Equity Commonwealth (EQC) 10-K13 Feb 242023 FY Annual reportFinancial data

Company Profile

Cover Page

Cover Page - USD ($) $ in Billions	12 Months Ended
Cover Page - USD ($) $ in Billions	Dec. 31, 2023	Feb. 05, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-9317
Entity Registrant Name	EQUITY COMMONWEALTH
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	04-6558834
Entity Address, Address Line One	Two North Riverside Plaza, Suite 2000
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60606
City Area Code	(312)
Local Phone Number	646-2800
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 2.2
Entity Common Stock, Shares Outstanding (in shares)		106,991,322
Documents Incorporated by Reference	Certain Information required by Items 10, 11, 12, 13 and 14 of Part III of this Annual Report on Form 10-K is incorporated herein by reference to the definitive Proxy Statement for the 2024 Annual Meeting of Shareholders, or the definitive Proxy Statement, which Equity Commonwealth intends to file no later than 120 days after the end of its fiscal year ended December 31, 2023.
Entity Central Index Key	0000803649
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Common Shares of Beneficial Interest
Document Information [Line Items]
Title of 12(b) Security	Common Shares of Beneficial Interest
Trading Symbol	EQC
Security Exchange Name	NYSE
6.50% Series D Cumulative Convertible Preferred Shares of Beneficial Interest
Document Information [Line Items]
Title of 12(b) Security	6.50% Series D Cumulative Convertible Preferred Shares of Beneficial Interest
Trading Symbol	EQCpD
Security Exchange Name	NYSE

Audit Information

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Chicago, Illinois

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Real estate properties:
Land	$ 44,060	$ 44,060
Buildings and improvements	367,827	364,063
Total real estate properties, at cost, gross	411,887	408,123
Accumulated depreciation	(180,535)	(169,530)
Total real estate properties, at cost, net	231,352	238,593
Cash and cash equivalents	2,160,535	2,582,222
Rents receivable	15,737	16,009
Other assets, net	17,417	18,061
Total assets	2,425,041	2,854,885
LIABILITIES AND EQUITY
Accounts payable, accrued expenses and other	27,298	25,935
Rent collected in advance	1,990	2,355
Distributions payable	5,640	2,863
Total liabilities	34,928	31,153
Commitments and contingencies
Shareholders’ equity:
Series D preferred shares; 6.50% cumulative convertible; 4,915,196 shares issued and outstanding, aggregate liquidation preference of $122,880	119,263	119,263
Common shares of beneficial interest, $0.01 par value: 350,000,000 shares authorized; 106,847,438 and 109,428,252 shares issued and outstanding, respectively	1,068	1,094
Additional paid in capital	3,935,873	3,979,566
Cumulative net income	3,926,979	3,835,815
Cumulative common distributions	(4,864,440)	(4,393,522)
Cumulative preferred distributions	(733,676)	(725,688)
Total shareholders’ equity	2,385,067	2,816,528
Noncontrolling interest	5,046	7,204
Total equity	2,390,113	2,823,732
Total liabilities and equity	$ 2,425,041	$ 2,854,885

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares of beneficial interest, shares authorized (in shares)	50,000,000	50,000,000
Preferred shares, dividend yield	6.50%	6.50%
Preferred shares of beneficial interest, shares issued (in shares)	4,915,196	4,915,196
Preferred shares, of beneficial interest, shares outstanding (in shares)	4,915,196	4,915,196
Preferred shares, aggregate liquidation preference	$ 122,880	$ 122,880
Common shares of beneficial interest, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares of beneficial interest, shares authorized (in shares)	350,000,000	350,000,000
Common shares of beneficial interest, shares issued (in shares)	106,847,438	109,428,252
Common shares of beneficial interest, shares outstanding (in shares)	106,847,438	109,428,252

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Rental revenue	$ 55,336	$ 58,763	$ 54,927
Other revenue	5,188	4,377	3,075
Total revenues	60,524	63,140	58,002
Expenses:
Operating expenses	27,462	24,184	25,893
Depreciation and amortization	17,444	17,810	17,774
General and administrative	36,974	30,378	37,444
Total expenses	81,880	72,372	81,111
Interest and other income, net	114,667	46,945	6,800
Gain on sale of properties, net	0	97	0
Income (loss) before income taxes	93,311	37,810	(16,309)
Income tax expense	(1,866)	(453)	(120)
Net income (loss)	91,445	37,357	(16,429)
Net (income) loss attributable to noncontrolling interest	(281)	(94)	33
Net income (loss) attributable to Equity Commonwealth	91,164	37,263	(16,396)
Preferred distributions	(7,988)	(7,988)	(7,988)
Net income (loss) attributable to Equity Commonwealth common shareholders	$ 83,176	$ 29,275	$ (24,384)
Weighted average common shares outstanding — basic (in shares)	108,841	111,674	121,411
Weighted average common shares outstanding — diluted (in shares)	110,185	112,825	121,411
Earnings per common share attributable to Equity Commonwealth common shareholders:
Basic (in dollars per share)	$ 0.76	$ 0.26	$ (0.20)
Diluted (in dollars per share)	$ 0.75	$ 0.26	$ (0.20)

CONSLIDATED STATEMENTS OF EQUIT

CONSLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Series D Preferred Shares	Common Shares	Additional Paid in Capital	Cumulative Net Income	Cumulative Common Distributions	Cumulative Preferred Distributions	Noncontrolling Interest
Beginning balance (in shares) at Dec. 31, 2020		4,915,196	121,522,555
Beginning balance at Dec. 31, 2020	$ 3,243,164	$ 119,263	$ 1,215	$ 4,294,632	$ 3,814,948	$ (4,283,668)	$ (709,712)	$ 6,486
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(16,429)				(16,396)			(33)
Repurchase of shares (in shares)			(6,735,810)
Repurchase of shares	(174,407)		$ (67)	(174,340)
Surrender of shares for tax withholding (in shares)			(245,560)
Surrender of shares for tax withholding	(7,081)		$ (2)	(7,079)
Share-based compensation (in shares)			664,633
Share-based compensation	15,442		$ 6	14,555				881
Distributions	(5,419)					2,473	(7,988)	96
Adjustment for noncontrolling interest				888				(888)
Ending balance (in shares) at Dec. 31, 2021		4,915,196	115,205,818
Ending balance at Dec. 31, 2021	3,055,270	$ 119,263	$ 1,152	4,128,656	3,798,552	(4,281,195)	(717,700)	6,542
Increase (Decrease) in Stockholders' Equity
Net income (loss)	37,357				37,263			94
Repurchase of shares (in shares)			(6,110,646)
Repurchase of shares	(155,710)		$ (61)	(155,649)
Surrender of shares for tax withholding (in shares)			(160,506)
Surrender of shares for tax withholding	(4,160)		$ (2)	(4,158)
Share-based compensation (in shares)			493,586
Share-based compensation	11,939		$ 5	10,455				1,479
Distributions	(120,965)					(112,327)	(7,988)	(650)
Adjustment for noncontrolling interest				262				(262)
Contributions	1							1
Ending balance (in shares) at Dec. 31, 2022		4,915,196	109,428,252
Ending balance at Dec. 31, 2022	2,823,732	$ 119,263	$ 1,094	3,979,566	3,835,815	(4,393,522)	(725,688)	7,204
Increase (Decrease) in Stockholders' Equity
Net income (loss)	91,445				91,164			281
Repurchase of shares (in shares)			(3,018,411)
Repurchase of shares	(56,803)		$ (30)	(56,773)
Surrender of shares for tax withholding (in shares)			(134,193)
Surrender of shares for tax withholding	(3,395)		$ (1)	(3,394)
Share-based compensation (in shares)			436,398
Share-based compensation	15,977		$ 4	13,255				2,718
Distributions	(480,843)					(470,918)	(7,988)	(1,937)
Adjustment for noncontrolling interest				648				(648)
OP unit redemption (in shares)			135,392
OP Unit redemption	0		$ 1	2,571				(2,572)
Ending balance (in shares) at Dec. 31, 2023		4,915,196	106,847,438
Ending balance at Dec. 31, 2023	$ 2,390,113	$ 119,263	$ 1,068	$ 3,935,873	$ 3,926,979	$ (4,864,440)	$ (733,676)	$ 5,046

