ 66,377.3 $ 62,780.0 (1) The fair value of securities collateral that was repledged or sold totaled $65.3 billion and $62.0 billion at September 30, 2024 and December 31, 2023, respectively. (2) This includes collateral accepted as related to the sponsored member program. Refer to Note 20—Commitments and Contingent Liabilities for further information.

Goodwill and Other Intangibles

Goodwill and Other Intangibles (Tables)	9 Months Ended
Goodwill and Other Intangibles (Tables)	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by Reporting Segment	Changes by reporting segment in the carrying amount of Goodwill for the nine months ended September 30, 2024, including the effect of foreign exchange rates on non-U.S. dollar denominated balances, were as follows. TABLE 58: GOODWILL (In Millions) ASSET WEALTH MANAGEMENT TOTAL Balance at December 31, 2023 $ 621.9 $ 80.4 $ 702.3 Foreign Exchange Rates 5.5 — 5.5 Balance at September 30, 2024 $ 627.4 $ 80.4 $ 707.8
Other Intangible Assets	The gross carrying amount and accumulated amortization of other intangible assets subject to amortization as of September 30, 2024 and December 31, 2023 were as follows. TABLE 59: OTHER INTANGIBLE ASSETS (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Gross Carrying Amount $ 136.0 $ 135.0 Less: Accumulated Amortization 71.1 63.4 Net Book Value $ 64.9 $ 71.6 The gross carrying amount and accumulated amortization of capitalized software as of September 30, 2024 and December 31, 2023 were as follows. TABLE 60: CAPITALIZED SOFTWARE (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Gross Carrying Amount $ 4,256.2 $ 3,781.7 Less: Accumulated Amortization 2,197.4 1,754.2 Net Book Value $ 2,058.8 $ 2,027.5

Reporting Segments (Tables)

Reporting Segments (Tables)	9 Months Ended
Reporting Segments (Tables)	Sep. 30, 2024
Segment Reporting [Abstract]
Results of Reporting Segments	The following table presents the earnings contributions and average assets of Northern Trust’s reporting segments for the three- and nine-month periods ended September 30, 2024 and 2023. TABLE 61: RESULTS OF REPORTING SEGMENTS ($ In Millions) ASSET SERVICING WEALTH MANAGEMENT OTHER (1) RECONCILING ITEMS TOTAL CONSOLIDATED THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees $ 667.1 $ 626.0 $ 529.5 $ 485.9 $ — $ — $ — $ — $ 1,196.6 $ 1,111.9 Foreign Exchange Trading Income (Loss) 59.5 54.3 (5.4) (2.5) — — — — 54.1 51.8 Other Noninterest Income (Loss) 67.3 66.1 35.7 38.1 52.5 2.4 — — 155.5 106.6 Total Noninterest Income (Loss) 793.9 746.4 559.8 521.5 52.5 2.4 — — 1,406.2 1,270.3 Net Interest Income 321.4 281.2 248.0 188.2 — — (7.1) (13.2) 562.3 456.2 Revenue 1,115.3 1,027.6 807.8 709.7 52.5 2.4 (7.1) (13.2) 1,968.5 1,726.5 Provision for Credit Losses (0.6) 3.1 12.4 10.9 (3.8) — — — 8.0 14.0 Noninterest Expense 860.7 809.3 491.3 456.9 7.4 12.0 — — 1,359.4 1,278.2 Income before Income Taxes 255.2 215.2 304.1 241.9 48.9 (9.6) (7.1) (13.2) 601.1 434.3 Provision for Income Taxes 57.1 54.3 75.1 67.7 11.1 (2.3) (7.1) (13.2) 136.2 106.5 Net Income $ 198.1 $ 160.9 $ 229.0 $ 174.2 $ 37.8 $ (7.3) $ — $ — $ 464.9 $ 327.8 Percentage of Consolidated Net Income 43 % 49 % 49 % 53 % 8 % (2) % N/A N/A 100 % 100 % Average Assets $ 108,108.0 $ 108,656.7 $ 38,734.9 $ 31,544.9 $ — $ — N/A N/A $ 146,842.9 $ 140,201.6 (1) Includes the current quarter gain related to the sale of an equity investment. (In Millions) ASSET SERVICING WEALTH MANAGEMENT OTHER (1) RECONCILING ITEMS TOTAL CONSOLIDATED NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees $ 1,957.3 $ 1,850.2 $ 1,548.3 $ 1,421.6 $ — $ — $ — $ — $ 3,505.6 $ 3,271.8 Foreign Exchange Trading Income (Loss) 181.6 161.2 (12.1) (6.3) — — — — 169.5 154.9 Other Noninterest Income (Loss) 199.2 199.0 105.3 112.8 737.9 (9.2) — — 1,042.4 302.6 Total Noninterest Income (Loss) 2,338.1 2,210.4 1,641.5 1,528.1 737.9 (9.2) — — 4,717.5 3,729.3 Net Interest Income 900.5 902.6 734.1 635.8 — — (21.3) (39.5) 1,613.3 1,498.9 Revenue 3,238.6 3,113.0 2,375.6 2,163.9 737.9 (9.2) (21.3) (39.5) 6,330.8 5,228.2 Provision for Credit Losses (1.9) (3.3) 15.7 16.8 (6.3) — — — 7.5 13.5 Noninterest Expense 2,634.0 2,459.7 1,504.9 1,402.4 119.1 33.6 — — 4,258.0 3,895.7 Income before Income Taxes 606.5 656.6 855.0 744.7 625.1 (42.8) (21.3) (39.5) 2,065.3 1,319.0 Provision for Income Taxes 146.1 167.4 223.0 207.5 141.8 (10.6) (21.3) (39.5) 489.6 324.8 Net Income $ 460.4 $ 489.2 $ 632.0 $ 537.2 $ 483.3 $ (32.2) $ — $ — $ 1,575.7 $ 994.2 Percentage of Consolidated Net Income 29 % 49 % 40 % 54 % 31 % (3) % N/A N/A 100 % 100 % Average Assets $ 108,025.6 $ 110,380.4 $ 38,629.2 $ 34,311.2 $ — $ — N/A N/A $ 146,654.8 $ 144,691.6 (1) Includes the current quarter gain related to the sale of an equity investment. Includes the gain related to the net impact from the Visa transactions in the second quarter of 2024, refer to Note 20—Commitments and Contingent Liabilities for further information. Note: Segment results are stated on an FTE basis. The FTE adjustments are eliminated in the reconciling items column with the Corporation’s total consolidated financial results stated on a GAAP basis. The adjustment to an FTE basis has no impact on Net Income.

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
Accumulated Other Comprehensive Income (Loss) (Tables)	Sep. 30, 2024
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Income (Loss)	The following tables summarize the components of Accumulated Other Comprehensive Income (Loss) (AOCI) at September 30, 2024 and 2023, and changes during the three and nine months then ended. TABLE 62: SUMMARY OF CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) THREE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at June 30, 2024 $ (667.1) $ — $ 215.2 $ (413.1) $ (865.0) Net Change 63.9 0.3 18.9 2.4 85.5 Balance at September 30, 2024 $ (603.2) $ 0.3 $ 234.1 $ (410.7) $ (779.5) NINE MONTHS ENDED SEPTEMBER 30, 2024 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at December 31, 2023 $ (923.9) $ 0.8 $ 203.6 $ (418.4) $ (1,137.9) Net Change 320.7 (0.5) 30.5 7.7 358.4 Balance at September 30, 2024 $ (603.2) $ 0.3 $ 234.1 $ (410.7) $ (779.5) THREE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at June 30, 2023 $ (1,229.4) $ 0.5 $ 189.2 $ (366.2) $ (1,405.9) Net Change 32.3 (0.4) 9.6 1.0 42.5 Balance at September 30, 2023 $ (1,197.1) $ 0.1 $ 198.8 $ (365.2) $ (1,363.4) NINE MONTHS ENDED SEPTEMBER 30, 2023 (In Millions) NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES NET FOREIGN CURRENCY ADJUSTMENT NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS TOTAL Balance at December 31, 2022 $ (1,367.6) $ 1.2 $ 164.6 $ (367.4) $ (1,569.2) Net Change 170.5 (1.1) 34.2 2.2 205.8 Balance at September 30, 2023 $ (1,197.1) $ 0.1 $ 198.8 $ (365.2) $ (1,363.4)
Details of Changes in Accumulated Other Comprehensive Income (Loss)	TABLE 63: DETAILS OF CHANGES IN ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 (In Millions) PRE-TAX TAX AFTER TAX PRE-TAX TAX AFTER TAX Unrealized Gains (Losses) on Available for Sale Debt Securities Unrealized Gains (Losses) on Available for Sale Debt Securities $ 63.7 $ (18.6) $ 45.1 $ 18.0 $ (5.6) $ 12.4 Reclassification Adjustments for (Gains) Losses Included in Net Income: Interest Income on Debt Securities (1) 24.9 (6.1) 18.8 26.7 (6.8) 19.9 Net (Gains) Losses on Debt Securities (2) — — — — — — Net Change $ 88.6 $ (24.7) $ 63.9 $ 44.7 $ (12.4) $ 32.3 Unrealized Gains (Losses) on Cash Flow Hedges Foreign Exchange Contracts $ 1.0 $ (0.2) $ 0.8 $ 14.3 $ (3.6) $ 10.7 Reclassification Adjustment for (Gains) Losses Included in Net Income (3) (0.6) 0.1 (0.5) (14.9) 3.8 (11.1) Net Change $ 0.4 $ (0.1) $ 0.3 $ (0.6) $ 0.2 $ (0.4) Foreign Currency Adjustments Foreign Currency Translation Adjustments $ 122.9 $ (2.4) $ 120.5 $ (89.2) $ 1.7 $ (87.5) Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) 1.0 (0.3) 0.7 (0.2) 0.1 (0.1) Net Investment Hedge Gains (Losses) (135.6) 33.3 (102.3) 129.9 (32.7) 97.2 Net Change $ (11.7) $ 30.6 $ 18.9 $ 40.5 $ (30.9) $ 9.6 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gains (Losses) $ (0.1) $ — $ (0.1) $ (0.2) $ — $ (0.2) Reclassification Adjustment for (Gains) Losses Included in Net Income (4) Amortization of Net Actuarial Loss 3.2 (0.7) 2.5 1.6 (0.4) 1.2 Net Change $ 3.1 $ (0.7) $ 2.4 $ 1.4 $ (0.4) $ 1.0 Total Net Change $ 80.4 $ 5.1 $ 85.5 $ 86.0 $ (43.5) $ 42.5 NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 (In Millions) PRE-TAX TAX AFTER TAX PRE-TAX TAX AFTER TAX Unrealized Gains (Losses) on Available for Sale Debt Securities Unrealized Gains (Losses) on Available for Sale Debt Securities $ 176.9 $ (55.1) $ 121.8 $ 158.6 $ (42.0) $ 116.6 Reclassification Adjustments for (Gains) Losses Included in Net Income: Interest Income on Debt Securities (1) 76.5 (19.0) 57.5 79.0 (19.9) 59.1 Net (Gains) Losses on Debt Securities (2) 189.3 (47.9) 141.4 (6.9) 1.7 (5.2) Net Change $ 442.7 $ (122.0) $ 320.7 $ 230.7 $ (60.2) $ 170.5 Unrealized Gains (Losses) on Cash Flow Hedges Foreign Exchange Contracts $ 6.4 $ (1.5) $ 4.9 $ 16.2 $ (4.1) $ 12.1 Reclassification Adjustment for (Gains) Losses Included in Net Income (3) (7.1) 1.7 (5.4) (17.7) 4.5 (13.2) Net Change $ (0.7) $ 0.2 $ (0.5) $ (1.5) $ 0.4 $ (1.1) Foreign Currency Adjustments Foreign Currency Translation Adjustments $ 52.5 $ (1.2) $ 51.3 $ (15.7) $ 1.2 $ (14.5) Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses) 0.2 (0.1) 0.1 (1.8) 0.5 (1.3) Net Investment Hedge Gains (Losses) (36.3) 15.4 (20.9) 66.8 (16.8) 50.0 Net Change $ 16.4 $ 14.1 $ 30.5 $ 49.3 $ (15.1) $ 34.2 Pension and Other Postretirement Benefit Adjustments Net Actuarial Gains (Losses) $ 0.9 $ (0.5) $ 0.4 $ (1.5) $ 0.1 $ (1.4) Reclassification Adjustment for (Gains) Losses Included in Net Income (4) Amortization of Net Actuarial Loss 9.6 (2.3) 7.3 4.8 (1.2) 3.6 Net Change $ 10.5 $ (2.8) $ 7.7 $ 3.3 $ (1.1) $ 2.2 Total Net Change $ 468.9 $ (110.5) $ 358.4 $ 281.8 $ (76.0) $ 205.8 (1) The before-tax reclassification adjustment is related to the unrealized gains (losses) amortization on AFS debt securities that were transferred to HTM debt securities during the second quarter of 2021 and third quarter of 2022. (2) The net gains (losses) on AFS debt securities before-tax reclassification adjustment is recorded in Investment Security Gains (Losses), net on the consolidated statements of income. (3) See Note 21—Derivative Financial Instruments for the location of the reclassification adjustment related to cash flow hedges. (4) The pension and other postretirement benefit before-tax reclassification adjustment is recorded in Employee Benefits expense on the consolidated statements of income.

Net Income Per Common Share (Ta

Net Income Per Common Share (Tables)	9 Months Ended
Net Income Per Common Share (Tables)	Sep. 30, 2024
Earnings Per Share [Abstract]
Net Income per Common Share	The computations of net income per common share are presented in the following table. TABLE 64: NET INCOME PER COMMON SHARE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, ($ In Millions Except Per Common Share Information) 2024 2023 2024 2023 Basic Net Income Per Common Share Average Number of Common Shares Outstanding 199,937,543 207,021,554 202,614,386 207,611,420 Net Income $ 464.9 $ 327.8 $ 1,575.7 $ 994.2 Less: Dividends on Preferred Stock 16.2 16.2 37.1 37.1 Net Income Applicable to Common Stock 448.7 311.6 1,538.6 957.1 Less: Earnings Allocated to Participating Securities 3.6 3.1 13.2 9.7 Earnings Allocated to Common Shares Outstanding 445.1 308.5 1,525.4 947.4 Basic Net Income Per Common Share $ 2.23 $ 1.49 $ 7.53 $ 4.56 Diluted Net Income Per Common Share Average Number of Common Shares Outstanding 199,937,543 207,021,554 202,614,386 207,611,420 Plus: Dilutive Effect of Share-based Compensation 611,520 231,438 517,014 316,300 Average Common and Potential Common Shares 200,549,063 207,252,992 203,131,400 207,927,720 Earnings Allocated to Common and Potential Common Shares $ 445.1 $ 308.5 $ 1,525.4 $ 947.3 Diluted Net Income Per Common Share 2.22 1.49 7.51 4.56

Revenue from Contracts with C_2

Revenue from Contracts with Clients (Tables)	9 Months Ended
Revenue from Contracts with Clients (Tables)	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue Disaggregation	The following table presents revenues disaggregated by major revenue source. TABLE 65: REVENUE DISAGGREGATION THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Noninterest Income Trust, Investment and Other Servicing Fees Custody and Fund Administration $ 482.5 $ 459.0 $ 1,427.1 $ 1,358.7 Investment Management and Advisory 634.8 574.1 1,838.3 1,673.4 Securities Lending 17.7 20.7 53.2 61.3 Other 61.6 58.1 187.0 178.4 Total Trust, Investment and Other Servicing Fees $ 1,196.6 $ 1,111.9 $ 3,505.6 $ 3,271.8 Other Noninterest Income Foreign Exchange Trading Income $ 54.1 $ 51.8 $ 169.5 $ 154.9 Treasury Management Fees 8.2 7.5 26.5 23.8 Security Commissions and Trading Income 35.5 30.9 107.7 101.7 Other Operating Income 111.8 68.2 1,097.5 170.2 Investment Security Gains (Losses), net — — (189.3) 6.9 Total Other Noninterest Income $ 209.6 $ 158.4 $ 1,211.9 $ 457.5 Total Noninterest Income $ 1,406.2 $ 1,270.3 $ 4,717.5 $ 3,729.3
Contract Balances	The table below represents receivables balances from contracts with clients, which are included in Other Assets on the consolidated balance sheets, at September 30, 2024 and December 31, 2023. TABLE 66: CLIENT RECEIVABLES (In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Trust Fees Receivable, net (1) $ 973.6 $ 863.5 Other 57.1 64.9 Total Client Receivables $ 1,030.7 $ 928.4 (1) Trust Fees Receivable is net of a $13.5 million and $15.9 million fee receivable allowance as of September 30, 2024 and December 31, 2023, respectively.

Net Interest Income (Tables)

Net Interest Income (Tables)	9 Months Ended
Net Interest Income (Tables)	Sep. 30, 2024
Banking and Thrift, Interest [Abstract]
Net Interest Income	The components of Net Interest Income were as follows. TABLE 67: NET INTEREST INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Interest Income Federal Reserve and Other Central Bank Deposits $ 451.7 $ 352.1 $ 1,369.0 $ 1,128.0 Interest-Bearing Due from and Deposits with Banks (1) 28.5 34.9 94.5 95.2 Federal Funds Sold — — — 0.3 Securities Purchased under Agreements to Resell 890.8 463.9 2,578.2 874.1 Securities — Taxable 486.3 402.4 1,409.0 1,106.5 — Nontaxable (2) 0.2 0.3 0.8 1.0 Loans 644.5 664.2 1,946.4 1,881.6 Other Interest-Earning Assets (3) 28.2 17.2 84.4 38.7 Total Interest Income $ 2,530.2 $ 1,935.0 $ 7,482.3 $ 5,125.4 Interest Expense Deposits $ 873.5 $ 716.6 $ 2,653.5 $ 1,914.7 Federal Funds Purchased 29.6 77.5 101.9 205.2 Securities Sold Under Agreements to Repurchase 869.7 454.0 2,535.1 843.5 Other Borrowings 94.8 154.8 278.7 446.3 Senior Notes 44.2 44.1 132.4 125.4 Long-Term Debt 56.1 31.8 167.4 91.4 Total Interest Expense $ 1,967.9 $ 1,478.8 $ 5,869.0 $ 3,626.5 Net Interest Income $ 562.3 $ 456.2 $ 1,613.3 $ 1,498.9 (1) Interest-Bearing Due from and Deposits with Banks includes the interest-bearing component of Cash and Due from Banks and Interest-Bearing Deposits with Banks as presented on the consolidated balance sheets. (2) Non-taxable Securities represent securities that are exempt from U.S. federal income taxes. (3) Other Interest-Earning Assets include certain community development investments, collateral deposits with certain securities depositories and clearing houses, Federal Home Loan Bank and Federal Reserve stock, and money market investments which are classified in Other Assets on the consolidated balance sheets.

