Markel (MKL) 10-Q1 Nov 222022 Q3 Quarterly reportFinancial data

Company Profile

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
Document And Entity Information - shares	Sep. 30, 2022	Oct. 25, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2022
Document Transition Report	false
Entity File Number	001-15811
Entity Registrant Name	MARKEL CORPORATION
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	54-1959284
Entity Address, Address Line One	4521 Highwoods Parkway
Entity Address, City or Town	Glen Allen
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	23060-6148
City Area Code	804
Local Phone Number	747-0136
Title of 12(b) Security	Common Stock, no par value
Trading Symbol	MKL
Security Exchange Name	NYSE
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		13,450,401
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001096343
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets [Abstract]
Fixed maturity securities, available-for-sale (amortized cost of $12,845,579 in 2022 and $12,061,467 in 2021)	$ 11,726,357	$ 12,587,305
Equity securities (cost of $3,005,729 in 2022 and $2,867,899 in 2021)	6,950,357	9,023,927
Short-term investments, available-for-sale (estimated fair value approximates cost)	2,424,844	1,799,988
Total Investments	21,101,558	23,411,220
Cash and cash equivalents	3,540,690	3,978,490
Restricted cash and cash equivalents	1,255,178	902,457
Receivables	2,956,686	2,413,938
Reinsurance recoverables	8,258,499	7,293,555
Deferred policy acquisition costs	946,064	794,145
Prepaid reinsurance premiums	2,285,959	1,798,571
Goodwill	2,797,426	2,899,140
Intangible assets	1,686,212	1,822,486
Other assets	3,593,083	3,163,094
Total Assets	48,421,355	48,477,096
Liabilities and Equity [Abstract]
Unpaid losses and loss adjustment expenses	20,194,374	18,178,894
Life and annuity benefits	733,489	902,980
Unearned premiums	6,514,980	5,383,619
Payables to insurance and reinsurance companies	685,294	616,665
Senior long-term debt and other debt (estimated fair value of $3,520,000 in 2022 and $5,017,000 in 2021)	4,131,165	4,361,266
Other liabilities	3,290,291	3,832,084
Total Liabilities	35,549,593	33,275,508
Redeemable noncontrolling interests	513,043	461,378
Commitments and contingencies
Shareholders' equity:
Preferred Stock	591,891	591,891
Common stock	3,482,828	3,441,079
Retained earnings	9,255,658	10,446,763
Accumulated other comprehensive income (loss)	(1,036,454)	237,617
Total Shareholders' Equity	12,293,923	14,717,350
Noncontrolling interests	64,796	22,860
Total Equity	12,358,719	14,740,210
Total Liabilities and Equity	$ 48,421,355	$ 48,477,096

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 12,845,579	$ 12,061,467
Equity securities, cost	3,005,729	2,867,899
Senior long-term debt and other debt, fair value	$ 3,520,000	$ 5,017,000

Consolidated Statements Of Inco

Consolidated Statements Of Income (Loss) And Comprehensive Income (Loss) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2022		Sep. 30, 2021
OPERATING REVENUES
Earned premiums		$ 1,956,830		$ 1,630,500		$ 5,549,704		$ 4,696,232
Net investment income		107,731		91,264		274,123		284,095
Net investment gains (losses)		(281,483)		(25,833)		(2,194,525)		1,175,791
Products revenues		586,531		405,711		1,845,111		1,327,144
Services and other revenues		696,536		585,712		1,990,175		1,605,058
Total Operating Revenues		3,066,145		2,687,354		7,464,588		9,088,320
OPERATING EXPENSES
Losses and loss adjustment expenses		1,185,313		948,241		3,216,495		2,643,114
Underwriting, acquisition and insurance expenses		643,272		569,756		1,843,106		1,644,863
Products expenses		580,830		374,407		1,726,367		1,173,135
Services and other expenses		540,569	[1]	513,994		1,692,203	[2]	1,442,342
Amortization of intangible assets		43,418	[3]	39,268	[4]	134,990	[5]	118,550	[6]
Total Operating Expenses		2,993,402		2,445,666		8,613,161		7,022,004
Operating Income (Loss)		72,743		241,688		(1,148,573)		2,066,316
Interest expense		(47,348)		(46,455)		(147,090)		(135,412)
Net foreign exchange gains		115,130		48,850		245,356		61,677
Income (Loss) Before Income Taxes		140,525		244,083		(1,050,307)		1,992,581
Income tax (expense) benefit		(17,995)		(54,415)		239,536		(419,898)
Net Income (Loss)		122,530		189,668		(810,771)		1,572,683
Net income attributable to noncontrolling interests		(57,161)		(1,598)		(93,062)		(18,809)
Net Income (Loss) to Shareholders		65,369		188,070		(903,833)		1,553,874
Preferred stock dividends		0		0		(18,000)		(18,000)
Net Income (Loss) to Common Shareholders		65,369		188,070		(921,833)		1,535,874
OTHER COMPREHENSIVE LOSS
Net holding losses arising during the period		(424,929)		(104,238)		(1,263,839)		(262,679)
Reclassification adjustments for net gains (losses) included in net income (loss)		591		224		2,289		(3,807)
Change in net unrealized gains (losses) on available-for-sale investments, net of taxes		(424,338)		(104,014)		(1,261,550)		(266,486)
Change in foreign currency translation adjustments, net of taxes		(8,872)		(4,437)		(14,395)		(330)
Change in net actuarial pension loss, net of taxes		303		586		1,808		1,832
Total Other Comprehensive Loss		(432,907)		(107,865)		(1,274,137)		(264,984)
Comprehensive Income (Loss)		(310,377)		81,803		(2,084,908)		1,307,699
Comprehensive income attributable to noncontrolling interests		(57,051)		(1,567)		(92,996)		(18,812)
Comprehensive Income (Loss) to Shareholders		$ (367,428)		$ 80,236		$ (2,177,904)		$ 1,288,887
NET INCOME (LOSS) PER COMMON SHARE
Basic		$ 3.51		$ 15.12		$ (72.31)		$ 114.39
Diluted	[7]	$ 3.50		$ 15.09		$ (72.31)		$ 114.20

[1]Services and other expenses for Other for the quarter ended September 30, 2022 included $53.4 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11.[2]Services and other expenses for Other for the nine months ended September 30, 2022 included $81.6 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11.[3]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[4]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[5]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[6]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[7]The impact of 28 thousand shares from restricted stock units and restricted stock was excluded from the computation of diluted net loss per common share for the nine months ended September 30, 2022 because the effect would have been anti-dilutive.

Consolidated Statements Of Chan

Consolidated Statements Of Changes In Equity - USD ($) $ in Thousands	Total	Total Equity [Member]	Total Shareholders' Equity [Member]	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]	Velocity [Member] Total Equity [Member]	Velocity [Member] Noncontrolling Interests [Member]	Metromont LLC [Member] Redeemable Noncontrolling Interests [Member]	Buckner HeavyLift Cranes [Member] Redeemable Noncontrolling Interests [Member]
Balance at Dec. 31, 2020		$ 12,814,681	$ 12,799,789	$ 591,891	$ 3,428,340	$ 8,195,182	$ 584,376	$ 14,892
Balance, redeemable noncontrolling interests at Dec. 31, 2020									$ 245,642
Net Income (Loss)	$ 1,572,683	1,561,834	1,553,874			1,553,874	0	7,960	10,849
Other comprehensive income (loss)	(264,984)	(264,987)	(264,987)			0	(264,987)	0	3
Comprehensive Income (Loss)	1,307,699	1,296,847	1,288,887					7,960	10,852
Repurchase of common stock		(122,377)	(122,377)	0	0	(122,377)	0	0	0
Preferred stock dividends		(18,000)	(18,000)	0	0	(18,000)	0	0	0
Restricted stock units expensed		27,783	27,783	0	27,783	0	0	0	0
Adjustment of redeemable noncontrolling interests		41,553	41,553	0	0	41,553	0	0	(41,553)
Purchase of noncontrolling interest		(1,551)	(1,551)	0	(1,551)	0	0	0	(1,179)
Acquisitions		0	0	0	0	0	0	0					$ (26,438)
Other		1,289	680	0	557	123	0	609	(8,288)
Balance at Sep. 30, 2021		14,062,527	14,039,066	591,891	3,455,129	9,672,657	319,389	23,461
Balance, redeemable noncontrolling interests at Sep. 30, 2021									231,912
Balance at Jun. 30, 2021		14,020,351	13,997,273	591,891	3,451,968	9,526,191	427,223	23,078
Balance, redeemable noncontrolling interests at Jun. 30, 2021									228,401
Net Income (Loss)	189,668	188,628	188,070			188,070	0	558	1,040
Other comprehensive income (loss)	(107,865)	(107,834)	(107,834)			0	(107,834)	0	(31)
Comprehensive Income (Loss)	81,803	80,794	80,236					558	1,009
Repurchase of common stock		(61,551)	(61,551)	0	0	(61,551)	0	0	0
Restricted stock units expensed		4,181	4,181	0	4,181	0	0	0	0
Adjustment of redeemable noncontrolling interests		19,930	19,930	0	0	19,930	0	0	(19,930)
Purchase of noncontrolling interest		(1,020)	(1,020)	0	(1,020)	0	0	0	(1,032)
Acquisitions		0	0	0	0	0	0	0					$ (26,438)
Other		(158)	17	0	0	17	0	(175)	(2,974)
Balance at Sep. 30, 2021		14,062,527	14,039,066	591,891	3,455,129	9,672,657	319,389	23,461
Balance, redeemable noncontrolling interests at Sep. 30, 2021									231,912
Balance at Dec. 31, 2021	14,740,210	14,740,210	14,717,350	591,891	3,441,079	10,446,763	237,617	22,860
Balance, redeemable noncontrolling interests at Dec. 31, 2021	461,378								461,378
Net Income (Loss)	(810,771)	(825,550)	(903,833)			(903,833)	0	78,283	14,779
Other comprehensive income (loss)	(1,274,137)	(1,274,071)	(1,274,071)			0	(1,274,071)	0	(66)
Comprehensive Income (Loss)	(2,084,908)	(2,099,621)	(2,177,904)					78,283	14,713
Repurchase of common stock		(208,090)	(208,090)	0	0	(208,090)	0	0	0
Preferred stock dividends		(18,000)	(18,000)	0	0	(18,000)	0	0	0
Restricted stock units expensed		37,531	37,531	0	37,531	0	0	0	0
Adjustment of redeemable noncontrolling interests		(62,168)	(62,168)	0	0	(62,168)	0	0	62,168
Acquisitions		0	0	0	0	0	0	0				$ (18,681)
Dispositions			0	0	0	0	0		0	$ (22,059)	$ (22,059)
Redemption of Markel CATCo Re noncontrolling interests		(22,261)	0	0	0	0	0	(22,261)	0
Other		13,177	5,204	0	4,218	986	0	7,973	(6,535)
Balance at Sep. 30, 2022	12,358,719	12,358,719	12,293,923	591,891	3,482,828	9,255,658	(1,036,454)	64,796
Balance, redeemable noncontrolling interests at Sep. 30, 2022	513,043								513,043
Balance at Jun. 30, 2022		12,767,332	12,756,207	591,891	3,478,153	9,289,820	(603,657)	11,125
Balance, redeemable noncontrolling interests at Jun. 30, 2022									495,378
Net Income (Loss)	122,530	118,236	65,369			65,369	0	52,867	4,294
Other comprehensive income (loss)	(432,907)	(432,797)	(432,797)			0	(432,797)	0	(110)
Comprehensive Income (Loss)	(310,377)	(314,561)	(367,428)					52,867	4,184
Repurchase of common stock		(81,799)	(81,799)	0	0	(81,799)	0	0	0
Restricted stock units expensed		4,661	4,661	0	4,661	0	0	0	0
Adjustment of redeemable noncontrolling interests		(17,730)	(17,730)	0	0	(17,730)	0	0	17,730
Other		816	12	0	14	(2)	0	804	(4,249)
Balance at Sep. 30, 2022	12,358,719	$ 12,358,719	$ 12,293,923	$ 591,891	$ 3,482,828	$ 9,255,658	$ (1,036,454)	$ 64,796
Balance, redeemable noncontrolling interests at Sep. 30, 2022	$ 513,043								$ 513,043

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
OPERATING ACTIVITIES
Net income (loss)	$ (810,771)	$ 1,572,683
Adjustments to reconcile net income (loss) to net cash provided by operating activities	2,691,043	49,759
Net Cash Provided By Operating Activities	1,880,272	1,622,442
INVESTING ACTIVITIES
Proceeds from sales, maturities, calls and prepayments of fixed maturity securities	557,742	491,319
Cost of fixed maturity securities purchased	(1,433,299)	(2,201,622)
Proceeds from sales of equity securities	164,277	157,891
Cost of equity securities purchased	(293,011)	(178,368)
Net change in short-term investments	(625,261)	(727,366)
Additions to property and equipment	(209,282)	(80,758)
Acquisitions, net of cash acquired	(14,000)	(241,210)
Consolidation of Markel CATCo Re, net	629,955	0
Distributions to Markel CATCo Re noncontrolling interests for buy-out transaction	(169,380)	0
Proceeds from sale of business, net	109,505	40,720
Other	(571)	6,903
Net Cash Used By Investing Activities	(1,283,325)	(2,732,491)
FINANCING ACTIVITIES
Additions to senior long-term debt and other debt	757,941	989,067
Repayment of senior long-term debt and other debt	(982,852)	(370,157)
Repurchases of common stock	(208,090)	(122,377)
Dividends paid on preferred stock	(18,000)	(18,000)
Other	(40,053)	(39,149)
Net Cash Provided (Used) By Financing Activities	(491,054)	439,384
Effect of foreign currency rate changes on cash, cash equivalents, restricted cash and restricted cash equivalents	(190,972)	(38,973)
Decrease in cash, cash equivalents, restricted cash and restricted cash equivalents	(85,079)	(709,638)
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of period	4,880,947	5,216,649
CASH, CASH EQUIVALENTS, RESTRICTED CASH AND RESTRICTED CASH EQUIVALENTS AT END OF PERIOD	$ 4,795,868	$ 4,507,011

Summary Of Significant Accounti

Summary Of Significant Accounting Policies	9 Months Ended
Summary Of Significant Accounting Policies	Sep. 30, 2022
Accounting Policies [Abstract]
Summary Of Significant Accounting Policies	Summary of Significant Accounting Policies Markel Corporation is a diverse financial holding company serving a variety of niche markets. Markel Corporation's principal business markets and underwrites specialty insurance products. Through its wholly owned subsidiary, Markel Ventures, Inc. (Markel Ventures), Markel Corporation also owns controlling interests in various businesses that operate outside of the specialty insurance marketplace. See note 2 for details regarding reportable segments. a) Basis of Presentation. The consolidated balance sheet as of September 30, 2022 and the related consolidated statements of income (loss) and comprehensive income (loss) and changes in equity for the quarters and nine months ended September 30, 2022 and 2021, and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. In the opinion of management, all adjustments necessary for fair presentation of such consolidated financial statements have been included. Except for the adjustment described in note 15, such adjustments consist only of normal, recurring items. Interim results are not necessarily indicative of results of operations for the entire year. The consolidated balance sheet as of December 31, 2021 was derived from Markel Corporation's audited annual consolidated financial statements. The accompanying consolidated financial statements have been prepared in accordance with United States (U.S.) generally accepted accounting principles (GAAP) and include the accounts of Markel Corporation and its consolidated subsidiaries, as well as any variable interest entities (VIEs) that meet the requirements for consolidation (the Company). All significant intercompany balances and transactions have been eliminated in consolidation. The Company consolidates the results of its Markel Ventures subsidiaries on a one-month lag, with the exception of significant transactions or events that occur during the intervening period. Certain prior period amounts have been reclassified to conform to the current period presentation. The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results may differ materially from the estimates and assumptions used in preparing the consolidated financial statements. The consolidated financial statements and notes are presented as permitted by Form 10-Q and do not contain certain information included in the Company's annual consolidated financial statements and notes. For a more complete description of the Company's business and accounting policies, readers are urged to review the Company's 2021 Annual Report on Form 10-K, as well as note 15 for details regarding a change to the Company's policy for accounting for deferred policy acquisition costs. b) Recent Accounting Pronouncements Accounting Standards Not Yet Adopted In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-12, Financial Services—Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts. The FASB subsequently issued several ASUs as amendments to ASU No. 2018-12. The standard requires insurance companies with long duration contracts to: (1) review and, if there is a change, update the assumptions used to measure expected cash flows at least annually; (2) update the discount rate assumption at each reporting date; and (3) enhance certain qualitative and quantitative disclosures. ASU No. 2018-12 becomes effective for the Company during the first quarter of 2023 and will be applied using a modified retrospective approach that requires restatement of prior periods presented, including a cumulative adjustment to accumulated other comprehensive income as of January 1, 2021 (the transition date). The standard will, among other things, impact the discount rate used in estimating reserves for the Company's life and annuity reinsurance portfolio, which is in runoff. Currently, the discount rate assumption is locked-in for the life of the contracts, unless there is a loss recognition event. Based on the Company's current estimate, the adoption of ASU 2018-12 is expected to result in a decrease to accumulated other comprehensive income of less than $25 million, net of taxes, as a result of changing the discount rate assumption as of the transition date. However, the cumulative impact of changes in the discount rate assumption upon adopting ASU 2018-12 in the first quarter of 2023 will be based on the discount rate assumption determined as of the January 1, 2023 adoption date. Based on increases in interest rates subsequent to the transition date, the Company expects that an update to the discount rate assumption as of September 30, 2022 would result in a cumulative increase to accumulated other comprehensive income. The Company is still determining the ultimate impact that adopting ASU No. 2018-12 will have on its consolidated financial statements. In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customer s, which becomes effective for the Company during the first quarter of 2023. ASU No. 2021-08 requires contract assets and liabilities accounted for under FASB Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers , to be recorded at the acquisition date as if the acquirer entered into those contracts itself on the contract inception dates, rather than at fair value. At adoption, ASU No. 2021-08 will not impact the Company's financial position, results of operations or cash flows, but prospectively, this ASU will impact amounts recorded by the Company for assets acquired and liabilities assumed in conjunction with certain acquisitions.