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 91,445	$ 37,357	$ (16,429)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	14,914	15,230	15,235
Straight-line rental income	(93)	238	(1,407)
Other amortization	2,530	2,580	2,539
Share-based compensation	15,977	11,939	15,442
Net gain on sale of properties	0	(97)	0
Change in assets and liabilities:
Rents receivable and other assets	(1,739)	(6,089)	81
Accounts payable, accrued expenses and other	(401)	5,513	(410)
Rent collected in advance	(365)	(1,631)	1,058
Net cash provided by operating activities	122,268	65,040	16,109
CASH FLOWS FROM INVESTING ACTIVITIES:
Real estate improvements	(5,691)	(3,577)	(6,803)
Proceeds from sale of properties, net	0	97	0
Net cash used in investing activities	(5,691)	(3,480)	(6,803)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchase and retirement of common shares	(60,198)	(159,870)	(181,488)
Contributions from holders of noncontrolling interest	0	1	0
Distributions to common shareholders	(468,232)	(112,199)	(6,024)
Distributions to preferred shareholders	(7,988)	(7,988)	(7,988)
Distributions to holders of noncontrolling interest	(1,846)	(280)	(33)
Net cash used in financing activities	(538,264)	(280,336)	(195,533)
Decrease in cash and cash equivalents	(421,687)	(218,776)	(186,227)
Cash and cash equivalents at beginning of year	2,582,222	2,800,998	2,987,225
Cash and cash equivalents at end of year	2,160,535	2,582,222	2,800,998
SUPPLEMENTAL CASH FLOW INFORMATION:
Taxes paid, net	1,946	456	246
NON-CASH INVESTING ACTIVITIES:
Accrued capital expenditures	2,881	934	509
NON-CASH FINANCING ACTIVITIES:
Distributions payable	5,640	2,863	2,365
OP Unit redemption	$ 2,572	$ 0	$ 0

Organization

Organization	12 Months Ended
Organization	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Equity Commonwealth, or the Company, is a real estate investment trust, or REIT, formed in 1986 under the laws of the State of Maryland. Our business is primarily the ownership and operation of office properties in the United States. The Company operates in an umbrella partnership real estate investment trust, or UPREIT, and conducts substantially all of its activities through EQC Operating Trust, a Maryland real estate investment trust, or the Operating Trust. The Company beneficially owned, 99.79% of the outstanding shares of beneficial interest, designated as units, in the Operating Trust, or OP Units, as of December 31, 2023, and the Company is the sole trustee of the Operating Trust. As the sole trustee, the Company generally has the power under the declaration of trust of the Operating Trust to manage and conduct the business of the Operating Trust, subject to certain limited approval and voting rights of other holders of OP Units. As of December 31, 2023, our portfolio consisted of four properties (eight buildings), with a combined 1.5 million square feet, and we had $2.2 billion of cash and cash equivalents. All numbers of properties, numbers of buildings and square feet are unaudited.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation. The consolidated financial statements include our investments in 100% owned subsidiaries and majority owned subsidiaries that are controlled by us. References to we, us, our and the Company, refer to Equity Commonwealth and its consolidated subsidiaries as of December 31, 2023, unless the context indicates otherwise. All intercompany transactions and balances have been eliminated. Dollar amounts presented may be approximate. Share amounts are presented in whole numbers, except where noted. Real Estate Properties. We record real estate properties at cost. We depreciate real estate investments on a straight-line basis over estimated useful lives of up to 40 years for buildings and improvements, and up to 12 years for personal property. Each time we enter into a new lease, or materially modify an existing lease, we evaluate its classification as either a finance or operating lease. The classification of a lease as finance or operating affects the carrying value of a property, as well as our recognition of rental payments as revenue. These evaluations require us to make estimates of, among other things, the remaining useful life and fair market value of a leased property, appropriate discount rates and future cash flows. We allocate the consideration paid for our properties among land, buildings and improvements and, for properties that qualify as acquired businesses under the Business Combinations Topic of the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, to identified intangible assets and liabilities, consisting of the value of above market and below market leases, the value of acquired in place leases and the value of tenant relationships. Purchase price allocations and the determination of useful lives are based on our estimates and, under some circumstances, studies from independent real estate appraisal firms to provide market information and evaluations that are relevant to our purchase price allocations and determinations of useful lives; however, we are ultimately responsible for the purchase price allocations and determination of useful lives. We allocate the consideration to land, buildings and improvements based on a determination of the fair values of these assets assuming the property is vacant. We determine the fair value of a property using methods that we believe are similar to those used by independent appraisers. Purchase price allocations for above market and below market leases are based on the estimated present value (using an interest rate which reflects our assessment of the risks associated with the leases acquired) of the difference between (1) the contractual amounts to be paid pursuant to the acquired in place leases and (2) our estimate of fair market lease rates for the corresponding leases, measured over a period equal to the remaining non-cancelable terms of the respective leases. Purchase price allocations to acquired in place leases and tenant relationships are determined as the excess of (1) the purchase price paid for a property after adjusting existing in place leases to estimated market rental rates over (2) the estimated fair value of the property as if vacant. We aggregate this value between acquired in place lease values and tenant relationships based on our evaluation of the specific characteristics of each tenant's lease; however, the value of tenant relationships has not been separated from acquired in place lease value for our properties because we believe such value and related amortization expense is immaterial for acquisitions reflected in our historical financial statements. We consider certain factors in performing these analyses including estimates of carrying costs during the expected lease up periods, including real estate taxes, insurance and other operating income and expenses and costs to execute similar leases in current market conditions, such as leasing commissions, legal and other related costs. If we believe the value of tenant relationships is material in the future, those amounts will be separately allocated and amortized over the estimated lives of the relationships. We recognize the excess, if any, of the consideration paid over amounts allocated to land, buildings and improvements and identified intangible assets and liabilities as goodwill and we recognize gains if amounts allocated exceed the consideration paid. We amortize capitalized above market lease values as a reduction to rental income over the remaining terms of the respective leases. We amortize capitalized below market lease values as an increase to rental income over the remaining terms of the respective leases. We amortize the value of acquired in place leases exclusive of the value of above market and below market acquired in place leases to expense over the remaining terms of the respective leases. If a lease is terminated prior to its stated expiration, the unamortized lease intangibles relating to that lease is written off. We review our properties for impairment quarterly, or whenever events or changes in circumstances indicate that their carrying amounts may not be recoverable. Impairment indicators may include our decision to dispose of an asset before the end of its estimated useful life, declining tenant occupancy, lack of progress releasing vacant space, tenant bankruptcies, low long-term prospects for improvement in property performance, weak or declining tenant profitability, and cash flow or liquidity. When indicators of potential impairment are present that suggest that the carrying amounts of real estate assets may not be recoverable, we assess the recoverability of these assets by determining whether the respective carrying values will be recovered through the estimated undiscounted future operating cash flows expected from the use of the assets and their eventual disposition. The determination of undiscounted cash flow includes consideration of many factors including income to be earned from the investment over our anticipated hold period, holding costs (exclusive of interest), estimated selling prices, and prevailing economic and market conditions. In the event that such expected undiscounted future cash flows do not exceed the carrying values, we estimate the fair value of the assets and record an impairment charge equal to the amount by which the carrying value exceeds the estimated fair value. Estimated fair values are calculated based on the following information, (i) recent third party estimates of market value, (ii) market prices for comparable properties, or (iii) the present value of future cash flows. During the years ended December 31, 2023, 2022 and 2021 we did not record any loss on asset impairment. When we classify properties as held for sale, we discontinue the recording of depreciation expense and estimate their fair value less costs to sell. If we determine that the carrying value for these properties exceed their estimated fair value less costs to sell, we record a loss on asset impairment. As of December 31, 2023 and 2022, we did not have any properties classified as held for sale. Certain of our real estate assets contain hazardous substances, including asbestos. We believe any asbestos in our buildings is contained in accordance with current regulations. If we remove the asbestos or renovate or demolish these properties, certain environmental regulations govern the manner in which the asbestos must be handled and removed. We do not believe that there are other environmental conditions or issues at any of our properties that have had or will have a material adverse effect on us. However, no assurances can be given that conditions or issues are not present at our properties or that costs we may be required to incur in the future to remediate contamination or comply with environmental, health and safety laws will not have a material adverse effect on our business or financial condition. As of December 31, 2023 and 2022, we did not have any accrued environmental remediation costs. Cash and Cash Equivalents. Our cash and cash equivalents consist of cash maintained in time deposits, depository accounts and money market accounts. We regularly monitor the credit ratings of the financial institutions holding our deposits to minimize our exposure to credit risk. Throughout the year, we have cash balances in excess of federally insured limits deposited with various financial institutions. We do not believe we are exposed to any significant credit risk on cash and cash equivalents. Other Assets, Net. Other assets consist principally of deferred leasing costs, capitalized lease incentives and prepaid property operating expenses. Deferred leasing costs are amortized on a straight-line basis over the terms of the respective leases. Capitalized lease incentives are amortized on a straight-line basis against rental income over the terms of the respective leases. Revenue Recognition. Rental revenue from operating leases, which includes rent concessions (including free rent and other lease incentives) and scheduled increases in rental rates during the lease term, represents the lease component and is recognized on a straight-line basis over the life of the lease agreements. We defer the recognition of contingent rental income, such as percentage rents, until the specific targets that trigger the contingent rental income are achieved. Rental revenue also includes non-lease components such as property level operating expenses reimbursed by our tenants and other incidental revenues, which are recorded as expenses are incurred. We concluded that the timing and pattern of transfer for non-lease components and the associated lease component are the same. We determined that the predominant component was the lease component and we have elected to account for and present the lease component and non-lease component of our leases as a single component in Rental revenue in our consolidated statements of operations in accordance with FASB Topic 842. Lessee Lease Classification . We classify leases as either finance or operating in accordance with FASB Topic 842, Leases. This classification determines whether the related expense is recognized based on an effective interest method for finance leases or on a straight-line basis over its life for operating leases. Additionally, lessees are required to record a right-of-use asset and lease liability for all leases with a term greater than 12 months. We have made an accounting policy election as permitted under ASC 842 to forgo recognition of a right-of-use asset and lease liability for short-term leases of less than 12 months. Earnings Per Common Share. Earnings per common share, or EPS, is computed using the weighted average number of common shares outstanding during the period. Diluted EPS reflects the potential dilution that could occur if our series D convertible preferred shares, our restricted share units, or RSUs, or beneficial interests in the Operating Trust, or LTIP Units, were converted into our common shares, which could result in a lower EPS amount. The effect of our series D convertible preferred shares on net income attributable to common shareholders is anti-dilutive for the years ended December 31, 2023, 2022 and 2021. Reclassifications. Reclassifications have been made to the prior years' financial statements and notes to conform to the current year's presentation. Legal Matters. We are or may become a party to various legal proceedings. We are not currently involved in any litigation nor, to our knowledge, is any litigation threatened against us where the outcome would, in our judgment based on information currently available to us, have a material adverse effect on the Company. Income Taxes. We are a REIT under the Internal Revenue Code of 1986, as amended, and are generally not subject to federal and state income taxes provided we distribute our taxable income to our shareholders and meet other requirements for qualifying as a REIT. We are also subject to certain state and local taxes without regard to our REIT status. The Income Taxes Topic of the FASB ASC prescribes how we should recognize, measure and present in our financial statements uncertain tax positions that have been taken or are expected to be taken in a tax return. Deferred tax assets are recognized to the extent that it is “more likely than not” that a particular tax position will be sustained upon examination or audit. To the extent the “more likely than not” standard has been satisfied, the benefit associated with a tax position is measured as the largest amount that has a greater than 50% likelihood of being realized upon settlement. We classify interest and penalties related to uncertain tax positions, if any, in our financial statements as a component of general and administrative expense. Use of Estimates. Preparation of these financial statements in conformity with U.S. generally accepted accounting principles, or GAAP, requires us to make estimates and assumptions that may affect the amounts reported in these financial statements and related notes. The actual results could differ from these estimates. New Accounting Pronouncements. In November 2023, the FASB issued Accounting Standards Update, or ASU, 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which improves the disclosures about a public entity's reportable segments and addresses requests from investors for additional, more detailed information about a reportable segment's expenses. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We do not expect the adoption of ASU 2023-07 to have a material impact on our consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the transparency and decision usefulness of income tax disclosures. This update is effective for annual periods beginning after December 15, 2024. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. We do not expect the adoption of ASU 2023-09 to have a material impact on our consolidated financial statements.