Other Operating Income (Tables)

Other Operating Income (Tables)	9 Months Ended
Other Operating Income (Tables)	Sep. 30, 2024
Other Income and Expenses [Abstract]
Components of Other Operating Income	The components of Other Operating Income were as follows. TABLE 68: OTHER OPERATING INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Loan Service Fees $ 14.0 $ 21.2 $ 43.4 $ 61.3 Banking Service Fees 14.2 15.0 40.8 40.8 Bank Owned Life Insurance 18.4 17.3 60.4 51.0 Other Income (1) (2) 65.2 14.7 952.9 17.1 Total Other Operating Income $ 111.8 $ 68.2 $ 1,097.5 $ 170.2 (1) Other Income for three months ended September 30, 2024 includes a $68.1 million pre-tax gain related to the sale of an equity investment.

Other Operating Expense (Tables

Other Operating Expense (Tables)	9 Months Ended
Other Operating Expense (Tables)	Sep. 30, 2024
Other Income and Expenses [Abstract]
Summary of Other Operating Expense	The components of Other Operating Expense were as follows. TABLE 69: OTHER OPERATING EXPENSE THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, In Millions) 2024 2023 2024 2023 Business Promotion $ 19.1 $ 16.2 $ 56.6 $ 53.5 Staff Related 12.4 11.0 34.8 27.7 FDIC Insurance Premiums (1) 7.1 8.3 35.6 21.1 Charitable Contributions (2) 3.3 3.8 79.3 11.3 Other Expenses 44.2 59.2 155.5 182.5 Total Other Operating Expense $ 86.1 $ 98.5 $ 361.8 $ 296.1 (1) FDIC Insurance Premiums for the nine months ended September 30, 2024 includes $14.7 million related to the FDIC Insurance Premium Special Assessment. Refer to Note 20—Commitments and Contingent Liabilities for further information. (2) Charitable Contributions includes a $70 million charitable contribution to the Northern Trust Foundation for the nine months ended September 30, 2024.

Pension (Tables)

Pension (Tables)	9 Months Ended
Pension (Tables)	Sep. 30, 2024
Retirement Benefits [Abstract]
Net Periodic Pension Expense (Benefit)	The following table sets forth the net periodic pension expense for Northern Trust’s U.S. Qualified Plan, Non-U.S. Pension Plans, and U.S. Non-Qualified Plan for the three and nine months ended September 30, 2024 and 2023. TABLE 70: NET PERIODIC PENSION EXPENSE (BENEFIT) U.S. QUALIFIED PLAN THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 13.4 $ 11.5 $ 40.2 $ 34.5 Interest Cost 13.9 13.5 41.7 40.5 Expected Return on Plan Assets (28.9) (25.3) (86.7) (75.9) Amortization Net Actuarial Loss 1.9 0.4 5.7 1.2 Net Periodic Pension Expense $ 0.3 $ 0.1 $ 0.9 $ 0.3 NON-U.S. PENSION PLANS THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 0.5 $ 0.4 $ 1.5 $ 1.1 Interest Cost 1.1 1.2 3.3 3.6 Expected Return on Plan Assets (1.6) (1.6) (4.8) (4.7) Amortization Net Actuarial (Gain) — (0.1) — (0.3) Net Periodic Pension (Benefit) $ — $ (0.1) $ — $ (0.3) U.S. NON-QUALIFIED PLAN THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Service Cost $ 1.2 $ 1.2 $ 3.6 $ 3.6 Interest Cost 1.2 1.3 3.6 3.9 Amortization Net Actuarial Loss 1.3 1.3 3.9 3.9 Net Periodic Pension Expense $ 3.7 $ 3.8 $ 11.1 $ 11.4

Share-Based Compensation Plans

Share-Based Compensation Plans (Tables)	9 Months Ended
Share-Based Compensation Plans (Tables)	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Total Compensation Expense for Share-Based Payment Arrangements	Total compensation expense for share-based payment arrangements and the associated tax impacts were as follows for the three and nine months ended September 30, 2024 and 2023. TABLE 71: TOTAL COMPENSATION EXPENSE FOR SHARE-BASED PAYMENT ARRANGEMENTS THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Restricted Stock Unit Awards $ 13.4 $ 14.7 $ 78.3 $ 80.5 Performance Stock Units 1.3 1.8 19.8 17.8 Total Share-Based Compensation Expense 14.7 16.5 98.1 98.3 Tax Benefits Recognized $ 3.6 $ 4.2 $ 24.0 $ 24.7

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
Variable Interest Entities (Tables)	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Variable Interest Entities	(In Millions) SEPTEMBER 30, 2024 DECEMBER 31, 2023 Investment Carrying Amount Affordable Housing $ 599.3 $ 622.8 New Markets 223.9 266.3 Total Investment Carrying Amount (1) $ 823.2 $ 889.1 Unfunded Commitments Affordable Housing $ 173.4 $ 178.8 New Markets — — Total Unfunded Commitments (2) $ 173.4 $ 178.8 (1) As of September 30, 2024 and December 31, 2023, $795.0 million and $857.0 million are VIEs, respectively. (2) As of September 30, 2024 and December 31, 2023, $167.3 million and $172.0 million relate to undrawn commitments on VIEs, respectively.
Schedule of Income Tax Credits and Other Tax Benefits and Amortization Expense	THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, (In Millions) 2024 2023 2024 2023 Income Tax Credits and Other Income Tax Benefits Affordable Housing $ 21.9 $ 22.5 $ 65.5 $ 67.3 New Markets 5.1 5.9 15.1 17.8 Total Income Tax Credits and Other Income Tax Benefits $ 27.0 $ 28.4 $ 80.6 $ 85.1 Amortization Expense Affordable Housing $ 19.6 $ 19.9 $ 58.5 $ 59.5 New Markets 4.4 4.7 13.3 14.1 Total Amortization Expense $ 24.0 $ 24.6 $ 71.8 $ 73.6

Commitments and Contingent Li_2

Commitments and Contingent Liabilities (Tables)	9 Months Ended
Commitments and Contingent Liabilities (Tables)	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Fair Value, Off-balance Sheet Risks	The following table provides details of Northern Trust's off-balance sheet financial instruments as of September 30, 2024 and December 31, 2023. TABLE 74: SUMMARY OF OFF-BALANCE SHEET FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) ONE YEAR AND LESS OVER ONE YEAR TOTAL ONE YEAR AND LESS OVER ONE YEAR TOTAL Undrawn Commitments (1) $ 11,202.5 $ 18,982.6 $ 30,185.1 $ 11,849.5 $ 18,909.6 $ 30,759.1 Standby Letters of Credit and Financial Guarantees (2)(3) 113,405.2 493.7 113,898.9 85,752.0 639.0 86,391.0 Commercial Letters of Credit 34.8 0.3 35.1 29.2 1.3 30.5 Securities Lent with Indemnification 146,058.1 — 146,058.1 140,539.1 — 140,539.1 Unsettled Reverse Repurchase Agreements 11,544.1 — 11,544.1 27,667.7 — 27,667.7 Total Off-Balance Sheet Financial Instruments $ 282,244.7 $ 19,476.6 $ 301,721.3 $ 265,837.5 $ 19,549.9 $ 285,387.4 (1) These amounts exclude $203.1 million and $222.2 million of commitments participated to others at September 30, 2024 and December 31, 2023, respectively. (2) These amounts include $101.8 million and $39.1 million of standby letters of credit secured by cash deposits or participated to others as of September 30, 2024 and December 31, 2023, respectively. (3)

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
Derivative Financial Instruments (Tables)	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional and Fair Value Amounts of Client-related and Trading Derivative Financial Instruments	The following table shows the notional and fair values of all derivative financial instruments as of September 30, 2024 and December 31, 2023. TABLE 75: NOTIONAL AND FAIR VALUES OF DERIVATIVE FINANCIAL INSTRUMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 NOTIONAL VALUE FAIR VALUE NOTIONAL VALUE FAIR VALUE (In Millions) ASSET (1) LIABILITY (2) ASSET (1) LIABILITY (2) Derivatives Designated as Hedging under GAAP Interest Rate Contracts Fair Value Hedges $ 9,706.3 $ 308.9 $ 289.7 $ 7,042.7 $ 94.7 $ 71.0 Foreign Exchange Contracts Cash Flow Hedges 454.6 1.5 0.5 1,453.6 15.0 42.2 Net Investment Hedges 4,650.7 6.7 103.9 4,077.4 13.3 31.9 Total Derivatives Designated as Hedging under GAAP $ 14,811.6 $ 317.1 $ 394.1 $ 12,573.7 $ 123.0 $ 145.1 Derivatives Not Designated as Hedging under GAAP Non-Designated Risk Management Derivatives Foreign Exchange Contracts $ 1.7 $ — $ — $ 20.7 $ — $ 0.1 Other Financial Derivatives (3) 458.3 — 27.8 867.9 — 25.4 Total Non-Designated Risk Management Derivatives $ 460.0 $ — $ 27.8 $ 888.6 $ — $ 25.5 Client-Related and Trading Derivatives Foreign Exchange Contracts $ 367,149.3 $ 3,044.7 $ 2,979.5 $ 313,336.9 $ 3,238.4 $ 3,181.0 Interest Rate Contracts 15,378.0 157.2 214.4 13,584.1 206.8 298.2 Total Client-Related and Trading Derivatives $ 382,527.3 $ 3,201.9 $ 3,193.9 $ 326,921.0 $ 3,445.2 $ 3,479.2 Total Derivatives Not Designated as Hedging under GAAP $ 382,987.3 $ 3,201.9 $ 3,221.7 $ 327,809.6 $ 3,445.2 $ 3,504.7 Total Gross Derivatives $ 397,798.9 $ 3,519.0 $ 3,615.8 $ 340,383.3 $ 3,568.2 $ 3,649.8 Less: Netting (4) 2,773.1 1,819.9 3,126.7 2,205.4 Total Derivative Financial Instruments $ 745.9 $ 1,795.9 $ 441.5 $ 1,444.4 (1) Derivative assets are reported in Other Assets on the consolidated balance sheets. (2) Derivative liabilities are reported in Other Liabilities on the consolidated balance sheets. (3) Includes swaps related to sales of certain Visa Class B common shares. (4) See further detail in Note 23—Offsetting of Assets and Liabilities.
Cash Flow Hedge Derivative Gains and Losses Recognized in AOCI and Reclassified to Income	The following tables provide fair value and cash flow hedge derivative gains and losses recognized in income during the three- and nine-month periods ended September 30, 2024 and 2023. TABLE 76: LOCATION AND AMOUNT OF FAIR VALUE AND CASH FLOW HEDGE DERIVATIVE GAINS AND LOSSES RECORDED IN INCOME (In Millions) INTEREST INCOME INTEREST EXPENSE OTHER OPERATING INCOME THREE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 Total amounts on the consolidated statements of income $ 2,530.2 $ 1,935.0 $ 1,967.9 $ 1,478.8 $ 111.8 $ 68.2 Gains (Losses) on fair value hedges recognized on Interest Rate Contracts Recognized on derivatives (251.6) 14.1 76.5 (41.8) — — Recognized on hedged items 251.6 (14.1) (76.5) 41.8 — — Amounts related to interest settlements on derivatives 29.3 11.1 (20.1) (24.9) — — Total gains (losses) recognized on fair value hedges $ 29.3 $ 11.1 $ (20.1) $ (24.9) $ — $ — Gains (Losses) on cash flow hedges recognized on Foreign Exchange Contracts Net gains (losses) reclassified from AOCI to net income $ 0.6 $ 14.6 $ — $ — $ — $ 0.3 Total gains (losses) reclassified from AOCI to net income on cash flow hedges $ 0.6 $ 14.6 $ — $ — $ — $ 0.3 (In Millions) INTEREST INCOME INTEREST EXPENSE OTHER OPERATING INCOME NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 2024 2023 Total amounts on the consolidated statements of income $ 7,482.3 $ 5,125.4 $ 5,869.0 $ 3,626.5 $ 1,097.5 $ 170.2 Gains (Losses) on fair value hedges recognized on Interest Rate Contracts Recognized on derivatives (94.1) 0.6 46.5 (42.5) — — Recognized on hedged items 94.1 (0.6) (46.5) 42.5 — — Amounts related to interest settlements on derivatives 79.9 34.7 (59.9) (65.9) — — Total gains (losses) recognized on fair value hedges $ 79.9 $ 34.7 $ (59.9) $ (65.9) $ — $ — Gains (Losses) on cash flow hedges recognized on Foreign Exchange Contracts Net gains (losses) reclassified from AOCI to net income $ 7.1 $ 15.8 $ — $ — $ — $ 1.9 Total gains (losses) reclassified from AOCI to net income on cash flow hedges $ 7.1 $ 15.8 $ — $ — $ — $ 1.9
Location and Amount of Fair Value Hedge Derivative Gains and Losses Recorded in Income	The following table provides the impact of fair value hedge accounting on the carrying value of the designated hedged items as of September 30, 2024 and December 31, 2023. TABLE 77: HEDGED ITEMS IN FAIR VALUE HEDGES SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) CARRYING VALUE OF THE HEDGED ITEMS CUMULATIVE HEDGE ACCOUNTING BASIS ADJUSTMENT (1)(3) CARRYING VALUE OF THE HEDGED ITEMS CUMULATIVE HEDGE ACCOUNTING BASIS ADJUSTMENT (2)(3) Available for Sale Debt Securities (4) $ 7,779.7 $ 171.9 $ 5,048.8 $ 77.5 Senior Notes and Long-Term Subordinated Debt 2,554.9 (190.3) 2,495.9 (248.7) (1) The cumulative hedge accounting basis adjustment includes $1.9 million related to discontinued hedging relationships of AFS debt securities and $17.7 million related to discontinued hedging relationships in the cumulative hedge accounting basis adjustment of senior notes and long-term debt as of September 30, 2024. (2) The cumulative hedge accounting basis adjustment includes $2.2 million related to discontinued hedging relationships of AFS debt securities and $29.6 million related to discontinued hedging relationships in the cumulative hedge accounting basis adjustment of senior notes and long-term debt as of December 31, 2023. (3) Positive (negative) amounts related to AFS securities represent cumulative fair value hedge basis adjustments that will reduce (increase) net interest income in future periods. Positive (negative) amounts related to Senior Notes and Long-Term Subordinated Debt represent cumulative fair value hedge basis adjustments that will increase (reduce) net interest income in future periods. (4) Carrying value represents amortized cost.
Location and Amount of Gains and Losses Recorded in Income for Non-Designated Risk Management Derivative Instruments	The following table provides the location and amount of gains and losses recorded in the consolidated statements of income for the three and nine months ended September 30, 2024 and 2023 for derivative instruments not designated as hedges under GAAP. TABLE 78: LOCATION AND AMOUNT OF GAINS AND LOSSES RECORDED IN INCOME FOR DERIVATIVES NOT DESIGNATED AS HEDGING UNDER GAAP (In Millions) DERIVATIVE GAINS (LOSSES) LOCATION RECOGNIZED IN INCOME AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME THREE MONTHS ENDED SEPTEMBER 30, NINE MONTHS ENDED SEPTEMBER 30, 2024 2023 2024 2023 Non-designated risk management derivatives Foreign Exchange Contracts Other Operating Income $ — $ 1.4 $ (0.2) $ 2.9 Other Financial Derivatives (1) Other Operating Income (13.8) 2.4 (30.4) (18.3) Gains (Losses) from non-designated risk management derivatives $ (13.8) $ 3.8 $ (30.6) $ (15.4) Client-related and trading derivatives Foreign Exchange Contracts Foreign Exchange Trading Income $ 54.1 $ 51.8 $ 169.5 $ 154.9 Interest Rate Contracts Security Commissions and Trading Income 0.9 1.2 2.8 8.1 Gains from client-related and trading derivatives $ 55.0 $ 53.0 $ 172.3 $ 163.0 Total gains from derivatives not designated as hedging under GAAP $ 41.2 $ 56.8 $ 141.7 $ 147.6 (1) Includes swaps related to the sale of certain Visa Class B common shares.

Securities Sold Under Agreeme_2

Securities Sold Under Agreements to Repurchase (Tables)	9 Months Ended
Securities Sold Under Agreements to Repurchase (Tables)	Sep. 30, 2024
Banking and Thrift, Other Disclosure [Abstract]
Repurchase Agreements Accounted for as Secured Borrowings	The following table provides information regarding repurchase agreements that are accounted for as secured borrowings as of September 30, 2024 and December 31, 2023. TABLE 79: REPURCHASE AGREEMENTS ACCOUNTED FOR AS SECURED BORROWINGS REMAINING CONTRACTUAL MATURITY OF THE AGREEMENTS SEPTEMBER 30, 2024 DECEMBER 31, 2023 (In Millions) OVERNIGHT AND CONTINUOUS U.S. Treasury and Agency Securities $ 170.8 $ 784.7 Total Borrowings 170.8 784.7 Net Amount of Recognized Liabilities for Repurchase Agreements in Note 23 170.8 784.7

Offsetting of Assets and Liab_2

Offsetting of Assets and Liabilities (Tables)	9 Months Ended
Offsetting of Assets and Liabilities (Tables)	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell	The following table provides information regarding the offsetting of derivative assets and securities purchased under agreements to resell within the consolidated balance sheets as of September 30, 2024 and December 31, 2023. TABLE 80: OFFSETTING OF DERIVATIVE ASSETS AND SECURITIES PURCHASED UNDER AGREEMENTS TO RESELL SEPTEMBER 30, 2024 (In Millions) GROSS RECOGNIZED ASSETS GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Assets (1) Foreign Exchange Contracts Over the Counter (OTC) $ 2,814.6 $ 2,664.5 $ 150.1 $ 10.3 $ 139.8 Interest Rate Swaps OTC 466.1 108.6 357.5 — 357.5 Total Derivatives Subject to a Master Netting Arrangement 3,280.7 2,773.1 507.6 10.3 497.3 Total Derivatives Not Subject to a Master Netting Arrangement 238.3 — 238.3 — 238.3 Total Derivatives 3,519.0 2,773.1 745.9 10.3 735.6 Securities Purchased under Agreements to Resell (2) $ 66,358.2 $ 65,376.6 $ 981.6 $ 981.6 $ — DECEMBER 31, 2023 (In Millions) GROSS RECOGNIZED ASSETS GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Assets (1) Foreign Exchange Contracts OTC $ 3,006.3 $ 2,937.2 $ 69.1 $ 12.2 $ 56.9 Interest Rate Swaps OTC 301.4 189.5 111.9 — 111.9 Interest Rate Swaps Exchange Cleared 0.1 — 0.1 — 0.1 Total Derivatives Subject to a Master Netting Arrangement 3,307.8 3,126.7 181.1 12.2 168.9 Total Derivatives Not Subject to a Master Netting Arrangement 260.4 — 260.4 — 260.4 Total Derivatives 3,568.2 3,126.7 441.5 12.2 429.3 Securities Purchased under Agreements to Resell (2) $ 62,860.2 $ 62,075.5 $ 784.7 $ 784.7 $ — (1) Derivative assets are reported in Other Assets on the consolidated balance sheets. Other Assets (excluding derivative assets) totaled $10.4 billion and $10.3 billion as of September 30, 2024 and December 31, 2023, respectively. (2) Offsetting of Securities Purchased under Agreements to Resell primarily relates to our involvement in the FICC. (3) Including cash collateral received from counterparties. (4) Including financial assets accepted as collateral which are received from counterparties. (5) Northern Trust did not possess any cash collateral that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of September 30, 2024 and December 31, 2023.
Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase	The following table provides information regarding the offsetting of derivative liabilities and securities sold under agreements to repurchase within the consolidated balance sheets as of September 30, 2024 and December 31, 2023. TABLE 81: OFFSETTING OF DERIVATIVE LIABILITIES AND SECURITIES SOLD UNDER AGREEMENTS TO REPURCHASE SEPTEMBER 30, 2024 (In Millions) GROSS RECOGNIZED LIABILITIES GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,226.4 $ 1,784.0 $ 442.4 $ — $ 442.4 Interest Rate Swaps OTC 504.1 9.1 495.0 — 495.0 Other Financial Derivatives 27.8 26.8 1.0 — 1.0 Total Derivatives Subject to a Master Netting Arrangement 2,758.3 1,819.9 938.4 — 938.4 Total Derivatives Not Subject to a Master Netting Arrangement 857.5 — 857.5 — 857.5 Total Derivatives 3,615.8 1,819.9 1,795.9 — 1,795.9 Securities Sold under Agreements to Repurchase (2) $ 65,547.4 $ 65,376.6 $ 170.8 $ 170.8 $ — DECEMBER 31, 2023 (In Millions) GROSS RECOGNIZED LIABILITIES GROSS AMOUNTS OFFSET IN THE BALANCE SHEET (3) NET AMOUNTS PRESENTED IN THE BALANCE SHEET GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET (4) NET AMOUNT (5) Derivative Liabilities (1) Foreign Exchange Contracts OTC $ 2,411.7 $ 2,175.7 $ 236.0 $ — $ 236.0 Interest Rate Swaps OTC 368.3 6.0 362.3 — 362.3 Interest Rate Swaps Exchange Cleared 0.9 — 0.9 — 0.9 Other Financial Derivatives 25.4 23.7 1.7 — 1.7 Total Derivatives Subject to a Master Netting Arrangement 2,806.3 2,205.4 600.9 — 600.9 Total Derivatives Not Subject to a Master Netting Arrangement 843.5 — 843.5 — 843.5 Total Derivatives 3,649.8 2,205.4 1,444.4 — 1,444.4 Securities Sold under Agreements to Repurchase (2) $ 62,860.2 $ 62,075.5 $ 784.7 $ 784.7 $ — (1) Derivative liabilities are reported in Other Liabilities on the consolidated balance sheets. Other Liabilities (excluding derivative liabilities) totaled $3.3 billion and $4.0 billion as of September 30, 2024 and December 31, 2023, respectively. (2) Offsetting of Securities Sold under Agreements to Repurchase primarily relates to our involvement in the FICC. (3) Including cash collateral deposited with counterparties. (4) Including financial assets accepted as collateral which are deposited with counterparties. (5) Northern Trust did not place any cash collateral with counterparties that was not offset in the consolidated balance sheets that could have been used to offset the net amounts presented in the consolidated balance sheets as of September 30, 2024 and December 31, 2023.