Segment Reporting Disclosures

Segment Reporting Disclosures	9 Months Ended
Segment Reporting Disclosures	Sep. 30, 2022
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Segment Reporting Disclosures	Segment Reporting Disclosures The chief operating decision maker reviews the Company's ongoing underwriting operations on a global basis in the following two segments: Insurance and Reinsurance. In determining how to allocate resources and assess the performance of the Company's underwriting results, management considers many factors, including the nature of the insurance product sold, the type of account written and the type of customer served. The Insurance segment includes all direct business and facultative placements written on a risk-bearing basis within the Company's underwriting operations. The Reinsurance segment includes all treaty reinsurance written on a risk-bearing basis within the Company's underwriting operations. All investing activities related to the Company's insurance operations are included in the Investing segment. The chief operating decision maker reviews and assesses Markel Ventures' performance in the aggregate, as a single operating segment. The Markel Ventures segment primarily consists of controlling interests in a diverse portfolio of businesses that operate in various industries. The Company's other operations primarily consist of the results of the Company's insurance-linked securities operations and program services business. Other operations also include results for lines of business discontinued prior to, or in conjunction with, acquisitions, including development on asbestos and environmental loss reserves and results attributable to the run-off of life and annuity reinsurance business, which are monitored separately from the Company's ongoing underwriting operations. For purposes of segment reporting, none of these other operations are considered to be reportable segments. Segment profit for each of the Company's underwriting segments is measured by underwriting profit. The property and casualty insurance industry commonly defines underwriting profit as earned premiums net of losses and loss adjustment expenses and underwriting, acquisition and insurance expenses. Underwriting profit does not replace operating income or net income computed in accordance with U.S. GAAP as a measure of profitability. Underwriting profit or loss provides a basis for management to evaluate the Company's underwriting performance. Segment profit for the Company's underwriting segments may also include other revenues and expenses that are attributable to the Company's underwriting operations that are not captured in underwriting profit. Segment profit for the Investing segment is measured by net investment income and net investment gains. Segment profit for the Markel Ventures segment is measured by operating income. For management reporting purposes, the Company allocates assets to its underwriting operations and to its Investing and Markel Ventures segments and certain of its other operations, including its insurance-linked securities and program services operations. Underwriting assets include assets attributed to the Company's Insurance and Reinsurance segments, discontinued underwriting lines of business, as well as assets that are not specifically allocated to the Company's other operations. Generally, the Company manages its underwriting assets in the aggregate and therefore does not allocate assets to individual underwriting segments. a) The following tables summarize the Company's segment disclosures. Quarter Ended September 30, 2022 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 2,299,325 $ 179,455 $ — $ — $ 995,991 $ 3,474,771 Net written premiums 1,849,983 154,029 — — 5,155 2,009,167 Earned premiums 1,695,029 260,535 — — 1,266 1,956,830 Losses and loss adjustment expenses: Current accident year (1,100,511) (166,485) — — — (1,266,996) Prior accident years 53,760 29,505 — — (1,582) 81,683 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (362,137) (68,662) — — (383) (431,182) Other underwriting expenses (200,604) (11,638) — — 152 (212,090) Underwriting profit (loss) 85,537 43,255 — — (547) 128,245 Net investment income — — 107,414 317 — 107,731 Net investment losses — — (281,483) — — (281,483) Products revenues — — — 586,531 — 586,531 Services and other revenues — — — 629,215 67,321 696,536 Products expenses — — — (580,830) — (580,830) Services and other expenses (3) — — — (556,207) 15,638 (540,569) Amortization of intangible assets (4) — — — (18,567) (24,851) (43,418) Segment profit (loss) $ 85,537 $ 43,255 $ (174,069) $ 60,459 $ 57,561 $ 72,743 Interest expense (47,348) Net foreign exchange gains 115,130 Income before income taxes $ 140,525 U.S. GAAP combined ratio (5) 95 % 83 % NM (6) 93 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $23.7 million for the quarter ended September 30, 2022. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $9.6 million for the quarter ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Services and other expenses for Other for the quarter ended September 30, 2022 included $53.4 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11. (4) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (5) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (6) NM - Ratio is not meaningful Quarter Ended September 30, 2021 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 1,899,592 $ 180,673 $ — $ — $ 888,337 $ 2,968,602 Net written premiums 1,545,428 141,642 — — (2,260) 1,684,810 Earned premiums 1,381,235 250,962 — — (1,697) 1,630,500 Losses and loss adjustment expenses: Current accident year (866,481) (221,872) — — — (1,088,353) Prior accident years 124,133 16,292 — — (313) 140,112 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (289,201) (63,723) — — — (352,924) Other underwriting expenses (202,961) (12,101) — — (1,770) (216,832) Underwriting profit (loss) 146,725 (30,442) — — (3,780) 112,503 Net investment income — — 91,261 3 — 91,264 Net investment losses — — (25,833) — — (25,833) Products revenues — — — 405,711 — 405,711 Services and other revenues — — — 502,471 83,241 585,712 Products expenses — — — (374,407) — (374,407) Services and other expenses — — — (465,268) (48,726) (513,994) Amortization of intangible assets (3) — — — (13,541) (25,727) (39,268) Segment profit (loss) $ 146,725 $ (30,442) $ 65,428 $ 54,969 $ 5,008 $ 241,688 Interest expense (46,455) Net foreign exchange gains 48,850 Income before income taxes $ 244,083 U.S. GAAP combined ratio (4) 89 % 112 % NM (5) 93 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $15.8 million for the quarter ended September 30, 2021. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $10.3 million for the quarter ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (4) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (5) NM - Ratio is not meaningful Nine Months Ended September 30, 2022 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 6,479,789 $ 1,044,827 $ — $ — $ 2,628,491 $ 10,153,107 Net written premiums 5,289,165 983,087 — — 1,444 6,273,696 Earned premiums 4,742,178 808,656 — — (1,130) 5,549,704 Losses and loss adjustment expenses: Current accident year (2,906,031) (514,875) — — — (3,420,906) Prior accident years 196,093 13,845 — — (5,527) 204,411 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (996,369) (209,541) — — (415) (1,206,325) Other underwriting expenses (596,426) (37,708) — — (2,647) (636,781) Underwriting profit (loss) 439,445 60,377 — — (9,719) 490,103 Net investment income — — 273,699 424 — 274,123 Net investment losses — — (2,194,525) — — (2,194,525) Products revenues — — — 1,845,111 — 1,845,111 Services and other revenues — — — 1,682,318 307,857 1,990,175 Products expenses — — — (1,726,367) — (1,726,367) Services and other expenses (3) — — — (1,524,167) (168,036) (1,692,203) Amortization of intangible assets (4) — — — (60,077) (74,913) (134,990) Segment profit (loss) $ 439,445 $ 60,377 $ (1,920,826) $ 217,242 $ 55,189 $ (1,148,573) Interest expense (147,090) Net foreign exchange gains 245,356 Loss before income taxes $ (1,050,307) U.S. GAAP combined ratio (5) 91 % 93 % NM (6) 91 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $75.3 million for the nine months ended September 30, 2022. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $29.0 million for the nine months ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Services and other expenses for Other for the nine months ended September 30, 2022 included $81.6 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11. (4) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (5) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (6) NM - Ratio is not meaningful Nine Months Ended September 30, 2021 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 5,359,293 $ 992,635 $ — $ — $ 2,305,539 $ 8,657,467 Net written premiums 4,427,301 893,082 — — (3,052) 5,317,331 Earned premiums 3,928,824 770,031 — — (2,623) 4,696,232 Losses and loss adjustment expenses: Current accident year (2,448,034) (561,226) — — — (3,009,260) Prior accident years 397,723 (34,104) — — 2,527 366,146 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (814,623) (193,697) — — — (1,008,320) Other underwriting expenses (594,880) (39,676) — — (1,987) (636,543) Underwriting profit (loss) 469,010 (58,672) — — (2,083) 408,255 Net investment income — — 284,087 8 — 284,095 Net investment gains — — 1,175,791 — — 1,175,791 Products revenues — — — 1,327,144 — 1,327,144 Services and other revenues — — — 1,363,141 241,917 1,605,058 Products expenses — — — (1,173,135) — (1,173,135) Services and other expenses — 109 — (1,260,957) (181,494) (1,442,342) Amortization of intangible assets (3) — — — (41,104) (77,446) (118,550) Segment profit (loss) $ 469,010 $ (58,563) $ 1,459,878 $ 215,097 $ (19,106) $ 2,066,316 Interest expense (135,412) Net foreign exchange gains 61,677 Income before income taxes $ 1,992,581 U.S. GAAP combined ratio (4) 88 % 108 % NM (5) 91 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $47.7 million for the nine months ended September 30, 2021. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $31.1 million for the nine months ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (4) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (5) NM - Ratio is not meaningful b) The following table reconciles segment assets to the Company's consolidated balance sheets. (dollars in thousands) September 30, 2022 December 31, 2021 Segment assets: Investing $ 25,389,047 $ 28,277,801 Underwriting 8,805,475 8,111,316 Markel Ventures 5,230,393 4,958,279 Total segment assets 39,424,915 41,347,396 Other operations 8,996,440 7,129,700 Total assets $ 48,421,355 $ 48,477,096

Acquisitions and Dispositions

Acquisitions and Dispositions	9 Months Ended
Acquisitions and Dispositions	Sep. 30, 2022
Business Combinations, Asset Acquisition and Disposition [Abstract]
Acquisitions and Dispositions	Acquisitions and Dispositions Velocity In February 2022, the Company sold the majority of its controlling interest in its Velocity managing general agent companies (Velocity) for total cash consideration of $181.3 million, which resulted in a gain of $107.3 million that was included in services and other revenues. Velocity provides risk origination services for the Company's Nephila insurance-linked securities fund management operations, as well as for third parties. The Company retained a minority interest in Velocity that was recorded at fair value as of the transaction date ($47.4 million) and is accounted for under the equity method. Volante In October 2022, the Company sold its controlling interest in its Volante managing general agent companies (Volante) for estimated total cash consideration of $155 million. Volante underwrites and administers specialty insurance and reinsurance policies and provides delegated underwriting services to third-party providers of insurance capital. The Company will complete the accounting for the disposition in the fourth quarter of 2022. Metromont LLC In December 2021, the Company acquired 51% of Metromont LLC (Metromont), a precast concrete manufacturer and concrete building solutions provider for commercial projects. Under the terms of the acquisition agreement, the Company has the option to acquire the remaining equity interests and the remaining equity holders have the option to sell their interests to the Company in the future. The redemption value of the remaining equity interests is generally based on Metromont's earnings in specified periods preceding the redemption dates. Total consideration for the transaction was $282.3 million, all of which was cash. As of December 31, 2021, the purchase price was preliminarily allocated to the acquired assets and liabilities based on estimated fair value at the acquisition date, which was subsequently updated during the first quarter of 2022. During the first quarter of 2022, the Company decreased the allocation to redeemable noncontrolling interests by $18.7 million with an offsetting decrease to goodwill of $18.7 million, resulting in a preliminary purchase price allocation that reflected goodwill of $200.6 million, intangible assets of $143.9 million and redeemable noncontrolling interests of $251.2 million. Goodwill is primarily attributable to expected future earnings and cash flow potential of Metromont, and it is expected to be deductible for income tax purposes. Results attributable to Metromont are included in the Company's Markel Ventures segment. The Company has not completed the process of determining the fair value of the assets acquired and liabilities assumed. These valuations are required to be completed within 12 months from the acquisition date. As a result, the fair value recorded for these items is a provisional estimate and is subject to adjustment. Once completed, any adjustments resulting from the valuations may impact the individual amounts recorded for assets acquired and liabilities assumed, as well as the residual goodwill. Buckner HeavyLift Cranes In August 2021, the Company acquired 90% of the holding company for the Buckner HeavyLift Cranes companies (Buckner), a provider of crane rental services for large commercial contractors. Under the terms of the acquisition agreement, the Company has the option to acquire the remaining equity interests and the remaining equity holders have the option to sell their interests to the Company in the future. The redemption value of the remaining equity interests is generally based on Buckner's earnings in specified periods preceding the redemption dates. Total consideration for the transaction was $237.9 million, all of which was cash. As of December 31, 2021, the purchase price was preliminarily allocated to the acquired assets and liabilities of Buckner based on estimated fair value at the acquisition date. During the third quarter of 2022, the Company completed the process of determining the fair value of the assets acquired and liabilities assumed with Buckner. The Company recognized goodwill of $109.9 million, intangible assets of $60.0 million and fixed assets of $290.4 million, primarily related to cranes. The final purchase price allocation reflected a decrease in the amount recognized for the cranes upon completion of a third-party valuation, which resulted in an increase to goodwill from the preliminary amount recognized. Goodwill is primarily attributable to expected future earnings and cash flow potential of Buckner, and it is not expected to be deductible for income tax purposes. Intangible assets include $50.0 million of customer relationships and $10.0 million of trade names, which are expected to be amortized over 7 years and 15 years, respectively. Additionally, the Company assumed long-term debt of $165.1 million and recognized redeemable noncontrolling interests of $26.4 million. Results attributable to Buckner are included in the Company's Markel Ventures segment.