Real Estate Properties

Real Estate Properties	12 Months Ended
Real Estate Properties	Dec. 31, 2023
Real Estate [Abstract]
Real Estate Properties	Real Estate Properties Acquisitions and Expenditures We did not make any acquisitions during the years ended December 31, 2023, 2022 or 2021. During the years ended December 31, 2023, 2022, and 2021, we made improvements, excluding tenant-funded improvements, to our properties totaling $7.6 million, $4.0 million and $6.3 million, respectively. We committed $9.6 million for expenditures related to 0.2 million square feet of leases executed during 2023. Committed but unspent tenant related obligations are leasing commissions and tenant improvements. Based on existing leases as of December 31, 2023, committed but unspent tenant related obligations were $13.1 million. Property Dispositions: We did not sell any properties during the years ended December 31, 2023, 2022 or 2021. Lease Payments Our real estate properties are generally leased on gross lease and modified gross lease bases pursuant to non-cancelable, fixed term operating leases expiring between 2024 and 2035. These gross leases and modified gross leases require us to pay all or some property operating expenses and to provide all or some property management services. A portion of these property operating expenses are reimbursed by the tenants. The future minimum lease payments, excluding tenant reimbursement revenue, scheduled to be received by us during the current terms of our leases as of December 31, 2023 are as follows (in thousands): 2024 $ 34,544 2025 32,955 2026 30,033 2027 25,066 2028 20,031 Thereafter 46,434 $ 189,063 Rental revenue consists of the following (in thousands): December 31, 2023 2022 2021 Lease payments $ 36,008 $ 37,846 $ 36,461 Variable lease payments 19,328 20,917 18,466 Rental revenue $ 55,336 $ 58,763 $ 54,927

Other Assets

Other Assets	12 Months Ended
Other Assets	Dec. 31, 2023
Other Assets [Abstract]
Other Assets	Other Assets Deferred Leasing Costs and Capitalized Lease Incentives The following table summarizes our deferred leasing costs and capitalized lease incentives as of December 31, 2023, and 2022 (in thousands): December 31, 2023 2022 Deferred leasing costs $ 21,356 $ 22,034 Accumulated amortization (10,540) (11,320) Deferred leasing costs, net $ 10,816 $ 10,714 Capitalized lease incentives $ 3,471 $ 3,352 Accumulated amortization (2,278) (1,873) Capitalized lease incentives, net $ 1,193 $ 1,479 Future amortization of deferred leasing costs, included in amortization expense, and capitalized lease incentives, included in rental revenues, to be recognized by us during the current terms of our leases as of December 31, 2023 are approximately (in thousands): Deferred Leasing Costs Capitalized Lease Incentives 2024 $ 2,548 $ 283 2025 1,833 222 2026 1,811 216 2027 1,411 170 2028 1,098 107 Thereafter 2,115 195 $ 10,816 $ 1,193