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) shares in Millions, $ in Millions	Sep. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security	Jun. 30, 2016 shares	Jun. 30, 2015 shares
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Aggregate market value	$ 28,311.9	$ 23,089.8
Visa Class B
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Shares issued (in shares) \| shares			1.1	1
LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of available for sale securities portfolio \| security	943	929
Aggregate market value	$ 21,800	$ 19,500
LEVEL 3 \| Fair Value, Measurements, Nonrecurring \| Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	25.8
LEVEL 3 \| Fair Value, Measurements, Nonrecurring \| Measurement Input, Discount Rate \| Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 25.8	$ 43.3
LEVEL 3 \| Fair Value, Measurements, Nonrecurring \| Measurement Input, Discount Rate \| Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input		0
LEVEL 3 \| Fair Value, Measurements, Nonrecurring \| Measurement Input, Discount Rate \| Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.200	0.200
LEVEL 3 \| Fair Value, Measurements, Nonrecurring \| Measurement Input, Discount Rate \| WEIGHTED-AVERAGE INPUT VALUES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.200	0.020

Fair Value Measurements (Level

Fair Value Measurements (Level 3 Significant Unobservable Inputs) (Details) $ in Millions	Sep. 30, 2024 USD ($) month	Dec. 31, 2023 USD ($) month
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities \| $	$ 1,795.9	$ 1,444.4
Swap \| Fair Value, Measurements, Recurring \| LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities \| $	$ 27.8	$ 25.4
Swap \| Conversion Rate \| Fair Value, Measurements, Recurring \| LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	1.54	1.59
Swap \| Visa Class A Appreciation \| Fair Value, Measurements, Recurring \| LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0.0906	0.1049
Swap \| Expected Duration \| Fair Value, Measurements, Recurring \| LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	26.5	13
Swap \| Expected Duration \| Fair Value, Measurements, Recurring \| LEVEL 3 \| Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	13	9
Swap \| Expected Duration \| Fair Value, Measurements, Recurring \| LEVEL 3 \| Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	35.5	27

Fair Value Measurements (Recurr

Fair Value Measurements (Recurring Basis Hierarchy Leveling) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	$ 28,311.9	$ 23,089.8
Derivative Assets	3,519	3,568.2
NETTING	(2,773.1)	(3,126.7)
Derivative Assets	745.9	441.5
Derivative Liabilities	3,615.8	3,649.8
NETTING	(1,819.9)	(2,205.4)
Derivative Liabilities	1,795.9	1,444.4
Cross Product Collateral Adjustment
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(2,000)	(2,100)
NETTING	(1,000)	(1,200)
U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	6,481.7	3,622.2
Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	306	295.8
Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	13,653.7	11,553
Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	327.1	264.4
Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	201.1	279.5
Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	239.7	347.1
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	3,988.1	2,899.9
Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	2,487.4	2,962.6
Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	627.1	865.3
LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	21,800	19,500
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	28,311.9	23,089.8
Fair Value, Measurements, Recurring \| U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	6,481.7	3,622.2
Fair Value, Measurements, Recurring \| Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	306	295.8
Fair Value, Measurements, Recurring \| Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	13,653.7	11,553
Fair Value, Measurements, Recurring \| Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	327.1	264.4
Fair Value, Measurements, Recurring \| Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	201.1	279.5
Fair Value, Measurements, Recurring \| Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	239.7	347.1
Fair Value, Measurements, Recurring \| Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	3,988.1	2,899.9
Fair Value, Measurements, Recurring \| Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	2,487.4	2,962.6
Fair Value, Measurements, Recurring \| Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	627.1	865.3
Fair Value, Measurements, Recurring \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	112.8
Money Market Investment		95
NETTING	(2,773.1)	(3,126.7)
Derivative Assets	745.9	441.5
Fair Value, Measurements, Recurring \| Other Assets \| Money market investment
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	85
Fair Value, Measurements, Recurring \| Other Assets \| Visa Class C shares
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	27.8
Fair Value, Measurements, Recurring \| Other Assets \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(2,664.5)	(2,937.2)
Derivative Assets	388.4	329.5
Fair Value, Measurements, Recurring \| Other Assets \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(108.6)	(189.5)
Derivative Assets	357.5	112
Fair Value, Measurements, Recurring \| Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(1,819.9)	(2,205.4)
Derivative Liabilities	1,795.9	1,444.4
Fair Value, Measurements, Recurring \| Other Liabilities \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(1,784)	(2,175.7)
Derivative Liabilities	1,299.9	1,079.5
Fair Value, Measurements, Recurring \| Other Liabilities \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(9.1)	(6)
Derivative Liabilities	495	363.2
Fair Value, Measurements, Recurring \| Other Liabilities \| Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
NETTING	(26.8)	(23.7)
Derivative Liabilities	1	1.7
Fair Value, Measurements, Recurring \| LEVEL 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	6,481.7	3,622.2
Fair Value, Measurements, Recurring \| LEVEL 1 \| U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	6,481.7	3,622.2
Fair Value, Measurements, Recurring \| LEVEL 1 \| Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	85
Money Market Investment		95
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Assets \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Assets \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Liabilities \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Liabilities \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 1 \| Other Liabilities \| Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	21,830.2	19,467.6
Fair Value, Measurements, Recurring \| LEVEL 2 \| U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 2 \| Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	306	295.8
Fair Value, Measurements, Recurring \| LEVEL 2 \| Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	13,653.7	11,553
Fair Value, Measurements, Recurring \| LEVEL 2 \| Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	327.1	264.4
Fair Value, Measurements, Recurring \| LEVEL 2 \| Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	201.1	279.5
Fair Value, Measurements, Recurring \| LEVEL 2 \| Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	239.7	347.1
Fair Value, Measurements, Recurring \| LEVEL 2 \| Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	3,988.1	2,899.9
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	2,487.4	2,962.6
Fair Value, Measurements, Recurring \| LEVEL 2 \| Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	627.1	865.3
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	27.8
Money Market Investment		0
Derivative Assets	3,519	3,568.2
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Assets \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	3,052.9	3,266.7
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Assets \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	466.1	301.5
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	3,588	3,624.4
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Liabilities \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	3,083.9	3,255.2
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Liabilities \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	504.1	369.2
Fair Value, Measurements, Recurring \| LEVEL 2 \| Other Liabilities \| Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 3
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Obligations of States and Political Subdivisions
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Government Sponsored Agency
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Non-U.S. Government
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Corporate Debt
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Covered Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Asset-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Commercial Mortgage-Backed
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available for Sale	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Equity Securities	0
Money Market Investment		0
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Assets \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Assets \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Assets	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	27.8	25.4
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Liabilities \| Foreign Exchange Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Liabilities \| Interest Rate Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	0	0
Fair Value, Measurements, Recurring \| LEVEL 3 \| Other Liabilities \| Other Financial Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative Liabilities	$ 27.8	$ 25.4

Fair Value Measurements (Change

Fair Value Measurements (Changes in Level 3 Liabilities) (Details) - SWAPS RELATED TO SALE OF CERTAIN VISA CLASS B COMMON SHARES - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value liabilities beginning balance	$ 30.6	$ 36.4	$ 25.4	$ 34.8
Total (Gains) Losses:
Included in Earnings	13.8	(2.4)	30.4	16.1
Purchases, Issues, Sales, and Settlements
Settlements	(16.6)	(5.1)	(28)	(22)
Fair value liabilities ending balance	$ 27.8	$ 28.9	$ 27.8	$ 28.9

Fair Value Measurements (Nonrec

Fair Value Measurements (Nonrecurring Basis Significant Unobservable Inputs) (Details) - Fair Value, Measurements, Nonrecurring - LEVEL 3 $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Measurement Input, Discount Rate \| Lower Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input		0
Measurement Input, Discount Rate \| Upper Limit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.200	0.200
Measurement Input, Discount Rate \| WEIGHTED-AVERAGE INPUT VALUES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans, measurement input	0.200	0.020
Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FAIR VALUE	$ 25.8
Loans \| Measurement Input, Discount Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
FAIR VALUE	$ 25.8	$ 43.3

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value of Financial Instruments) (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023
FINANCIAL ASSETS
Cash and Due from Banks	$ 6,871,700,000	$ 4,791,500,000
Federal Reserve and Other Central Bank Deposits	40,848,800,000	34,326,200,000
Interest-Bearing Deposits with Banks	1,606,800,000	1,939,000,000
Securities Purchased under Agreements to Resell	981,600,000	784,700,000
Debt Securities - Held to Maturity	21,372,000,000	24,473,000,000
FINANCIAL LIABILITIES
Deposits	121,183,300,000	116,164,000,000
Federal Funds Purchased	2,761,900,000	3,045,400,000
Securities Sold Under Agreements to Repurchase	170,800,000	784,700,000
Other Borrowings	6,903,200,000	6,567,800,000
Senior Notes	2,820,900,000	2,773,200,000
Unfunded Commitments	0	0
BOOK VALUE
FINANCIAL ASSETS
Cash and Due from Banks	6,871,700,000	4,791,500,000
Federal Reserve and Other Central Bank Deposits	40,848,800,000	34,326,200,000
Interest-Bearing Deposits with Banks	1,606,800,000	1,939,000,000
Securities Purchased under Agreements to Resell	981,600,000	784,700,000
Debt Securities - Held to Maturity	22,708,600,000	26,221,700,000
Loans
Held for Investment	41,765,500,000	47,438,300,000
Other Assets	1,450,500,000	1,476,600,000
FINANCIAL LIABILITIES
Deposits	121,183,300,000	116,164,000,000
Federal Funds Purchased	2,761,900,000	3,045,400,000
Securities Sold Under Agreements to Repurchase	170,800,000	784,700,000
Other Borrowings	6,903,200,000	6,567,800,000
Senior Notes	2,820,900,000	2,773,200,000
Long-Term Debt	4,077,200,000	4,065,000,000
Unfunded Commitments	173,400,000	178,800,000
Other Liabilities	47,900,000	74,900,000
TOTAL ESTIMATED FAIR VALUE
FINANCIAL ASSETS
Cash and Due from Banks	6,871,700,000	4,791,500,000
Federal Reserve and Other Central Bank Deposits	40,848,800,000	34,326,200,000
Interest-Bearing Deposits with Banks	1,606,800,000	1,939,000,000
Securities Purchased under Agreements to Resell	981,600,000	784,700,000
Debt Securities - Held to Maturity	21,372,000,000	24,473,000,000
Loans
Held for Investment	41,488,700,000	47,598,300,000
Other Assets	1,446,000,000	1,458,000,000
FINANCIAL LIABILITIES
Deposits	123,302,500,000	116,207,600,000
Federal Funds Purchased	2,761,900,000	3,045,400,000
Securities Sold Under Agreements to Repurchase	170,800,000	784,700,000
Other Borrowings	6,940,000,000	6,607,400,000
Senior Notes	2,869,100,000	2,798,100,000
Long-Term Debt	4,248,100,000	4,186,800,000
Unfunded Commitments	173,400,000	178,800,000
Other Liabilities	47,900,000	74,900,000
TOTAL ESTIMATED FAIR VALUE \| LEVEL 1
FINANCIAL ASSETS
Cash and Due from Banks	6,871,700,000	4,791,500,000
Federal Reserve and Other Central Bank Deposits	0	0
Interest-Bearing Deposits with Banks	0	0
Securities Purchased under Agreements to Resell	0	0
Debt Securities - Held to Maturity	0	0
Loans
Held for Investment	0	0
Other Assets	87,900,000	86,100,000
FINANCIAL LIABILITIES
Deposits	0	0
Federal Funds Purchased	0	0
Securities Sold Under Agreements to Repurchase	0	0
Other Borrowings	0	0
Senior Notes	0	0
Long-Term Debt	0	0
Unfunded Commitments	0	0
Other Liabilities	0	0
TOTAL ESTIMATED FAIR VALUE \| LEVEL 2
FINANCIAL ASSETS
Cash and Due from Banks	0	0
Federal Reserve and Other Central Bank Deposits	40,848,800,000	34,326,200,000
Interest-Bearing Deposits with Banks	1,606,800,000	1,939,000,000
Securities Purchased under Agreements to Resell	981,600,000	784,700,000
Debt Securities - Held to Maturity	21,372,000,000	24,473,000,000
Loans
Held for Investment	0	0
Other Assets	1,358,100,000	1,371,900,000
FINANCIAL LIABILITIES
Deposits	123,302,500,000	116,207,600,000
Federal Funds Purchased	2,761,900,000	3,045,400,000
Securities Sold Under Agreements to Repurchase	170,800,000	784,700,000
Other Borrowings	6,940,000,000	6,607,400,000
Senior Notes	2,869,100,000	2,798,100,000
Long-Term Debt	4,248,100,000	4,186,800,000
Unfunded Commitments	173,400,000	178,800,000
Other Liabilities	0	0
TOTAL ESTIMATED FAIR VALUE \| LEVEL 3
FINANCIAL ASSETS
Cash and Due from Banks	0	0
Federal Reserve and Other Central Bank Deposits	0	0
Interest-Bearing Deposits with Banks	0	0
Securities Purchased under Agreements to Resell	0	0
Debt Securities - Held to Maturity	0	0
Loans
Held for Investment	41,488,700,000	47,598,300,000
Other Assets	0	0
FINANCIAL LIABILITIES
Deposits	0	0
Federal Funds Purchased	0	0
Securities Sold Under Agreements to Repurchase	0	0
Other Borrowings	0	0
Senior Notes	0	0
Long-Term Debt	0	0
Unfunded Commitments	0	0
Other Liabilities	$ 47,900,000	$ 74,900,000

Securities (Reconciliation of A

Securities (Reconciliation of Amortized Cost to Fair Value of Securities Available for Sale) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Summary of Investment Holdings [Line Items]
AMORTIZED COST	$ 28,513.1	$ 23,659
GROSS UNREALIZED GAINS	44.3	13.2
GROSS UNREALIZED LOSSES	245.5	582.4
FAIR VALUE	28,311.9	23,089.8
U.S. Government
Summary of Investment Holdings [Line Items]
AMORTIZED COST	6,497.4	3,681.5
GROSS UNREALIZED GAINS	3.4	2.2
GROSS UNREALIZED LOSSES	19.1	61.5
FAIR VALUE	6,481.7	3,622.2
Obligations of States and Political Subdivisions
Summary of Investment Holdings [Line Items]
AMORTIZED COST	321.6	315.8
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	15.6	20
FAIR VALUE	306	295.8
Government Sponsored Agency
Summary of Investment Holdings [Line Items]
AMORTIZED COST	13,749	11,744.3
GROSS UNREALIZED GAINS	19	9
GROSS UNREALIZED LOSSES	114.3	200.3
FAIR VALUE	13,653.7	11,553
Non-U.S. Government
Summary of Investment Holdings [Line Items]
AMORTIZED COST	341.5	284.8
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	14.4	20.4
FAIR VALUE	327.1	264.4
Corporate Debt
Summary of Investment Holdings [Line Items]
AMORTIZED COST	205	287.5
GROSS UNREALIZED GAINS	0.1	0.1
GROSS UNREALIZED LOSSES	4	8.1
FAIR VALUE	201.1	279.5
Covered Bonds
Summary of Investment Holdings [Line Items]
AMORTIZED COST	242.2	356.8
GROSS UNREALIZED GAINS	0.6	0
GROSS UNREALIZED LOSSES	3.1	9.7
FAIR VALUE	239.7	347.1
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Summary of Investment Holdings [Line Items]
AMORTIZED COST	4,019.7	3,013.8
GROSS UNREALIZED GAINS	14	0.1
GROSS UNREALIZED LOSSES	45.6	114
FAIR VALUE	3,988.1	2,899.9
Other Asset-Backed
Summary of Investment Holdings [Line Items]
AMORTIZED COST	2,494.5	3,061
GROSS UNREALIZED GAINS	7.1	1.6
GROSS UNREALIZED LOSSES	14.2	100
FAIR VALUE	2,487.4	2,962.6
Commercial Mortgage-Backed
Summary of Investment Holdings [Line Items]
AMORTIZED COST	642.2	913.5
GROSS UNREALIZED GAINS	0.1	0.2
GROSS UNREALIZED LOSSES	15.2	48.4
FAIR VALUE	$ 627.1	$ 865.3