Investments

Investments	9 Months Ended
Investments	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Investments	Investments a) The following tables summarize the Company's available-for-sale investments. Commercial and residential mortgage-backed securities include securities issued by U.S. government-sponsored enterprises and U.S. government agencies. The net unrealized holding gains (losses) in the tables below are presented before taxes and any reserve deficiency adjustments for life and annuity benefit reserves. See note 9. September 30, 2022 (dollars in thousands) Amortized Gross Gross Estimated Fixed maturity securities: U.S. Treasury securities $ 3,145,087 $ — $ (186,666) $ 2,958,421 U.S. government-sponsored enterprises 838,518 42 (113,378) 725,182 Obligations of states, municipalities and political subdivisions 3,975,846 3,479 (265,982) 3,713,343 Foreign governments 1,388,221 — (215,332) 1,172,889 Commercial mortgage-backed securities 2,103,907 1 (171,243) 1,932,665 Residential mortgage-backed securities 582,833 127 (25,627) 557,333 Asset-backed securities 2,066 — (54) 2,012 Corporate bonds 809,101 10 (144,599) 664,512 Total fixed maturity securities 12,845,579 3,659 (1,122,881) 11,726,357 Short-term investments 2,441,719 147 (17,022) 2,424,844 Investments, available-for-sale $ 15,287,298 $ 3,806 $ (1,139,903) $ 14,151,201 December 31, 2021 (dollars in thousands) Amortized Gross Gross Estimated Fixed maturity securities: U.S. Treasury securities $ 2,489,032 $ 2,633 $ (21,471) $ 2,470,194 U.S. government-sponsored enterprises 753,029 28,997 (6,439) 775,587 Obligations of states, municipalities and political subdivisions 4,007,211 266,575 (7,862) 4,265,924 Foreign governments 1,394,771 134,071 (9,488) 1,519,354 Commercial mortgage-backed securities 1,928,775 69,810 (8,152) 1,990,433 Residential mortgage-backed securities 699,136 27,084 (170) 726,050 Asset-backed securities 3,035 46 — 3,081 Corporate bonds 786,478 54,475 (4,271) 836,682 Total fixed maturity securities 12,061,467 583,691 (57,853) 12,587,305 Short-term investments 1,805,300 28 (5,340) 1,799,988 Investments, available-for-sale $ 13,866,767 $ 583,719 $ (63,193) $ 14,387,293 b) The following tables summarize gross unrealized investment losses on available-for-sale investments by the length of time that securities have continuously been in an unrealized loss position. September 30, 2022 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Gross Estimated Gross Estimated Gross Fixed maturity securities: U.S. Treasury securities $ 1,208,818 $ (59,585) $ 1,749,603 $ (127,081) $ 2,958,421 $ (186,666) U.S. government-sponsored enterprises 486,025 (63,103) 224,076 (50,275) 710,101 (113,378) Obligations of states, municipalities and political subdivisions 2,955,371 (205,139) 253,651 (60,843) 3,209,022 (265,982) Foreign governments 1,006,658 (177,900) 166,232 (37,432) 1,172,890 (215,332) Commercial mortgage-backed securities 1,677,058 (122,811) 255,181 (48,432) 1,932,239 (171,243) Residential mortgage-backed securities 510,227 (24,860) 3,899 (767) 514,126 (25,627) Asset-backed securities 2,012 (54) — — 2,012 (54) Corporate bonds 551,417 (118,451) 105,459 (26,148) 656,876 (144,599) Total fixed maturity securities 8,397,586 (771,903) 2,758,101 (350,978) 11,155,687 (1,122,881) Short-term investments 1,107,053 (17,022) — — 1,107,053 (17,022) Total $ 9,504,639 $ (788,925) $ 2,758,101 $ (350,978) $ 12,262,740 $ (1,139,903) At September 30, 2022, the Company held 1,548 available-for-sale securities in an unrealized loss position with a total estimated fair value of $12.3 billion and gross unrealized losses of $1.1 billion. Of these 1,548 securities, 172 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $2.8 billion and gross unrealized losses of $351.0 million. December 31, 2021 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Gross Estimated Gross Estimated Gross Fixed maturity securities: U.S. Treasury securities $ 2,236,637 $ (18,433) $ 97,173 $ (3,038) $ 2,333,810 $ (21,471) U.S. government-sponsored enterprises 381,495 (5,640) 14,010 (799) 395,505 (6,439) Obligations of states, municipalities and political subdivisions 393,249 (6,941) 23,589 (921) 416,838 (7,862) Foreign governments 322,813 (8,596) 25,564 (892) 348,377 (9,488) Commercial mortgage-backed securities 345,616 (7,765) 9,189 (387) 354,805 (8,152) Residential mortgage-backed securities 12,828 (159) 269 (11) 13,097 (170) Corporate bonds 193,786 (4,271) — — 193,786 (4,271) Total fixed maturity securities 3,886,424 (51,805) 169,794 (6,048) 4,056,218 (57,853) Short-term investments 228,870 (5,340) — — 228,870 (5,340) Total $ 4,115,294 $ (57,145) $ 169,794 $ (6,048) $ 4,285,088 $ (63,193) At December 31, 2021, the Company held 277 available-for-sale securities in an unrealized loss position with a total estimated fair value of $4.3 billion and gross unrealized losses of $63.2 million. Of these 277 securities, 13 securities had been in a continuous unrealized loss position for one year or longer and had a total estimated fair value of $169.8 million and gross unrealized losses of $6.0 million. The Company completes a detailed analysis each quarter to assess whether the decline in the fair value of any investment below its cost basis is the result of a credit loss. All available-for-sale securities with unrealized losses are reviewed. The Company considers many factors in completing its quarterly review of securities with unrealized losses for credit-related impairment to determine whether a credit loss exists, including the extent to which fair value is below cost, the implied yield to maturity, rating downgrades of the security and whether or not the issuer has failed to make scheduled principal or interest payments. The Company also takes into consideration information about the financial condition of the issuer and industry factors that could negatively impact the capital markets. If the decline in fair value of an available-for-sale security below its amortized cost is considered to be the result of a credit loss, the Company compares the estimated present value of the cash flows expected to be collected to the amortized cost of the security. The extent to which the estimated present value of the cash flows expected to be collected is less than the amortized cost of the security represents the credit loss, which is recorded as an allowance and recognized in net income. The allowance is limited to the difference between the fair value and the amortized cost of the security. Any remaining decline in fair value represents the non-credit portion of the impairment, which is recognized in other comprehensive income. The Company did not have an allowance for credit losses as of September 30, 2022 or December 31, 2021. Quarterly, the Company also considers whether it intends to sell an available-for-sale security or if it is more likely than not that it will be required to sell a security before recovery of its amortized cost. In these instances, a decline in fair value is recognized in net income based on the fair value of the security at the time of assessment, resulting in a new cost basis for the security. As of September 30, 2022, t he Company did not intend to sell or believe it would be required to sell any available-for-sale securities in an unrealized loss position before recovery of their amortized cost. c) The amortized cost and estimated fair value of fixed maturity securities at September 30, 2022 are shown below by contractual maturity. (dollars in thousands) Amortized Estimated Due in one year or less $ 1,392,651 $ 1,357,060 Due after one year through five years 3,943,834 3,649,795 Due after five years through ten years 2,993,861 2,618,759 Due after ten years 1,826,427 1,608,733 10,156,773 9,234,347 Commercial mortgage-backed securities 2,103,907 1,932,665 Residential mortgage-backed securities 582,833 557,333 Asset-backed securities 2,066 2,012 Total fixed maturity securities $ 12,845,579 $ 11,726,357 d) The following table presents the components of net investment income. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Interest: Tax-exempt municipal bonds $ 12,673 $ 14,293 $ 39,408 $ 43,631 Taxable municipal bonds 17,488 16,320 52,613 49,236 Other taxable bonds 42,316 39,705 123,520 119,718 Short-term investments, including overnight deposits 17,633 633 24,634 2,179 Dividends on equity securities 25,962 23,400 74,289 68,583 Income (loss) from equity method investments (5,509) 882 (35,002) 13,825 Other 1,103 (335) 7,041 (947) 111,666 94,898 286,503 296,225 Investment expenses (3,935) (3,634) (12,380) (12,130) Net investment income $ 107,731 $ 91,264 $ 274,123 $ 284,095 e) The following table presents the components of net investment gains (losses) and the change in net unrealized gains (losses) included in other comprehensive loss. Gross realized investment gains and losses on fixed maturity securities, short-term investments and other investments were not material to the consolidated financial statements and are presented on a net basis in the following table. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Fixed maturity securities, short-term investments and other investments: Net realized investment gains (losses) $ 2,032 $ (2,578) $ 6,001 $ 5,233 Equity securities: Change in fair value of securities sold during the period 2,553 (400) (29,015) 22,254 Change in fair value of securities held at the end of the period (286,068) (22,855) (2,171,511) 1,148,304 Total change in fair value (283,515) (23,255) (2,200,526) 1,170,558 Net investment gains (losses) $ (281,483) $ (25,833) $ (2,194,525) $ 1,175,791 Change in net unrealized gains (losses) on available-for-sale investments included in other comprehensive loss: Fixed maturity securities $ (530,161) $ (133,244) $ (1,645,060) $ (391,528) Short-term investments (8,186) (4,855) (11,563) (3,076) Reserve deficiency adjustment for life and annuity benefit reserves (see note 9) — 6,428 56,560 56,690 Net decrease $ (538,347) $ (131,671) $ (1,600,063) $ (337,914) f) The Company's equity method investments, which totaled $483.1 million and $459.7 million as of September 30, 2022 and December 31, 2021, respectively, are included in other assets on the consolidated balance sheets. The Company's most significant equity method investment is an investment in Hagerty, Inc. (Hagerty), which is accounted for on a quarter lag. Hagerty is an automotive enthusiast brand offering integrated membership products and programs as well as a specialty insurance provider focused on the global automobile enthusiast market. The Company's ownership interest in Hagerty was 23% as of September 30, 2022 and December 31, 2021. The Company's investment is comprised of Class A common shares, which are listed for trading on the New York Stock Exchange, as well as Class V common shares, associated with the Company's original investment in 2019, that have special voting rights and can be converted on a one-for-one basis into Class A common shares. The Company accounts for its investment under the equity method as it is deemed to have the ability to exercise significant influence over Hagerty's operating and financial policies through a combination of its voting interest, its right to designate a board member and business it conducts with Hagerty. As of September 30, 2022 and December 31, 2021, the carrying value of the Company's investment in Hagerty was $239.0 million and $256.6 million, respectively. As of September 30, 2022 and December 31, 2021, the estimated value of the Company's investment, based on the closing stock price of Hagerty's Class A common shares, was $701.2 million and $1.1 billion, respectively. See note 12 for further details regarding related party transactions with Hagerty.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements FASB ASC 820, Fair Value Measurements and Disclosures, establishes a three-level hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). If the inputs used to measure the assets or liabilities fall within different levels of the hierarchy, the classification is based on the lowest level input that is significant to the fair value measurement of the asset or liability. Classification of assets and liabilities within the hierarchy considers the markets in which the assets and liabilities are traded and the reliability and transparency of the assumptions used to determine fair value. The hierarchy requires the use of observable market data when available. The levels of the hierarchy are defined as follows: • Level 1 – Inputs to the valuation methodology are quoted prices (unadjusted) for identical assets or liabilities traded in active markets. • Level 2 – Inputs to the valuation methodology include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability and market-corroborated inputs. • Level 3 – Inputs to the valuation methodology are unobservable for the asset or liability and are significant to the fair value measurement. In accordance with ASC 820, the Company determines fair value based on the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. In determining fair value, the Company uses various methods, including the market, income and cost approaches. The Company uses valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs. The following section describes the valuation methodologies used by the Company to measure assets and liabilities at fair value, including an indication of the level within the fair value hierarchy in which each asset or liability is generally classified. Available-for-sale investments and equity securities. Available-for-sale investments and equity securities are recorded at fair value on a recurring basis. Available-for-sale investments include fixed maturity securities and short-term investments. Short-term investments include certificates of deposit, commercial paper, discount notes and treasury bills with original maturities of one year or less. Fair value is determined by the Company after considering various sources of information, including information provided by a third-party pricing service. The pricing service provides prices for substantially all of the Company's fixed maturity securities and equity securities. In determining fair value, the Company generally does not adjust the prices obtained from the pricing service. The Company obtains an understanding of the pricing service's valuation methodologies and related inputs, which include, but are not limited to, reported trades, benchmark yields, issuer spreads, bids, offers, duration, credit ratings, estimated cash flows and prepayment speeds. The Company validates prices provided by the pricing service by reviewing prices from other pricing sources and analyzing pricing data in certain instances. The Company has evaluated the various types of securities in its investment portfolio to determine an appropriate fair value hierarchy level based upon trading activity and the observability of market inputs. Level 1 investments include those traded on an active exchange, such as the New York Stock Exchange. Level 2 investments include U.S. Treasury securities, U.S. government-sponsored enterprises, municipal bonds, foreign government bonds, commercial mortgage-backed securities, residential mortgage-backed securities, asset-backed securities and corporate debt securities. Level 3 investments include the Company's investments in insurance-linked securities funds that are not traded on an active exchange and are valued using unobservable inputs. Fair value for available-for-sale investments and equity securities is measured based upon quoted prices in active markets, if available. Due to variations in trading volumes and the lack of quoted market prices, fixed maturity securities are classified as Level 2 investments. The fair value of fixed maturity securities is normally derived through recent reported trades for identical or similar securities, making adjustments through the reporting date based upon available market observable data previously described. If there are no recent reported trades, the fair value of fixed maturity securities may be derived through the use of matrix pricing or model processes, where future cash flow expectations are developed based upon collateral performance and discounted at an estimated market rate. Significant inputs used to determine the fair value of obligations of states, municipalities and political subdivisions, corporate bonds and obligations of foreign governments include reported trades, benchmark yields, issuer spreads, bids, offers, credit information and estimated cash flows. Significant inputs used to determine the fair value of commercial mortgage-backed securities, residential mortgage-backed securities and asset-backed securities include the type of underlying assets, benchmark yields, prepayment speeds, collateral information, tranche type and volatility, estimated cash flows, credit information, default rates, recovery rates, issuer spreads and the year of issue. Due to the significance of unobservable inputs required in measuring the fair value of the Company's investments in certain insurance-linked securities funds, these investments are classified as Level 3 within the fair value hierarchy. The fair value of the securities is derived using their reported net asset value (NAV) as the primary input, as well as other observable and unobservable inputs as deemed necessary by management. Management has obtained an understanding of the inputs, assumptions, process and controls used to determine NAV, which is calculated by an independent third party. Unobservable inputs to the NAV calculations include assumptions around premium earnings patterns and loss reserve estimates for the underlying securitized reinsurance contracts. The Company's valuation policies and procedures for Level 3 investments are determined by management. Fair value measurements are analyzed quarterly to ensure the change in fair value from prior periods is reasonable relative to management's understanding of the underlying investments, recent market trends and external market data. Senior long-term debt and other debt. Senior long-term debt and other debt is carried at amortized cost with the estimated fair value disclosed on the consolidated balance sheets. Senior long-term debt and other debt is classified as Level 2 within the fair value hierarchy due to variations in trading volumes and the lack of quoted market prices. Fair value is generally derived through recent reported trades for identical securities, making adjustments through the reporting date, if necessary, based upon available market observable data including U.S. Treasury securities and implied credit spreads. Significant inputs used to determine the fair value of senior long-term debt and other debt include reported trades, benchmark yields, issuer spreads, bids and offers. The following tables present the balances of assets measured at fair value on a recurring basis by level within the fair value hierarchy. September 30, 2022 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments: Fixed maturity securities, available-for-sale: U.S. Treasury securities $ — $ 2,958,421 $ — $ 2,958,421 U.S. government-sponsored enterprises — 725,182 — 725,182 Obligations of states, municipalities and political subdivisions — 3,713,343 — 3,713,343 Foreign governments — 1,172,889 — 1,172,889 Commercial mortgage-backed securities — 1,932,665 — 1,932,665 Residential mortgage-backed securities — 557,333 — 557,333 Asset-backed securities — 2,012 — 2,012 Corporate bonds — 664,512 — 664,512 Total fixed maturity securities, available-for-sale — 11,726,357 — 11,726,357 Equity securities: Insurance, banks and other financial institutions 2,614,609 — 921 2,615,530 Industrial, consumer and all other 4,334,827 — — 4,334,827 Total equity securities 6,949,436 — 921 6,950,357 Short-term investments, available-for-sale 2,277,172 147,672 — 2,424,844 Total investments $ 9,226,608 $ 11,874,029 $ 921 $ 21,101,558 December 31, 2021 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments: Fixed maturity securities, available-for-sale: U.S. Treasury securities $ — $ 2,470,194 $ — $ 2,470,194 U.S. government-sponsored enterprises — 775,587 — 775,587 Obligations of states, municipalities and political subdivisions — 4,265,924 — 4,265,924 Foreign governments — 1,519,354 — 1,519,354 Commercial mortgage-backed securities — 1,990,433 — 1,990,433 Residential mortgage-backed securities — 726,050 — 726,050 Asset-backed securities — 3,081 — 3,081 Corporate bonds — 836,682 — 836,682 Total fixed maturity securities, available-for-sale — 12,587,305 — 12,587,305 Equity securities: Insurance, banks and other financial institutions 3,307,755 — 56,472 3,364,227 Industrial, consumer and all other 5,659,700 — — 5,659,700 Total equity securities 8,967,455 — 56,472 9,023,927 Short-term investments, available-for-sale 1,619,496 180,492 — 1,799,988 Total investments $ 10,586,951 $ 12,767,797 $ 56,472 $ 23,411,220 The following table summarizes changes in Level 3 investments measured at fair value on a recurring basis. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Equity securities, beginning of period $ 4,380 $ 41,066 $ 56,472 $ 58,493 Purchases — 18,900 — 18,900 Sales (3,528) — (56,335) (15,015) Net investment gains (losses) 69 (3,341) 784 (5,753) Equity securities, end of period $ 921 $ 56,625 $ 921 $ 56,625 As of September 30, 2022, the Company's remaining Level 3 investment relates to its investment in Lodgepine Fund Limited, an insurance-linked securities fund managed through the Company's Lodgepine operations, which are currently in run-off. Previously, Level 3 investments also included the Company's investment in an insurance-linked securities fund managed by Markel CATCo Investment Management Ltd. (MCIM). During the first quarter of 2022, the Company's remaining investment was redeemed ($41.3 million) in conjunction with a buy-out transaction that provided for an accelerated return of all remaining capital to investors. See note 11 for further details about the Company's Markel CATCo operations and the buy-out transaction. Except as disclosed in note 3, the Company did not have any assets or liabilities measured at fair value on a non-recurring basis during the nine months ended September 30, 2022 and 2021.

Products, Services and Other Re

Products, Services and Other Revenues	9 Months Ended
Products, Services and Other Revenues	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Products, Services and Other Revenues	Products, Services and Other Revenues The amount of revenues from contracts with customers was $1.2 billion and $933.0 million for the quarters ended September 30, 2022 and 2021, respectively, and $3.5 billion and $2.8 billion for the nine months ended September 30, 2022 and 2021, respectively. The following tables present revenues from contracts with customers by segment and type, all of which are included in products revenues and services and other revenues in the consolidated statements of income (loss) and comprehensive income (loss), along with a reconciliation to total products revenues and services and other revenues. Quarter Ended September 30, 2022 2021 (dollars in thousands) Markel Ventures Other Total Markel Ventures Other Total Products $ 575,277 $ — $ 575,277 $ 394,444 $ — $ 394,444 Services 614,519 11,529 626,048 487,942 30,027 517,969 Investment management — 15,641 15,641 — 20,571 20,571 Total revenues from contracts with customers 1,189,796 27,170 1,216,966 882,386 50,598 932,984 Program services and other fronting — 40,033 40,033 — 32,298 32,298 Other 25,950 118 26,068 25,796 345 26,141 Total $ 1,215,746 $ 67,321 $ 1,283,067 $ 908,182 $ 83,241 $ 991,423 Nine Months Ended September 30, 2022 2021 (dollars in thousands) Markel Ventures Other Total Markel Ventures Other Total Products $ 1,809,276 $ — $ 1,809,276 $ 1,294,407 $ — $ 1,294,407 Services 1,633,353 41,547 1,674,900 1,313,054 95,908 1,408,962 Investment management — 55,197 55,197 — 57,693 57,693 Total revenues from contracts with customers 3,442,629 96,744 3,539,373 2,607,461 153,601 2,761,062 Program services and other fronting — 103,096 103,096 — 87,314 87,314 Disposition gain — 107,293 107,293 — — — Other 84,800 724 85,524 82,824 1,002 83,826 Total $ 3,527,429 $ 307,857 $ 3,835,286 $ 2,690,285 $ 241,917 $ 2,932,202 Receivables from contracts with customers were $649.6 million and $626.1 million as of September 30, 2022 and December 31, 2021, respectively.

Unpaid Losses And Loss Adjustme

Unpaid Losses And Loss Adjustment Expenses	9 Months Ended
Unpaid Losses And Loss Adjustment Expenses	Sep. 30, 2022
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Unpaid Losses And Loss Adjustment Expenses	Unpaid Losses and Loss Adjustment Expenses The following table presents a reconciliation of consolidated beginning and ending reserves for losses and loss adjustment expenses. Nine Months Ended September 30, (dollars in thousands) 2022 2021 Net reserves for losses and loss adjustment expenses, beginning of year $ 11,302,577 $ 10,485,717 Effect of foreign currency rate changes on beginning of year balance (275,364) (52,117) Adjusted net reserves for losses and loss adjustment expenses, beginning of year 11,027,213 10,433,600 Incurred losses and loss adjustment expenses: Current accident year 3,420,906 3,009,260 Prior accident years (204,411) (366,171) Total incurred losses and loss adjustment expenses 3,216,495 2,643,089 Payments: Current accident year 350,684 365,640 Prior accident years 1,880,471 1,678,164 Total payments 2,231,155 2,043,804 Effect of foreign currency rate changes on current year activity (7,499) (1,339) Net reserves for losses and loss adjustment expenses of Markel CATCo Re (see note 11) 375,222 — Net reserves for losses and loss adjustment expenses of insurance companies sold — (2,762) Net reserves for losses and loss adjustment expenses, end of period 12,380,276 11,028,784 Reinsurance recoverables on unpaid losses 7,814,098 6,582,415 Gross reserves for losses and loss adjustment expenses, end of period $ 20,194,374 $ 17,611,199 For the nine months ended September 30, 2022, current accident year losses and loss adjustment expenses included $70.0 million of net losses and loss adjustment expenses attributed to Hurricane Ian, all of which were within the Company's Insurance segment. These losses and loss adjustment expenses were net of ceded losses of $100.0 million. The Company also had gross losses and loss adjustment expenses of $850.0 million within its program services and other fronting operations attributed to Hurricane Ian, all of which were ceded to third-party reinsurers managed through the Company's insurance-linked securities operations, which hold sufficient investor collateral to support the Company's related reinsurance recoverables. See note 12 for further details regarding related party transactions with third parties managed through the Company's insurance-linked securities operations. The gross and net losses and loss adjustment expenses attributed to Hurricane Ian as of September 30, 2022 represent the Company's best estimates based upon information currently available. The estimates for these losses are based on preliminary industry loss estimates and output from industry, broker and proprietary models, as well as policy and reinsurance contract level reviews and analysis of the Company's ceded reinsurance contracts. Due to limited claims activity, these estimates are based on various assumptions about coverage, liability and reinsurance and are therefore subject to change. While the Company believes its net reserves for Hurricane Ian as of September 30, 2022 are adequate, it continues to closely monitor reported claims and will adjust the estimates of gross and net losses as new information becomes available. For the nine months ended September 30, 2022, current accident year losses and loss adjustment expenses also included $35.0 million of net losses and loss adjustment expenses attributed to the Russia-Ukraine conflict. These losses and loss adjustment expenses were net of ceded losses of $70.0 million. All of the gross and net losses and loss adjustment expenses attributed to the Russia-Ukraine conflict were recognized in the first quarter of 2022. There were no additional losses recognized or adjustments to the Company's initial loss estimates in the second or third quarters of 2022. Both the gross and net loss estimates for incurred losses attributed to the Russia-Ukraine conflict continue to represent the Company's best estimates as of September 30, 2022 based upon information currently available. The Company's estimates for these losses are based on reported claims, detailed underwriting, actuarial and claims reviews of policies and in-force assumed reinsurance contracts for potential exposures, as well as analysis of ceded reinsurance contracts and analysis provided by the Company's brokers and claims counsel. These estimates include various assumptions about what areas within the affected regions have incurred losses, the nature and extent of such losses, which remain difficult to verify, as well as assumptions about coverage, liability and reinsurance. Due to the inherent uncertainty associated with the assumptions surrounding the Russia-Ukraine conflict, these estimates may be subject to a wide range of variability. Additionally, as the Russia-Ukraine conflict is ongoing, the Company believes it is possible that additional losses could be incurred in subsequent periods. Given the significant levels of ceded reinsurance on certain of the Company's impacted policies, a significant portion of any additional incurred losses may be ceded. Additionally, increases in ceded losses may require payment of additional reinstatement premiums. Further, if coverage under the Company's existing ceded reinsurance contracts is exhausted, the Company may need to purchase additional reinsurance to ensure that its net retained risks on the impacted product lines are within the Company's corporate risk tolerances. While the Company believes the gross and net reserves for losses and loss adjustment expenses for the Russia-Ukraine conflict as of September 30, 2022 are adequate based on information currently available, the Company continues to closely monitor reported claims, ceded reinsurance contract attachment, government actions and areas impacted by the conflict and may adjust the estimates of gross and net losses as new information becomes available. Any such adjustments or additional incurred losses may be material to the Company's results of operations, financial condition and cash flows. For the nine months ended September 30, 2021, current accident year losses and loss adjustment expenses included $182.3 million of net losses and loss adjustment expenses from Winter Storm Uri, the floods in Europe and Hurricane Ida (2021 Catastrophes). For the nine months ended September 30, 2022, prior accident years losses and loss adjustment expenses included $204.4 million of favorable development on prior years loss reserves, which included $155.0 million of favorable development on the Company's workers' compensation, property, marine and energy and programs product lines within its Insurance segment and $41.7 million of favorable development on the Company's property and credit and surety product lines within its Reinsurance segment. For the nine months ended September 30, 2021, prior accident years losses and loss adjustment expenses included $366.2 million of favorable development on prior years loss reserves, which included $324.8 million of favorable development on the Company's general liability, property, workers' compensation, professional liability and marine and energy product lines within the Insurance segment. Favorable development on prior years loss reserves for the nine months ended September 30, 2021 was partially offset by $30.6 million of adverse development on the Company's property product lines within the Reinsurance segment, due in part to losses related to COVID-19. The Company's loss estimates for COVID-19 continue to represent the Company's best estimate as of September 30, 2022 based on information currently available, however, the assumptions on which these estimates are based are subject to a wide range of variability. The Company is closely monitoring reported claims, ceded reinsurance contract attachment, government actions and judicial decisions and may adjust the estimates of gross and net losses as new information becomes available. Such adjustments may be material to the Company's results of operations, financial condition and cash flows. For additional details on the Company's COVID-19 loss estimates, readers are urged to review the Company's 2021 Annual Report on Form 10-K.