Shareholders' Equity

Shareholders' Equity	12 Months Ended
Shareholders' Equity	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity Common Share Issuances: See Note 8 for information regarding equity issuances related to share-based compensation. Common Share Repurchases: On August 24, 2015, our Board of Trustees approved a common share repurchase program. On March 1, 2021, our Board of Trustees authorized the repurchase of up to $150.0 million of our outstanding common shares through June 30, 2022, and on December 14, 2021, our Board of Trustees authorized the repurchase of up to an additional $150.0 million of our outstanding common shares through December 31, 2022. On March 15, 2022, our Board of Trustees authorized the repurchase of up to $150.0 million of our outstanding common shares through June 30, 2023. On June 13, 2023, our Board of Trustees authorized the repurchase of up to $150.0 million of our outstanding common shares from July 1, 2023 through June 30, 2024. During the year ended December 31, 2023, we repurchased and retired 3,018,411 of our common shares at a weighted average price of $18.78 per share, for a total investment of $56.7 million. During the year ended December 31, 2022, we repurchased and retired 6,110,646 of our common shares at a weighted average dividend adjusted price of $24.64 per share, for a total investment of $155.5 million. During the year ended December 31, 2021, we repurchased and retired 6,735,810 of our common shares at a weighted average price of $25.85 per share, for a total investment of $174.1 million. The share repurchases in 2022 discussed in this paragraph were completed prior to the special, one-time cash distributions in that year, which was in the amount of $1.00 per common share/unit paid on October 18, 2022. As of December 31, 2023, we had $93.3 million of remaining availability under our share repurchase program, which expires on June 30, 2024. During the years ended December 31, 2023, 2022 and 2021, certain of our employees and former employees surrendered 134,193, 160,506 and 245,560 common shares owned by them, respectively, to satisfy their statutory tax withholding obligations in connection with the vesting of such common shares pursuant to our equity compensation plans. Common Share and Unit Distributions: On February 13, 2023, our Board of Trustees declared a special, one-time cash distribution of $4.25 per common share/unit to shareholders/unitholders of record on February 23, 2023. On March 9, 2023, we paid this distribution to such shareholders/unitholders in the aggregate amount of $468.3 million. On September 8, 2022, our Board of Trustees declared a special, one-time cash distribution of $1.00 per common share/unit to shareholders/unitholders of record on September 29, 2022. On October 18, 2022, we paid this distribution to such shareholders/unitholders in the aggregate amount of $111.0 million. In February 2023, 2022 and 2021, the number of earned awards for recipients of the Company’s restricted stock units and market-based LTIP Units granted in January 2020, 2019, and 2018, respectively, was determined. Pursuant to the terms of such awards, we paid one-time catch-up cash distributions to these recipients in the aggregate amounts of $1.8 million, $1.5 million, and $6.0 million, in February 2023, 2022, and 2021, respectively, for distributions to common shareholders and unitholders declared by our Board of Trustees during such awards’ performance measurement period. The following characterizes distributions paid per common share for the years ended December 31, 2023, 2022, and 2021: Year Ended December 31, 2023 2022 2021 Ordinary income 63.91 % 99.07 % — % Return of capital 36.09 % 0.93 % — % Capital gain — % — % — % Unrecaptured Section 1250 gain — % — % — % 100.00 % 100.00 % — % Series D Preferred Shares: Each of our 4,915,196 series D cumulative convertible preferred shares accrue dividends of $1.625, or 6.50% per annum of the liquidation amount, payable in equal quarterly payments. Our series D preferred shares are convertible, at the holder’s option, into our common shares at a conversion rate of 0.8204 common shares per series D preferred share, which is equivalent to a conversion price of $30.47 per common share, or 4,032,427 additional common shares at December 31, 2023. The conversion rate changed from 0.6846 to 0.8204 common shares per series D preferred share effective February 24, 2023 as a result of the common share distribution declared by our Board of Trustees in 2023. The conversion rate changed from 0.6585 to 0.6846 common shares per series D preferred share effective September 30, 2022 as a result of the common share distribution declared by our Board of Trustees in 2022. If our common shares trade at or above the then applicable conversion price, we may, at our option, convert some or all of the series D preferred shares into common shares at the then applicable conversion rate. If a fundamental change occurs, which generally will be deemed to occur upon a change in control or a termination of trading of our common shares (or other equity securities into which our series D preferred shares are then convertible), holders of our series D preferred shares will have a special right to convert their series D preferred shares into a number of our common shares per $25.00 liquidation preference, plus accrued and unpaid distributions, divided by 98% of the average closing market price of our common shares for a specified period before such event is effective, unless we exercise our right to repurchase these series D preferred shares for cash, at a purchase price equal to 100% of their liquidation preference, plus accrued and unpaid distributions. The issuance of a large number of common shares as a result of the exercise of this conversion right after a fundamental change may have a dilutive effect on net income attributable to Equity Commonwealth common shareholders per share for future periods. As of December 31, 2023, we had 4,915,196 outstanding series D preferred shares that were convertible into 4,032,427 of our common shares. Preferred Share Distributions: Under our governing documents and Maryland law, distributions to our shareholders are to be authorized and declared by our Board of Trustees. In 2023, our Board of Trustees declared distributions on our series D preferred shares to date as follows: Declaration Date Record Date Payment Date Dividend Per Share January 13, 2023 January 31, 2023 February 15, 2023 $ 0.40625 April 13, 2023 April 28, 2023 May 15, 2023 $ 0.40625 July 13, 2023 July 31, 2023 August 15, 2023 $ 0.40625 October 16, 2023 October 31, 2023 November 15, 2023 $ 0.40625 The following characterizes distributions paid per preferred share for the years ended December 31, 2023, 2022, and 2021: Year Ended December 31, 2023 2022 2021 Ordinary income 100.00 % 100.00 % — % Return of capital — % — % 100.00 % Capital gain — % — % — % Unrecaptured Section 1250 gain — % — % — % 100.0 % 100.0 % 100.00 %

Noncontrolling Interest

Noncontrolling Interest	12 Months Ended
Noncontrolling Interest	Dec. 31, 2023
Noncontrolling Interest [Abstract]
Noncontrolling Interest	Noncontrolling Interest Noncontrolling interest represents the portion of the OP Units not beneficially owned by the Company. The ownership of an OP Unit and a common share of beneficial interest have essentially the same economic characteristics. Distributions with respect to OP Units will generally mirror distributions with respect to the Company’s common shares. Unitholders (other than the Company) generally have the right, commencing six months from the date of issuance of such OP Units, to cause the Operating Trust to redeem their OP Units in exchange for cash or, at the option of the Company, common shares of the Company on a one-for-one basis. As sole trustee, the Company has the sole discretion to elect whether the redemption right will be satisfied by the Company in cash or the Company’s common shares. As a result, the Noncontrolling interest is classified as permanent equity. As of December 31, 2023, the portion of the Operating Trust not beneficially owned by the Company is in the form of OP Units and LTIP Units (see Note 8 for a description of LTIP Units). LTIP Units may be subject to additional vesting requirements. The following table presents the changes in Equity Commonwealth’s issued and outstanding common shares and units for the year ended December 31, 2023: Common Shares OP Units and LTIP Units Total Outstanding at January 1, 2023 109,428,252 279,892 109,708,144 Repurchase and surrender of shares (3,152,604) — (3,152,604) OP Unit redemption 135,392 (135,392) — Share-based compensation grants and vesting, net of forfeitures 436,398 81,518 517,916 Outstanding at December 31, 2023 106,847,438 226,018 107,073,456 Noncontrolling ownership interest in the Operating Trust 0.21 % The carrying value of the Noncontrolling interest is allocated based on the number of OP Units and LTIP Units in proportion to the number of OP Units and LTIP Units plus the number of common shares. We adjust the Noncontrolling interest balance at the end of each period to reflect the noncontrolling partners’ interest in the net assets of the Operating Trust. Net income is allocated to the Noncontrolling interest in the Operating Trust based on the weighted average ownership percentage during the period. Equity Commonwealth’s weighted average ownership interest in the Operating Trust was 99.69%, 99.75% and 99.80%, respectively, for the years ended December 31, 2023, 2022 and 2021.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our provision for income taxes consists of the following (in thousands): Year Ended December 31, 2023 2022 2021 Current: State and local $ (50) $ (103) $ (120) Federal (1,816) (350) — Income tax expense $ (1,866) $ (453) $ (120) During the years ended December 31, 2023, 2022 and 2021, we recorded benefit of $0.1 million, $0.0 million and $0.1 million, respectively, related to uncertain tax positions, as part of our income tax provision. A reconciliation of our effective tax rate and the U.S. Federal statutory income tax rate is as follows: Year Ended December 31, 2023 2022 2021 Taxes at statutory U.S. federal income tax rate 21.00 % 21.00 % 21.00 % Dividends paid deduction and net operating loss utilization (21.00) % (21.00) % (21.00) % Federal taxes 1.95 % 0.93 % — % State and local income taxes 0.05 % 0.27 % (0.74) % Effective tax rate 2.00 % 1.20 % (0.74) % On November 30, 2023 and August 31, 2022, the Company completed internal restructurings intended to comply with Section 351 of the Internal Revenue Code. As a result, for the years ended December 31, 2023 and 2022, the Operating Trust recognized $200.0 million and $82.0 million taxable gains, respectively, for federal income tax purposes. The gains were distributed by the Company and have no impact on the Company’s provision for income taxes for the years ended December 31, 2023 and 2022.