Securities (Remaining Maturity

Securities (Remaining Maturity of Securities Available for Sale and Held to Maturity) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Available for Sale - Amortized Cost
ONE YEAR OR LESS	$ 4,274.1
ONE TO FIVE YEARS	17,685.9
FIVE TO TEN YEARS	5,564.3
OVER TEN YEARS	988.8
AMORTIZED COST	28,513.1	$ 23,659
Available for Sale - Fair Value
ONE YEAR OR LESS	4,252.4
ONE TO FIVE YEARS	17,573.1
FIVE TO TEN YEARS	5,515.8
OVER TEN YEARS	970.6
FAIR VALUE	28,311.9	23,089.8
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	5,531.2
ONE TO FIVE YEARS	10,933.3
FIVE TO TEN YEARS	4,163.8
OVER TEN YEARS	2,080.3
Amortized Cost	22,708.6	26,221.7
Held to Maturity - Fair Value
ONE YEAR OR LESS	5,426.7
ONE TO FIVE YEARS	10,316.7
FIVE TO TEN YEARS	3,873.8
OVER TEN YEARS	1,754.8
Fair Value	21,372	24,473
U.S. Government
Available for Sale - Amortized Cost
ONE YEAR OR LESS	496.2
ONE TO FIVE YEARS	3,862
FIVE TO TEN YEARS	2,139.2
OVER TEN YEARS	0
AMORTIZED COST	6,497.4	3,681.5
Available for Sale - Fair Value
ONE YEAR OR LESS	493.9
ONE TO FIVE YEARS	3,852.1
FIVE TO TEN YEARS	2,135.7
OVER TEN YEARS	0
FAIR VALUE	6,481.7	3,622.2
Obligations of States and Political Subdivisions
Available for Sale - Amortized Cost
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	206.3
FIVE TO TEN YEARS	115.3
OVER TEN YEARS	0
AMORTIZED COST	321.6	315.8
Available for Sale - Fair Value
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	198
FIVE TO TEN YEARS	108
OVER TEN YEARS	0
FAIR VALUE	306	295.8
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	106.8
ONE TO FIVE YEARS	1,302.2
FIVE TO TEN YEARS	935.6
OVER TEN YEARS	205.3
Amortized Cost	2,549.9	2,563.9
Held to Maturity - Fair Value
ONE YEAR OR LESS	106.3
ONE TO FIVE YEARS	1,298.7
FIVE TO TEN YEARS	931.9
OVER TEN YEARS	202.6
Fair Value	2,539.5	2,492
Government Sponsored Agency
Available for Sale - Amortized Cost
ONE YEAR OR LESS	3,223.6
ONE TO FIVE YEARS	7,181
FIVE TO TEN YEARS	2,472.3
OVER TEN YEARS	872.1
AMORTIZED COST	13,749	11,744.3
Available for Sale - Fair Value
ONE YEAR OR LESS	3,209.3
ONE TO FIVE YEARS	7,141.1
FIVE TO TEN YEARS	2,449.7
OVER TEN YEARS	853.6
FAIR VALUE	13,653.7	11,553
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	917.4
ONE TO FIVE YEARS	3,345.6
FIVE TO TEN YEARS	2,874.6
OVER TEN YEARS	1,689.2
Amortized Cost	8,826.8	9,355.3
Held to Maturity - Fair Value
ONE YEAR OR LESS	843.7
ONE TO FIVE YEARS	3,056.6
FIVE TO TEN YEARS	2,617.6
OVER TEN YEARS	1,487.7
Fair Value	8,005.6	8,345.2
Non-U.S. Government
Available for Sale - Amortized Cost
ONE YEAR OR LESS	69.2
ONE TO FIVE YEARS	272.3
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
AMORTIZED COST	341.5	284.8
Available for Sale - Fair Value
ONE YEAR OR LESS	68.8
ONE TO FIVE YEARS	258.3
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
FAIR VALUE	327.1	264.4
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	1,254.9
ONE TO FIVE YEARS	1,072.4
FIVE TO TEN YEARS	34
OVER TEN YEARS	0
Amortized Cost	2,361.3	4,789.1
Held to Maturity - Fair Value
ONE YEAR OR LESS	1,252.6
ONE TO FIVE YEARS	1,013.1
FIVE TO TEN YEARS	30.6
OVER TEN YEARS	0
Fair Value	2,296.3	4,698.6
Corporate Debt
Available for Sale - Amortized Cost
ONE YEAR OR LESS	114.6
ONE TO FIVE YEARS	90.4
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
AMORTIZED COST	205	287.5
Available for Sale - Fair Value
ONE YEAR OR LESS	114.1
ONE TO FIVE YEARS	87
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
FAIR VALUE	201.1	279.5
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	249.3
ONE TO FIVE YEARS	226.1
FIVE TO TEN YEARS	15.7
OVER TEN YEARS	0
Amortized Cost	491.1	646.1
Held to Maturity - Fair Value
ONE YEAR OR LESS	245.5
ONE TO FIVE YEARS	217.2
FIVE TO TEN YEARS	13.7
OVER TEN YEARS	0
Fair Value	476.4	617.9
Covered Bonds
Available for Sale - Amortized Cost
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	242.2
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
AMORTIZED COST	242.2	356.8
Available for Sale - Fair Value
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	239.7
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
FAIR VALUE	239.7	347.1
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	660.6
ONE TO FIVE YEARS	1,254.4
FIVE TO TEN YEARS	209.8
OVER TEN YEARS	0
Amortized Cost	2,124.8	2,208.6
Held to Maturity - Fair Value
ONE YEAR OR LESS	656.9
ONE TO FIVE YEARS	1,200.5
FIVE TO TEN YEARS	195
OVER TEN YEARS	0
Fair Value	2,052.4	2,100.6
Certificates of Deposit
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	542.6
ONE TO FIVE YEARS	0
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
Amortized Cost	542.6	585.1
Held to Maturity - Fair Value
ONE YEAR OR LESS	542.3
ONE TO FIVE YEARS	0
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
Fair Value	542.3	584.4
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Available for Sale - Amortized Cost
ONE YEAR OR LESS	192.8
ONE TO FIVE YEARS	3,520.1
FIVE TO TEN YEARS	306.8
OVER TEN YEARS	0
AMORTIZED COST	4,019.7	3,013.8
Available for Sale - Fair Value
ONE YEAR OR LESS	190.9
ONE TO FIVE YEARS	3,501.1
FIVE TO TEN YEARS	296.1
OVER TEN YEARS	0
FAIR VALUE	3,988.1	2,899.9
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	1,723.9
ONE TO FIVE YEARS	3,332.5
FIVE TO TEN YEARS	5.7
OVER TEN YEARS	0
Amortized Cost	5,062.1	5,245.5
Held to Maturity - Fair Value
ONE YEAR OR LESS	1,705.6
ONE TO FIVE YEARS	3,156.7
FIVE TO TEN YEARS	4.8
OVER TEN YEARS	0
Fair Value	4,867.1	4,953.8
Other Asset-Backed
Available for Sale - Amortized Cost
ONE YEAR OR LESS	154.6
ONE TO FIVE YEARS	1,726.6
FIVE TO TEN YEARS	496.6
OVER TEN YEARS	116.7
AMORTIZED COST	2,494.5	3,061
Available for Sale - Fair Value
ONE YEAR OR LESS	152.6
ONE TO FIVE YEARS	1,719.6
FIVE TO TEN YEARS	498.2
OVER TEN YEARS	117
FAIR VALUE	2,487.4	2,962.6
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	4.7
ONE TO FIVE YEARS	69.2
FIVE TO TEN YEARS	37.7
OVER TEN YEARS	0
Amortized Cost	111.6	214.2
Held to Maturity - Fair Value
ONE YEAR OR LESS	4.5
ONE TO FIVE YEARS	69.7
FIVE TO TEN YEARS	37.7
OVER TEN YEARS	0
Fair Value	111.9	214.4
Commercial Mortgage-Backed
Available for Sale - Amortized Cost
ONE YEAR OR LESS	23.1
ONE TO FIVE YEARS	585
FIVE TO TEN YEARS	34.1
OVER TEN YEARS	0
AMORTIZED COST	642.2	913.5
Available for Sale - Fair Value
ONE YEAR OR LESS	22.8
ONE TO FIVE YEARS	576.2
FIVE TO TEN YEARS	28.1
OVER TEN YEARS	0
FAIR VALUE	627.1	865.3
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	37.6
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
Amortized Cost	37.6	37.6
Held to Maturity - Fair Value
ONE YEAR OR LESS	0
ONE TO FIVE YEARS	36.6
FIVE TO TEN YEARS	0
OVER TEN YEARS	0
Fair Value	36.6	36.8
Other
Held to Maturity - Amortized Cost
ONE YEAR OR LESS	71
ONE TO FIVE YEARS	293.3
FIVE TO TEN YEARS	50.7
OVER TEN YEARS	185.8
Amortized Cost	600.8	576.3
Held to Maturity - Fair Value
ONE YEAR OR LESS	69.3
ONE TO FIVE YEARS	267.6
FIVE TO TEN YEARS	42.5
OVER TEN YEARS	64.5
Fair Value	$ 443.9	$ 429.3

Securities (Securities with Unr

Securities (Securities with Unrealized Losses) (Details) $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($) security
FAIR VALUE
LESS THAN 12 MONTHS	$ 8,034.3	$ 503
12 MONTHS OR LONGER	10,098.5	18,932.3
TOTAL	18,132.8	19,435.3
UNREALIZED LOSSES
LESS THAN 12 MONTHS	11.2	24.1
12 MONTHS OR LONGER	232.7	544.2
TOTAL	243.9	568.3
U.S. Government
FAIR VALUE
LESS THAN 12 MONTHS	5,293	0
12 MONTHS OR LONGER	630.9	3,364.7
TOTAL	5,923.9	3,364.7
UNREALIZED LOSSES
LESS THAN 12 MONTHS	6.9	0
12 MONTHS OR LONGER	12.2	61.5
TOTAL	19.1	61.5
Obligations of States and Political Subdivisions
FAIR VALUE
LESS THAN 12 MONTHS	0	87.8
12 MONTHS OR LONGER	305.9	208
TOTAL	305.9	295.8
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	5.9
12 MONTHS OR LONGER	15.6	14.1
TOTAL	15.6	20
Government Sponsored Agency
FAIR VALUE
LESS THAN 12 MONTHS	2,028.2	331
12 MONTHS OR LONGER	6,676.9	9,486.6
TOTAL	8,705.1	9,817.6
UNREALIZED LOSSES
LESS THAN 12 MONTHS	3.6	11.5
12 MONTHS OR LONGER	110.7	188.8
TOTAL	114.3	200.3
Non-U.S. Government
FAIR VALUE
LESS THAN 12 MONTHS	55.3	0
12 MONTHS OR LONGER	271.9	264.5
TOTAL	327.2	264.5
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	0
12 MONTHS OR LONGER	14.4	20.4
TOTAL	14.4	20.4
Corporate Debt
FAIR VALUE
LESS THAN 12 MONTHS	0	4.4
12 MONTHS OR LONGER	104.5	143
TOTAL	104.5	147.4
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	0.1
12 MONTHS OR LONGER	2.4	2.1
TOTAL	2.4	$ 2.2
Number of debt securities, available-for-sale \| security		3
Debt securities, available-for-sale, continuous unrealized loss position with credit loss	43.1	$ 98.4
Debt securities, available-for-sale, continuous unrealized loss position, accumulated loss, with credit loss	1.6	5.9
Net amount of recognized liabilities for repurchase agreements	0.2	1.2
Covered Bonds
FAIR VALUE
LESS THAN 12 MONTHS	0	0
12 MONTHS OR LONGER	126.7	213.2
TOTAL	126.7	213.2
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	0
12 MONTHS OR LONGER	3.1	9.7
TOTAL	3.1	9.7
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
FAIR VALUE
LESS THAN 12 MONTHS	645.3	0
12 MONTHS OR LONGER	917.6	2,477
TOTAL	1,562.9	2,477
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0.7	0
12 MONTHS OR LONGER	44.9	105.8
TOTAL	45.6	$ 105.8
Number of debt securities, available-for-sale \| security		1
Debt securities, available-for-sale, continuous unrealized loss position with credit loss		$ 71
Debt securities, available-for-sale, continuous unrealized loss position, accumulated loss, with credit loss		8.2
Other Asset-Backed
FAIR VALUE
LESS THAN 12 MONTHS	0	19.8
12 MONTHS OR LONGER	476.3	1,998.7
TOTAL	476.3	2,018.5
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	2
12 MONTHS OR LONGER	14.2	98
TOTAL	14.2	100
Commercial Mortgage-Backed
FAIR VALUE
LESS THAN 12 MONTHS	12.5	60
12 MONTHS OR LONGER	587.8	776.6
TOTAL	600.3	836.6
UNREALIZED LOSSES
LESS THAN 12 MONTHS	0	4.6
12 MONTHS OR LONGER	15.2	43.8
TOTAL	$ 15.2	$ 48.4

Securities (Narrative) (Details

Securities (Narrative) (Details) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
Securities (Narrative) (Details) $ in Millions	Jan. 31, 2024 USD ($)	Nov. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) security	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) security	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) security
Debt and Equity Securities, FV-NI [Line Items]
Number of securities in an unrealized loss position \| security			693		693		898
Total fair value			$ 18,132.8		$ 18,132.8		$ 19,435.3
Debt securities, unrealized losses			243.9		243.9		568.3
Investment security gains (losses)	$ (189.4)	$ (176.4)	0	$ 0	(189.3)	$ 6.9
Provision for (release of) credit losses			8.4	14.6	8.5	14.1
Held to maturity securities			22,708.6		22,708.6		26,221.7
Debt securities, held-to-maturity, accumulated unrecognized loss			$ 1,347.2		$ 1,347.2		$ 1,755.6
Percentage of debt securities, held-to-maturity, portfolio			1		1		1
Proceeds from sale of investment securities			$ 0	17.1	$ 2,000	2,200
Realized investment gains (losses)			$ 0	0	$ (189.3)	6.9
Moodys And Standard Poors A Or Higher Rating
Debt and Equity Securities, FV-NI [Line Items]
Percentage of debt securities, held-to-maturity, portfolio			0.96		0.96		0.97
BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			$ 337.1		$ 337.1		$ 334
Percentage of debt securities, held-to-maturity, portfolio			0.01		0.01		0.01
NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			$ 575.5		$ 575.5		$ 560.9
Percentage of debt securities, held-to-maturity, portfolio			0.03		0.03		0.02
Government Sponsored Agency
Debt and Equity Securities, FV-NI [Line Items]
Total fair value			$ 8,705.1		$ 8,705.1		$ 9,817.6
Debt securities, unrealized losses			114.3		114.3		200.3
Held to maturity securities			8,826.8		8,826.8		9,355.3
Debt securities, held-to-maturity, accumulated unrecognized loss			823.8		823.8		1,012.4
Realized investment gains (losses)			0	0	(23)	0
Government Sponsored Agency \| BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Government Sponsored Agency \| NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Debt and Equity Securities, FV-NI [Line Items]
Total fair value			1,562.9		1,562.9		2,477
Debt securities, unrealized losses			45.6		45.6		105.8
Held to maturity securities			5,062.1		5,062.1		5,245.5
Debt securities, held-to-maturity, accumulated unrecognized loss			197.6		197.6		294.9
Realized investment gains (losses)			0	0	(48.2)	0
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			1.1		1.1		1.1
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
U.S. Government
Debt and Equity Securities, FV-NI [Line Items]
Total fair value			5,923.9		5,923.9		3,364.7
Debt securities, unrealized losses			19.1		19.1		61.5
Realized investment gains (losses)			0	0	(34.8)	0
Other Asset-Backed
Debt and Equity Securities, FV-NI [Line Items]
Total fair value			476.3		476.3		2,018.5
Debt securities, unrealized losses			14.2		14.2		100
Held to maturity securities			111.6		111.6		214.2
Debt securities, held-to-maturity, accumulated unrecognized loss			0.2		0.2		0.2
Realized investment gains (losses)			0	0	(56.5)	(0.8)
Other Asset-Backed \| BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Other Asset-Backed \| NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Corporate Debt
Debt and Equity Securities, FV-NI [Line Items]
Total fair value			104.5		104.5		147.4
Debt securities, unrealized losses			2.4		2.4		2.2
Provision for (release of) credit losses			(0.4)	(0.6)	(1)	(0.6)
Net amount of recognized liabilities for repurchase agreements			0.2		0.2		1.2
Held to maturity securities			491.1		491.1		646.1
Debt securities, held-to-maturity, accumulated unrecognized loss			14.7		14.7		28.2
Realized investment gains (losses)			0	$ 0	0	$ (1.2)
Corporate Debt \| BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Corporate Debt \| NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Other
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			600.8		600.8		576.3
Debt securities, held-to-maturity, accumulated unrecognized loss			156.9		156.9		147
Other \| BBB
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			0		0		0
Other \| NOT RATED
Debt and Equity Securities, FV-NI [Line Items]
Held to maturity securities			$ 546.1		$ 546.1		$ 521.5

Securities (Reconciliation of_2

Securities (Reconciliation of Amortized Cost to Fair Value of Securities Held to Maturity) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 22,708.6	$ 26,221.7
GROSS UNREALIZED GAINS	10.6	6.9
GROSS UNREALIZED LOSSES	1,347.2	1,755.6
FAIR VALUE	21,372	24,473
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,549.9	2,563.9
GROSS UNREALIZED GAINS	4.4	0.5
GROSS UNREALIZED LOSSES	14.8	72.4
FAIR VALUE	2,539.5	2,492
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	8,826.8	9,355.3
GROSS UNREALIZED GAINS	2.6	2.3
GROSS UNREALIZED LOSSES	823.8	1,012.4
FAIR VALUE	8,005.6	8,345.2
Non-U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,361.3	4,789.1
GROSS UNREALIZED GAINS	0.2	0.2
GROSS UNREALIZED LOSSES	65.2	90.7
FAIR VALUE	2,296.3	4,698.6
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	491.1	646.1
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	14.7	28.2
FAIR VALUE	476.4	617.9
Covered Bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	2,124.8	2,208.6
GROSS UNREALIZED GAINS	0.3	0.3
GROSS UNREALIZED LOSSES	72.7	108.3
FAIR VALUE	2,052.4	2,100.6
Certificates of Deposit
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	542.6	585.1
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	0.3	0.7
FAIR VALUE	542.3	584.4
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	5,062.1	5,245.5
GROSS UNREALIZED GAINS	2.6	3.2
GROSS UNREALIZED LOSSES	197.6	294.9
FAIR VALUE	4,867.1	4,953.8
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	111.6	214.2
GROSS UNREALIZED GAINS	0.5	0.4
GROSS UNREALIZED LOSSES	0.2	0.2
FAIR VALUE	111.9	214.4
Commercial Mortgage-Backed
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	37.6	37.6
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	1	0.8
FAIR VALUE	36.6	36.8
Other
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	600.8	576.3
GROSS UNREALIZED GAINS	0	0
GROSS UNREALIZED LOSSES	156.9	147
FAIR VALUE	$ 443.9	$ 429.3