Reinsurance

Reinsurance	9 Months Ended
Reinsurance	Sep. 30, 2022
Reinsurance Disclosures [Abstract]
Reinsurance	Reinsurance The following tables summarize the effect of reinsurance and retrocessional reinsurance on premiums written and earned. Quarter Ended September 30, 2022 2021 (dollars in thousands) Direct Assumed Ceded Net Premiums Direct Assumed Ceded Net Premiums Underwriting: Written $ 2,133,822 $ 349,650 $ (473,885) $ 2,009,587 $ 1,776,716 $ 303,551 $ (393,195) $ 1,687,072 Earned 1,899,816 408,561 (351,118) 1,957,259 1,599,931 363,665 (331,397) 1,632,199 Program services and other fronting: Written 663,631 327,668 (991,719) (420) 711,182 177,153 (890,597) (2,262) Earned 729,312 218,439 (948,180) (429) 634,520 103,008 (739,227) (1,699) Consolidated: Written 2,797,453 677,318 (1,465,604) 2,009,167 2,487,898 480,704 (1,283,792) 1,684,810 Earned $ 2,629,128 $ 627,000 $ (1,299,298) $ 1,956,830 $ 2,234,451 $ 466,673 $ (1,070,624) $ 1,630,500 Nine Months Ended September 30, 2022 2021 (dollars in thousands) Direct Assumed Ceded Net Premiums Direct Assumed Ceded Net Premiums Underwriting: Written $ 6,065,936 $ 1,466,036 $ (1,255,226) $ 6,276,746 $ 5,082,494 $ 1,269,578 $ (1,031,546) $ 5,320,526 Earned 5,370,481 1,194,504 (1,012,485) 5,552,500 4,542,680 1,081,494 (925,176) 4,698,998 Program services and other fronting: Written 2,025,195 595,940 (2,624,185) (3,050) 2,056,328 249,067 (2,308,590) (3,195) Earned 2,036,016 332,415 (2,371,227) (2,796) 1,800,489 141,676 (1,944,931) (2,766) Consolidated: Written 8,091,131 2,061,976 (3,879,411) 6,273,696 7,138,822 1,518,645 (3,340,136) 5,317,331 Earned $ 7,406,497 $ 1,526,919 $ (3,383,712) $ 5,549,704 $ 6,343,169 $ 1,223,170 $ (2,870,107) $ 4,696,232 Substantially all of the premiums written and earned in the Company's program services and other fronting operations for the quarters and nine months ended September 30, 2022 and 2021 were ceded. The percentage of consolidated ceded earned premiums to gross earned premiums was 40% for the quarters ended September 30, 2022 and 2021 and 38% for the nine months ended September 30, 2022 and 2021. The percentage of consolidated assumed earned premiums to net earned premiums was 32% and 28% for the quarter and nine months ended September 30, 2022, respectively, and 29% and 26% for the quarter and nine months ended September 30, 2021, respectively. Substantially all of the incurred losses and loss adjustment expenses in the Company's program services and other fronting operations were ceded. These losses totaled $1.3 billion and $2.3 billion for the quarter and nine months ended September 30, 2022, respectively, and $620.1 million and $1.7 billion for the quarter and nine months ended September 30, 2021, respectively. The following table summarizes the effect of reinsurance and retrocessional reinsurance on losses and loss adjustment expenses in the Company's underwriting operations. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Gross losses and loss adjustment expenses $ 1,423,526 $ 1,238,974 $ 3,760,566 $ 3,306,035 Ceded losses and loss adjustment expenses (238,220) (290,834) (544,109) (660,479) Net losses and loss adjustment expenses $ 1,185,306 $ 948,140 $ 3,216,457 $ 2,645,556

Life and Annuity Benefits Life

Life and Annuity Benefits Life and Annuity Benefits	9 Months Ended
Life and Annuity Benefits Life and Annuity Benefits	Sep. 30, 2022
Liability for Future Policy Benefit, before Reinsurance [Abstract]
Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]	Life and Annuity BenefitsLife and annuity benefits are compiled on a reinsurance contract-by-contract basis and are discounted using standard actuarial techniques and cash flow models. Since the development of the life and annuity reinsurance reserves is based upon cash flow projection models, the Company must make estimates and assumptions based on cedent experience, industry mortality tables, and expense and investment experience, including a provision for adverse deviation. The assumptions used to determine policy benefit reserves are generally locked-in for the life of the contract unless an unlocking event occurs. Loss recognition testing is performed to determine if existing policy benefit reserves, together with the present value of future gross premiums and expected investment income earned thereon, are adequate to cover the present value of future benefits, settlement and maintenance costs. If the existing policy benefit reserves are not sufficient, the locked-in assumptions are revised to current best estimate assumptions and a charge to earnings for life and annuity benefits is recognized at that time.Life and annuity benefits are also adjusted to the extent unrealized gains on the investments supporting the policy benefit reserves would result in a reserve deficiency if those gains were realized. As of December 31, 2021, the cumulative increase to life and annuity benefits attributable to unrealized gains on the underlying investment portfolio totaled $56.6 million, all of which reversed during the first quarter of 2022 as a result of an increase in the market yield on the investment securities supporting the policy benefit reserves. As the market yield continued to increase through September 30, 2022, there was no adjustment to life and annuity benefits in the third quarter of 2022. During the quarter and nine months ended September 30, 2021, the Company decreased life and annuity benefits by $6.4 million and $56.7 million, respectively and increased the change in net unrealized holding gains included in other comprehensive loss by a corresponding amount.

Debt

Debt	9 Months Ended
Debt	Sep. 30, 2022
Debt Disclosure [Abstract]
Debt Disclosure	Senior Long-Term Debt and Other Debt In July 2022, the Company retired its 4.90% unsecured senior notes due July 1, 2022 ($350.0 million aggregate principal outstanding at December 31, 2021). The Company maintains a corporate revolving credit facility which provides up to $300 million of capacity for future acquisitions, investments and stock repurchases, and for other working capital and general corporate purposes. At the Company's discretion, up to $200 million of the total capacity may be used for letters of credit. The Company may increase the capacity of the facility by up to $200 million subject to obtaining commitments for the increase and certain other terms and conditions. At September 30, 2022 and December 31, 2021, the Company had no borrowings outstanding under this revolving credit facility. This facility expires in April 2024. Various of the Company's Markel Ventures subsidiaries maintain revolving credit facilities or lines of credit, which provide up to $550 million of aggregate capacity for working capital and other general operational purposes. A portion of the capacity on certain of these credit facilities may be used as security for letters of credit and other obligations. At September 30, 2022 and December 31, 2021, the Company had $253.2 million and $94.3 million, respectively, of borrowings outstanding under these credit facilities. To the extent that the Company or any of its subsidiaries are not in compliance with the covenants under their respective credit facilities, access to such credit facilities could be restricted. At September 30, 2022, the Company and all of the Company's subsidiaries were in compliance with all covenants contained in their respective credit facilities.

Variable Interest Entities

Variable Interest Entities	9 Months Ended
Variable Interest Entities	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	Variable Interest Entities MCIM, a wholly-owned consolidated subsidiary of the Company, is an insurance-linked securities investment fund manager and reinsurance manager headquartered in Bermuda. Results attributable to MCIM are not included in a reportable segment. MCIM serves as the insurance manager for Markel CATCo Re Ltd. (Markel CATCo Re), a Bermuda Class 3 reinsurance company, and as the investment manager for Markel CATCo Reinsurance Fund Ltd., a Bermuda exempted mutual fund company comprised of multiple segregated accounts (Markel CATCo Funds). Voting shares in Markel CATCo Reinsurance Fund Ltd. and Markel CATCo Re are held by MCIM, which has the power to direct the activities that most significantly impact the economic performance of these entities. The Markel CATCo Funds issued multiple classes of nonvoting, redeemable preference shares to investors, and the Markel CATCo Funds are primarily invested in nonvoting preference shares of Markel CATCo Re. The underwriting results of Markel CATCo Re are attributed to investors through its nonvoting preference shares. Both Markel CATCo Re and the Markel CATCo Funds were placed into run-off in July 2019. In March 2022, the Company completed a buy-out transaction with Markel CATCo Re and the Markel CATCo Funds that provided for an accelerated return of all remaining capital to investors in the Markel CATCo Funds. Under the terms of the transaction, the Company provided cash funding of $45.1 million to purchase substantially all of the Markel CATCo Funds' interests in Markel CATCo Re. See note 14 for further details regarding the terms of the buy-out transaction. As part of the transaction, substantially all of the preference shares held by investors in the Markel CATCo Funds were redeemed, including preference shares previously held by the Company. See note 5 for details regarding the Company's investment in the Markel CATCo Funds. During June 2022, the Company received a return of $24.9 million of the capital it provided in March 2022 and the related preference shares were redeemed. As of September 30, 2022, the Company's investment in preference shares of Markel CATCo Re totaled $20.1 million, which comprised 25% of the equity of Markel CATCo Re. Through that investment, the Company has exposure to adverse loss development on reinsurance contracts previously written by Markel CATCo Re for loss events that occurred from 2014 to 2020. If loss reserves held by Markel CATCo Re are sufficient to settle claims on the remaining open contracts, the Company will receive a full return of the remaining $20.1 million in capital provided in March 2022. Favorable development on loss reserves held by Markel CATCo Re, less operating expenses, will be distributed to the Markel CATCo Funds, and ultimately to investors in the Markel CATCo Funds. Markel CATCo Re is considered a VIE, as the equity at risk does not have the right to receive residual returns that exceed the capital provided by the Company in the buy-out transaction. As a result of the preference shares acquired by the Company in the buy-out transaction, and the voting shares held by its consolidated subsidiary, MCIM, the Company consolidates Markel CATCo Re as its primary beneficiary. Results attributed to the run-off of Markel CATCo Re are reported with the Company's other ILS operations, within services and other revenues and expenses, and are not included in a reportable segment. The Company's consolidated balance sheet includes the following amounts attributable to Markel CATCo Re. (dollars in thousands) September 30, 2022 Assets Cash and cash equivalents $ 83,103 Restricted cash and cash equivalents 355,905 Other assets and receivables due from cedents 44,102 Total Assets $ 483,110 Liabilities and Equity Unpaid losses and loss adjustment expenses $ 375,222 Other liabilities 27,448 Total Liabilities 402,670 Shareholders' equity 21,139 Noncontrolling interests 59,301 Total Equity 80,440 Total Liabilities and Equity $ 483,110 In connection with the buy-out transaction, the Company also entered into a tail risk cover with Markel CATCo Re. Through this contract, the Company has $142.7 million of uncollateralized exposure to adverse development on loss reserves held by Markel CATCo Re for loss exposures in excess of limits that the Company believes are unlikely to be exceeded.

Related Party Transactions Rela

Related Party Transactions Related Party Transactions	9 Months Ended
Related Party Transactions Related Party Transactions	Sep. 30, 2022
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	Related Party Transactions The Company engages in certain related party transactions in the normal course of business at arm's length. Insurance-Linked Securities Within the Company's insurance-linked securities operations, the Company provides investment and insurance management services through Nephila Holdings Ltd. (together with its subsidiaries, Nephila). Nephila serves as the investment manager to several Bermuda, Ireland and U.S. based private funds (the Nephila Funds). To provide access for investors in the Nephila Funds to the insurance, reinsurance and weather markets, Nephila also acts as an insurance manager to certain Bermuda Class 3 and 3A reinsurance companies and Lloyd's of London Syndicate 2357 (Syndicate 2357) (collectively, the Nephila Reinsurers). Nephila receives management fees for investment and insurance management services provided through its insurance-linked securities operations based on the net asset value of the accounts managed, and, for certain funds, incentive fees based on the annual performance of the funds managed. Prior to the disposition of Velocity in February 2022, Nephila also provided managing general agent services to the Nephila Reinsurers in exchange for commissions. For the quarter and nine months ended September 30, 2022, total revenues attributed to unconsolidated entities managed by Nephila were $17.1 million and $57.0 million, respectively. For the quarter and nine months ended September 30, 2021, total revenues attributed to unconsolidated entities managed by Nephila were $32.8 million and $103.5 million, respectively. Through the Company's program services operations and other fronting arrangements, the Company has programs with Nephila through which the Company writes insurance policies that are ceded to Syndicate 2357 and certain other Nephila Reinsurers. Through these programs, Nephila utilizes certain of the Company's licensed insurance companies to write U.S. catastrophe-exposed property risk that is then ceded to Nephila Reinsurers. Gross premiums written through these programs with Nephila were $398.9 million and $889.6 million for the quarter and nine months ended September 30, 2022, respectively, and $283.7 million and $587.7 million for the quarter and nine months ended September 30, 2021, respectively, all of which were ceded to Nephila Reinsurers. As of September 30, 2022 and December 31, 2021, reinsurance recoverables on the consolidated balance sheets included $1.3 billion and $751.0 million, respectively, due from Nephila Reinsurers. Under these programs, the Company bears underwriting risk for annual aggregate agreement year losses in excess of a limit the Company believes is unlikely to be exceeded. To the extent losses under these programs exceed the prescribed limits, the Company is obligated to pay such losses to the cedents without recourse to the Nephila Reinsurers. While the Company believes losses under these programs are unlikely, those losses, if incurred, could be material to the Company's consolidated results of operations and financial condition. The Company has also entered into other assumed and ceded reinsurance transactions with the Nephila Reinsurers in the normal course of business, which are not material to the Company's consolidated financial statements. Hagerty The Company holds a minority ownership interest in Hagerty, which operates primarily as a managing general agent and also includes Hagerty Re, a Bermuda Class 3 reinsurance company. Through the Company's underwriting operations, the Company underwrites insurance for Hagerty, and a portion of this insurance is ceded to Hagerty Re. For the quarter and nine months ended September 30, 2022, the Company's gross written premiums attributable to Hagerty were $197.0 million and $540.4 million, respectively, of which $130.4 million and $357.7 million, respectively, were ceded to Hagerty Re. For the quarter and nine months ended September 30, 2021, the Company's gross written premiums attributable to Hagerty were $170.1 million and $467.6 million, respectively, of which $96.6 million and $265.4 million, respectively, were ceded to Hagerty Re.

Shareholders' Equity

Shareholders' Equity	9 Months Ended
Shareholders' Equity	Sep. 30, 2022
Stockholders' Equity Note [Abstract]
Shareholders' Equity Note Disclosure	Shareholders' Equity a) The Company has 50,000,000 shares of no par value common stock authorized. The following table presents a rollforward of changes in common shares issued and outstanding. Quarter Ended September 30, Nine Months Ended September 30, (in thousands) 2022 2021 2022 2021 Issued and outstanding common shares, beginning of period 13,538 13,734 13,632 13,783 Issuance of common shares — 1 2 4 Repurchase of common shares (67) (50) (163) (102) Issued and outstanding common shares, end of period 13,471 13,685 13,471 13,685 b) The Company also has 10,000,000 shares of no par value preferred stock authorized, of which 600,000 shares were issued and outstanding at September 30, 2022 and December 31, 2021. The Company declared and paid dividends on preferred shares of $18.0 million, or $30 per share, in the second quarter of 2022 and 2021. c) Net income (loss) per common share was determined by dividing adjusted net income (loss) to common shareholders by the applicable weighted average common shares outstanding. Basic common shares outstanding include restricted stock units that are no longer subject to any contingencies for issuance, but for which corresponding shares have not been issued. Diluted net income (loss) per common share is computed by dividing adjusted net income (loss) to common shareholders by the weighted average number of common shares and dilutive potential common shares outstanding during the period. The following table presents net income (loss) per common share and diluted net income (loss) per common share. Quarter Ended September 30, Nine Months Ended September 30, (in thousands, except per share amounts) 2022 2021 2022 2021 Net income (loss) to common shareholders $ 65,369 $ 188,070 $ (921,833) $ 1,535,874 Adjustment of redeemable noncontrolling interests (17,730) 19,930 (62,168) 41,553 Adjusted net income (loss) to common shareholders $ 47,639 $ 208,000 $ (984,001) $ 1,577,427 Basic common shares outstanding 13,564 13,758 13,609 13,790 Dilutive potential common shares from restricted stock units and restricted stock (1) 31 27 — 23 Diluted common shares outstanding 13,595 13,785 13,609 13,813 Basic net income (loss) per common share $ 3.51 $ 15.12 $ (72.31) $ 114.39 Diluted net income (loss) per common share (1) $ 3.50 $ 15.09 $ (72.31) $ 114.20 (1) The impact of 28 thousand shares from restricted stock units and restricted stock was excluded from the computation of diluted net loss per common share for the nine months ended September 30, 2022 because the effect would have been anti-dilutive.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2022
Loss Contingency [Abstract]
Commitments and Contingencies	Commitments and Contingencies a) In March 2022, the Company completed a buy-out transaction with Markel CATCo Re and the Markel CATCo Funds, which are currently in run-off, that provided for an accelerated return of all remaining capital to investors in the Markel CATCo Funds. Under the terms of the transaction, the Company provided cash funding of $45.1 million to purchase substantially all of the Markel CATCo Funds' investments in Markel CATCo Re and also provided tail risk cover of $142.7 million to Markel CATCo Re to allow for the release of collateral to investors. In order to complete the transaction, the Company also made $101.9 million in additional payments, net of insurance proceeds, to or for the benefit of investors, which were recognized as an expense to the Company in the first quarter of 2022 and included in services and other expenses for the nine months ended September 30, 2022. In conjunction with the buy-out transaction, all investors holding securities in the Markel CATCo Funds, the Markel CATCo Group Companies (MCIM, the Markel CATCo Funds and Markel CATCo Re), Markel Corporation and each of their related parties, among others, granted mutual releases of all claims related to the transaction, the Markel CATCo Group Companies' businesses and the investors' investments in the Funds, including any pending litigation. See note 11 for further details about the Company's Markel CATCo operations and the buy-out transaction. b) Contingencies arise in the normal course of the Company's operations and are not expected to have a material impact on the Company's financial condition or results of operations.