Share-Based Compensation

Share-Based Compensation	12 Months Ended
Share-Based Compensation	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation Equity Commonwealth 2015 Omnibus Incentive Plan (2015 Incentive Plan) On June 16, 2015, at our 2015 annual meeting of shareholders, our shareholders approved the 2015 Incentive Plan. The 2015 Incentive Plan replaced the Equity Commonwealth 2012 Equity Compensation Plan (as amended, the 2012 Plan). The Board of Trustees approved the 2015 Incentive Plan, subject to shareholder approval, on March 18, 2015 (the Effective Date). On January 26, 2016, the Board of Trustees approved an amendment to the 2015 Incentive Plan to allow the Compensation Committee (Committee) to authorize in an award agreement a transfer of all or a part of certain equity awards not for value to a “family member” (as defined in the 2015 Incentive Plan). At our annual meeting of shareholders on June 20, 2019, our shareholders approved an amendment to the 2015 Incentive Plan to increase the number of common shares of beneficial interest authorized thereunder by 2,500,000 (hereafter, as amended, the 2015 Incentive Plan). At our annual meeting of shareholders on June 13, 2023, our shareholders approved an amendment to the 2015 Incentive Plan to increase the number of common shares of beneficial interest authorized thereunder by 1,650,000 The following description of certain terms of the 2015 Incentive Plan is qualified in all respects by the terms of the 2015 Incentive Plan. Eligibility. Awards may be granted under the 2015 Incentive Plan to employees, officers and non-employee directors of the Company, its subsidiaries or its affiliates, or consultants and advisors (who are natural persons) providing services to the Company, its subsidiaries or its affiliates, or any other person whose participation in the 2015 Incentive Plan is determined by the Committee to be in the best interests of the Company. Term . The 2015 Incentive Plan terminates automatically ten years after the Effective Date, unless it is terminated earlier by the Board of Trustees. Shares Available for Issuance. Subject to adjustment as provided in the 2015 Incentive Plan, the maximum number of common shares of the Company that are available for issuance under the 2015 Incentive Plan is 7,400,000 shares. Awards. The following types of awards may be made under the 2015 Incentive Plan, subject to limitations set forth in the 2015 Incentive Plan: · Stock options; · Stock appreciation rights; · Restricted stock; · Restricted stock units; · Unrestricted stock; · Dividend equivalent rights; · Performance shares and other performance-based awards; · Limited partnership interests in any partnership entity through which the Company may conduct its business in the future; · Other equity-based awards; and · Cash bonus awards. Recipients of the Company’s restricted shares have the same voting rights as any other common shareholder. During the period of restriction, holders of unvested restricted shares are eligible to receive dividend payments on their shares at the same rate and on the same date as any other common shareholder. The restricted shares are service based awards and vest over a service period determined by the Committee. Recipients of the Company’s restricted stock units, or RSUs, are entitled to receive dividends with respect to the common shares underlying the RSUs if and when the RSUs are earned, at which time the recipient will be entitled to receive an amount in cash equal to the aggregate amount of cash dividends that would have been paid in respect to the common shares underlying the recipient’s earned RSUs had such common shares been issued to the recipient on the first day of the performance period. To the extent that an award does not vest, the dividends related to unvested RSUs will be forfeited. The RSUs are market-based awards with a service condition and recipients may earn RSUs based on the Company’s total shareholder return, or TSR, relative to the TSRs of the companies that comprise the Nareit Office Index over a three-year performance period. Following the end of the three-year performance period, the number of earned awards will be determined. The earned awards vest in two tranches with 50% of the earned award vesting following the end of the performance period on the date the Committee determines the level of achievement of the performance metric and the remaining 50% of the earned award vesting approximately one year thereafter, subject to the grant recipient’s continued employment. Compensation expense for the RSUs is determined using a Monte Carlo simulation model and is recognized ratably from the grant date to the vesting date of each tranche. LTIP Units are a class of beneficial interests in the Operating Trust that may be issued to employees, officers or trustees of the Operating Trust, the Company or their subsidiaries, or LTIP Units. Time-based LTIP Units have the same general characteristics as restricted shares and market-based LTIP Units have the same general characteristics as RSUs. Each LTIP Unit will convert automatically into an OP Unit on a one-for-one basis when the LTIP Unit becomes vested and its capital account is equalized with the per-unit capital account of the OP Units. Holders of LTIP Units generally will be entitled to receive the same per-unit distributions as the other outstanding OP Units in the Operating Trust, except that market-based LTIP Units will not participate in distributions until expiration of the applicable performance period, at which time any earned market-based LTIP Units generally will become entitled to receive a catch-up distribution for the periods prior to such time. Administration. The 2015 Incentive Plan will be administered by the Committee, which will determine all terms and recipients of awards under the 2015 Incentive Plan. 2023 Equity Award Activity On January 26, 2023, the Compensation Committee approved grants in the aggregate amount of 132,794 restricted shares and 269,609 RSUs at target (672,000 RSUs at maximum) to the Company’s officers, certain employees, and to Mr. Zell, the former Chairman of our Board of Trustees, as part of their compensation for fiscal year 2022. The restricted shares were valued at $25.61 per share, the closing price of our common shares on the New York Stock Exchange, or the NYSE, on the grant date. On June 13, 2023, in accordance with the Company’s compensation program for independent Trustees, the Committee awarded each of the six independent Trustees $0.1 million in restricted shares or time-based LTIP Units as part of their compensation for the 2023-2024 year of service on the Board of Trustees. These awards equated to 5,773 shares or time-based LTIP Units per Trustee, for a total of 28,865 shares and 5,773 time-based LTIP Units, valued at $20.79 per share and unit, the closing price of our common shares on the NYSE on that day. These shares and time-based LTIP Units vest one year after the date of the award, on June 13, 2024. During the year ended December 31, 2023, 274,739 RSUs vested, and, as a result, we issued 274,739 common shares, prior to certain employees surrendering their common shares to satisfy tax withholding obligations (see Note 5). 2022 Equity Award Activity On January 26, 2022, the Compensation Committee approved grants in the aggregate amount of 29,071 time-based LTIP Units, 59,024 market-based LTIP Units at target (147,117 market-based LTIP Units at maximum) 92,573 restricted shares and 187,951 RSUs at target (468,468 RSUs at maximum) to the Company’s officers, certain employees, and to Mr. Zell, the former Chairman of our Board of Trustees, as part of their compensation for fiscal year 2021. The restricted shares and time-based LTIP Units were valued at $25.50 per share/unit, the closing price of our common shares on the NYSE, on the grant date. On June 21, 2022, in accordance with the Company’s compensation program for independent Trustees, the Committee awarded each of the six independent Trustees $0.1 million in restricted shares or time-based LTIP Units as part of their compensation for the 2022-2023 year of service on the Board of Trustees. These awards equated to 3,604 shares or time-based LTIP Units per Trustee, for a total of 18,020 shares and 3,604 time-based LTIP Units, valued at $27.75 per share and unit, the closing price of our common shares on the NYSE on that day. These shares and time-based LTIP Units vested on June 21, 2023. During the year ended December 31, 2022, 382,993 RSUs vested, and, as a result, we issued 382,993 common shares, prior to certain employees surrendering their common shares to satisfy tax withholding obligations (see Note 5). 