Securities (Credit Quality Indi

Securities (Credit Quality Indicators) (Details) $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 22,708.6	$ 26,221.7
Percent of Total	1	1
AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 16,931.7	$ 18,234.4
Percent of Total	0.75	0.70
AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 3,880.2	$ 4,257.7
Percent of Total	0.17	0.16
A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 984.1	$ 2,834.7
Percent of Total	0.04	0.11
BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 337.1	$ 334
Percent of Total	0.01	0.01
NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 575.5	$ 560.9
Percent of Total	0.03	0.02
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 2,549.9	$ 2,563.9
Obligations of States and Political Subdivisions \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	980.8	954.7
Obligations of States and Political Subdivisions \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	1,569.1	1,609
Obligations of States and Political Subdivisions \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Obligations of States and Political Subdivisions \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Obligations of States and Political Subdivisions \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0.2
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	8,826.8	9,355.3
Government Sponsored Agency \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	8,826.8	9,355.3
Government Sponsored Agency \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Government Sponsored Agency \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Government Sponsored Agency \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Government Sponsored Agency \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Non-U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	2,361.3	4,789.1
Non-U.S. Government \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	456.4	813.3
Non-U.S. Government \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	816.2	1,179.6
Non-U.S. Government \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	752.7	2,463.3
Non-U.S. Government \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	336	332.9
Non-U.S. Government \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	491.1	646.1
Corporate Debt \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	2.1
Corporate Debt \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	290.4	302.6
Corporate Debt \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	200.7	341.4
Corporate Debt \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Corporate Debt \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Covered Bonds
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	2,124.8	2,208.6
Covered Bonds \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	2,124.8	2,208.6
Covered Bonds \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Covered Bonds \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Covered Bonds \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Covered Bonds \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Certificates of Deposit
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	542.6	585.1
Certificates of Deposit \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	513.2	545.9
Certificates of Deposit \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Certificates of Deposit \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Certificates of Deposit \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Certificates of Deposit \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	29.4	39.2
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	5,062.1	5,245.5
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	3,825.8	4,047.9
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	1,204.5	1,166.5
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	30.7	30
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	1.1	1.1
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	111.6	214.2
Other Asset-Backed \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	111.6	214.2
Other Asset-Backed \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other Asset-Backed \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other Asset-Backed \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other Asset-Backed \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Commercial Mortgage-Backed
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	37.6	37.6
Commercial Mortgage-Backed \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	37.6	37.6
Commercial Mortgage-Backed \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Commercial Mortgage-Backed \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Commercial Mortgage-Backed \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Commercial Mortgage-Backed \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	600.8	576.3
Other \| AAA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	54.7	54.8
Other \| AA
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other \| A
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other \| BBB
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	0	0
Other \| NOT RATED
Schedule of Held-to-maturity Securities [Line Items]
Held to Maturity	$ 546.1	$ 521.5

Securities (Investment Security

Securities (Investment Security Gains and Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Gross Realized Debt Securities Gains	$ 0	$ 0	$ 185.2	$ 213
Gross Realized Debt Securities Losses	0	0	(374.5)	(206.1)
Investment Security Gains (Losses), net	$ 0	$ 0	$ (189.3)	$ 6.9

Securities (Investment Securi_2

Securities (Investment Security Gains and Losses by Security Type) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ 0	$ 0	$ (189.3)	$ 6.9
U.S. Government
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	(34.8)	0
Obligations of States and Political Subdivisions
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	9.8
Government Sponsored Agency
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	(23)	0
Corporate Debt
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	0	(1.2)
Covered Bonds
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	(4.2)	0
Sub-Sovereign, Supranational and Non-U.S. Agency Bonds
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	(48.2)	0
Other Asset-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	0	0	(56.5)	(0.8)
Commercial Mortgage-Backed
Schedule of Held-to-maturity Securities [Line Items]
Investment Security Gains (Losses), net	$ 0	$ 0	$ (22.6)	$ (0.9)

Loans (Loans) (Details)

Loans (Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 41,950.3	$ 47,617
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	20,833.8	25,412.8
Commercial \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	10,391.3	11,555.3
Commercial \| Commercial and Institutional \| Private Equity Funds
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	3,800	4,500
Commercial \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,251	5,134.2
Commercial \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,742.6	2,778.5
Commercial \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,448.9	5,944.8
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,116.5	22,204.2
Personal \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	14,195.5	14,360
Personal \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,141.2	6,327.1
Personal \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	457.2	428.8
Personal \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 322.6	$ 1,088.3

Loans (Narrative) (Details)

Loans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
Loans (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 41,950.3		$ 41,950.3		$ 47,617
Other U.S. loans and non-U.S. loans, short duration advances	4,500		4,500		8,400
Demand deposits	19		19		12.1
Financing receivable, nonaccrual, interest income	0.5	$ 0.9	1.7	$ 2.3
Loans in process of foreclosure	5.2		5.2		3.5
Modified loans, charged off	0		8.5
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, held-for-sale, not part of disposal group, after valuation allowance	0		0		0
90 days or greater past due \| Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans modified	1		1
Personal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 21,116.5		$ 21,116.5		22,204.2
Personal \| Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collateral required on Residential real estate loan, lower limit	65%		65%
Collateral required on Residential real estate loan, upper limit	80%		80%
Loans and leases	$ 6,141.2		$ 6,141.2		6,327.1
Personal \| Home Equity Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Draw period for credit line products			10 years
Loans and leases	221.1		$ 221.1		$ 228.7
Percentage of total equity credit lines			98%		96%
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and leases	$ 20,833.8		$ 20,833.8		$ 25,412.8

Loans (Credit Quality Indicator

Loans (Credit Quality Indicator At Amortized Cost By Origination Year) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	$ 6,534.1		$ 6,534.1		$ 13,006.4
2023/2022	4,136.7		4,136.7		4,823.9
2022/2021	3,954.2		3,954.2		4,177.6
2021/2020	3,457.4		3,457.4		1,765.4
2020/2019	1,660.2		1,660.2		1,208.7
PRIOR	2,941.5		2,941.5		2,681.5
REVOLVING LOANS	18,548.1		18,548.1		19,233.5
REVOLVING LOANS CONVERTED TO TERM LOANS	718.1		718.1		720
TOTAL LOANS	41,950.3		41,950.3		47,617
2024/2023, Charge-offs			0		(2.1)
2023/2022, Charge-offs			(7.3)		(4.4)
2022/2021, Charge-offs			(3.7)		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			(0.4)		(1)
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs	0	$ (0.8)	(11.4)	$ (5.6)	(7.5)
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	5,559.1		5,559.1		10,601.2
2023/2022	2,932.9		2,932.9		3,008.8
2022/2021	2,370.5		2,370.5		2,212.4
2021/2020	1,838		1,838		536.3
2020/2019	506.2		506.2		590.8
PRIOR	893.7		893.7		899
REVOLVING LOANS	6,643.5		6,643.5		7,467.6
REVOLVING LOANS CONVERTED TO TERM LOANS	89.9		89.9		96.7
TOTAL LOANS	20,833.8		20,833.8		25,412.8
2024/2023, Charge-offs			0		(1.3)
2023/2022, Charge-offs			(7.3)		(4.4)
2022/2021, Charge-offs			(3.7)		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			0		0
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs	0	(0.5)	(11)	(4.5)	(5.7)
Commercial \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	902.4		902.4		1,259.1
2023/2022	867		867		1,395
2022/2021	892.3		892.3		1,458.6
2021/2020	1,164		1,164		228.8
2020/2019	172.2		172.2		257.8
PRIOR	525.2		525.2		590.3
REVOLVING LOANS	5,783.6		5,783.6		6,276.9
REVOLVING LOANS CONVERTED TO TERM LOANS	84.6		84.6		88.8
TOTAL LOANS	10,391.3		10,391.3		11,555.3
2024/2023, Charge-offs			0
2023/2022, Charge-offs			(7.3)
2022/2021, Charge-offs			(1.3)
2021/2020, Charge-offs			0
2020/2019, Charge-offs			0
Prior, Charge-offs			0
REVOLVING LOANS, Charge-offs			0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0
Charge-Offs			(8.6)
Commercial \| Commercial and Institutional \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	322.6		322.6		443.9
2023/2022	247.5		247.5		534.1
2022/2021	371.2		371.2		668.3
2021/2020	588.1		588.1		78.1
2020/2019	66.1		66.1		137.2
PRIOR	381		381		409.9
REVOLVING LOANS	4,222		4,222		4,909.8
REVOLVING LOANS CONVERTED TO TERM LOANS	21.3		21.3		15
TOTAL LOANS	6,219.8		6,219.8		7,196.3
Commercial \| Commercial and Institutional \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	544.9		544.9		801.4
2023/2022	538.1		538.1		790.9
2022/2021	458.1		458.1		729.5
2021/2020	494.4		494.4		138.7
2020/2019	103.8		103.8		120.5
PRIOR	141.9		141.9		178.7
REVOLVING LOANS	1,513.4		1,513.4		1,332.4
REVOLVING LOANS CONVERTED TO TERM LOANS	56.3		56.3		72
TOTAL LOANS	3,850.9		3,850.9		4,164.1
Commercial \| Commercial and Institutional \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	34.9		34.9		13.8
2023/2022	81.4		81.4		70
2022/2021	63		63		60.8
2021/2020	81.5		81.5		12
2020/2019	2.3		2.3		0.1
PRIOR	2.3		2.3		1.7
REVOLVING LOANS	48.2		48.2		34.7
REVOLVING LOANS CONVERTED TO TERM LOANS	7		7		1.8
TOTAL LOANS	320.6		320.6		194.9
Commercial \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	385.5		385.5		1,933.2
2023/2022	2,025.2		2,025.2		1,598.7
2022/2021	1,463.6		1,463.6		710.6
2021/2020	672.8		672.8		242.3
2020/2019	216.3		216.3		298.8
PRIOR	269		269		155.4
REVOLVING LOANS	213.3		213.3		187.3
REVOLVING LOANS CONVERTED TO TERM LOANS	5.3		5.3		7.9
TOTAL LOANS	5,251		5,251		5,134.2
2024/2023, Charge-offs			0		(0.7)
2023/2022, Charge-offs			0		(4.4)
2022/2021, Charge-offs			(2.4)		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			0		0
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs			(2.4)		(5.1)
Commercial \| Commercial Real Estate \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	97.3		97.3		403.6
2023/2022	339.5		339.5		389.9
2022/2021	289.1		289.1		159.1
2021/2020	219.5		219.5		23.9
2020/2019	18.8		18.8		37.8
PRIOR	68.5		68.5		44.8
REVOLVING LOANS	53.7		53.7		51
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	1,086.4		1,086.4		1,110.1
Commercial \| Commercial Real Estate \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	274.1		274.1		1,513.5
2023/2022	1,669.7		1,669.7		1,208.8
2022/2021	1,048.1		1,048.1		521
2021/2020	436.2		436.2		218.4
2020/2019	193.2		193.2		252.8
PRIOR	200.1		200.1		96
REVOLVING LOANS	159.6		159.6		136.3
REVOLVING LOANS CONVERTED TO TERM LOANS	5.3		5.3		7.9
TOTAL LOANS	3,986.3		3,986.3		3,954.7
Commercial \| Commercial Real Estate \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	14.1		14.1		16.1
2023/2022	16		16		0
2022/2021	126.4		126.4		30.5
2021/2020	17.1		17.1		0
2020/2019	4.3		4.3		8.2
PRIOR	0.4		0.4		14.6
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	178.3		178.3		69.4
Commercial \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	1,822.3		1,822.3		1,464.1
2023/2022	40.7		40.7		15.1
2022/2021	14.6		14.6		43.2
2021/2020	1.2		1.2		65.2
2020/2019	117.7		117.7		34.2
PRIOR	99.5		99.5		153.3
REVOLVING LOANS	646.6		646.6		1,003.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	2,742.6		2,742.6		2,778.5
Commercial \| Non-U.S. \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	1,215.8		1,215.8		487.9
2023/2022	24.2		24.2		0
2022/2021	0		0		43.2
2021/2020	0		0		65.2
2020/2019	117.7		117.7		34.2
PRIOR	30.2		30.2		3.3
REVOLVING LOANS	577		577		760
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	1,964.9		1,964.9		1,393.8
Commercial \| Non-U.S. \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	606		606		974.7
2023/2022	16.5		16.5		0.8
2022/2021	0.8		0.8		0
2021/2020	1.2		1.2		0
2020/2019	0		0		0
PRIOR	69.3		69.3		150
REVOLVING LOANS	69.6		69.6		243.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	763.4		763.4		1,368.9
Commercial \| Non-U.S. \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	0.5		0.5		1.5
2023/2022	0		0		14.3
2022/2021	13.8		13.8		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	14.3		14.3		15.8
Commercial \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	2,448.9		2,448.9		5,944.8
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	2,448.9		2,448.9		5,944.8
2024/2023, Charge-offs			0		(0.6)
2023/2022, Charge-offs			0		0
2022/2021, Charge-offs			0		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			0		0
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs			0		(0.6)
Commercial \| Other \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	1,183.9		1,183.9		4,313.2
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	1,183.9		1,183.9		4,313.2
Commercial \| Other \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	1,264.9		1,264.9		1,631.6
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	1,264.9		1,264.9		1,631.6
Commercial \| Other \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	0.1		0.1
2023/2022	0		0
2022/2021	0		0
2021/2020	0		0
2020/2019	0		0
PRIOR	0		0
REVOLVING LOANS	0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0
TOTAL LOANS	0.1		0.1
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	975		975		2,405.2
2023/2022	1,203.8		1,203.8		1,815.1
2022/2021	1,583.7		1,583.7		1,965.2
2021/2020	1,619.4		1,619.4		1,229.1
2020/2019	1,154		1,154		617.9
PRIOR	2,047.8		2,047.8		1,782.5
REVOLVING LOANS	11,904.6		11,904.6		11,765.9
REVOLVING LOANS CONVERTED TO TERM LOANS	628.2		628.2		623.3
TOTAL LOANS	21,116.5		21,116.5		22,204.2
2024/2023, Charge-offs			0		(0.8)
2023/2022, Charge-offs			0		0
2022/2021, Charge-offs			0		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			(0.4)		(1)
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs	0	$ (0.3)	(0.4)	$ (1.1)	(1.8)
Personal \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	348.6		348.6		818.4
2023/2022	731.5		731.5		629.3
2022/2021	462.7		462.7		707.4
2021/2020	462.7		462.7		168.4
2020/2019	143.2		143.2		167.5
PRIOR	227.8		227.8		197.7
REVOLVING LOANS	11,200.2		11,200.2		11,055.4
REVOLVING LOANS CONVERTED TO TERM LOANS	618.8		618.8		615.9
TOTAL LOANS	14,195.5		14,195.5		14,360
2024/2023, Charge-offs			0
2023/2022, Charge-offs			0
2022/2021, Charge-offs			0
2021/2020, Charge-offs			0
2020/2019, Charge-offs			0
Prior, Charge-offs			(0.3)
REVOLVING LOANS, Charge-offs			0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0
Charge-Offs			(0.3)
Personal \| Private Client \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	206.7		206.7		504.7
2023/2022	80		80		140.8
2022/2021	39.5		39.5		52.3
2021/2020	38.3		38.3		67.5
2020/2019	19.1		19.1		8.7
PRIOR	39.8		39.8		134.7
REVOLVING LOANS	4,503.2		4,503.2		5,320.9
REVOLVING LOANS CONVERTED TO TERM LOANS	144.1		144.1		168.1
TOTAL LOANS	5,070.7		5,070.7		6,397.7
Personal \| Private Client \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	141.8		141.8		290.1
2023/2022	635.2		635.2		488.2
2022/2021	423.2		423.2		655.1
2021/2020	424.4		424.4		100.9
2020/2019	124.1		124.1		158.8
PRIOR	188		188		44.7
REVOLVING LOANS	6,688.7		6,688.7		5,721.5
REVOLVING LOANS CONVERTED TO TERM LOANS	474.7		474.7		447.8
TOTAL LOANS	9,100.1		9,100.1		7,907.1
Personal \| Private Client \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	0.1		0.1		23.6
2023/2022	16.3		16.3		0.3
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		18.3
REVOLVING LOANS	8.3		8.3		13
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	24.7		24.7		55.2
Personal \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	273.1		273.1		470.3
2023/2022	455.3		455.3		1,169.8
2022/2021	1,105.7		1,105.7		1,218
2021/2020	1,117.4		1,117.4		1,060.7
2020/2019	1,010.8		1,010.8		434
PRIOR	1,794		1,794		1,571.3
REVOLVING LOANS	382.8		382.8		403
REVOLVING LOANS CONVERTED TO TERM LOANS	2.1		2.1		0
TOTAL LOANS	6,141.2		6,141.2		6,327.1
2024/2023, Charge-offs			0		(0.8)
2023/2022, Charge-offs			0		0
2022/2021, Charge-offs			0		0
2021/2020, Charge-offs			0		0
2020/2019, Charge-offs			0		0
Prior, Charge-offs			(0.1)		(1)
REVOLVING LOANS, Charge-offs			0		0
REVOLVING LOANS CONVERTED TO TERM LOANS, Charge-offs			0		0
Charge-Offs			(0.1)		(1.8)
Personal \| Residential Real Estate \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	138.5		138.5		278.7
2023/2022	231.3		231.3		464
2022/2021	433.6		433.6		500.6
2021/2020	407.3		407.3		373.3
2020/2019	332		332		142.4
PRIOR	816.6		816.6		722.4
REVOLVING LOANS	189.9		189.9		219.8
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	2,549.2		2,549.2		2,701.2
Personal \| Residential Real Estate \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	134.6		134.6		191.6
2023/2022	224		224		694.9
2022/2021	664.6		664.6		717.4
2021/2020	706.2		706.2		686.7
2020/2019	678.4		678.4		290
PRIOR	940.4		940.4		805.3
REVOLVING LOANS	165.6		165.6		170.3
REVOLVING LOANS CONVERTED TO TERM LOANS	2.1		2.1		0
TOTAL LOANS	3,515.9		3,515.9		3,556.2
Personal \| Residential Real Estate \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	0		0		0
2023/2022	0		0		10.9
2022/2021	7.5		7.5		0
2021/2020	3.9		3.9		0.7
2020/2019	0.4		0.4		1.6
PRIOR	37		37		43.6
REVOLVING LOANS	27.3		27.3		12.9
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	76.1		76.1		69.7
Personal \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	30.7		30.7		28.2
2023/2022	17		17		16
2022/2021	15.3		15.3		39.8
2021/2020	39.3		39.3		0
2020/2019	0		0		16.4
PRIOR	26		26		13.5
REVOLVING LOANS	321.6		321.6		307.5
REVOLVING LOANS CONVERTED TO TERM LOANS	7.3		7.3		7.4
TOTAL LOANS	457.2		457.2		428.8
Personal \| Non-U.S. \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	3.2		3.2		15.5
2023/2022	1		1		0
2022/2021	0		0		0.6
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	6.8		6.8		4.6
REVOLVING LOANS	158		158		71.4
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	169		169		92.1
Personal \| Non-U.S. \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	19.6		19.6		12.7
2023/2022	16		16		16
2022/2021	15.3		15.3		39.2
2021/2020	39.3		39.3		0
2020/2019	0		0		16.4
PRIOR	19.2		19.2		8.9
REVOLVING LOANS	163.6		163.6		236.1
REVOLVING LOANS CONVERTED TO TERM LOANS	7.3		7.3		7.4
TOTAL LOANS	280.3		280.3		336.7
Personal \| Non-U.S. \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	7.9		7.9		0
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	7.9		7.9		0
Personal \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	322.6		322.6		1,088.3
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	322.6		322.6		1,088.3
Personal \| Other \| 1 to 3 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	199.4		199.4		461.7
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	199.4		199.4		461.7
Personal \| Other \| 4 to 5 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	123.1		123.1		626.6
2023/2022	0		0		0
2022/2021	0		0		0
2021/2020	0		0		0
2020/2019	0		0		0
PRIOR	0		0		0
REVOLVING LOANS	0		0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0		0
TOTAL LOANS	123.1		123.1		$ 626.6
Personal \| Other \| 6 to 9 Category
Financing Receivable, Credit Quality Indicator [Line Items]
2024/2023	0.1		0.1
2023/2022	0		0
2022/2021	0		0
2021/2020	0		0
2020/2019	0		0
PRIOR	0		0
REVOLVING LOANS	0		0
REVOLVING LOANS CONVERTED TO TERM LOANS	0		0
TOTAL LOANS	$ 0.1		$ 0.1