Accounting Changes and Error Co

Accounting Changes and Error Corrections	Jan. 01, 2021
Accounting Changes and Error Corrections [Abstract]
Immaterial Correction to Prior Period Financial Statements for Accounting Policy Change	Immaterial Correction to Prior Period Financial Statements for Accounting Policy Change The Company defers and amortizes costs directly related to the successful acquisition of new or renewal insurance contracts over the related policy period, generally one year. Previously, the Company did not defer salaries and benefits associated with the successful acquisition of insurance contracts, as such amounts were quantified and assessed each period and were deemed not to be material to the consolidated financial statements. Effective January 1, 2022, the Company changed its accounting policy to defer salaries and benefits associated with the successful acquisition of insurance contracts in accordance with the requirements of FASB ASC 944, Financial Services—Insurance . To reflect the change in accounting policy, the Company made a cumulative adjustment to increase deferred policy acquisition costs by $28.2 million, increase deferred tax liabilities by $5.9 million and increase retained earnings by $22.3 million as of January 1, 2020, which is the beginning of the earliest year that will be presented in the consolidated financial statements included in the Company's 2022 Annual Report on Form 10-K. These increases in deferred policy acquisition costs, deferred tax liabilities and retained earnings are also reflected as increases to the previously reported amounts in the Company's consolidated balance sheet as of December 31, 2021 and as an adjustment to retained earnings as of January 1, 2021 in the accompanying consolidated statement of changes in equity for the nine months ended September 30, 2021. The Company considered both the quantitative and qualitative factors within the provisions of U.S. Securities and Exchange Commission Staff Accounting Bulletin (SAB) No. 99, Materiality , and SAB No. 108, Considering the Effect of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements

Summary Of Significant Accoun_2

Summary Of Significant Accounting Policies (Policies)	9 Months Ended
Summary Of Significant Accounting Policies (Policies)	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. The consolidated balance sheet as of September 30, 2022 and the related consolidated statements of income (loss) and comprehensive income (loss) and changes in equity for the quarters and nine months ended September 30, 2022 and 2021, and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. In the opinion of management, all adjustments necessary for fair presentation of such consolidated financial statements have been included. Except for the adjustment described in note 15, such adjustments consist only of normal, recurring items. Interim results are not necessarily indicative of results of operations for the entire year. The consolidated balance sheet as of December 31, 2021 was derived from Markel Corporation's audited annual consolidated financial statements. The accompanying consolidated financial statements have been prepared in accordance with United States (U.S.) generally accepted accounting principles (GAAP) and include the accounts of Markel Corporation and its consolidated subsidiaries, as well as any variable interest entities (VIEs) that meet the requirements for consolidation (the Company). All significant intercompany balances and transactions have been eliminated in consolidation. The Company consolidates the results of its Markel Ventures subsidiaries on a one-month lag, with the exception of significant transactions or events that occur during the intervening period. Certain prior period amounts have been reclassified to conform to the current period presentation. The preparation of financial statements in accordance with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities. Actual results may differ materially from the estimates and assumptions used in preparing the consolidated financial statements. The consolidated financial statements and notes are presented as permitted by Form 10-Q and do not contain certain information included in the Company's annual consolidated financial statements and notes. For a more complete description of the Company's business and accounting policies, readers are urged to review the Company's 2021 Annual Report on Form 10-K, as well as note 15 for details regarding a change to the Company's policy for accounting for deferred policy acquisition costs.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Standards Not Yet Adopted In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2018-12, Financial Services—Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts. The FASB subsequently issued several ASUs as amendments to ASU No. 2018-12. The standard requires insurance companies with long duration contracts to: (1) review and, if there is a change, update the assumptions used to measure expected cash flows at least annually; (2) update the discount rate assumption at each reporting date; and (3) enhance certain qualitative and quantitative disclosures. ASU No. 2018-12 becomes effective for the Company during the first quarter of 2023 and will be applied using a modified retrospective approach that requires restatement of prior periods presented, including a cumulative adjustment to accumulated other comprehensive income as of January 1, 2021 (the transition date). The standard will, among other things, impact the discount rate used in estimating reserves for the Company's life and annuity reinsurance portfolio, which is in runoff. Currently, the discount rate assumption is locked-in for the life of the contracts, unless there is a loss recognition event. Based on the Company's current estimate, the adoption of ASU 2018-12 is expected to result in a decrease to accumulated other comprehensive income of less than $25 million, net of taxes, as a result of changing the discount rate assumption as of the transition date. However, the cumulative impact of changes in the discount rate assumption upon adopting ASU 2018-12 in the first quarter of 2023 will be based on the discount rate assumption determined as of the January 1, 2023 adoption date. Based on increases in interest rates subsequent to the transition date, the Company expects that an update to the discount rate assumption as of September 30, 2022 would result in a cumulative increase to accumulated other comprehensive income. The Company is still determining the ultimate impact that adopting ASU No. 2018-12 will have on its consolidated financial statements. In October 2021, the FASB issued ASU No. 2021-08, Business Combinations (Topic 805): Accounting for Contract Assets and Contract Liabilities from Contracts with Customer s, which becomes effective for the Company during the first quarter of 2023. ASU No. 2021-08 requires contract assets and liabilities accounted for under FASB Accounting Standards Codification (ASC) 606, Revenue from Contracts with Customers , to be recorded at the acquisition date as if the acquirer entered into those contracts itself on the contract inception dates, rather than at fair value. At adoption, ASU No. 2021-08 will not impact the Company's financial position, results of operations or cash flows, but prospectively, this ASU will impact amounts recorded by the Company for assets acquired and liabilities assumed in conjunction with certain acquisitions.

Segment Reporting Disclosures (

Segment Reporting Disclosures (Tables)	9 Months Ended
Segment Reporting Disclosures (Tables)	Sep. 30, 2022
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Company's Segment Disclosures	The following tables summarize the Company's segment disclosures. Quarter Ended September 30, 2022 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 2,299,325 $ 179,455 $ — $ — $ 995,991 $ 3,474,771 Net written premiums 1,849,983 154,029 — — 5,155 2,009,167 Earned premiums 1,695,029 260,535 — — 1,266 1,956,830 Losses and loss adjustment expenses: Current accident year (1,100,511) (166,485) — — — (1,266,996) Prior accident years 53,760 29,505 — — (1,582) 81,683 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (362,137) (68,662) — — (383) (431,182) Other underwriting expenses (200,604) (11,638) — — 152 (212,090) Underwriting profit (loss) 85,537 43,255 — — (547) 128,245 Net investment income — — 107,414 317 — 107,731 Net investment losses — — (281,483) — — (281,483) Products revenues — — — 586,531 — 586,531 Services and other revenues — — — 629,215 67,321 696,536 Products expenses — — — (580,830) — (580,830) Services and other expenses (3) — — — (556,207) 15,638 (540,569) Amortization of intangible assets (4) — — — (18,567) (24,851) (43,418) Segment profit (loss) $ 85,537 $ 43,255 $ (174,069) $ 60,459 $ 57,561 $ 72,743 Interest expense (47,348) Net foreign exchange gains 115,130 Income before income taxes $ 140,525 U.S. GAAP combined ratio (5) 95 % 83 % NM (6) 93 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $23.7 million for the quarter ended September 30, 2022. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $9.6 million for the quarter ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Services and other expenses for Other for the quarter ended September 30, 2022 included $53.4 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11. (4) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (5) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (6) NM - Ratio is not meaningful Quarter Ended September 30, 2021 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 1,899,592 $ 180,673 $ — $ — $ 888,337 $ 2,968,602 Net written premiums 1,545,428 141,642 — — (2,260) 1,684,810 Earned premiums 1,381,235 250,962 — — (1,697) 1,630,500 Losses and loss adjustment expenses: Current accident year (866,481) (221,872) — — — (1,088,353) Prior accident years 124,133 16,292 — — (313) 140,112 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (289,201) (63,723) — — — (352,924) Other underwriting expenses (202,961) (12,101) — — (1,770) (216,832) Underwriting profit (loss) 146,725 (30,442) — — (3,780) 112,503 Net investment income — — 91,261 3 — 91,264 Net investment losses — — (25,833) — — (25,833) Products revenues — — — 405,711 — 405,711 Services and other revenues — — — 502,471 83,241 585,712 Products expenses — — — (374,407) — (374,407) Services and other expenses — — — (465,268) (48,726) (513,994) Amortization of intangible assets (3) — — — (13,541) (25,727) (39,268) Segment profit (loss) $ 146,725 $ (30,442) $ 65,428 $ 54,969 $ 5,008 $ 241,688 Interest expense (46,455) Net foreign exchange gains 48,850 Income before income taxes $ 244,083 U.S. GAAP combined ratio (4) 89 % 112 % NM (5) 93 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $15.8 million for the quarter ended September 30, 2021. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $10.3 million for the quarter ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (4) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (5) NM - Ratio is not meaningful Nine Months Ended September 30, 2022 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 6,479,789 $ 1,044,827 $ — $ — $ 2,628,491 $ 10,153,107 Net written premiums 5,289,165 983,087 — — 1,444 6,273,696 Earned premiums 4,742,178 808,656 — — (1,130) 5,549,704 Losses and loss adjustment expenses: Current accident year (2,906,031) (514,875) — — — (3,420,906) Prior accident years 196,093 13,845 — — (5,527) 204,411 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (996,369) (209,541) — — (415) (1,206,325) Other underwriting expenses (596,426) (37,708) — — (2,647) (636,781) Underwriting profit (loss) 439,445 60,377 — — (9,719) 490,103 Net investment income — — 273,699 424 — 274,123 Net investment losses — — (2,194,525) — — (2,194,525) Products revenues — — — 1,845,111 — 1,845,111 Services and other revenues — — — 1,682,318 307,857 1,990,175 Products expenses — — — (1,726,367) — (1,726,367) Services and other expenses (3) — — — (1,524,167) (168,036) (1,692,203) Amortization of intangible assets (4) — — — (60,077) (74,913) (134,990) Segment profit (loss) $ 439,445 $ 60,377 $ (1,920,826) $ 217,242 $ 55,189 $ (1,148,573) Interest expense (147,090) Net foreign exchange gains 245,356 Loss before income taxes $ (1,050,307) U.S. GAAP combined ratio (5) 91 % 93 % NM (6) 91 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $75.3 million for the nine months ended September 30, 2022. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $29.0 million for the nine months ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Services and other expenses for Other for the nine months ended September 30, 2022 included $81.6 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11. (4) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (5) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (6) NM - Ratio is not meaningful Nine Months Ended September 30, 2021 (dollars in thousands) Insurance Reinsurance Investing Markel Ventures (1) Other (2) Consolidated Gross premium volume $ 5,359,293 $ 992,635 $ — $ — $ 2,305,539 $ 8,657,467 Net written premiums 4,427,301 893,082 — — (3,052) 5,317,331 Earned premiums 3,928,824 770,031 — — (2,623) 4,696,232 Losses and loss adjustment expenses: Current accident year (2,448,034) (561,226) — — — (3,009,260) Prior accident years 397,723 (34,104) — — 2,527 366,146 Underwriting, acquisition and insurance expenses: Amortization of policy acquisition costs (814,623) (193,697) — — — (1,008,320) Other underwriting expenses (594,880) (39,676) — — (1,987) (636,543) Underwriting profit (loss) 469,010 (58,672) — — (2,083) 408,255 Net investment income — — 284,087 8 — 284,095 Net investment gains — — 1,175,791 — — 1,175,791 Products revenues — — — 1,327,144 — 1,327,144 Services and other revenues — — — 1,363,141 241,917 1,605,058 Products expenses — — — (1,173,135) — (1,173,135) Services and other expenses — 109 — (1,260,957) (181,494) (1,442,342) Amortization of intangible assets (3) — — — (41,104) (77,446) (118,550) Segment profit (loss) $ 469,010 $ (58,563) $ 1,459,878 $ 215,097 $ (19,106) $ 2,066,316 Interest expense (135,412) Net foreign exchange gains 61,677 Income before income taxes $ 1,992,581 U.S. GAAP combined ratio (4) 88 % 108 % NM (5) 91 % (1) Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $47.7 million for the nine months ended September 30, 2021. (2) Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $31.1 million for the nine months ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments. (3) Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments. (4) The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums. (5) NM - Ratio is not meaningful
Reconciliation Of Segment Assets To The Company's Consolidated Balance Sheets	The following table reconciles segment assets to the Company's consolidated balance sheets. (dollars in thousands) September 30, 2022 December 31, 2021 Segment assets: Investing $ 25,389,047 $ 28,277,801 Underwriting 8,805,475 8,111,316 Markel Ventures 5,230,393 4,958,279 Total segment assets 39,424,915 41,347,396 Other operations 8,996,440 7,129,700 Total assets $ 48,421,355 $ 48,477,096

Investments (Tables)

Investments (Tables)	6 Months Ended	9 Months Ended
Investments (Tables)	Jun. 30, 2022	Sep. 30, 2022
Investments, Debt and Equity Securities [Abstract]
Available-For-Sale Investments		The following tables summarize the Company's available-for-sale investments. Commercial and residential mortgage-backed securities include securities issued by U.S. government-sponsored enterprises and U.S. government agencies. The net unrealized holding gains (losses) in the tables below are presented before taxes and any reserve deficiency adjustments for life and annuity benefit reserves. See note 9. September 30, 2022 (dollars in thousands) Amortized Gross Gross Estimated Fixed maturity securities: U.S. Treasury securities $ 3,145,087 $ — $ (186,666) $ 2,958,421 U.S. government-sponsored enterprises 838,518 42 (113,378) 725,182 Obligations of states, municipalities and political subdivisions 3,975,846 3,479 (265,982) 3,713,343 Foreign governments 1,388,221 — (215,332) 1,172,889 Commercial mortgage-backed securities 2,103,907 1 (171,243) 1,932,665 Residential mortgage-backed securities 582,833 127 (25,627) 557,333 Asset-backed securities 2,066 — (54) 2,012 Corporate bonds 809,101 10 (144,599) 664,512 Total fixed maturity securities 12,845,579 3,659 (1,122,881) 11,726,357 Short-term investments 2,441,719 147 (17,022) 2,424,844 Investments, available-for-sale $ 15,287,298 $ 3,806 $ (1,139,903) $ 14,151,201 December 31, 2021 (dollars in thousands) Amortized Gross Gross Estimated Fixed maturity securities: U.S. Treasury securities $ 2,489,032 $ 2,633 $ (21,471) $ 2,470,194 U.S. government-sponsored enterprises 753,029 28,997 (6,439) 775,587 Obligations of states, municipalities and political subdivisions 4,007,211 266,575 (7,862) 4,265,924 Foreign governments 1,394,771 134,071 (9,488) 1,519,354 Commercial mortgage-backed securities 1,928,775 69,810 (8,152) 1,990,433 Residential mortgage-backed securities 699,136 27,084 (170) 726,050 Asset-backed securities 3,035 46 — 3,081 Corporate bonds 786,478 54,475 (4,271) 836,682 Total fixed maturity securities 12,061,467 583,691 (57,853) 12,587,305 Short-term investments 1,805,300 28 (5,340) 1,799,988 Investments, available-for-sale $ 13,866,767 $ 583,719 $ (63,193) $ 14,387,293
Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position	December 31, 2021 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Gross Estimated Gross Estimated Gross Fixed maturity securities: U.S. Treasury securities $ 2,236,637 $ (18,433) $ 97,173 $ (3,038) $ 2,333,810 $ (21,471) U.S. government-sponsored enterprises 381,495 (5,640) 14,010 (799) 395,505 (6,439) Obligations of states, municipalities and political subdivisions 393,249 (6,941) 23,589 (921) 416,838 (7,862) Foreign governments 322,813 (8,596) 25,564 (892) 348,377 (9,488) Commercial mortgage-backed securities 345,616 (7,765) 9,189 (387) 354,805 (8,152) Residential mortgage-backed securities 12,828 (159) 269 (11) 13,097 (170) Corporate bonds 193,786 (4,271) — — 193,786 (4,271) Total fixed maturity securities 3,886,424 (51,805) 169,794 (6,048) 4,056,218 (57,853) Short-term investments 228,870 (5,340) — — 228,870 (5,340) Total $ 4,115,294 $ (57,145) $ 169,794 $ (6,048) $ 4,285,088 $ (63,193)	The following tables summarize gross unrealized investment losses on available-for-sale investments by the length of time that securities have continuously been in an unrealized loss position. September 30, 2022 Less than 12 months 12 months or longer Total (dollars in thousands) Estimated Gross Estimated Gross Estimated Gross Fixed maturity securities: U.S. Treasury securities $ 1,208,818 $ (59,585) $ 1,749,603 $ (127,081) $ 2,958,421 $ (186,666) U.S. government-sponsored enterprises 486,025 (63,103) 224,076 (50,275) 710,101 (113,378) Obligations of states, municipalities and political subdivisions 2,955,371 (205,139) 253,651 (60,843) 3,209,022 (265,982) Foreign governments 1,006,658 (177,900) 166,232 (37,432) 1,172,890 (215,332) Commercial mortgage-backed securities 1,677,058 (122,811) 255,181 (48,432) 1,932,239 (171,243) Residential mortgage-backed securities 510,227 (24,860) 3,899 (767) 514,126 (25,627) Asset-backed securities 2,012 (54) — — 2,012 (54) Corporate bonds 551,417 (118,451) 105,459 (26,148) 656,876 (144,599) Total fixed maturity securities 8,397,586 (771,903) 2,758,101 (350,978) 11,155,687 (1,122,881) Short-term investments 1,107,053 (17,022) — — 1,107,053 (17,022) Total $ 9,504,639 $ (788,925) $ 2,758,101 $ (350,978) $ 12,262,740 $ (1,139,903)
Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date		The amortized cost and estimated fair value of fixed maturity securities at September 30, 2022 are shown below by contractual maturity. (dollars in thousands) Amortized Estimated Due in one year or less $ 1,392,651 $ 1,357,060 Due after one year through five years 3,943,834 3,649,795 Due after five years through ten years 2,993,861 2,618,759 Due after ten years 1,826,427 1,608,733 10,156,773 9,234,347 Commercial mortgage-backed securities 2,103,907 1,932,665 Residential mortgage-backed securities 582,833 557,333 Asset-backed securities 2,066 2,012 Total fixed maturity securities $ 12,845,579 $ 11,726,357
Components Of Net Investment Income		The following table presents the components of net investment income. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Interest: Tax-exempt municipal bonds $ 12,673 $ 14,293 $ 39,408 $ 43,631 Taxable municipal bonds 17,488 16,320 52,613 49,236 Other taxable bonds 42,316 39,705 123,520 119,718 Short-term investments, including overnight deposits 17,633 633 24,634 2,179 Dividends on equity securities 25,962 23,400 74,289 68,583 Income (loss) from equity method investments (5,509) 882 (35,002) 13,825 Other 1,103 (335) 7,041 (947) 111,666 94,898 286,503 296,225 Investment expenses (3,935) (3,634) (12,380) (12,130) Net investment income $ 107,731 $ 91,264 $ 274,123 $ 284,095
Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Available-For-Sale Investments		The following table presents the components of net investment gains (losses) and the change in net unrealized gains (losses) included in other comprehensive loss. Gross realized investment gains and losses on fixed maturity securities, short-term investments and other investments were not material to the consolidated financial statements and are presented on a net basis in the following table. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Fixed maturity securities, short-term investments and other investments: Net realized investment gains (losses) $ 2,032 $ (2,578) $ 6,001 $ 5,233 Equity securities: Change in fair value of securities sold during the period 2,553 (400) (29,015) 22,254 Change in fair value of securities held at the end of the period (286,068) (22,855) (2,171,511) 1,148,304 Total change in fair value (283,515) (23,255) (2,200,526) 1,170,558 Net investment gains (losses) $ (281,483) $ (25,833) $ (2,194,525) $ 1,175,791 Change in net unrealized gains (losses) on available-for-sale investments included in other comprehensive loss: Fixed maturity securities $ (530,161) $ (133,244) $ (1,645,060) $ (391,528) Short-term investments (8,186) (4,855) (11,563) (3,076) Reserve deficiency adjustment for life and annuity benefit reserves (see note 9) — 6,428 56,560 56,690 Net decrease $ (538,347) $ (131,671) $ (1,600,063) $ (337,914)