2021 Equity Award Activity On January 25, 2021, the Committee approved grants in the aggregate amount of 122,466 restricted shares and 248,646 RSUs at target (619,750 RSUs at maximum) to the Company’s officers, certain employees, and to Mr. Zell, the former Chairman of our Board of Trustees, as part of their compensation for fiscal year 2020. The restricted shares were valued at $28.25 per share, the closing price of our common shares on the NYSE on the grant date. On June 23, 2021, in accordance with the Company’s compensation plan for independent Trustees, the Committee awarded each of the six independent Trustees $0.1 million in restricted shares or time-based LTIP Units as part of their compensation for the 2021-2022 year of service on the Board of Trustees. These awards equated to 3,701 shares or time-based LTIP Units per Trustee, for a total of 18,505 shares and 3,701 time-based LTIP Units, valued at $27.02 per share and unit, the closing price of our common shares on the New York Stock Exchange, or NYSE, on that day. These shares and time-based LTIP Units vested on June 23, 2022. During the year ended December 31, 2021, 523,662 RSUs vested, and, as a result, we issued 523,662 common shares, prior to certain employees surrendering their common shares to satisfy tax withholding obligations (see Note 5). Additionally, 81,434 market-based LTIP Units vested and converted into OP Units. Outstanding Equity Awards The table below presents a summary of restricted share, RSU and LTIP Unit activity for the years ended December 31, 2023, 2022 and 2021: Number Weighted Number Weighted Outstanding at December 31, 2020 385,688 $ 31.52 1,964,918 $ 15.65 Granted 144,672 28.06 619,750 15.19 Vested (188,990) 30.99 (605,096) 15.31 Not earned (1) — — — — Forfeited — — — — Outstanding at December 31, 2021 341,370 $ 30.35 1,979,572 $ 15.61 Granted 143,268 25.84 615,585 14.09 Vested (125,958) 30.15 (382,993) 15.46 Not earned (1) — — (358,692) 15.91 Forfeited — — — — Outstanding at December 31, 2022 358,680 $ 28.62 1,853,472 $ 15.13 Granted 167,432 24.61 672,000 14.65 Vested (195,521) 29.07 (350,484) 16.07 Not earned (1) — — (136,212) 16.12 Forfeited — — — — Outstanding at December 31, 2023 330,591 $ 26.32 2,038,776 $ 14.74 (1) The table presents the maximum number of shares issued or issuable from outstanding equity awards. RSUs and market-based LTIP Units not earned are the shares market-based award recipients do not receive based on the performance measurement completed at the end of the performance period. The 330,591 unvested restricted shares and time-based LTIP Units as of December 31, 2023 are scheduled to vest as follows: 113,107 shares/units in 2024, 90,554 shares/units in 2025, 73,427 shares/units in 2026 and 53,503 shares/units in 2027. As of December 31, 2023, the estimated future compensation expense for all unvested restricted shares and time-based LTIP Units was $4.3 million. Compensation expense for the restricted share and time-based LTIP Units is being recognized on a straight-line basis over the requisite service period for each separately vesting portion of the award. The weighted average period over which the future compensation expense will be recorded for the restricted shares and time-based LTIP Units is approximately 2.3 years. As of December 31, 2023, the estimated future compensation expense for all unvested RSUs and market-based LTIP Units was $9.7 million. The weighted average period over which the future compensation expense will be recorded for the RSUs and market-based LTIP Units is approximately 2.2 years. The assumptions and fair values for the RSUs and market-based LTIP Units granted for the years ended December 31, 2023, 2022 and 2021 are included in the following table on a per share and unit basis. 2023 2022 2021 Fair value of RSUs and market-based LTIP Units granted at the target amount $ 36.51 $ 35.11 $ 37.87 Fair value of RSUs and market-based LTIP Units granted at the maximum amount $ 14.65 $ 14.09 $ 15.19 Expected term (years) 4 4 4 Expected volatility 18.47 % 17.04 % 16.99 % Expected dividend yield — % — % — % Risk-free rate 3.84 % 1.39 % 0.17 % During the years ended December 31, 2023, 2022 and 2021, we recorded $16.0 million, $11.9 million and $15.4 million, respectively, of compensation expense, net of forfeitures, in general and administrative expense for grants to our trustees, employees and an eligible consultant related to our equity compensation plans. Compensation expense recorded during the years ended December 31, 2023, 2022 and 2021 includes $5.2 million, $0.4 million and $3.5 million, respectively, of accelerated vesting due to the passing of our former Chairman in 2023 and staffing reductions in 2022 and 2021. Forfeitures are recognized as they occur. At December 31, 2023, 2,073,350 shares/units remain available for issuance under the 2015 Incentive Plan.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	12 Months Ended
Fair Value of Assets and Liabilities	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities As of December 31, 2023 and 2022, we do not have any assets or liabilities measured at fair value. Financial Instruments Our financial instruments include our cash and cash equivalents. At December 31, 2023 and 2022, the fair value of these financial instruments was not different from their carrying values.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
Earnings Per Common Share	Dec. 31, 2023
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings Per Common Share The following table sets forth the computation of basic and diluted earnings per share (amounts in thousands except per share amounts): Year Ended December 31, 2023 2022 2021 Numerator for earnings per common share - basic: Net income (loss) $ 91,445 $ 37,357 $ (16,429) Net (income) loss attributable to noncontrolling interest (281) (94) 33 Preferred distributions (7,988) (7,988) (7,988) Numerator for net income (loss) per share - basic $ 83,176 $ 29,275 $ (24,384) Numerator for earnings per common share - diluted: Net income (loss) $ 91,445 $ 37,357 $ (16,429) Net (income) loss attributable to noncontrolling interest (281) (94) 33 Preferred distributions (7,988) (7,988) (7,988) Numerator for net income (loss) per share - diluted $ 83,176 $ 29,275 $ (24,384) Denominator for earnings per common share - basic and diluted: Weighted average number of common shares outstanding - basic (1) 108,841 111,674 121,411 RSUs (2) 1,224 970 — LTIP Units (3) 120 181 — Weighted average number of common shares outstanding - diluted 110,185 112,825 121,411 Net income (loss) per common share attributable to Equity Commonwealth common shareholders: Basic $ 0.76 $ 0.26 $ (0.20) Diluted $ 0.75 $ 0.26 $ (0.20) Anti-dilutive securities (4) : Effect of Series D preferred shares; 6.50% cumulative convertible 4,032 3,365 3,237 Effect of RSUs (2) — — 549 Effect of LTIP Units (3) — — 47 Effect of OP Units and time-based LTIP Units (5) 335 276 245 (1) The years ended December 31, 2023, 2022 and 2021, include 127, 105, and 256 weighted-average, unvested, earned RSUs, respectively. (2) Represents the weighted-average number of common shares that would have been issued if the year-end was the measurement date for unvested, unearned RSUs. (3) Represents the weighted-average dilutive shares issuable from market-based LTIP Units if the year-end was the measurement date for the periods shown. (4) These securities are excluded from the diluted earnings per share calculation for one or more of the years presented because including them results in anti-dilution. (5) Beneficial interests in the Operating Trust.