Loans (Delinquency Status) (Det

Loans (Delinquency Status) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 41,911	$ 47,553.4
NONACCRUAL	39.3	63.6
TOTAL LOANS	41,950.3	47,617
NONACCRUAL WITH NO ALLOWANCE	36.8	49.4
Other Real Estate Owned	0	1.5
Total Nonaccrual Assets	39.3	65.1
CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	41,489.4	47,261.1
30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	271.7	239.5
60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	62.7	32.7
90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	87.2	20.1
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20,819.6	25,396.5
NONACCRUAL	14.2	16.3
TOTAL LOANS	20,833.8	25,412.8
NONACCRUAL WITH NO ALLOWANCE	13.7	4.1
Commercial \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	10,383.2	11,539
NONACCRUAL	8.1	16.3
TOTAL LOANS	10,391.3	11,555.3
NONACCRUAL WITH NO ALLOWANCE	8.1	4.1
Commercial \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,245.4	5,134.2
NONACCRUAL	5.6	0
TOTAL LOANS	5,251	5,134.2
NONACCRUAL WITH NO ALLOWANCE	5.6	0
Commercial \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2,742.1	2,778.5
NONACCRUAL	0.5	0
TOTAL LOANS	2,742.6	2,778.5
NONACCRUAL WITH NO ALLOWANCE	0	0
Commercial \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2,448.9	5,944.8
NONACCRUAL	0	0
TOTAL LOANS	2,448.9	5,944.8
NONACCRUAL WITH NO ALLOWANCE	0	0
Commercial \| CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20,607.2	25,221.6
Commercial \| CURRENT \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	10,246.1	11,374.6
Commercial \| CURRENT \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5,220.6	5,123.7
Commercial \| CURRENT \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2,691.6	2,778.5
Commercial \| CURRENT \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	2,448.9	5,944.8
Commercial \| 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	132	168.1
Commercial \| 30 – 59 DAYS PAST DUE \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	65.3	163.7
Commercial \| 30 – 59 DAYS PAST DUE \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	19.8	4.4
Commercial \| 30 – 59 DAYS PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	46.9	0
Commercial \| 30 – 59 DAYS PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Commercial \| 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21.4	6.8
Commercial \| 60 – 89 DAYS PAST DUE \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	16.4	0.7
Commercial \| 60 – 89 DAYS PAST DUE \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	5	6.1
Commercial \| 60 – 89 DAYS PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Commercial \| 60 – 89 DAYS PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Commercial \| 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	59	0
Commercial \| 90 DAYS OR MORE PAST DUE \| Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	55.4	0
Commercial \| 90 DAYS OR MORE PAST DUE \| Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Commercial \| 90 DAYS OR MORE PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	3.6	0
Commercial \| 90 DAYS OR MORE PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	21,091.4	22,156.9
NONACCRUAL	25.1	47.3
TOTAL LOANS	21,116.5	22,204.2
NONACCRUAL WITH NO ALLOWANCE	23.1	45.3
Personal \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	14,193.5	14,339.7
NONACCRUAL	2	20.3
TOTAL LOANS	14,195.5	14,360
NONACCRUAL WITH NO ALLOWANCE	0	18.3
Personal \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,118.1	6,300.1
NONACCRUAL	23.1	27
TOTAL LOANS	6,141.2	6,327.1
NONACCRUAL WITH NO ALLOWANCE	23.1	27
Personal \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	457.2	428.8
NONACCRUAL	0	0
TOTAL LOANS	457.2	428.8
NONACCRUAL WITH NO ALLOWANCE	0	0
Personal \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	322.6	1,088.3
NONACCRUAL	0	0
TOTAL LOANS	322.6	1,088.3
NONACCRUAL WITH NO ALLOWANCE	0	0
Personal \| CURRENT
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	20,882.2	22,039.5
Personal \| CURRENT \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	14,015.9	14,240
Personal \| CURRENT \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	6,086.6	6,283
Personal \| CURRENT \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	457.1	428.2
Personal \| CURRENT \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	322.6	1,088.3
Personal \| 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	139.7	71.4
Personal \| 30 – 59 DAYS PAST DUE \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	131.1	63.9
Personal \| 30 – 59 DAYS PAST DUE \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	8.5	7.5
Personal \| 30 – 59 DAYS PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0.1	0
Personal \| 30 – 59 DAYS PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Personal \| 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	41.3	25.9
Personal \| 60 – 89 DAYS PAST DUE \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	18.3	24.8
Personal \| 60 – 89 DAYS PAST DUE \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	23	0.5
Personal \| 60 – 89 DAYS PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0.6
Personal \| 60 – 89 DAYS PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Personal \| 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	28.2	20.1
Personal \| 90 DAYS OR MORE PAST DUE \| Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	28.2	11
Personal \| 90 DAYS OR MORE PAST DUE \| Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	9.1
Personal \| 90 DAYS OR MORE PAST DUE \| Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	0	0
Personal \| 90 DAYS OR MORE PAST DUE \| Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL ACCRUAL	$ 0	$ 0

Allowance for Credit Losses (Ch

Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
LOANS
Balance at Beginning of Period	$ 167.7	$ 152.5	$ 178.7	$ 144.3	$ 144.3
Charge-Offs	0	(0.8)	(11.4)	(5.6)	(7.5)
Recoveries	2.4	1.1	3.5	3
Net Recoveries (Charge-Offs)	2.4	0.3	(7.9)	(2.6)
Provision for Credit Losses	14.7	14	14	25.1
Balance at End of Period	184.8	166.8	184.8	166.8	178.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	29.5	26	26.9	38.5	38.5
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	(3)	2.3	(0.4)	(10.2)
Balance at End of Period	26.5	28.3	26.5	28.3	26.9
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	10.9	16.7	12.7	16	16
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	(3.4)	(1.8)	(5.2)	(1.1)
Balance at End of Period	7.5	14.9	7.5	14.9	12.7
OTHER FINANCIAL ASSETS
Balance at Beginning of Period	0.9	1	0.9	0.8	0.8
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	0.1	0.1	0.1	0.3
Balance at End of Period	1	1.1	1	1.1	0.9
TOTAL
Balance at Beginning of Period	209	196.2	219.2	199.6	199.6
Charge-Offs	0	(0.8)	(11.4)	(5.6)
Recoveries	2.4	1.1	3.5	3
Net Recoveries (Charge-Offs)	2.4	0.3	(7.9)	(2.6)
Provision for credit losses	8.4	14.6	8.5	14.1
Balance at End of Period	219.8	211.1	219.8	211.1	219.2
Corporate Debt
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	0.5	1.4	0.9	1.9	1.9
Provision for Credit Losses	0	(0.1)	(0.4)	(0.6)
Balance at End of Period	0.5	1.3	0.5	1.3	$ 0.9
TOTAL
Provision for credit losses	$ (0.4)	$ (0.6)	$ (1)	$ (0.6)

Allowance for Credit Losses (Na

Allowance for Credit Losses (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Receivables [Abstract]
Provision for (release of) credit losses	$ 8.4	$ 14.6	$ 8.5	$ 14.1
Net charge-offs (recoveries)	(2.4)	(0.3)	$ 7.9	2.6
Time period used for projecting future conditions to estimate credit losses			2 years
Other financial assets, allowance for credit loss	$ 1	$ 1.1	$ 1	$ 1.1	$ 0.9	$ 0.9	$ 1	$ 0.8

Allowance for Credit Losses (_2

Allowance for Credit Losses (Changes in Allowance for Credit Losses Related to Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
LOANS
Balance at Beginning of Period	$ 167.7	$ 152.5	$ 178.7	$ 144.3	$ 144.3
Charge-Offs	0	(0.8)	(11.4)	(5.6)	(7.5)
Recoveries	2.4	1.1	3.5	3
Net Recoveries (Charge-Offs)	2.4	0.3	(7.9)	(2.6)
Provision for Credit Losses	14.7	14	14	25.1
Balance at End of Period	184.8	166.8	184.8	166.8	178.7
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	29.5	26	26.9	38.5	38.5
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	(3)	2.3	(0.4)	(10.2)
Balance at End of Period	26.5	28.3	26.5	28.3	26.9
COMMERCIAL
LOANS
Balance at Beginning of Period	136.9	124	146.8	116.2	116.2
Charge-Offs	0	(0.5)	(11)	(4.5)	(5.7)
Recoveries	0	0	0	0.1
Net Recoveries (Charge-Offs)	0	(0.5)	(11)	(4.4)
Provision for Credit Losses	15.7	13.9	16.8	25.6
Balance at End of Period	152.6	137.4	152.6	137.4	146.8
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	27.2	23.3	24.9	36.3	36.3
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	(2.7)	2.2	(0.4)	(10.8)
Balance at End of Period	24.5	25.5	24.5	25.5	24.9
PERSONAL
LOANS
Balance at Beginning of Period	30.8	28.5	31.9	28.1	28.1
Charge-Offs	0	(0.3)	(0.4)	(1.1)	(1.8)
Recoveries	2.4	1.1	3.5	2.9
Net Recoveries (Charge-Offs)	2.4	0.8	3.1	1.8
Provision for Credit Losses	(1)	0.1	(2.8)	(0.5)
Balance at End of Period	32.2	29.4	32.2	29.4	31.9
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	2.3	2.7	2	2.2	2.2
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	(0.3)	0.1	0	0.6
Balance at End of Period	$ 2	$ 2.8	$ 2	$ 2.8	$ 2

Allowance for Credit Losses (Re

Allowance for Credit Losses (Recorded Investments in Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Loans
Evaluated on an Individual Basis	$ 73.4		$ 96.3
Evaluated on a Collective Basis	41,876.9		47,520.7
TOTAL LOANS	41,950.3		47,617
Allowance for Credit Losses on Loans
Evaluated on an Individual Basis	5.5		13.4
Evaluated on a Collective Basis	179.3		165.3
Allowance Assigned to Loans	184.8	$ 167.7	178.7	$ 166.8	$ 152.5	$ 144.3
Allowance Assigned to Undrawn Loan Commitments and Standby Letters of Credit - Evaluated on a Collective Basis	26.5	29.5	26.9	28.3	26	38.5
Total Allowance Assigned to Loans and Undrawn Loan Commitments and Standby Letters of Credit	211.3		205.6
COMMERCIAL
Loans
Evaluated on an Individual Basis	38.1		33.7
Evaluated on a Collective Basis	20,795.7		25,379.1
TOTAL LOANS	20,833.8		25,412.8
Allowance for Credit Losses on Loans
Evaluated on an Individual Basis	3.3		11.4
Evaluated on a Collective Basis	149.3		135.4
Allowance Assigned to Loans	152.6	136.9	146.8	137.4	124	116.2
Allowance Assigned to Undrawn Loan Commitments and Standby Letters of Credit - Evaluated on a Collective Basis	24.5	27.2	24.9	25.5	23.3	36.3
Total Allowance Assigned to Loans and Undrawn Loan Commitments and Standby Letters of Credit	177.1		171.7
PERSONAL
Loans
Evaluated on an Individual Basis	35.3		62.6
Evaluated on a Collective Basis	21,081.2		22,141.6
TOTAL LOANS	21,116.5		22,204.2
Allowance for Credit Losses on Loans
Evaluated on an Individual Basis	2.2		2
Evaluated on a Collective Basis	30		29.9
Allowance Assigned to Loans	32.2	30.8	31.9	29.4	28.5	28.1
Allowance Assigned to Undrawn Loan Commitments and Standby Letters of Credit - Evaluated on a Collective Basis	2	$ 2.3	2	$ 2.8	$ 2.7	$ 2.2
Total Allowance Assigned to Loans and Undrawn Loan Commitments and Standby Letters of Credit	$ 34.2		$ 33.9

Allowance for Credit Losses (_3

Allowance for Credit Losses (Changes in The Allowance for Credit Losses Related to Debt Securities Held to Maturity) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	$ 10.9	$ 16.7	$ 12.7	$ 16
Provision for Credit Losses	(3.4)	(1.8)	(5.2)	(1.1)
Balance at End of Period	7.5	14.9	7.5	14.9
CORPORATE DEBT
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	0.5	1.4	0.9	1.9
Provision for Credit Losses	0	(0.1)	(0.4)	(0.6)
Balance at End of Period	0.5	1.3	0.5	1.3
NON-U.S. GOVERNMENT
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	2.6	5.4	3.5	3.6
Provision for Credit Losses	(0.1)	(0.8)	(1)	1
Balance at End of Period	2.5	4.6	2.5	4.6
SUB-SOVEREIGN, SUPRANATIONAL, AND NON-U.S. AGENCY BONDS
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	1.7	3.4	2.2	4
Provision for Credit Losses	(0.1)	(0.5)	(0.6)	(1.1)
Balance at End of Period	1.6	2.9	1.6	2.9
OBLIGATIONS OF STATES AND POICITAL SUBDIVISIONS
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	1	1.3	1.2	1.5
Provision for Credit Losses	0	(0.1)	(0.2)	(0.3)
Balance at End of Period	1	1.2	1	1.2
COVERED BONDS
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	0.1	0.1	0.1	0.1
Provision for Credit Losses	(0.1)	0	(0.1)	0
Balance at End of Period	0	0.1	0	0.1
OTHER
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	5	5.1	4.8	4.9
Provision for Credit Losses	(3.1)	(0.3)	(2.9)	(0.1)
Balance at End of Period	$ 1.9	$ 4.8	$ 1.9	$ 4.8

Allowance for Credit Losses (Ac

Allowance for Credit Losses (Accrued Interest) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Receivables [Abstract]
Loans	$ 220.2	$ 241.7
Debt Securities
Held to Maturity	75.1	72
Available for Sale	177.2	129.2
Other Financial Assets	79.2	86
Total	$ 551.7	$ 528.9

Pledged Assets, Accepted Coll_3

Pledged Assets, Accepted Collateral and Restricted Assets (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financial Instruments Owned and Pledged as Collateral [Line Items]
Cash, held in foreign currency	$ 1,000		$ 1,000		$ 722.2
Restricted cash	519.8		519.8		575.2
Average deposits maintained to meet Federal Reserve Bank reserve requirements	0	$ 0	0	$ 0
Debt Securities And Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral that may be repledged or sold	$ 1,200		$ 1,200		$ 1,100

Pledged Assets, Accepted Coll_4

Pledged Assets, Accepted Collateral and Restricted Assets (Type of Pledged Assets) (Details) - Collateral that may be repledged or sold - USD ($) $ in Billions	Sep. 30, 2024	Dec. 31, 2023
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 41.1	$ 43.3
Debt Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	31.1	33
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 10	$ 10.3

Pledged Assets, Accepted Coll_5

Pledged Assets, Accepted Collateral and Restricted Assets (Accepted Collateral) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Collateral Accepted	$ 66,377.3	$ 62,780
Fair value of securities received as collateral that have been resold or repledged	65,300	62,000
Reverse repurchase agreements
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral that may be repledged or sold	66,367	62,767.8
Reverse repurchase agreements	0	0
Derivative contracts
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral that may be repledged or sold	$ 10.3	$ 12.2

Goodwill and Other Intangible_2

Goodwill and Other Intangibles (Goodwill by Reporting Segment) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 702.3
Foreign Exchange Rates	5.5
Goodwill, Ending Balance	707.8
ASSET SERVICING
Goodwill [Roll Forward]
Goodwill, Beginning Balance	621.9
Foreign Exchange Rates	5.5
Goodwill, Ending Balance	627.4
WEALTH MANAGEMENT
Goodwill [Roll Forward]
Goodwill, Beginning Balance	80.4
Foreign Exchange Rates	0
Goodwill, Ending Balance	$ 80.4

Goodwill and Other Intangible_3

Goodwill and Other Intangibles (Other Intangible Assets and Capitalized Software) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 136	$ 135
Less: Accumulated Amortization	71.1	63.4
Net Book Value	64.9	71.6
Computer Software
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	4,256.2	3,781.7
Less: Accumulated Amortization	2,197.4	1,754.2
Net Book Value	$ 2,058.8	$ 2,027.5

Goodwill and Other Intangible_4

Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets amortization	$ 2.4	$ 2.3	$ 7.1	$ 7
Estimated future amortization expense for the remainder of 2024	2.3		2.3
Estimated future amortization expense for 2025	9		9
Estimated future amortization expense for 2026	8.6		8.6
Estimated future amortization expense for 2027	8.4		8.4
Estimated future amortization expense for 2028	7.7		7.7
Computer Software
Acquired Finite-Lived Intangible Assets [Line Items]
Other intangible assets amortization	$ 153.1	$ 126.7	$ 444.1	$ 370.8

Reporting Segments (Narrative)

Reporting Segments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Net Interest Income	$ 562.3	$ 456.2	$ 1,613.3	$ 1,498.9
Scenario, Adjustment \| Asset Servicing segment
Segment Reporting Information [Line Items]
Net Interest Income	(36)		(99)
Scenario, Adjustment \| Wealth Management segment
Segment Reporting Information [Line Items]
Net Interest Income	$ 36		$ 99