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Balances Of Assets Measured At Fair Value On A Recurring Basis	The following tables present the balances of assets measured at fair value on a recurring basis by level within the fair value hierarchy. September 30, 2022 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments: Fixed maturity securities, available-for-sale: U.S. Treasury securities $ — $ 2,958,421 $ — $ 2,958,421 U.S. government-sponsored enterprises — 725,182 — 725,182 Obligations of states, municipalities and political subdivisions — 3,713,343 — 3,713,343 Foreign governments — 1,172,889 — 1,172,889 Commercial mortgage-backed securities — 1,932,665 — 1,932,665 Residential mortgage-backed securities — 557,333 — 557,333 Asset-backed securities — 2,012 — 2,012 Corporate bonds — 664,512 — 664,512 Total fixed maturity securities, available-for-sale — 11,726,357 — 11,726,357 Equity securities: Insurance, banks and other financial institutions 2,614,609 — 921 2,615,530 Industrial, consumer and all other 4,334,827 — — 4,334,827 Total equity securities 6,949,436 — 921 6,950,357 Short-term investments, available-for-sale 2,277,172 147,672 — 2,424,844 Total investments $ 9,226,608 $ 11,874,029 $ 921 $ 21,101,558 December 31, 2021 (dollars in thousands) Level 1 Level 2 Level 3 Total Assets: Investments: Fixed maturity securities, available-for-sale: U.S. Treasury securities $ — $ 2,470,194 $ — $ 2,470,194 U.S. government-sponsored enterprises — 775,587 — 775,587 Obligations of states, municipalities and political subdivisions — 4,265,924 — 4,265,924 Foreign governments — 1,519,354 — 1,519,354 Commercial mortgage-backed securities — 1,990,433 — 1,990,433 Residential mortgage-backed securities — 726,050 — 726,050 Asset-backed securities — 3,081 — 3,081 Corporate bonds — 836,682 — 836,682 Total fixed maturity securities, available-for-sale — 12,587,305 — 12,587,305 Equity securities: Insurance, banks and other financial institutions 3,307,755 — 56,472 3,364,227 Industrial, consumer and all other 5,659,700 — — 5,659,700 Total equity securities 8,967,455 — 56,472 9,023,927 Short-term investments, available-for-sale 1,619,496 180,492 — 1,799,988 Total investments $ 10,586,951 $ 12,767,797 $ 56,472 $ 23,411,220
Summary Of Changes In Level 3 Investments Measured At Fair Value On A Recurring Basis	The following table summarizes changes in Level 3 investments measured at fair value on a recurring basis. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Equity securities, beginning of period $ 4,380 $ 41,066 $ 56,472 $ 58,493 Purchases — 18,900 — 18,900 Sales (3,528) — (56,335) (15,015) Net investment gains (losses) 69 (3,341) 784 (5,753) Equity securities, end of period $ 921 $ 56,625 $ 921 $ 56,625

Products, Services and Other _2

Products, Services and Other Revenues (Tables)	9 Months Ended
Products, Services and Other Revenues (Tables)	Sep. 30, 2022
Revenue from Contract with Customer [Abstract]
Schedule Of Revenues From Contracts With Customers By Type	The following tables present revenues from contracts with customers by segment and type, all of which are included in products revenues and services and other revenues in the consolidated statements of income (loss) and comprehensive income (loss), along with a reconciliation to total products revenues and services and other revenues. Quarter Ended September 30, 2022 2021 (dollars in thousands) Markel Ventures Other Total Markel Ventures Other Total Products $ 575,277 $ — $ 575,277 $ 394,444 $ — $ 394,444 Services 614,519 11,529 626,048 487,942 30,027 517,969 Investment management — 15,641 15,641 — 20,571 20,571 Total revenues from contracts with customers 1,189,796 27,170 1,216,966 882,386 50,598 932,984 Program services and other fronting — 40,033 40,033 — 32,298 32,298 Other 25,950 118 26,068 25,796 345 26,141 Total $ 1,215,746 $ 67,321 $ 1,283,067 $ 908,182 $ 83,241 $ 991,423 Nine Months Ended September 30, 2022 2021 (dollars in thousands) Markel Ventures Other Total Markel Ventures Other Total Products $ 1,809,276 $ — $ 1,809,276 $ 1,294,407 $ — $ 1,294,407 Services 1,633,353 41,547 1,674,900 1,313,054 95,908 1,408,962 Investment management — 55,197 55,197 — 57,693 57,693 Total revenues from contracts with customers 3,442,629 96,744 3,539,373 2,607,461 153,601 2,761,062 Program services and other fronting — 103,096 103,096 — 87,314 87,314 Disposition gain — 107,293 107,293 — — — Other 84,800 724 85,524 82,824 1,002 83,826 Total $ 3,527,429 $ 307,857 $ 3,835,286 $ 2,690,285 $ 241,917 $ 2,932,202

Unpaid Losses And Loss Adjust_2

Unpaid Losses And Loss Adjustment Expenses (Tables)	9 Months Ended
Unpaid Losses And Loss Adjustment Expenses (Tables)	Sep. 30, 2022
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Reconciliation Of Consolidated Reserves For Losses And Loss Adjustment Expenses	The following table presents a reconciliation of consolidated beginning and ending reserves for losses and loss adjustment expenses. Nine Months Ended September 30, (dollars in thousands) 2022 2021 Net reserves for losses and loss adjustment expenses, beginning of year $ 11,302,577 $ 10,485,717 Effect of foreign currency rate changes on beginning of year balance (275,364) (52,117) Adjusted net reserves for losses and loss adjustment expenses, beginning of year 11,027,213 10,433,600 Incurred losses and loss adjustment expenses: Current accident year 3,420,906 3,009,260 Prior accident years (204,411) (366,171) Total incurred losses and loss adjustment expenses 3,216,495 2,643,089 Payments: Current accident year 350,684 365,640 Prior accident years 1,880,471 1,678,164 Total payments 2,231,155 2,043,804 Effect of foreign currency rate changes on current year activity (7,499) (1,339) Net reserves for losses and loss adjustment expenses of Markel CATCo Re (see note 11) 375,222 — Net reserves for losses and loss adjustment expenses of insurance companies sold — (2,762) Net reserves for losses and loss adjustment expenses, end of period 12,380,276 11,028,784 Reinsurance recoverables on unpaid losses 7,814,098 6,582,415 Gross reserves for losses and loss adjustment expenses, end of period $ 20,194,374 $ 17,611,199

Reinsurance (Tables)

Reinsurance (Tables)	9 Months Ended
Reinsurance (Tables)	Sep. 30, 2022
Reinsurance Disclosures [Abstract]
Effect Of Reinsurance And Retrocessional Reinsurance On Premiums Written And Earned	The following tables summarize the effect of reinsurance and retrocessional reinsurance on premiums written and earned. Quarter Ended September 30, 2022 2021 (dollars in thousands) Direct Assumed Ceded Net Premiums Direct Assumed Ceded Net Premiums Underwriting: Written $ 2,133,822 $ 349,650 $ (473,885) $ 2,009,587 $ 1,776,716 $ 303,551 $ (393,195) $ 1,687,072 Earned 1,899,816 408,561 (351,118) 1,957,259 1,599,931 363,665 (331,397) 1,632,199 Program services and other fronting: Written 663,631 327,668 (991,719) (420) 711,182 177,153 (890,597) (2,262) Earned 729,312 218,439 (948,180) (429) 634,520 103,008 (739,227) (1,699) Consolidated: Written 2,797,453 677,318 (1,465,604) 2,009,167 2,487,898 480,704 (1,283,792) 1,684,810 Earned $ 2,629,128 $ 627,000 $ (1,299,298) $ 1,956,830 $ 2,234,451 $ 466,673 $ (1,070,624) $ 1,630,500 Nine Months Ended September 30, 2022 2021 (dollars in thousands) Direct Assumed Ceded Net Premiums Direct Assumed Ceded Net Premiums Underwriting: Written $ 6,065,936 $ 1,466,036 $ (1,255,226) $ 6,276,746 $ 5,082,494 $ 1,269,578 $ (1,031,546) $ 5,320,526 Earned 5,370,481 1,194,504 (1,012,485) 5,552,500 4,542,680 1,081,494 (925,176) 4,698,998 Program services and other fronting: Written 2,025,195 595,940 (2,624,185) (3,050) 2,056,328 249,067 (2,308,590) (3,195) Earned 2,036,016 332,415 (2,371,227) (2,796) 1,800,489 141,676 (1,944,931) (2,766) Consolidated: Written 8,091,131 2,061,976 (3,879,411) 6,273,696 7,138,822 1,518,645 (3,340,136) 5,317,331 Earned $ 7,406,497 $ 1,526,919 $ (3,383,712) $ 5,549,704 $ 6,343,169 $ 1,223,170 $ (2,870,107) $ 4,696,232
Effect Of Reinsurance And Retrocessional Reinsurance On Losses and Loss Adjustment Expenses	The following table summarizes the effect of reinsurance and retrocessional reinsurance on losses and loss adjustment expenses in the Company's underwriting operations. Quarter Ended September 30, Nine Months Ended September 30, (dollars in thousands) 2022 2021 2022 2021 Gross losses and loss adjustment expenses $ 1,423,526 $ 1,238,974 $ 3,760,566 $ 3,306,035 Ceded losses and loss adjustment expenses (238,220) (290,834) (544,109) (660,479) Net losses and loss adjustment expenses $ 1,185,306 $ 948,140 $ 3,216,457 $ 2,645,556

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
Variable Interest Entities (Tables)	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Amounts attributable to Markel CATCo Re in Markel's consolidated balance sheet	The Company's consolidated balance sheet includes the following amounts attributable to Markel CATCo Re. (dollars in thousands) September 30, 2022 Assets Cash and cash equivalents $ 83,103 Restricted cash and cash equivalents 355,905 Other assets and receivables due from cedents 44,102 Total Assets $ 483,110 Liabilities and Equity Unpaid losses and loss adjustment expenses $ 375,222 Other liabilities 27,448 Total Liabilities 402,670 Shareholders' equity 21,139 Noncontrolling interests 59,301 Total Equity 80,440 Total Liabilities and Equity $ 483,110

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	9 Months Ended
Shareholders' Equity (Tables)	Sep. 30, 2022
Stockholders' Equity Note [Abstract]
Schedule of Common Stock Outstanding Roll Forward	The Company has 50,000,000 shares of no par value common stock authorized. The following table presents a rollforward of changes in common shares issued and outstanding. Quarter Ended September 30, Nine Months Ended September 30, (in thousands) 2022 2021 2022 2021 Issued and outstanding common shares, beginning of period 13,538 13,734 13,632 13,783 Issuance of common shares — 1 2 4 Repurchase of common shares (67) (50) (163) (102) Issued and outstanding common shares, end of period 13,471 13,685 13,471 13,685
Schedule Of Net Income (Loss) Per Common Share	The following table presents net income (loss) per common share and diluted net income (loss) per common share. Quarter Ended September 30, Nine Months Ended September 30, (in thousands, except per share amounts) 2022 2021 2022 2021 Net income (loss) to common shareholders $ 65,369 $ 188,070 $ (921,833) $ 1,535,874 Adjustment of redeemable noncontrolling interests (17,730) 19,930 (62,168) 41,553 Adjusted net income (loss) to common shareholders $ 47,639 $ 208,000 $ (984,001) $ 1,577,427 Basic common shares outstanding 13,564 13,758 13,609 13,790 Dilutive potential common shares from restricted stock units and restricted stock (1) 31 27 — 23 Diluted common shares outstanding 13,595 13,785 13,609 13,813 Basic net income (loss) per common share $ 3.51 $ 15.12 $ (72.31) $ 114.39 Diluted net income (loss) per common share (1) $ 3.50 $ 15.09 $ (72.31) $ 114.20 (1) The impact of 28 thousand shares from restricted stock units and restricted stock was excluded from the computation of diluted net loss per common share for the nine months ended September 30, 2022 because the effect would have been anti-dilutive.

Segment Reporting Disclosures_2

Segment Reporting Disclosures (Company's Segment Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2022		Sep. 30, 2021		Sep. 30, 2022		Sep. 30, 2021
Segment Reporting Information [Line Items]
Gross premium volume	$ 3,474,771		$ 2,968,602		$ 10,153,107		$ 8,657,467
Net written premiums	2,009,167		1,684,810		6,273,696		5,317,331
Earned premiums	1,956,830		1,630,500		5,549,704		4,696,232
Losses and loss adjustment expenses, current accident year	(1,266,996)		(1,088,353)		(3,420,906)		(3,009,260)
Losses and loss adjustment expenses, prior accident year	81,683		140,112		204,411		366,146
Amortization of policy acquisition costs	(431,182)		(352,924)		(1,206,325)		(1,008,320)
Other underwriting expenses	(212,090)		(216,832)		(636,781)		(636,543)
Underwriting profit (loss)	128,245		112,503		490,103		408,255
Net investment income	107,731		91,264		274,123		284,095
Net investment gains (losses)	(281,483)		(25,833)		(2,194,525)		1,175,791
Products revenues	586,531		405,711		1,845,111		1,327,144
Services and other revenues	696,536		585,712		1,990,175		1,605,058
Products expenses	(580,830)		(374,407)		(1,726,367)		(1,173,135)
Services and other expenses	(540,569)	[1]	(513,994)		(1,692,203)	[2]	(1,442,342)
Amortization of intangible assets	(43,418)	[3]	(39,268)	[4]	(134,990)	[5]	(118,550)	[6]
Segment profit (loss)	72,743		241,688		(1,148,573)		2,066,316
Interest expense	(47,348)		(46,455)		(147,090)		(135,412)
Net foreign exchange gains	115,130		48,850		245,356		61,677
Income (Loss) before income taxes	$ 140,525		$ 244,083		$ (1,050,307)		$ 1,992,581
U.S. GAAP combined ratio	93%	[7]	93%	[8]	91%	[9]	91%	[10]
Favorable development on prior years' loss reserves, Markel CATCo Re					$ (204,411)		$ (366,171)
Insurance [Member]
Segment Reporting Information [Line Items]
Gross premium volume	$ 2,299,325		$ 1,899,592		6,479,789		5,359,293
Net written premiums	1,849,983		1,545,428		5,289,165		4,427,301
Earned premiums	1,695,029		1,381,235		4,742,178		3,928,824
Losses and loss adjustment expenses, current accident year	(1,100,511)		(866,481)		(2,906,031)		(2,448,034)
Losses and loss adjustment expenses, prior accident year	53,760		124,133		196,093		397,723
Amortization of policy acquisition costs	(362,137)		(289,201)		(996,369)		(814,623)
Other underwriting expenses	(200,604)		(202,961)		(596,426)		(594,880)
Underwriting profit (loss)	85,537		146,725		439,445		469,010
Net investment income	0		0		0		0
Net investment gains (losses)	0		0		0		0
Products revenues	0		0		0		0
Services and other revenues	0		0		0		0
Products expenses	0		0		0		0
Services and other expenses	0	[1]	0		0	[2]	0
Amortization of intangible assets	0	[3]	0	[4]	0	[5]	0	[6]
Segment profit (loss)	$ 85,537		$ 146,725		$ 439,445		$ 469,010
U.S. GAAP combined ratio	95%	[7]	89%	[8]	91%	[9]	88%	[10]
Reinsurance [Member]
Segment Reporting Information [Line Items]
Gross premium volume	$ 179,455		$ 180,673		$ 1,044,827		$ 992,635
Net written premiums	154,029		141,642		983,087		893,082
Earned premiums	260,535		250,962		808,656		770,031
Losses and loss adjustment expenses, current accident year	(166,485)		(221,872)		(514,875)		(561,226)
Losses and loss adjustment expenses, prior accident year	29,505		16,292		13,845		(34,104)
Amortization of policy acquisition costs	(68,662)		(63,723)		(209,541)		(193,697)
Other underwriting expenses	(11,638)		(12,101)		(37,708)		(39,676)
Underwriting profit (loss)	43,255		(30,442)		60,377		(58,672)
Net investment income	0		0		0		0
Net investment gains (losses)	0		0		0		0
Products revenues	0		0		0		0
Services and other revenues	0		0		0		0
Products expenses	0		0		0		0
Services and other expenses	0	[1]	0		0	[2]	109
Amortization of intangible assets	0	[3]	0	[4]	0	[5]	0	[6]
Segment profit (loss)	$ 43,255		$ (30,442)		$ 60,377		$ (58,563)
U.S. GAAP combined ratio	83%	[7]	112%	[8]	93%	[9]	108%	[10]
Investing [Member]
Segment Reporting Information [Line Items]
Gross premium volume	$ 0		$ 0		$ 0		$ 0
Net written premiums	0		0		0		0
Earned premiums	0		0		0		0
Losses and loss adjustment expenses, current accident year	0		0		0		0
Losses and loss adjustment expenses, prior accident year	0		0		0		0
Amortization of policy acquisition costs	0		0		0		0
Other underwriting expenses	0		0		0		0
Underwriting profit (loss)	0		0		0		0
Net investment income	107,414		91,261		273,699		284,087
Net investment gains (losses)	(281,483)		(25,833)		(2,194,525)		1,175,791
Products revenues	0		0		0		0
Services and other revenues	0		0		0		0
Products expenses	0		0		0		0
Services and other expenses	0	[1]	0		0	[2]	0
Amortization of intangible assets	0	[3]	0	[4]	0	[5]	0	[6]
Segment profit (loss)	(174,069)		65,428		(1,920,826)		1,459,878
Markel Ventures [Member]
Segment Reporting Information [Line Items]
Gross premium volume	0	[11]	0	[12]	0	[13]	0	[14]
Net written premiums	0	[11]	0	[12]	0	[13]	0	[14]
Earned premiums	0	[11]	0	[12]	0	[13]	0	[14]
Losses and loss adjustment expenses, current accident year	0	[11]	0	[12]	0	[13]	0	[14]
Losses and loss adjustment expenses, prior accident year	0	[11]	0	[12]	0	[13]	0	[14]
Amortization of policy acquisition costs	0	[11]	0	[12]	0	[13]	0	[14]
Other underwriting expenses	0	[11]	0	[12]	0	[13]	0	[14]
Underwriting profit (loss)	0	[11]	0	[12]	0	[13]	0	[14]
Net investment income	317	[11]	3	[12]	424	[13]	8	[14]
Net investment gains (losses)	0	[11]	0	[12]	0	[13]	0	[14]
Products revenues	586,531	[11]	405,711	[12]	1,845,111	[13]	1,327,144	[14]
Services and other revenues	629,215	[11]	502,471	[12]	1,682,318	[13]	1,363,141	[14]
Products expenses	(580,830)	[11]	(374,407)	[12]	(1,726,367)	[13]	(1,173,135)	[14]
Services and other expenses	(556,207)	[1],[11]	(465,268)	[12]	(1,524,167)	[2],[13]	(1,260,957)	[14]
Amortization of intangible assets	(18,567)	[3],[11]	(13,541)	[4],[12]	(60,077)	[5],[13]	(41,104)	[6],[14]
Segment profit (loss)	60,459	[11]	54,969	[12]	217,242	[13]	215,097	[14]
Depreciation	23,700	[11]	15,800	[12]	75,300	[13]	47,700	[14]
Underwriting Segments [Member]
Segment Reporting Information [Line Items]
Amortization of intangible assets	9,600	[15]	10,300	[16]	29,000	[17]	31,100	[18]
Other [Member]
Segment Reporting Information [Line Items]
Gross premium volume	995,991	[15]	888,337	[16]	2,628,491	[17]	2,305,539	[18]
Net written premiums	5,155	[15]	(2,260)	[16]	1,444	[17]	(3,052)	[18]
Earned premiums	1,266	[15]	(1,697)	[16]	(1,130)	[17]	(2,623)	[18]
Losses and loss adjustment expenses, current accident year	0	[15]	0	[16]	0	[17]	0	[18]
Losses and loss adjustment expenses, prior accident year	(1,582)	[15]	(313)	[16]	(5,527)	[17]	2,527	[18]
Amortization of policy acquisition costs	(383)	[15]	0	[16]	(415)	[17]	0	[18]
Other underwriting expenses	152	[15]	(1,770)	[16]	(2,647)	[17]	(1,987)	[18]
Underwriting profit (loss)	(547)	[15]	(3,780)	[16]	(9,719)	[17]	(2,083)	[18]
Net investment income	0	[15]	0	[16]	0	[17]	0	[18]
Net investment gains (losses)	0	[15]	0	[16]	0	[17]	0	[18]
Products revenues	0	[15]	0	[16]	0	[17]	0	[18]
Services and other revenues	67,321	[15]	83,241	[16]	307,857	[17]	241,917	[18]
Products expenses	0	[15]	0	[16]	0	[17]	0	[18]
Services and other expenses	15,638	[1],[15]	(48,726)	[16]	(168,036)	[2],[17]	(181,494)	[18]
Amortization of intangible assets	(24,851)	[3],[15]	(25,727)	[4],[16]	(74,913)	[5],[17]	(77,446)	[6],[18]
Segment profit (loss)	57,561	[15]	$ 5,008	[16]	55,189	[17]	$ (19,106)	[14]
Other [Member] \| Markel CATCo Re
Segment Reporting Information [Line Items]
Favorable development on prior years' loss reserves, Markel CATCo Re	$ 53,400	[1]			$ 81,600	[2]

[1]Services and other expenses for Other for the quarter ended September 30, 2022 included $53.4 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11.[2]Services and other expenses for Other for the nine months ended September 30, 2022 included $81.6 million of favorable loss reserve development on the run-off of reinsurance contracts written by Markel CATCo Re Ltd., all of which was attributable to noncontrolling interests. See Note 11.[3]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[4]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[5]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[6]Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to the Company's Insurance and Reinsurance segments.[7]The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.[8]The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.[9]The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.[10]The U.S. GAAP combined ratio is a measure of underwriting performance and represents the relationship of incurred losses, loss adjustment expenses and underwriting, acquisition and insurance expenses to earned premiums.[11]Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $23.7 million for the quarter ended September 30, 2022.[12]Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $15.8 million for the quarter ended September 30, 2021.[13]Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $75.3 million for the nine months ended September 30, 2022.[14]Products expenses and services and other expenses for the Markel Ventures segment include depreciation expense of $47.7 million for the nine months ended September 30, 2021.[15]Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $9.6 million for the quarter ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments.[16]Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $10.3 million for the quarter ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments.[17]Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $29.0 million for the nine months ended September 30, 2022, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments.[18]Other represents the total profit (loss) attributable to the Company's operations that are not included in a reportable segment as well as any amortization of intangible assets that is not allocated to a reportable segment. Amortization of intangible assets attributable to the Company's underwriting segments was $31.1 million for the nine months ended September 30, 2021, however, the Company does not allocate amortization of intangible assets between the Insurance and Reinsurance segments.