Segment Information

Segment Information	12 Months Ended
Segment Information	Dec. 31, 2023
Segment Reporting [Abstract]
Segment Information	Segment Information Our primary business is the ownership and operation of office properties, and we currently have one reportable segment. One hundred percent of our revenues for the year ended December 31, 2023 were from office properties.

Related Person Transactions

Related Person Transactions	12 Months Ended
Related Person Transactions	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Person Transactions	Related Person Transactions The following discussion includes a description of our related person transactions for the years ended December 31, 2023, 2022 and 2021. We lease office space for our corporate headquarters from Two North Riverside Plaza Joint Venture Limited Partnership, an entity associated with Equity Group Investments (EGI), a private entrepreneurial investment firm founded by Sam Zell, our former Chairman who passed away on May 18, 2023. Messrs. Helfand and Weinberg continue to be advisors to EGI and certain other members of our team are expected to continue to have limited involvement in its activities. In December 2020, we entered into an amendment to a July 2015 lease with Two North Riverside Plaza Joint Venture Limited Partnership to occupy office space on the twentieth and twenty-first floors of Two North Riverside Plaza in Chicago, Illinois (Two North Office Lease). The amendment extended the lease term for one year, through December 31, 2021, with no renewal options. The lease payment for the extended term was $0.3 million. In December 2021, we entered into a second amendment to the Two North Office Lease, extending the lease term for one year, through December 31, 2022, with no renewal options. The lease payment for the second extended term was $0.4 million. In December 2022, we entered into a third amendment to the Two North Office Lease extending the lease term for one year, through December 31, 2023, with no renewal options. The lease payment for the third extended term was $0.4 million. In August 2023, we entered into a fourth amendment to the Two North Office Lease extending the lease term for one year, through December 31, 2024, with no renewal options and contracting square feet to the existing space on the twentieth floor. The lease payment for the fourth extended term is $0.4 million. During the years ended December 31, 2023, 2022 and 2021, we recognized expense of $0.4 million, $0.4 million and $0.3 million, respectively, pursuant to the Two North Office Lease. The future minimum lease payments scheduled to be paid by us during the term of this lease as of December 31, 2023 are $0.4 million in 2024. As of December 31, 2023 and 2022, we did not have any amounts due to Two North Riverside Plaza Joint Venture Limited Partnership pursuant to the Two North Office Lease.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Preferred Share Distribution On January 16, 2024, we announced that our Board of Trustees declared a dividend of $0.40625 per series D preferred share, which will be paid on February 15, 2024 to shareholders of record on January 31, 2024.

SCHEDULE III REAL ESTATE AND AC

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION	12 Months Ended
SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION	Dec. 31, 2023
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Schedule III Real Estate and Accumulated Depreciation	Initial Cost to Company Cost Amount Carried at Close of Period Property City State Land Buildings and Costs Impairment/Write Downs Land Buildings and Total(1) Accumulated Date Original 1225 Seventeenth Street Denver CO $ 22,400 $ 110,090 $ 48,374 $ (4,877) $ 22,400 $ 153,587 $ 175,987 $ 65,171 6/24/2009 1982 1250 H Street, NW Washington DC 5,975 53,778 22,316 (6,046) 5,975 70,048 76,023 41,761 6/23/1998 1992 206 East 9th Street Austin TX 7,900 38,533 9,952 (1,710) 7,900 46,775 54,675 14,003 5/31/2012 1984 Bridgepoint Square Austin TX 7,785 70,526 32,150 (5,259) 7,785 97,417 105,202 59,600 12/5/1997 1986;1996; $ 44,060 $ 272,927 $ 112,792 $ (17,892) $ 44,060 $ 367,827 $ 411,887 $ 180,535 Analysis of the carrying amount of real estate properties and accumulated depreciation: Real Estate Accumulated Balance at January 1, 2021 $ 401,710 $ 143,319 Additions 6,326 15,054 Disposals (1,934) (1,934) Balance at December 31, 2021 406,102 156,439 Additions 4,002 15,072 Disposals (1,981) (1,981) Balance at December 31, 2022 408,123 169,530 Additions 7,638 14,879 Disposals (3,874) (3,874) Balance at December 31, 2023 $ 411,887 $ 180,535 (1) Excludes value of real estate intangibles. Aggregate cost for federal income tax purposes is $545,860. (2) Depreciation is calculated using the straight-line method over estimated useful lives of up to 40 years for buildings and improvements and up to 12 years for personal property.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss) Attributable to Parent	$ 91,164	$ 37,263	$ (16,396)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation. The consolidated financial statements include our investments in 100% owned subsidiaries and majority owned subsidiaries that are controlled by us. References to we, us, our and the Company, refer to Equity Commonwealth and its consolidated subsidiaries as of December 31, 2023, unless the context indicates otherwise. All intercompany transactions and balances have been eliminated. Dollar amounts presented may be approximate. Share amounts are presented in whole numbers, except where noted.
Real Estate Properties	Real Estate Properties. We record real estate properties at cost. We depreciate real estate investments on a straight-line basis over estimated useful lives of up to 40 years for buildings and improvements, and up to 12 years for personal property. Each time we enter into a new lease, or materially modify an existing lease, we evaluate its classification as either a finance or operating lease. The classification of a lease as finance or operating affects the carrying value of a property, as well as our recognition of rental payments as revenue. These evaluations require us to make estimates of, among other things, the remaining useful life and fair market value of a leased property, appropriate discount rates and future cash flows. We allocate the consideration paid for our properties among land, buildings and improvements and, for properties that qualify as acquired businesses under the Business Combinations Topic of the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, to identified intangible assets and liabilities, consisting of the value of above market and below market leases, the value of acquired in place leases and the value of tenant relationships. Purchase price allocations and the determination of useful lives are based on our estimates and, under some circumstances, studies from independent real estate appraisal firms to provide market information and evaluations that are relevant to our purchase price allocations and determinations of useful lives; however, we are ultimately responsible for the purchase price allocations and determination of useful lives. We allocate the consideration to land, buildings and improvements based on a determination of the fair values of these assets assuming the property is vacant. We determine the fair value of a property using methods that we believe are similar to those used by independent appraisers. Purchase price allocations for above market and below market leases are based on the estimated present value (using an interest rate which reflects our assessment of the risks associated with the leases acquired) of the difference between (1) the contractual amounts to be paid pursuant to the acquired in place leases and (2) our estimate of fair market lease rates for the corresponding leases, measured over a period equal to the remaining non-cancelable terms of the respective leases. Purchase price allocations to acquired in place leases and tenant relationships are determined as the excess of (1) the purchase price paid for a property after adjusting existing in place leases to estimated market rental rates over (2) the estimated fair value of the property as if vacant. We aggregate this value between acquired in place lease values and tenant relationships based on our evaluation of the specific characteristics of each tenant's lease; however, the value of tenant relationships has not been separated from acquired in place lease value for our properties because we believe such value and related amortization expense is immaterial for acquisitions reflected in our historical financial statements. We consider certain factors in performing these analyses including estimates of carrying costs during the expected lease up periods, including real estate taxes, insurance and other operating income and expenses and costs to execute similar leases in current market conditions, such as leasing commissions, legal and other related costs. If we believe the value of tenant relationships is material in the future, those amounts will be separately allocated and amortized over the estimated lives of the relationships. We recognize the excess, if any, of the consideration paid over amounts allocated to land, buildings and improvements and identified intangible assets and liabilities as goodwill and we recognize gains if amounts allocated exceed the consideration paid. We amortize capitalized above market lease values as a reduction to rental income over the remaining terms of the respective leases. We amortize capitalized below market lease values as an increase to rental income over the remaining terms of the respective leases. We amortize the value of acquired in place leases exclusive of the value of above market and below market acquired in place leases to expense over the remaining terms of the respective leases. If a lease is terminated prior to its stated expiration, the unamortized lease intangibles relating to that lease is written off. We review our properties for impairment quarterly, or whenever events or changes in circumstances indicate that their carrying amounts may not be recoverable. Impairment indicators may include our decision to dispose of an asset before the end of its estimated useful life, declining tenant occupancy, lack of progress releasing vacant space, tenant bankruptcies, low long-term prospects for improvement in property performance, weak or declining tenant profitability, and cash flow or liquidity. When indicators of potential impairment are present that suggest that the carrying amounts of real estate assets may not be recoverable, we assess the recoverability of these assets by determining whether the respective carrying values will be recovered through the estimated undiscounted future operating cash flows expected from the use of the assets and their eventual disposition. The determination of undiscounted cash flow includes consideration of many factors including income to be earned from the investment over our anticipated hold period, holding costs (exclusive of interest), estimated selling prices, and prevailing economic and market conditions. In the event that such expected undiscounted future cash flows do not exceed the carrying values, we estimate the fair value of the assets and record an impairment charge equal to the amount by which the carrying value exceeds the estimated fair value. Estimated fair values are calculated based on the following information, (i) recent third party estimates of market value, (ii) market prices for comparable properties, or (iii) the present value of future cash flows. During the years ended December 31, 2023, 2022 and 2021 we did not record any loss on asset impairment. When we classify properties as held for sale, we discontinue the recording of depreciation expense and estimate their fair value less costs to sell. If we determine that the carrying value for these properties exceed their estimated fair value less costs to sell, we record a loss on asset impairment. As of December 31, 2023 and 2022, we did not have any properties classified as held for sale.
Cash and Cash Equivalents	Cash and Cash Equivalents.
Other Assets, Net	Other Assets, Net.
Revenue Recognition	Revenue Recognition. Rental revenue from operating leases, which includes rent concessions (including free rent and other lease incentives) and scheduled increases in rental rates during the lease term, represents the lease component and is recognized on a straight-line basis over the life of the lease agreements. We defer the recognition of contingent rental income, such as percentage rents, until the specific targets that trigger the contingent rental income are achieved. Rental revenue also includes non-lease components such as property level operating expenses reimbursed by our tenants and other incidental revenues, which are recorded as expenses are incurred. We concluded that the timing and pattern of transfer for non-lease components and the associated lease component are the same. We determined that the predominant component was the lease component and we have elected to account for and present the lease component and non-lease component of our leases as a single component in Rental revenue in our consolidated statements of operations in accordance with FASB Topic 842.
Lessee Lease Classification	Lessee Lease Classification
Earnings Per Common Share	Earnings Per Common Share.
Reclassifications	Reclassifications. Reclassifications have been made to the prior years' financial statements and notes to conform to the current year's presentation.
Legal Matters	Legal Matters. We are or may become a party to various legal proceedings. We are not currently involved in any litigation nor, to our knowledge, is any litigation threatened against us where the outcome would, in our judgment based on information currently available to us, have a material adverse effect on the Company.
Income Taxes	Income Taxes. We are a REIT under the Internal Revenue Code of 1986, as amended, and are generally not subject to federal and state income taxes provided we distribute our taxable income to our shareholders and meet other requirements for qualifying as a REIT. We are also subject to certain state and local taxes without regard to our REIT status. The Income Taxes Topic of the FASB ASC prescribes how we should recognize, measure and present in our financial statements uncertain tax positions that have been taken or are expected to be taken in a tax return. Deferred tax assets are recognized to the extent that it is “more likely than not” that a particular tax position will be sustained upon examination or audit. To the extent the “more likely than not” standard has been satisfied, the benefit associated with a tax position is measured as the largest amount that has a greater than 50% likelihood of being realized upon settlement. We classify interest and penalties related to uncertain tax positions, if any, in our financial statements as a component of general and administrative expense.
Use of Estimates	Use of Estimates. Preparation of these financial statements in conformity with U.S. generally accepted accounting principles, or GAAP, requires us to make estimates and assumptions that may affect the amounts reported in these financial statements and related notes. The actual results could differ from these estimates.
New Accounting Pronouncements	New Accounting Pronouncements. In November 2023, the FASB issued Accounting Standards Update, or ASU, 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which improves the disclosures about a public entity's reportable segments and addresses requests from investors for additional, more detailed information about a reportable segment's expenses. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. We do not expect the adoption of ASU 2023-07 to have a material impact on our consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which enhances the transparency and decision usefulness of income tax disclosures. This update is effective for annual periods beginning after December 15, 2024. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. We do not expect the adoption of ASU 2023-09 to have a material impact on our consolidated financial statements.