Reporting Segments (Results of

Reporting Segments (Results of Reporting Segments) (Details) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Sep. 30, 2024 USD ($) segment	Sep. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments \| segment							2
Noninterest Income
Trust, Investment and Other Servicing Fees	$ 1,196.6			$ 1,111.9			$ 3,505.6	$ 3,271.8
Foreign Exchange Trading Income	54.1			51.8			169.5	154.9
Other Noninterest Income (Loss)	155.5			106.6			1,042.4	302.6
Total Noninterest Income	1,406.2			1,270.3			4,717.5	3,729.3
Net Interest Income	562.3			456.2			1,613.3	1,498.9
Revenue	1,968.5			1,726.5			6,330.8	5,228.2
Provision for Credit Losses	8			14			7.5	13.5
Noninterest Expense	1,359.4			1,278.2			4,258	3,895.7
Income before Income Taxes	601.1			434.3			2,065.3	1,319
Provision for Income Taxes	136.2			106.5			489.6	324.8
Net Income	$ 464.9	$ 896.1	$ 214.7	$ 327.8	$ 331.8	$ 334.6	$ 1,575.7	$ 994.2
Percentage of Consolidated Net Income	100%			100%			100%	100%
Average Assets	$ 146,842.9			$ 140,201.6			$ 146,654.8	$ 144,691.6
OTHER
Noninterest Income
Trust, Investment and Other Servicing Fees	0			0			0	0
Foreign Exchange Trading Income	0			0			0	0
Other Noninterest Income (Loss)	52.5			2.4			737.9	(9.2)
Total Noninterest Income	52.5			2.4			737.9	(9.2)
Net Interest Income	0			0			0	0
Revenue	52.5			2.4			737.9	(9.2)
Provision for Credit Losses	(3.8)			0			(6.3)	0
Noninterest Expense	7.4			12			119.1	33.6
Income before Income Taxes	48.9			(9.6)			625.1	(42.8)
Provision for Income Taxes	11.1			(2.3)			141.8	(10.6)
Net Income	$ 37.8			$ (7.3)			$ 483.3	$ (32.2)
Percentage of Consolidated Net Income	8%			(2.00%)			31%	(3.00%)
Average Assets	$ 0			$ 0			$ 0	$ 0
RECONCILING ITEMS
Noninterest Income
Trust, Investment and Other Servicing Fees	0			0			0	0
Foreign Exchange Trading Income	0			0			0	0
Other Noninterest Income (Loss)	0			0			0	0
Total Noninterest Income	0			0			0	0
Net Interest Income	(7.1)			(13.2)			(21.3)	(39.5)
Revenue	(7.1)			(13.2)			(21.3)	(39.5)
Provision for Credit Losses	0			0			0	0
Noninterest Expense	0			0			0	0
Income before Income Taxes	(7.1)			(13.2)			(21.3)	(39.5)
Provision for Income Taxes	(7.1)			(13.2)			(21.3)	(39.5)
Net Income	0			0			0	0
ASSET SERVICING \| Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	667.1			626			1,957.3	1,850.2
Foreign Exchange Trading Income	59.5			54.3			181.6	161.2
Other Noninterest Income (Loss)	67.3			66.1			199.2	199
Total Noninterest Income	793.9			746.4			2,338.1	2,210.4
Net Interest Income	321.4			281.2			900.5	902.6
Revenue	1,115.3			1,027.6			3,238.6	3,113
Provision for Credit Losses	(0.6)			3.1			(1.9)	(3.3)
Noninterest Expense	860.7			809.3			2,634	2,459.7
Income before Income Taxes	255.2			215.2			606.5	656.6
Provision for Income Taxes	57.1			54.3			146.1	167.4
Net Income	$ 198.1			$ 160.9			$ 460.4	$ 489.2
Percentage of Consolidated Net Income	43%			49%			29%	49%
Average Assets	$ 108,108			$ 108,656.7			$ 108,025.6	$ 110,380.4
WEALTH MANAGEMENT \| Operating Segments
Noninterest Income
Trust, Investment and Other Servicing Fees	529.5			485.9			1,548.3	1,421.6
Foreign Exchange Trading Income	(5.4)			(2.5)			(12.1)	(6.3)
Other Noninterest Income (Loss)	35.7			38.1			105.3	112.8
Total Noninterest Income	559.8			521.5			1,641.5	1,528.1
Net Interest Income	248			188.2			734.1	635.8
Revenue	807.8			709.7			2,375.6	2,163.9
Provision for Credit Losses	12.4			10.9			15.7	16.8
Noninterest Expense	491.3			456.9			1,504.9	1,402.4
Income before Income Taxes	304.1			241.9			855	744.7
Provision for Income Taxes	75.1			67.7			223	207.5
Net Income	$ 229			$ 174.2			$ 632	$ 537.2
Percentage of Consolidated Net Income	49%			53%			40%	54%
Average Assets	$ 38,734.9			$ 31,544.9			$ 38,629.2	$ 34,311.2

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($)	3 Months Ended						9 Months Ended
Stockholders' Equity (Details) - USD ($)	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Oct. 31, 2021
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares)	10,000,000						10,000,000		10,000,000
Stockholders' equity	$ 12,749,000,000	$ 12,655,800,000	$ 12,101,800,000	$ 11,847,200,000	$ 11,635,700,000	$ 11,587,800,000	$ 12,749,000,000	$ 11,847,200,000	$ 11,897,900,000	$ 11,259,500,000
Stock repurchase program, number of shares authorized to be repurchased (in shares)											25,000,000
Stock repurchase, shares (in shares)	3,463,546			14,738			8,112,288	2,426,793
Stock repurchase, aggregate cost	$ 301,400,000	250,800,000	132,000,000	$ 1,100,000	99,300,000	100,900,000	$ 684,200,000	$ 201,300,000
Share-based payment arrangement, shares withheld for tax withholding obligation (in shares)	15,629			14,738			398,646	356,145
Average price paid per share for common stock repurchased (in usd per share)	$ 87.01			$ 77.39			$ 84.34	$ 82.95
Preferred Stock
Class of Stock [Line Items]
Stockholders' equity	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000	$ 884,900,000
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)	5,000						5,000		5,000
Preferred stock, without par value (in dollars per share)	$ 0						$ 0
Preferred stock, liquidation preference	$ 100,000						$ 100,000
Depository shares, liquidation preference per share (in dollars per share)	$ 1,000						$ 1,000
Preferred stock, annual dividend rate							4.60%
Preferred stock, dividend payment rate, variable rate							3.202%
Preferred stock, dividends declared (in usd per share)	$ 2,300
Series D Preferred Stock \| Preferred Stock
Class of Stock [Line Items]
Stockholders' equity	$ 493,500,000						$ 493,500,000		$ 493,500,000
Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)	16,000						16,000		16,000
Percentage of ownership interest per each depository shares	0.10%						0.10%
Preferred stock, without par value (in dollars per share)	$ 0						$ 0
Preferred stock, liquidation preference	$ 25,000						$ 25,000
Depository shares, liquidation preference per share (in dollars per share)	$ 25						$ 25
Preferred stock, annual dividend rate							4.70%
Preferred stock, dividends declared (in usd per share)	$ 293.75
Series E Preferred Stock \| Preferred Stock
Class of Stock [Line Items]
Stockholders' equity	$ 391,400,000						$ 391,400,000		$ 391,400,000
Series D Preferred Stock, Depositary Shares
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)	500,000						500,000
Preferred stock, shares issued (in shares)	500,000						500,000
Percentage of ownership interest per each depository shares	1%						1%
Series E Preferred Stock Depositary Shares
Class of Stock [Line Items]
Preferred stock, outstanding (in shares)	16,000,000						16,000,000
Preferred stock, shares issued (in shares)	16,000,000						16,000,000

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) (Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 12,655.8	$ 12,101.8	$ 11,897.9	$ 11,635.7	$ 11,587.8	$ 11,259.5	$ 11,897.9	$ 11,259.5
Net Change	85.5	52.6	220.3	42.5	(39.7)	203	358.4	205.8
Ending balance	12,749	12,655.8	12,101.8	11,847.2	11,635.7	11,587.8	12,749	11,847.2
TOTAL
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(865)	(917.6)	(1,137.9)	(1,405.9)	(1,366.2)	(1,569.2)	(1,137.9)	(1,569.2)
Net Change	85.5	52.6	220.3	42.5	(39.7)	203
Ending balance	(779.5)	(865)	(917.6)	(1,363.4)	(1,405.9)	(1,366.2)	(779.5)	(1,363.4)
NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(667.1)		(923.9)	(1,229.4)		(1,367.6)	(923.9)	(1,367.6)
Net Change	63.9			32.3			320.7	170.5
Ending balance	(603.2)	(667.1)		(1,197.1)	(1,229.4)		(603.2)	(1,197.1)
NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	0		0.8	0.5		1.2	0.8	1.2
Net Change	0.3			(0.4)			(0.5)	(1.1)
Ending balance	0.3	0		0.1	0.5		0.3	0.1
NET FOREIGN CURRENCY ADJUSTMENT
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	215.2		203.6	189.2		164.6	203.6	164.6
Net Change	18.9			9.6			30.5	34.2
Ending balance	234.1	215.2		198.8	189.2		234.1	198.8
NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(413.1)		$ (418.4)	(366.2)		$ (367.4)	(418.4)	(367.4)
Net Change	2.4			1			7.7	2.2
Ending balance	$ (410.7)	$ (413.1)		$ (365.2)	$ (366.2)		$ (410.7)	$ (365.2)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
PRE-TAX
Net Change	$ 80.4			$ 86			$ 468.9	$ 281.8
TAX
Net Change	5.1			(43.5)			(110.5)	(76)
AFTER TAX
Other Comprehensive Income (Loss)	85.5	$ 52.6	$ 220.3	42.5	$ (39.7)	$ 203	358.4	205.8
Unrealized Gains (Losses) on Available for Sale Debt Securities
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	63.7			18			176.9	158.6
Net Change	88.6			44.7			442.7	230.7
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(18.6)			(5.6)			(55.1)	(42)
Net Change	(24.7)			(12.4)			(122)	(60.2)
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	45.1			12.4			121.8	116.6
Other Comprehensive Income (Loss)	63.9			32.3			320.7	170.5
Interest Income on Debt Securities
PRE-TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	24.9			26.7			76.5	79
TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(6.1)			(6.8)			(19)	(19.9)
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	18.8			19.9			57.5	59.1
Net Losses on Debt Securities
PRE-TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	0			0			189.3	(6.9)
TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	0			0			(47.9)	1.7
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	0			0			141.4	(5.2)
Unrealized Gains (Losses) on Cash Flow Hedges
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	1			14.3			6.4	16.2
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.6)			(14.9)			(7.1)	(17.7)
Net Change	0.4			(0.6)			(0.7)	(1.5)
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(0.2)			(3.6)			(1.5)	(4.1)
Reclassification Adjustment for (Gains) Losses Included in Net Income	0.1			3.8			1.7	4.5
Net Change	(0.1)			0.2			0.2	0.4
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0.8			10.7			4.9	12.1
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.5)			(11.1)			(5.4)	(13.2)
Other Comprehensive Income (Loss)	0.3			(0.4)			(0.5)	(1.1)
Foreign Currency Adjustments
PRE-TAX
Net Change	(11.7)			40.5			16.4	49.3
TAX
Net Change	30.6			(30.9)			14.1	(15.1)
AFTER TAX
Other Comprehensive Income (Loss)	18.9			9.6			30.5	34.2
Foreign Currency Translation Adjustments
PRE-TAX
Net Change	122.9			(89.2)			52.5	(15.7)
TAX
Net Change	(2.4)			1.7			(1.2)	1.2
AFTER TAX
Other Comprehensive Income (Loss)	120.5			(87.5)			51.3	(14.5)
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
PRE-TAX
Net Change	1			(0.2)			0.2	(1.8)
TAX
Net Change	(0.3)			0.1			(0.1)	0.5
AFTER TAX
Other Comprehensive Income (Loss)	0.7			(0.1)			0.1	(1.3)
Net Investment Hedge Gains (Losses)
PRE-TAX
Net Change	(135.6)			129.9			(36.3)	66.8
TAX
Net Change	33.3			(32.7)			15.4	(16.8)
AFTER TAX
Other Comprehensive Income (Loss)	(102.3)			97.2			(20.9)	50
Pension and Other Postretirement Benefit Adjustments
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(0.1)			(0.2)			0.9	(1.5)
Net Change	3.1			1.4			10.5	3.3
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0			0			(0.5)	0.1
Net Change	(0.7)			(0.4)			(2.8)	(1.1)
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(0.1)			(0.2)			0.4	(1.4)
Other Comprehensive Income (Loss)	2.4			1			7.7	2.2
Amortization of Net Actuarial Loss
PRE-TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	3.2			1.6			9.6	4.8
TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	(0.7)			(0.4)			(2.3)	(1.2)
AFTER TAX
Reclassification Adjustment for (Gains) Losses Included in Net Income	$ 2.5			$ 1.2			$ 7.3	$ 3.6

Net Income Per Common Share (De

Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Basic Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	199,937,543			207,021,554			202,614,386	207,611,420
Net Income	$ 464.9	$ 896.1	$ 214.7	$ 327.8	$ 331.8	$ 334.6	$ 1,575.7	$ 994.2
Less: Dividends on Preferred Stock	16.2			16.2			37.1	37.1
Net Income Applicable to Common Stock	448.7			311.6			1,538.6	957.1
Less: Earnings Allocated to Participating Securities	3.6			3.1			13.2	9.7
Earnings Allocated to Common Shares Outstanding	$ 445.1			$ 308.5			$ 1,525.4	$ 947.4
Basic Net Income Per Common Share (in dollars per share)	$ 2.23			$ 1.49			$ 7.53	$ 4.56
Diluted Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	199,937,543			207,021,554			202,614,386	207,611,420
Plus: Dilutive Effect of Share-based Compensation (in shares)	611,520			231,438			517,014	316,300
Average Common and Potential Common Shares (in shares)	200,549,063			207,252,992			203,131,400	207,927,720
Earnings Allocated to Common and Potential Common Shares	$ 445.1			$ 308.5			$ 1,525.4	$ 947.3
Diluted Net Income Per Common Share (in dollars per share)	$ 2.22			$ 1.49			$ 7.51	$ 4.56
Common stock equivalents not included in the computation of diluted earnings per share because their inclusion would have been antidilutive (in shares)	0			0			200,000	100,000

Revenue from Contracts with C_3

Revenue from Contracts with Clients (Revenue Disaggregation) (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Jan. 31, 2024	Nov. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenue from contract with client			$ 1,196.6	$ 1,111.9	$ 3,505.6	$ 3,271.8
Foreign Exchange Trading Income			54.1	51.8	169.5	154.9
Treasury Management Fees			8.2	7.5	26.5	23.8
Security Commissions and Trading Income			35.5	30.9	107.7	101.7
Other Operating Income			111.8	68.2	1,097.5	170.2
Investment Security Gains (Losses), net	$ (189.4)	$ (176.4)	0	0	(189.3)	6.9
Total Other Noninterest Income			209.6	158.4	1,211.9	457.5
Total Noninterest Income			1,406.2	1,270.3	4,717.5	3,729.3
Custody and Fund Administration
Disaggregation of Revenue [Line Items]
Revenue from contract with client			482.5	459	1,427.1	1,358.7
Investment Management and Advisory
Disaggregation of Revenue [Line Items]
Revenue from contract with client			634.8	574.1	1,838.3	1,673.4
Securities Lending
Disaggregation of Revenue [Line Items]
Revenue from contract with client			17.7	20.7	53.2	61.3
Other
Disaggregation of Revenue [Line Items]
Revenue from contract with client			$ 61.6	$ 58.1	$ 187	$ 178.4

Revenue from Contracts with C_4

Revenue from Contracts with Clients (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	$ 1,196.6	$ 1,111.9	$ 3,505.6	$ 3,271.8
Security commissions and trading income	35.5	30.9	107.7	101.7
Other operating income	111.8	68.2	1,097.5	170.2
Securities Commissions and Trading Income
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	31	27.4	95.7	86.3
Other Operating Income
Disaggregation of Revenue [Line Items]
Trust, investment and other servicing fees	$ 9.7	$ 11.2	$ 29	$ 30.5

Revenue from Contracts with C_5

Revenue from Contracts with Clients (Contract Receivables) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 1,030.7	$ 928.4
Trust Fees Receivable, net
Disaggregation of Revenue [Line Items]
Total Client Receivables	973.6	863.5
Contract with customer, asset, allowance for credit loss	13.5	15.9
Other
Disaggregation of Revenue [Line Items]
Total Client Receivables	$ 57.1	$ 64.9

Net Interest Income (Details)

Net Interest Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Net Interest Income (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Interest Income
Federal Reserve and Other Central Bank Deposits	$ 451.7	$ 352.1	$ 1,369	$ 1,128
Interest-Bearing Due from and Deposits with Banks	28.5	34.9	94.5	95.2
Federal Funds Sold	0	0	0	0.3
Securities Purchased under Agreements to Resell	890.8	463.9	2,578.2	874.1
Securities — Taxable	486.3	402.4	1,409	1,106.5
Securities - Non-Taxable	0.2	0.3	0.8	1
Loans	644.5	664.2	1,946.4	1,881.6
Other Interest-Earning Assets	28.2	17.2	84.4	38.7
Total Interest Income	2,530.2	1,935	7,482.3	5,125.4
Interest Expense
Deposits	873.5	716.6	2,653.5	1,914.7
Federal Funds Purchased	29.6	77.5	101.9	205.2
Securities Sold Under Agreements to Repurchase	869.7	454	2,535.1	843.5
Other Borrowings	94.8	154.8	278.7	446.3
Senior Notes	44.2	44.1	132.4	125.4
Long-Term Debt	56.1	31.8	167.4	91.4
Total Interest Expense	1,967.9	1,478.8	5,869	3,626.5
Net Interest Income	$ 562.3	$ 456.2	$ 1,613.3	$ 1,498.9

Other Operating Income (Details

Other Operating Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Other Operating Income (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 111.8	$ 68.2	$ 1,097.5	$ 170.2
Pre-tax gain related to the sale of an equity investment	68.1
Loan Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	14	21.2	43.4	61.3
Banking Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	14.2	15	40.8	40.8
Bank Owned Life Insurance
Components of Other Operating Income [Line Items]
Total Other Operating Income	18.4	17.3	60.4	51
Other Income
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 65.2	$ 14.7	$ 952.9	$ 17.1

Other Operating Expense (Detail

Other Operating Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Other Operating Expense (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other Income and Expenses [Abstract]
Business Promotion	$ 19.1	$ 16.2	$ 56.6	$ 53.5
Staff Related	12.4	11	34.8	27.7
FDIC Insurance Premiums	7.1	8.3	35.6	21.1
Charitable Contributions	3.3	3.8	79.3	11.3
Other Expenses	44.2	59.2	155.5	182.5
Total Other Operating Expense	86.1	98.5	361.8	296.1
FDIC, special assessment			14.7
Other Operating Expense [Line Items]
Charitable Contributions	$ 3.3	$ 3.8	79.3	$ 11.3
Northern Trust Foundation
Other Income and Expenses [Abstract]
Charitable Contributions			70
Other Operating Expense [Line Items]
Charitable Contributions			$ 70

Pension (Details)

Pension (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Pension (Details) - Pension Plan - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Non-U.S. Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Service Cost	$ 0.5	$ 0.4	$ 1.5	$ 1.1
Interest Cost	1.1	1.2	3.3	3.6
Expected Return on Plan Assets	(1.6)	(1.6)	(4.8)	(4.7)
Amortization
Actuarial Loss (Gain)	0	(0.1)	0	(0.3)
Total Pension (Benefit) Expense	0	(0.1)	0	(0.3)
Qualified Plan \| U.S. Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Service Cost	13.4	11.5	40.2	34.5
Interest Cost	13.9	13.5	41.7	40.5
Expected Return on Plan Assets	(28.9)	(25.3)	(86.7)	(75.9)
Amortization
Actuarial Loss (Gain)	1.9	0.4	5.7	1.2
Total Pension (Benefit) Expense	0.3	0.1	0.9	0.3
Contribution to pension plan			200	0
Non-Qualified Plan \| U.S. Plan
Defined Benefit Plan, Net Periodic Benefit Cost
Service Cost	1.2	1.2	3.6	3.6
Interest Cost	1.2	1.3	3.6	3.9
Amortization
Actuarial Loss (Gain)	1.3	1.3	3.9	3.9
Total Pension (Benefit) Expense	$ 3.7	$ 3.8	11.1	11.4
Contribution to pension plan			$ 8	$ 16.5