Segment Reporting Disclosures_3

Segment Reporting Disclosures (Reconciliation Of Segment Assets To The Company's Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Assets	$ 48,421,355	$ 48,477,096
Other [Member]
Segment Reporting Information [Line Items]
Assets	8,996,440	7,129,700
Segment assets [Member]
Segment Reporting Information [Line Items]
Assets	39,424,915	41,347,396
Segment assets [Member] \| Investing [Member]
Segment Reporting Information [Line Items]
Assets	25,389,047	28,277,801
Segment assets [Member] \| Underwriting [Member]
Segment Reporting Information [Line Items]
Assets	8,805,475	8,111,316
Segment assets [Member] \| Markel Ventures [Member]
Segment Reporting Information [Line Items]
Assets	$ 5,230,393	$ 4,958,279

Acquisitions and Dispositions (

Acquisitions and Dispositions (Narratives) (Details) - USD ($) $ in Thousands					9 Months Ended
	Oct. 01, 2022	Feb. 01, 2022	Dec. 21, 2021	Aug. 31, 2021	Sep. 30, 2022
Velocity [Member]
Schedule of Business Dispositions, by Dispositions [Line Items]
Proceeds from sale of business		$ 181,300
Gain on sale of business		107,300
Business combination, disposition of less than 100 percent, noncontrolling interest, fair value		$ 47,400
Volante [Member]
Schedule of Business Dispositions, by Dispositions [Line Items]
Proceeds from sale of business	$ 155,000
Metromont LLC [Member]
Business Acquisition [Line Items]
Percentage acquired			51%
Total purchase consideration			$ 282,300
Cash consideration			$ 282,300
Goodwill, period decrease					$ 18,700
Noncontrolling interest, period decrease					18,700
Goodwill recognized					200,600
Expected tax deductible goodwill					200,600
Intangible Assets					143,900
Redeemable noncontrolling interest					$ 251,200
Buckner HeavyLift Cranes [Member]
Business Acquisition [Line Items]
Percentage acquired				90%
Total purchase consideration				$ 237,900
Cash consideration				237,900
Goodwill recognized				109,900
Expected tax deductible goodwill				0
Finite-lived intangible assets				60,000
Fixed assets				290,400
Long-term debt				165,100
Redeemable noncontrolling interest				26,400
Buckner HeavyLift Cranes [Member] \| Customer relationships [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets				$ 50,000
Definite-lived intangible assets, weighted-average amortization period				7 years
Buckner HeavyLift Cranes [Member] \| Trade names [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets				$ 10,000
Definite-lived intangible assets, weighted-average amortization period				15 years

Investments (Narrative) (Detail

Investments (Narrative) (Details) $ in Thousands	Sep. 30, 2022 USD ($) securities	Dec. 31, 2021 USD ($) securities
Schedule of Investments [Line Items]
Available-for-sale fixed maturity securities in unrealized loss position, number of positions \| securities	1,548	277
Available-for-sale securities, estimated fair value	$ 12,262,740	$ 4,285,088
Available-for-sale securities, gross unrealized holding losses	$ (1,139,903)	$ (63,193)
Number of available-for-sale fixed maturity securities positions in a continuous unrealized loss position for one year or longer at period end \| securities	172	13
Available-for-sale securities, estimated fair value, 12 months or longer	$ 2,758,101	$ 169,794
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(350,978)	(6,048)
Available-for-sale, allowance for credit losses	0	0
Equity method investments	483,100	459,700
Hagerty, Inc. [Member]
Schedule of Investments [Line Items]
Equity method investments	$ 239,000	$ 256,600
Equity method investment, ownership percentage	23%	23%
Equity method investment, quoted market value	$ 701,200	$ 1,100,000
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Available-for-sale securities, estimated fair value	11,155,687	4,056,218
Available-for-sale securities, gross unrealized holding losses	(1,122,881)	(57,853)
Available-for-sale securities, estimated fair value, 12 months or longer	2,758,101	169,794
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	$ (350,978)	$ (6,048)

Investments (Available-For-Sale

Investments (Available-For-Sale Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	$ 12,845,579	$ 12,061,467
Available-for-sale fixed maturity investments, gross unrealized holding gains	3,659	583,691
Available-for-sale fixed maturity investments, gross unrealized holding losses	(1,122,881)	(57,853)
Available-for-sale fixed maturity investments, estimated fair value	11,726,357	12,587,305
Short-term investments, available-for-sale, amortized cost	2,441,719	1,805,300
Short-term investments, available-for-sale, gross unrealized holding gains	147	28
Short-term investments, available-for-sale, gross unrealized holding losses	(17,022)	(5,340)
Short-term investments, available-for-sale, estimated fair value	2,424,844	1,799,988
Investments, available-for-sale, amortized cost	15,287,298	13,866,767
Investments, available-for-sale, gross unrealized holding gains	3,806	583,719
Investments, available-for-sale, gross unrealized holding losses	(1,139,903)	(63,193)
Investments, available-for-sale, estimated fair value	14,151,201	14,387,293
U.S. Treasury securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,145,087	2,489,032
Available-for-sale fixed maturity investments, gross unrealized holding gains	0	2,633
Available-for-sale fixed maturity investments, gross unrealized holding losses	(186,666)	(21,471)
Available-for-sale fixed maturity investments, estimated fair value	2,958,421	2,470,194
U.S. government-sponsored enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	838,518	753,029
Available-for-sale fixed maturity investments, gross unrealized holding gains	42	28,997
Available-for-sale fixed maturity investments, gross unrealized holding losses	(113,378)	(6,439)
Available-for-sale fixed maturity investments, estimated fair value	725,182	775,587
Obligations of states, municipalities and political subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	3,975,846	4,007,211
Available-for-sale fixed maturity investments, gross unrealized holding gains	3,479	266,575
Available-for-sale fixed maturity investments, gross unrealized holding losses	(265,982)	(7,862)
Available-for-sale fixed maturity investments, estimated fair value	3,713,343	4,265,924
Foreign governments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	1,388,221	1,394,771
Available-for-sale fixed maturity investments, gross unrealized holding gains	0	134,071
Available-for-sale fixed maturity investments, gross unrealized holding losses	(215,332)	(9,488)
Available-for-sale fixed maturity investments, estimated fair value	1,172,889	1,519,354
Commercial mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	2,103,907	1,928,775
Available-for-sale fixed maturity investments, gross unrealized holding gains	1	69,810
Available-for-sale fixed maturity investments, gross unrealized holding losses	(171,243)	(8,152)
Available-for-sale fixed maturity investments, estimated fair value	1,932,665	1,990,433
Residential mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	582,833	699,136
Available-for-sale fixed maturity investments, gross unrealized holding gains	127	27,084
Available-for-sale fixed maturity investments, gross unrealized holding losses	(25,627)	(170)
Available-for-sale fixed maturity investments, estimated fair value	557,333	726,050
Asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	2,066	3,035
Available-for-sale fixed maturity investments, gross unrealized holding gains	0	46
Available-for-sale fixed maturity investments, gross unrealized holding losses	(54)	0
Available-for-sale fixed maturity investments, estimated fair value	2,012	3,081
Corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, available-for-sale, amortized cost	809,101	786,478
Available-for-sale fixed maturity investments, gross unrealized holding gains	10	54,475
Available-for-sale fixed maturity investments, gross unrealized holding losses	(144,599)	(4,271)
Available-for-sale fixed maturity investments, estimated fair value	$ 664,512	$ 836,682

Investments (Summary Of Gross U

Investments (Summary Of Gross Unrealized Investment Losses By Length Of Time That Securities Have Continuously Been In An Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	$ 9,504,639	$ 4,115,294
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(788,925)	(57,145)
Available-for-sale securities, estimated fair value, 12 months or longer	2,758,101	169,794
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(350,978)	(6,048)
Available-for-sale securities, estimated fair value	12,262,740	4,285,088
Available-for-sale securities, gross unrealized holding losses	(1,139,903)	(63,193)
Short-term investments, estimated fair value, less than 12 months	1,107,053	228,870
Short-term investments, gross unrealized holding losses, less than 12 months	(17,022)	(5,340)
Short-term investments, estimated fair value, 12 months or longer	0	0
Short-term investments, gross unrealized holding losses, 12 months or longer	0	0
Short-term investments, estimated fair value	1,107,053	228,870
Short-term investments, gross unrealized holding losses	(17,022)	(5,340)
U.S. Treasury securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	1,208,818	2,236,637
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(59,585)	(18,433)
Available-for-sale securities, estimated fair value, 12 months or longer	1,749,603	97,173
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(127,081)	(3,038)
Available-for-sale securities, estimated fair value	2,958,421	2,333,810
Available-for-sale securities, gross unrealized holding losses	(186,666)	(21,471)
U.S. government-sponsored enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	486,025	381,495
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(63,103)	(5,640)
Available-for-sale securities, estimated fair value, 12 months or longer	224,076	14,010
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(50,275)	(799)
Available-for-sale securities, estimated fair value	710,101	395,505
Available-for-sale securities, gross unrealized holding losses	(113,378)	(6,439)
Obligations of states, municipalities and political subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	2,955,371	393,249
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(205,139)	(6,941)
Available-for-sale securities, estimated fair value, 12 months or longer	253,651	23,589
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(60,843)	(921)
Available-for-sale securities, estimated fair value	3,209,022	416,838
Available-for-sale securities, gross unrealized holding losses	(265,982)	(7,862)
Foreign governments [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	1,006,658	322,813
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(177,900)	(8,596)
Available-for-sale securities, estimated fair value, 12 months or longer	166,232	25,564
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(37,432)	(892)
Available-for-sale securities, estimated fair value	1,172,890	348,377
Available-for-sale securities, gross unrealized holding losses	(215,332)	(9,488)
Commercial mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	1,677,058	345,616
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(122,811)	(7,765)
Available-for-sale securities, estimated fair value, 12 months or longer	255,181	9,189
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(48,432)	(387)
Available-for-sale securities, estimated fair value	1,932,239	354,805
Available-for-sale securities, gross unrealized holding losses	(171,243)	(8,152)
Residential mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	510,227	12,828
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(24,860)	(159)
Available-for-sale securities, estimated fair value, 12 months or longer	3,899	269
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(767)	(11)
Available-for-sale securities, estimated fair value	514,126	13,097
Available-for-sale securities, gross unrealized holding losses	(25,627)	(170)
Asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	2,012
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(54)
Available-for-sale securities, estimated fair value, 12 months or longer	0
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	0
Available-for-sale securities, estimated fair value	2,012
Available-for-sale securities, gross unrealized holding losses	(54)
Corporate bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	551,417	193,786
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(118,451)	(4,271)
Available-for-sale securities, estimated fair value, 12 months or longer	105,459	0
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(26,148)	0
Available-for-sale securities, estimated fair value	656,876	193,786
Available-for-sale securities, gross unrealized holding losses	(144,599)	(4,271)
Total fixed maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities, estimated fair value, less than 12 months	8,397,586	3,886,424
Available-for-sale securities, gross unrealized holding losses, less than 12 months	(771,903)	(51,805)
Available-for-sale securities, estimated fair value, 12 months or longer	2,758,101	169,794
Available-for-sale securities, gross unrealized holding losses, 12 months or longer	(350,978)	(6,048)
Available-for-sale securities, estimated fair value	11,155,687	4,056,218
Available-for-sale securities, gross unrealized holding losses	$ (1,122,881)	$ (57,853)

Investments (Schedule Of Amorti

Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturity Securities By Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Due in one year or less, amortized cost	$ 1,392,651
Due after one year through five years, amortized cost	3,943,834
Due after five years through ten years, amortized cost	2,993,861
Due after ten years, amortized cost	1,826,427
Amortized cost, sub-total	10,156,773
Total fixed maturities, amortized cost	12,845,579	$ 12,061,467
Due in one year or less, estimated fair value	1,357,060
Due after one year through five years, estimated fair value	3,649,795
Due after five years through ten years, estimated fair value	2,618,759
Due after ten years, estimated fair value	1,608,733
Estimated fair value, sub-total	9,234,347
Total fixed maturities, estimated fair value	11,726,357	12,587,305
Commercial mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	2,103,907
Total fixed maturities, amortized cost	2,103,907	1,928,775
Fixed maturities, estimated fair value	1,932,665
Total fixed maturities, estimated fair value	1,932,665	1,990,433
Residential mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	582,833
Total fixed maturities, amortized cost	582,833	699,136
Fixed maturities, estimated fair value	557,333
Total fixed maturities, estimated fair value	557,333	726,050
Asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed maturities, amortized cost	2,066
Total fixed maturities, amortized cost	2,066	3,035
Fixed maturities, estimated fair value	2,012
Total fixed maturities, estimated fair value	$ 2,012	$ 3,081

Investments (Components Of Net

Investments (Components Of Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Tax-exempt municipal bonds	$ 12,673	$ 14,293	$ 39,408	$ 43,631
Short-term investments, including overnight deposits	17,633	633	24,634	2,179
Dividends on equity securities	25,962	23,400	74,289	68,583
Income (loss) from equity method investments	(5,509)	882	(35,002)	13,825
Other	1,103	(335)	7,041	(947)
Total investment income	111,666	94,898	286,503	296,225
Investment expenses	(3,935)	(3,634)	(12,380)	(12,130)
Net investment income	107,731	91,264	274,123	284,095
Taxable municipal bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	17,488	16,320	52,613	49,236
Other taxable bonds [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Taxable bonds	$ 42,316	$ 39,705	$ 123,520	$ 119,718

Investments (Summary Of Net Inv

Investments (Summary Of Net Investment Gains (Losses) And The Change In Net Unrealized Gains On Investments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Gain (Loss) on Securities [Line Items]
Net realized investment gains (losses)	$ 2,032	$ (2,578)	$ 6,001	$ 5,233
Equity securities, Change in fair value of securities sold during the period	2,553	(400)	(29,015)	22,254
Equity securities, Change in fair value of securities held at the end of the period	(286,068)	(22,855)	(2,171,511)	1,148,304
Total change in fair value of equity securities	(283,515)	(23,255)	(2,200,526)	1,170,558
Net investment gains (losses)	(281,483)	(25,833)	(2,194,525)	1,175,791
Change in net unrealized gains on available-for-sale investments included in other comprehensive income	(538,347)	(131,671)	(1,600,063)	(337,914)
Reserve deficiency adjustment for life and annuity benefit reserves	0	6,428	56,560	56,690
Fixed Maturities [Member]
Gain (Loss) on Securities [Line Items]
Change in net unrealized gains on available-for-sale investments included in other comprehensive income	(530,161)	(133,244)	(1,645,060)	(391,528)
Short-term investments [Member]
Gain (Loss) on Securities [Line Items]
Change in net unrealized gains on available-for-sale investments included in other comprehensive income	$ (8,186)	$ (4,855)	$ (11,563)	$ (3,076)

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net investment gains (losses)	$ (281,483)	$ (25,833)	$ (2,194,525)	$ 1,175,791
Equity securities	6,950,357		6,950,357		$ 9,023,927
Purchases	0	18,900	0	18,900
Sales	(3,528)	0	(56,335)	(15,015)
Unconsolidated Markel CATCo Fund 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales			(41,300)
Fair value, recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, level 1 to level 2 transfers, amount			0	0
Fair value, level 2 to level 1 transfers, amount			0	0
Equity securities	6,950,357		6,950,357		$ 9,023,927
Fair value, nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on a nonrecurring basis	0	0	0	0
Liabilities measured at fair value on a nonrecurring basis	$ 0	$ 0	$ 0	$ 0

Fair Value Measurements (Balanc

Fair Value Measurements (Balances Of Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	$ 11,726,357	$ 12,587,305
Equity securities	6,950,357	9,023,927
Short-term investments, available-for-sale	2,424,844	1,799,988
Total Investments	21,101,558	23,411,220
U.S. Treasury securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,958,421	2,470,194
U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	725,182	775,587
Obligations of states, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	3,713,343	4,265,924
Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,172,889	1,519,354
Commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,932,665	1,990,433
Residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	557,333	726,050
Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,012	3,081
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	664,512	836,682
Fair value, recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	11,726,357	12,587,305
Equity securities	6,950,357	9,023,927
Short-term investments, available-for-sale	2,424,844	1,799,988
Total Investments	21,101,558	23,411,220
Fair value, recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Equity securities	6,949,436	8,967,455
Short-term investments, available-for-sale	2,277,172	1,619,496
Total Investments	9,226,608	10,586,951
Fair value, recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	11,726,357	12,587,305
Equity securities	0	0
Short-term investments, available-for-sale	147,672	180,492
Total Investments	11,874,029	12,767,797
Fair value, recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Equity securities	921	56,472
Short-term investments, available-for-sale	0	0
Total Investments	921	56,472
Fair value, recurring [Member] \| U.S. Treasury securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,958,421	2,470,194
Fair value, recurring [Member] \| U.S. Treasury securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| U.S. Treasury securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,958,421	2,470,194
Fair value, recurring [Member] \| U.S. Treasury securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| U.S. government-sponsored enterprises [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	725,182	775,587
Fair value, recurring [Member] \| U.S. government-sponsored enterprises [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| U.S. government-sponsored enterprises [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	725,182	775,587
Fair value, recurring [Member] \| U.S. government-sponsored enterprises [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Obligations of states, municipalities and political subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	3,713,343	4,265,924
Fair value, recurring [Member] \| Obligations of states, municipalities and political subdivisions [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Obligations of states, municipalities and political subdivisions [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	3,713,343	4,265,924
Fair value, recurring [Member] \| Obligations of states, municipalities and political subdivisions [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Foreign governments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,172,889	1,519,354
Fair value, recurring [Member] \| Foreign governments [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Foreign governments [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,172,889	1,519,354
Fair value, recurring [Member] \| Foreign governments [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,932,665	1,990,433
Fair value, recurring [Member] \| Commercial mortgage-backed securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Commercial mortgage-backed securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	1,932,665	1,990,433
Fair value, recurring [Member] \| Commercial mortgage-backed securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	557,333	726,050
Fair value, recurring [Member] \| Residential mortgage-backed securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Residential mortgage-backed securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	557,333	726,050
Fair value, recurring [Member] \| Residential mortgage-backed securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,012	3,081
Fair value, recurring [Member] \| Asset-backed securities [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Asset-backed securities [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	2,012	3,081
Fair value, recurring [Member] \| Asset-backed securities [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	664,512	836,682
Fair value, recurring [Member] \| Corporate bonds [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Corporate bonds [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	664,512	836,682
Fair value, recurring [Member] \| Corporate bonds [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale fixed maturity investments, estimated fair value	0	0
Fair value, recurring [Member] \| Insurance, banks and other financial institutions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,615,530	3,364,227
Fair value, recurring [Member] \| Insurance, banks and other financial institutions [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	2,614,609	3,307,755
Fair value, recurring [Member] \| Insurance, banks and other financial institutions [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0	0
Fair value, recurring [Member] \| Insurance, banks and other financial institutions [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	921	56,472
Fair value, recurring [Member] \| Industrial, consumer and all other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	4,334,827	5,659,700
Fair value, recurring [Member] \| Industrial, consumer and all other [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	4,334,827	5,659,700
Fair value, recurring [Member] \| Industrial, consumer and all other [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	0	0
Fair value, recurring [Member] \| Industrial, consumer and all other [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities	$ 0	$ 0

Fair Value Measurements (Summar

Fair Value Measurements (Summary Of Changes In Level 3 Investments Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities, beginning of period	$ 4,380	$ 41,066	$ 56,472	$ 58,493
Purchases	0	18,900	0	18,900
Sales	(3,528)	0	(56,335)	(15,015)
Net investment gains (losses) on Level 3 investments	69	(3,341)	784	(5,753)
Equity securities, end of period	$ 921	$ 56,625	921	$ 56,625
Unconsolidated Markel CATCo Fund 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales			$ (41,300)

Products, Services and Other _3

Products, Services and Other Revenues (Schedule Of Revenues From Contracts With Customers By Type) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Other revenues	$ 1,283,067	$ 991,423	$ 3,835,286	$ 2,932,202
Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	1,216,966	932,984	3,539,373	2,761,062
Products [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	575,277	394,444	1,809,276	1,294,407
Services [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	626,048	517,969	1,674,900	1,408,962
Investment management [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	15,641	20,571	55,197	57,693
Program services and other fronting [Member]
Disaggregation of Revenue [Line Items]
Other revenues	40,033	32,298	103,096	87,314
Disposition gain
Disaggregation of Revenue [Line Items]
Other revenues			107,293	0
Other [Member]
Disaggregation of Revenue [Line Items]
Other revenues	26,068	26,141	85,524	83,826
Markel Ventures [Member]
Disaggregation of Revenue [Line Items]
Other revenues	1,215,746	908,182	3,527,429	2,690,285
Markel Ventures [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	1,189,796	882,386	3,442,629	2,607,461
Markel Ventures [Member] \| Products [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	575,277	394,444	1,809,276	1,294,407
Markel Ventures [Member] \| Services [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	614,519	487,942	1,633,353	1,313,054
Markel Ventures [Member] \| Investment management [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	0	0	0	0
Markel Ventures [Member] \| Program services and other fronting [Member]
Disaggregation of Revenue [Line Items]
Other revenues	0	0	0	0
Markel Ventures [Member] \| Disposition gain
Disaggregation of Revenue [Line Items]
Other revenues			0	0
Markel Ventures [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Other revenues	25,950	25,796	84,800	82,824
Other [Member]
Disaggregation of Revenue [Line Items]
Other revenues	67,321	83,241	307,857	241,917
Other [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	27,170	50,598	96,744	153,601
Other [Member] \| Products [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	0	0	0	0
Other [Member] \| Services [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	11,529	30,027	41,547	95,908
Other [Member] \| Investment management [Member] \| Revenue from contracts with customers [Member]
Disaggregation of Revenue [Line Items]
Other revenues	15,641	20,571	55,197	57,693
Other [Member] \| Program services and other fronting [Member]
Disaggregation of Revenue [Line Items]
Other revenues	40,033	32,298	103,096	87,314
Other [Member] \| Disposition gain
Disaggregation of Revenue [Line Items]
Other revenues			107,293	0
Other [Member] \| Other [Member]
Disaggregation of Revenue [Line Items]
Other revenues	$ 118	$ 345	$ 724	$ 1,002

Products, Services and Other _4

Products, Services and Other Revenues (Schedule Of Receivables And Customer Deposits Related To Contracts With Customers) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Contracts with customers [Member]
Receivables [Line Items]
Trade and Other Receivables, Net	$ 649.6	$ 626.1

Unpaid Losses And Loss Adjust_3

Unpaid Losses And Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years	$ 1,266,996	$ 1,088,353	$ 3,420,906	$ 3,009,260
Favorable (adverse) development on prior years' loss reserves			204,411	366,171
2021 Catastrophes [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years				182,300
Russia-Ukraine conflict
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years			35,000
Ceded losses			70,000
Hurricane Ian
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years			70,000
Ceded losses			100,000
Insurance [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years	1,100,511	866,481	2,906,031	2,448,034
Insurance [Member] \| Workers Comp, Property, Marine and Energy and Programs Insurance Segment [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable (adverse) development on prior years' loss reserves			155,000
Insurance [Member] \| General Liab Property Workers Comp Prof Liability and Marine and Energy Insurance Segment [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable (adverse) development on prior years' loss reserves				324,800
Reinsurance [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years	166,485	221,872	514,875	561,226
Reinsurance [Member] \| Property and Credit and Surety Reinsurance Segment
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable (adverse) development on prior years' loss reserves			41,700
Reinsurance [Member] \| Property Reinsurance Segment
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Favorable (adverse) development on prior years' loss reserves				(30,600)
Program services and other fronting [Member]
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Ceded losses	$ (1,300,000)	$ (620,000)	(2,300,000)	$ (1,700,000)
Program services and other fronting [Member] \| Hurricane Ian
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Incurred losses and loss adjustment expenses, current accident years			850,000
Ceded losses			$ 850,000

Unpaid Losses And Loss Adjust_4

Unpaid Losses And Loss Adjustment Expenses (Reconciliation Of Consolidated Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Net reserves for losses and loss adjustment expenses, beginning of year			$ 11,302,577	$ 10,485,717
Effect of foreign currency rate changes on beginning of year balance	$ (275,364)	$ (52,117)	(275,364)	(52,117)
Adjusted net reserves for losses and loss adjustment expenses, beginning of year			11,027,213	10,433,600
Incurred losses and loss adjustment expenses, current accident years	1,266,996	1,088,353	3,420,906	3,009,260
Incurred losses and loss adjustment expenses, prior accident years			(204,411)	(366,171)
Total incurred losses and loss adjustment expenses			3,216,495	2,643,089
Payments, current accident year			350,684	365,640
Payments, prior accident years			1,880,471	1,678,164
Total payments			2,231,155	2,043,804
Effect of foreign currency rate changes on current year activity			(7,499)	(1,339)
Net reserves for losses and loss adjustment expenses of Markel CATCo Re			375,222	0
Net reserves for losses and loss adjustment expenses of insurance companies sold			0	(2,762)
Net reserves for losses and loss adjustment expenses, end of period	12,380,276	11,028,784	12,380,276	11,028,784
Reinsurance recoverable on unpaid losses	7,814,098	6,582,415	7,814,098	6,582,415
Gross reserves for losses and loss adjustment expenses, end of period	$ 20,194,374	$ 17,611,199	$ 20,194,374	$ 17,611,199

Reinsurance (Narrative) (Detail

Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Reinsurance (Narrative) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Percentage of ceded earned premiums to gross earned premiums	40%	40%	38%	38%
Percentage of assumed earned premiums to net earned premiums	32%	29%	28%	26%
Underwriting [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross losses and loss adjustment expenses	$ 1,423,526	$ 1,238,974	$ 3,760,566	$ 3,306,035
Ceded losses	238,220	290,834	544,109	660,479
Program services and other fronting [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross losses and loss adjustment expenses	1,300,000	620,100	2,300,000	1,700,000
Ceded losses	$ (1,300,000)	$ (620,000)	$ (2,300,000)	$ (1,700,000)

Reinsurance (Effect Of Reinsura

Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Premiums Written And Earned) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Effects of Reinsurance [Line Items]
Direct premiums written	$ 2,797,453	$ 2,487,898	$ 8,091,131	$ 7,138,822
Direct premiums earned	2,629,128	2,234,451	7,406,497	6,343,169
Assumed premiums written	677,318	480,704	2,061,976	1,518,645
Assumed premiums earned	627,000	466,673	1,526,919	1,223,170
Ceded premiums written	(1,465,604)	(1,283,792)	(3,879,411)	(3,340,136)
Ceded premiums earned	(1,299,298)	(1,070,624)	(3,383,712)	(2,870,107)
Net premiums written	2,009,167	1,684,810	6,273,696	5,317,331
Net premiums earned	1,956,830	1,630,500	5,549,704	4,696,232
Underwriting [Member]
Effects of Reinsurance [Line Items]
Direct premiums written	2,133,822	1,776,716	6,065,936	5,082,494
Direct premiums earned	1,899,816	1,599,931	5,370,481	4,542,680
Assumed premiums written	349,650	303,551	1,466,036	1,269,578
Assumed premiums earned	408,561	363,665	1,194,504	1,081,494
Ceded premiums written	(473,885)	(393,195)	(1,255,226)	(1,031,546)
Ceded premiums earned	(351,118)	(331,397)	(1,012,485)	(925,176)
Net premiums written	2,009,587	1,687,072	6,276,746	5,320,526
Net premiums earned	1,957,259	1,632,199	5,552,500	4,698,998
Program services and other fronting [Member]
Effects of Reinsurance [Line Items]
Direct premiums written	663,631	711,182	2,025,195	2,056,328
Direct premiums earned	729,312	634,520	2,036,016	1,800,489
Assumed premiums written	327,668	177,153	595,940	249,067
Assumed premiums earned	218,439	103,008	332,415	141,676
Ceded premiums written	(991,719)	(890,597)	(2,624,185)	(2,308,590)
Ceded premiums earned	(948,180)	(739,227)	(2,371,227)	(1,944,931)
Net premiums written	(420)	(2,262)	(3,050)	(3,195)
Net premiums earned	$ (429)	$ (1,699)	$ (2,796)	$ (2,766)

Reinsurance Reinsurance (Effect

Reinsurance Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Losses) (Details) - Underwriting [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Effects of Reinsurance [Line Items]
Gross losses and loss adjustment expenses	$ 1,423,526	$ 1,238,974	$ 3,760,566	$ 3,306,035
Ceded losses and loss adjustment expenses	(238,220)	(290,834)	(544,109)	(660,479)
Net losses and loss adjustment expenses	$ 1,185,306	$ 948,140	$ 3,216,457	$ 2,645,556

Life and Annuity Benefits Lif_2

Life and Annuity Benefits Life and Annuity Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Liability for Future Policy Benefit, before Reinsurance [Abstract]
Cumulative adjustment to life and annuity benefits	$ 0		$ 0		$ 56.6
Adjustment to life and annuity benefits	$ 0	$ (6.4)	$ (56.6)	$ (56.7)

Debt (Details)

Debt (Details) - USD ($) $ in Millions	9 Months Ended
Debt (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Line of Credit Facility [Line Items]
Line of Credit Facility, Initiation Date	Apr. 10, 2019
Line of Credit Facility, Expiration Date	Apr. 10, 2024
Senior Notes \| Four point nine zero percent unsecured senior notes due July 1, 2022
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.90%
Debt Instrument, Face Amount	$ 350
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	300
Line of Credit Facility, Increase (Decrease), Net	200
Long-term Line of Credit	0	$ 0
Revolving Credit Facility \| Markel Ventures [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	550
Long-term Line of Credit	253.2	$ 94.3
Revolving Credit Facility \| Secured Letters of Credit
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200

Variable Interest Entities (Nar

Variable Interest Entities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Sep. 30, 2022	Mar. 31, 2022
Variable Interest Entity [Line Items]
Cash funding used to purchase Markel CATCo Funds' interests in Markel CATCo Re			$ 45.1
Returned capital from Markel CATCo Re	$ 24.9
Investment in Markel CATCo Re		$ 20.1
Percentage of Markel CATCo Re net equity held by the Company		25%
Tail risk cover in Markel CATCo transaction		$ 142.7

Variable Interest Entities (Mar

Variable Interest Entities (Markel CATCo Re Balance Sheet) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 3,540,690	$ 3,978,490
Restricted cash and cash equivalents	1,255,178	902,457
Total Assets	48,421,355	48,477,096
Unpaid losses and loss adjustment expenses	20,194,374	18,178,894	$ 17,611,199
Other liabilities	3,290,291	3,832,084
Total Liabilities	35,549,593	33,275,508
Shareholders' equity	12,293,923	14,717,350
Noncontrolling interests	64,796	22,860
Total Equity	12,358,719	14,740,210
Total Liabilities and Equity	48,421,355	$ 48,477,096
Markel CATCo Re
Variable Interest Entity [Line Items]
Cash and cash equivalents	83,103
Restricted cash and cash equivalents	355,905
Other assets and receivables due from cedents	44,102
Total Assets	483,110
Unpaid losses and loss adjustment expenses	375,222
Other liabilities	27,448
Total Liabilities	402,670
Shareholders' equity	21,139
Noncontrolling interests	59,301
Total Equity	80,440
Total Liabilities and Equity	$ 483,110

Related Party Transactions Re_2

Related Party Transactions Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Services and other revenues	$ 696,536	$ 585,712	$ 1,990,175	$ 1,605,058
Gross premium volume	3,474,771	2,968,602	10,153,107	8,657,467
Reinsurance recoverables	8,258,499		8,258,499		$ 7,293,555
Ceded premiums written	1,465,604	1,283,792	3,879,411	3,340,136
Syndicate 2357 and certain other Nephila Reinsurers [Member]
Related Party Transaction [Line Items]
Gross premium volume	398,900	283,700	889,600	587,700
Reinsurance recoverables	1,300,000		1,300,000		$ 751,000
Ceded premiums written	398,900	283,700	889,600	587,700
Hagerty, Inc. [Member]
Related Party Transaction [Line Items]
Gross premium volume	197,000	170,100	540,400	467,600
Ceded premiums written	130,400	96,600	357,700	265,400
Insurance-linked Securities Operations [Member] \| Unconsolidated entities managed by Nephila [Member]
Related Party Transaction [Line Items]
Services and other revenues	$ 17,100	$ 32,800	$ 57,000	$ 103,500

Shareholders' Equity (Schedule

Shareholders' Equity (Schedule of Common Stock Outstanding Roll Forward) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock, shares authorized	50,000,000		50,000,000
Common stock, no par value	$ 0		$ 0
Common Stock [Member]
Class of Stock [Line Items]
Shares, Issued, Beginning Balance	13,538,000	13,734,000	13,632,000	13,783,000
Repurchase of common shares	67,000	50,000	163,000	102,000
Shares, Issued, Ending Balance	13,471,000	13,685,000	13,471,000	13,685,000
Shares, outstanding	13,471,000	13,685,000	13,471,000	13,685,000	13,538,000	13,632,000	13,734,000	13,783,000
Common Stock [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Issuance of common shares	0	1,000	2,000	4,000

Shareholders' Equity (Schedul_2

Shareholders' Equity (Schedule Of Net Income (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Line Items]
Net income (loss) to common shareholders		$ 65,369	$ 188,070	$ (921,833)	$ 1,535,874
Adjustment of redeemable noncontrolling interests		(17,730)	19,930	(62,168)	41,553
Adjusted net income (loss) to common shareholders		$ 47,639	$ 208,000	$ (984,001)	$ 1,577,427
Basic common shares outstanding		13,564	13,758	13,609	13,790
Diluted common shares outstanding		13,595	13,785	13,609	13,813
Basic net income (loss) per common share		$ 3.51	$ 15.12	$ (72.31)	$ 114.39
Earnings Per Share, Diluted	[1]	$ 3.50	$ 15.09	$ (72.31)	$ 114.20
Restricted Stock Units (RSUs) [Member]
Earnings Per Share [Line Items]
Dilutive potential common shares from restricted stock units and restricted stock	[1]	31	27	0	23
Potential incremental common shares attributable to share-based payment arrangements				28

[1]The impact of 28 thousand shares from restricted stock units and restricted stock was excluded from the computation of diluted net loss per common share for the nine months ended September 30, 2022 because the effect would have been anti-dilutive.

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Sep. 30, 2022	Dec. 31, 2021
Earnings Per Share [Line Items]
Preferred stock, shares authorized			10,000,000
Preferred stock, no par value			$ 0
Preferred stock dividends	$ (18)	$ (18)
Preferred stock, dividends per share, declared	$ 30	$ 30
Preferred stock, dividends, per share, cash paid	$ 30	$ 30
Series A preferred stock [Member]
Earnings Per Share [Line Items]
Preferred stock, shares issued			600,000	600,000
Preferred stock, shares outstanding			600,000	600,000

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Mar. 31, 2022
Loss Contingencies [Line Items]
Cash funding used to purchase Markel CATCo Funds' interests in Markel CATCo Re		$ 45.1
Tail risk cover in Markel CATCo transaction	$ 142.7
Additional payments made, net of insurance in proceeds, to Markel CATCo Funds investors	$ 101.9

Accounting Changes and Error _2

Accounting Changes and Error Corrections (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Jan. 01, 2021
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred policy acquisition costs	$ 946,064	$ 794,145
Retained earnings	$ 9,255,658	$ 10,446,763
Revision of Prior Period, Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Deferred policy acquisition costs			$ 28,200
Deferred tax liabilities			5,900
Retained earnings			$ 22,300

Uncategorized Items - mkl-20220

Label	Element	Value
Total Equity [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	$ 12,836,983,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	22,302,000
Common Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	3,428,340,000
Preferred Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	591,891,000
Redeemable Noncontrolling Interests, Temporary Equity [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	245,642,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	0
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	14,892,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	0
Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	12,822,091,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	22,302,000
AOCI Attributable to Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	584,376,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	0
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance	mkl_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAdjustedBalance	8,217,484,000
Cumulative effect of change in accounting principle	mkl_CumulativeEffectOfChangeInAccountingPrinciple	$ 22,302,000