Share-Based Compensation Plan_2

Share-Based Compensation Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 14.7	$ 16.5	$ 98.1	$ 98.3
Tax Benefits Recognized	3.6	4.2	24	24.7
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	13.4	14.7	78.3	80.5
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Share-Based Compensation Expense	$ 1.3	$ 1.8	$ 19.8	$ 17.8

Variable Interest Entities (Sum

Variable Interest Entities (Summary) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Variable Interest Entity [Line Items]
Assets	$ 155,753.8	$ 150,783.1
Liabilities	143,004.8	138,885.2
Other Assets
Variable Interest Entity [Line Items]
Investment Carrying Amount	823.2	889.1
Other Assets \| Affordable Housing
Variable Interest Entity [Line Items]
Investment Carrying Amount	599.3	622.8
Other Assets \| New Markets
Variable Interest Entity [Line Items]
Investment Carrying Amount	223.9	266.3
Other Liabilities
Variable Interest Entity [Line Items]
Unfunded Commitments	173.4	178.8
Other Liabilities \| Affordable Housing
Variable Interest Entity [Line Items]
Unfunded Commitments	173.4	178.8
Other Liabilities \| New Markets
Variable Interest Entity [Line Items]
Unfunded Commitments	0	0
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	795	857
Liabilities	$ 167.3	$ 172

Variable Interest Entities (Inc

Variable Interest Entities (Income Tax Credits and Other Tax Benefits and Amortization Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	$ 27	$ 28.4	$ 80.6	$ 85.1
Amortization Expense	24	24.6	71.8	73.6
Affordable Housing
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	21.9	22.5	65.5	67.3
Amortization Expense	19.6	19.9	58.5	59.5
New Markets
Variable Interest Entity [Line Items]
Income Tax Credits and Other Income Tax Benefits	5.1	5.9	15.1	17.8
Amortization Expense	$ 4.4	$ 4.7	$ 13.3	$ 14.1

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Contractual obligation to provide financial support	$ 0
Unfunded commitments	$ 0	$ 0

Commitments and Contingent Li_3

Commitments and Contingent Liabilities (Summary of Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Loss Contingencies [Line Items]
ONE YEAR AND LESS	$ 282,244.7	$ 265,837.5
OVER ONE YEAR	19,476.6	19,549.9
TOTAL	301,721.3	285,387.4
Undrawn Commitments
Loss Contingencies [Line Items]
Commitments, participated to others	203.1	222.2
Securities Lent with Indemnification
Loss Contingencies [Line Items]
ONE YEAR AND LESS	146,058.1	140,539.1
OVER ONE YEAR	0	0
TOTAL	146,058.1	140,539.1
Secured by Cash Deposits or Participated to Others \| Standby Letters of Credit
Loss Contingencies [Line Items]
TOTAL	101.8	39.1
Standby Letter of Credit and Financial Guarantee
Loss Contingencies [Line Items]
Guarantor obligations, current carrying value	112,000	84,600
Undrawn Commitments
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,202.5	11,849.5
OVER ONE YEAR	18,982.6	18,909.6
TOTAL	30,185.1	30,759.1
Standby Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	113,405.2	85,752
OVER ONE YEAR	493.7	639
TOTAL	113,898.9	86,391
Commercial Letters of Credit
Loss Contingencies [Line Items]
ONE YEAR AND LESS	34.8	29.2
OVER ONE YEAR	0.3	1.3
TOTAL	35.1	30.5
Reverse repurchase agreements
Loss Contingencies [Line Items]
ONE YEAR AND LESS	11,544.1	27,667.7
OVER ONE YEAR	0	0
TOTAL	$ 11,544.1	$ 27,667.7

Commitments and Contingent Li_4

Commitments and Contingent Liabilities (Narrative) (Details)		1 Months Ended	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended	81 Months Ended
	Mar. 05, 2024 EUR (€)	May 31, 2024 exchange_offer shares	Dec. 31, 2023 USD ($)	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) $ / shares	Dec. 31, 2015 trust	Sep. 30, 2024 USD ($) $ / shares
Loss Contingencies [Line Items]
Minimum securities lending related collateral percentage				100%	100%		100%
Commitments and letters of credit			$ 285,387,400,000	$ 301,721,300,000	$ 301,721,300,000		$ 301,721,300,000
Resell agreements, period end amounts excluding effects of agreements reported net by counterparty			27,700,000,000	11,500,000,000	11,500,000,000		11,500,000,000
Repurchase agreement counterparty, amount at risk			0	0	0		0
Loss contingency accrual				$ 0	$ 0		$ 0
Common stock, convertible, conversion price				1.5430	1.5430		1.5430
Securities Lent with Indemnification
Loss Contingencies [Line Items]
Commitments and letters of credit			140,539,100,000	$ 146,058,100,000	$ 146,058,100,000		$ 146,058,100,000
Indemnification Agreement
Loss Contingencies [Line Items]
Credit loss liability			0	0	0		0
FDIC Special Assessment
Loss Contingencies [Line Items]
Additional cost			84,600,000		14,700,000
Loss contingency accrual			$ 84,600,000	99,300,000	99,300,000		99,300,000
Northern Trust Fiduciary Services (Guernsey) Limited
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party \| €	€ 187,500
Visa
Loss Contingencies [Line Items]
Escrow deposit							4,300,000,000
Visa Class A Common Stock
Loss Contingencies [Line Items]
Exchange offer program, number of exchange offers \| exchange_offer		3
Exchange offer program, length of time between exchanges		12 months
Exchange offer program, claim reduction percentage		50%
Visa Class B
Loss Contingencies [Line Items]
Carryover basis				0	0		0
Conversion of stock, amount converted				$ 876,000,000
Visa Class B-2 Shares
Loss Contingencies [Line Items]
Exchange offer program, shares received upon expiration (in shares) \| shares		2,100,000
Visa Class C shares
Loss Contingencies [Line Items]
Exchange offer program, shares received upon expiration (in shares) \| shares		819,500
Number of shares sold (in shares) \| shares				794,200
Realized gain recorded					864,800,000
Equity securities				$ 27,800,000	$ 27,800,000		$ 27,800,000
Visa Class B Convertible Into Visa Class A \| Visa
Loss Contingencies [Line Items]
Share price (in USD) \| $ / shares				$ 274.95	$ 274.95		$ 274.95
Northern Trust Fiduciary Services (Guernsey) Limited \| Subsidiaries
Loss Contingencies [Line Items]
Number of administrated trusts serving as trustee on \| trust						2
Lower Limit
Loss Contingencies [Line Items]
Estimated loss				$ 0	$ 0		$ 0
Upper Limit
Loss Contingencies [Line Items]
Estimated loss				$ 20,000,000	$ 20,000,000		$ 20,000,000

Derivative Financial Instrume_3

Derivative Financial Instruments (Notional and Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivative [Line Items]
NOTIONAL VALUE	$ 397,798.9	$ 340,383.3
FAIR VALUE, ASSET	3,280.7	3,307.8
Total Gross Derivatives, asset	3,519	3,568.2
Less: Netting	2,773.1	3,126.7
Derivative Assets	745.9	441.5
FAIR VALUE, LIABILITY	2,758.3	2,806.3
Derivative Liabilities	3,615.8	3,649.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,819.9	2,205.4
Derivative Liabilities	1,795.9	1,444.4
Derivatives Designated as Hedging under GAAP
Derivative [Line Items]
NOTIONAL VALUE	14,811.6	12,573.7
FAIR VALUE, ASSET	317.1	123
FAIR VALUE, LIABILITY	394.1	145.1
Fair Value Hedges \| Derivatives Designated as Hedging under GAAP \| Interest Rate Contracts
Derivative [Line Items]
NOTIONAL VALUE	9,706.3	7,042.7
FAIR VALUE, ASSET	308.9	94.7
FAIR VALUE, LIABILITY	289.7	71
Fair Value Hedges \| Derivatives Not Designated as Hedging under GAAP
Derivative [Line Items]
NOTIONAL VALUE	382,987.3	327,809.6
FAIR VALUE, ASSET	3,201.9	3,445.2
FAIR VALUE, LIABILITY	3,221.7	3,504.7
Fair Value Hedges \| Non-Designated Risk Management Derivatives
Derivative [Line Items]
NOTIONAL VALUE	460	888.6
FAIR VALUE, ASSET	0	0
FAIR VALUE, LIABILITY	27.8	25.5
Fair Value Hedges \| Non-Designated Risk Management Derivatives \| Foreign Exchange Contracts
Derivative [Line Items]
NOTIONAL VALUE	1.7	20.7
FAIR VALUE, ASSET	0	0
FAIR VALUE, LIABILITY	0	0.1
Fair Value Hedges \| Non-Designated Risk Management Derivatives \| Other Financial Derivatives
Derivative [Line Items]
NOTIONAL VALUE	458.3	867.9
FAIR VALUE, ASSET	0	0
FAIR VALUE, LIABILITY	27.8	25.4
Fair Value Hedges \| Client-Related and Trading Derivatives
Derivative [Line Items]
NOTIONAL VALUE	382,527.3	326,921
FAIR VALUE, ASSET	3,201.9	3,445.2
FAIR VALUE, LIABILITY	3,193.9	3,479.2
Fair Value Hedges \| Client-Related and Trading Derivatives \| Foreign Exchange Contracts
Derivative [Line Items]
NOTIONAL VALUE	367,149.3	313,336.9
FAIR VALUE, ASSET	3,044.7	3,238.4
FAIR VALUE, LIABILITY	2,979.5	3,181
Fair Value Hedges \| Client-Related and Trading Derivatives \| Interest Rate Contracts
Derivative [Line Items]
NOTIONAL VALUE	15,378	13,584.1
FAIR VALUE, ASSET	157.2	206.8
FAIR VALUE, LIABILITY	214.4	298.2
Cash Flow Hedges \| Derivatives Designated as Hedging under GAAP \| Foreign Exchange Contracts
Derivative [Line Items]
NOTIONAL VALUE	454.6	1,453.6
FAIR VALUE, ASSET	1.5	15
FAIR VALUE, LIABILITY	0.5	42.2
Net Investment Hedges \| Derivatives Designated as Hedging under GAAP \| Foreign Exchange Contracts
Derivative [Line Items]
NOTIONAL VALUE	4,650.7	4,077.4
FAIR VALUE, ASSET	6.7	13.3
FAIR VALUE, LIABILITY	$ 103.9	$ 31.9

Derivative Financial Instrume_4

Derivative Financial Instruments (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gains or losses reclassified into earnings	$ 0	$ 0	$ 0	$ 0
Estimated net gain (loss) to be reclassified into net income within the next twelve months relating to cash flow hedges			$ 2,700,000
Maximum length of time over which exposure was being hedged			3 months
Net investment gains (losses) recognized in AOCI	$ (135,600,000)	$ 129,900,000	$ (36,300,000)	$ 66,800,000

Derivative Financial Instrume_5

Derivative Financial Instruments (Location and Amount of Fair Value And Cash Flow Hedge Derivative Gains And Losses Recorded In Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Interest Income	$ 2,530.2	$ 1,935	$ 7,482.3	$ 5,125.4
Interest Expense	1,967.9	1,478.8	5,869	3,626.5
Other Operating Income	111.8	68.2	1,097.5	170.2
INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	29.3	11.1	79.9	34.7
Gains (Losses) on cash flow hedges recognized on	0.6	14.6	7.1	15.8
INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	(20.1)	(24.9)	(59.9)	(65.9)
Gains (Losses) on cash flow hedges recognized on	0	0	0	0
OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Total gains (losses) recognized on fair value hedges	0	0	0	0
Gains (Losses) on cash flow hedges recognized on	0	0.3	0	1.9
Interest Rate Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	(251.6)	14.1	(94.1)	0.6
Recognized on hedged items	251.6	(14.1)	94.1	(0.6)
Amounts related to interest settlements on derivatives	29.3	11.1	79.9	34.7
Interest Rate Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	76.5	(41.8)	46.5	(42.5)
Recognized on hedged items	(76.5)	41.8	(46.5)	42.5
Amounts related to interest settlements on derivatives	(20.1)	(24.9)	(59.9)	(65.9)
Interest Rate Contracts \| OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Recognized on derivatives	0	0	0	0
Recognized on hedged items	0	0	0	0
Amounts related to interest settlements on derivatives	0	0	0	0
Foreign Exchange Contracts \| INTEREST INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	0.6	14.6	7.1	15.8
Foreign Exchange Contracts \| INTEREST EXPENSE
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	0	0	0	0
Foreign Exchange Contracts \| OTHER OPERATING INCOME
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Losses) on cash flow hedges recognized on	$ 0	$ 0.3	$ 0	$ 1.9

Derivative Financial Instrume_6

Derivative Financial Instruments (Hedged Items In Fair Value Hedges) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Carrying value of the hedged items, available for sale debt securities	$ 7,779.7	$ 5,048.8
Cumulative hedge accounting basis adjustment, available for sale debt securities	171.9	77.5
Carrying value of the hedged items, senior notes and long-term subordinated debt	2,554.9	2,495.9
Cumulative hedge accounting basis adjustment, senior notes and long-term subordinated debt	(190.3)	(248.7)
Hedged asset fair value hedge discontinued cumulative increase decrease	1.9	2.2
Hedged liability fair value hedge discontinued cumulative increase decrease	$ 17.7	$ 29.6

Derivative Financial Instrume_7

Derivative Financial Instruments (Location and Amount of Gains and Losses Recorded in Income for Derivatives Not Designated As Hedging Under GAAP) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivatives Not Designated as Hedging under GAAP
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ 41.2	$ 56.8	$ 141.7	$ 147.6
Non-Designated Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	(13.8)	3.8	(30.6)	(15.4)
Non-Designated Risk Management Derivatives \| Foreign Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ 0	$ 1.4	$ (0.2)	$ 2.9
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Operating Income	Other Operating Income	Other Operating Income	Other Operating Income
Non-Designated Risk Management Derivatives \| Other Financial Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ (13.8)	$ 2.4	$ (30.4)	$ (18.3)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Operating Income	Other Operating Income	Other Operating Income	Other Operating Income
Client-Related and Trading Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ 55	$ 53	$ 172.3	$ 163
Client-Related and Trading Derivatives \| Foreign Exchange Contracts
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ 54.1	$ 51.8	$ 169.5	$ 154.9
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Foreign Exchange Trading Income	Foreign Exchange Trading Income	Foreign Exchange Trading Income	Foreign Exchange Trading Income
Client-Related and Trading Derivatives \| Interest Rate Contracts
Derivative Instruments, Gain (Loss) [Line Items]
AMOUNT OF DERIVATIVE GAINS (LOSSES) RECOGNIZED IN INCOME	$ 0.9	$ 1.2	$ 2.8	$ 8.1
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Security Commissions and Trading Income	Security Commissions and Trading Income	Security Commissions and Trading Income	Security Commissions and Trading Income

Securities Sold Under Agreeme_3

Securities Sold Under Agreements to Repurchase (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Securities Sold Under Agreements to Repurchase	$ 170.8	$ 784.7
OVERNIGHT AND CONTINUOUS
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	170.8	784.7
OVERNIGHT AND CONTINUOUS \| U.S. Treasury and Agency Securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Borrowings	$ 170.8	$ 784.7

Offsetting of Assets and Liab_3

Offsetting of Assets and Liabilities (Offsetting of Derivative Assets and Securities Purchased Under Agreements to Resell) (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	$ 3,280.7	$ 3,307.8
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,773.1	3,126.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	507.6	181.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	10.3	12.2
NET AMOUNT	497.3	168.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	238.3	260.4
Total Derivatives
GROSS RECOGNIZED ASSETS	3,519	3,568.2
Derivative Assets	745.9	441.5
NET AMOUNT	735.6	429.3
Securities Purchased under Agreements to Resell
GROSS RECOGNIZED ASSETS	66,358.2	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	65,376.6	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	981.6	784.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	981.6	784.7
NET AMOUNT	0	0
Other assets excluding derivatives and non financial instruments	10,400	10,300
Foreign Exchange Contracts \| Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	2,814.6	3,006.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	2,664.5	2,937.2
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	150.1	69.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	10.3	12.2
NET AMOUNT	139.8	56.9
Interest Rate Swap Contracts \| Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS	466.1	301.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	108.6	189.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	357.5	111.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0	0
NET AMOUNT	$ 357.5	111.9
Interest Rate Swap Contracts \| Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED ASSETS		0.1
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		0.1
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET		0
NET AMOUNT		$ 0.1

Offsetting of Assets and Liab_4

Offsetting of Assets and Liabilities (Offsetting of Derivative Liabilities and Securities Sold Under Agreements to Repurchase) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	$ 2,758.3	$ 2,806.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,819.9	2,205.4
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	938.4	600.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0	0
NET AMOUNT	938.4	600.9
Total Derivatives Not Subject to a Master Netting Arrangement
Total Derivatives Not Subject to a Master Netting Arrangement	857.5	843.5
Offsetting Derivative Liabilities [Abstract]
GROSS RECOGNIZED LIABILITIES	3,615.8	3,649.8
Derivative Liabilities	1,795.9	1,444.4
NET AMOUNT	1,795.9	1,444.4
Securities Sold under Agreements to Repurchase
GROSS RECOGNIZED LIABILITIES	65,547.4	62,860.2
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	65,376.6	62,075.5
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	170.8	784.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	170.8	784.7
NET AMOUNT	0	0
Other liabilities	3,300	4,000
Foreign Exchange Contracts \| Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	2,226.4	2,411.7
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	1,784	2,175.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	442.4	236
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0	0
NET AMOUNT	442.4	236
Interest Rate Swap Contracts \| Over the Counter Derivative
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	504.1	368.3
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	9.1	6
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	495	362.3
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0	0
NET AMOUNT	495	362.3
Interest Rate Swap Contracts \| Interest Rate Swaps Exchange Cleared
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES		0.9
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET		0
NET AMOUNTS PRESENTED IN THE BALANCE SHEET		0.9
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET		0
NET AMOUNT		0.9
Other Financial Derivatives \| Other Financial Derivatives
Total Derivatives Subject to a Master Netting Arrangement
GROSS RECOGNIZED LIABILITIES	27.8	25.4
GROSS AMOUNTS OFFSET IN THE BALANCE SHEET	26.8	23.7
NET AMOUNTS PRESENTED IN THE BALANCE SHEET	1	1.7
GROSS AMOUNTS NOT OFFSET IN THE BALANCE SHEET	0	0
NET AMOUNT	$ 1	$ 1.7

Offsetting of Assets and Liab_5

Offsetting of Assets and Liabilities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Offsetting Assets and Liabilities [Line Items]
Collateral received	$ 10.3	$ 12.2
Gross amounts not offset in the balance sheet	0	0
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	1,200	1,200
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	929.3	1,100
Net maximum amount of termination payments that could have been required	270.9	52.2
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Collateral received	140.3
Gross amounts not offset in the balance sheet	$ 10
Cash collateral received from derivative counterparties and not offset against derivative assets		373.1
Cash collateral deposited with derivative counterparties not offset against derivative liabilities		$ 21.3