Real Estate Properties (Tables)

Real Estate Properties (Tables)	12 Months Ended
Real Estate Properties (Tables)	Dec. 31, 2023
Real Estate [Abstract]
Schedule of Future Minimum Lease Payments, Excluding Tenant Reimbursement Revenue, Scheduled to be Received	The future minimum lease payments, excluding tenant reimbursement revenue, scheduled to be received by us during the current terms of our leases as of December 31, 2023 are as follows (in thousands): 2024 $ 34,544 2025 32,955 2026 30,033 2027 25,066 2028 20,031 Thereafter 46,434 $ 189,063
Schedule of Rental Revenue	Rental revenue consists of the following (in thousands): December 31, 2023 2022 2021 Lease payments $ 36,008 $ 37,846 $ 36,461 Variable lease payments 19,328 20,917 18,466 Rental revenue $ 55,336 $ 58,763 $ 54,927

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
Other Assets (Tables)	Dec. 31, 2023
Other Assets [Abstract]
Summary of Deferred Financing Fees, Deferred Leasing Costs and Capitalized Lease Incentives	The following table summarizes our deferred leasing costs and capitalized lease incentives as of December 31, 2023, and 2022 (in thousands): December 31, 2023 2022 Deferred leasing costs $ 21,356 $ 22,034 Accumulated amortization (10,540) (11,320) Deferred leasing costs, net $ 10,816 $ 10,714 Capitalized lease incentives $ 3,471 $ 3,352 Accumulated amortization (2,278) (1,873) Capitalized lease incentives, net $ 1,193 $ 1,479
Summary of Future Amortization of Deferred Leasing Costs and Capitalized Lease Incentives	Future amortization of deferred leasing costs, included in amortization expense, and capitalized lease incentives, included in rental revenues, to be recognized by us during the current terms of our leases as of December 31, 2023 are approximately (in thousands): Deferred Leasing Costs Capitalized Lease Incentives 2024 $ 2,548 $ 283 2025 1,833 222 2026 1,811 216 2027 1,411 170 2028 1,098 107 Thereafter 2,115 195 $ 10,816 $ 1,193

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
Shareholders' Equity (Tables)	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Schedule of Paid Distributions and Declared Distributions	The following characterizes distributions paid per common share for the years ended December 31, 2023, 2022, and 2021: Year Ended December 31, 2023 2022 2021 Ordinary income 63.91 % 99.07 % — % Return of capital 36.09 % 0.93 % — % Capital gain — % — % — % Unrecaptured Section 1250 gain — % — % — % 100.00 % 100.00 % — % Declaration Date Record Date Payment Date Dividend Per Share January 13, 2023 January 31, 2023 February 15, 2023 $ 0.40625 April 13, 2023 April 28, 2023 May 15, 2023 $ 0.40625 July 13, 2023 July 31, 2023 August 15, 2023 $ 0.40625 October 16, 2023 October 31, 2023 November 15, 2023 $ 0.40625 The following characterizes distributions paid per preferred share for the years ended December 31, 2023, 2022, and 2021: Year Ended December 31, 2023 2022 2021 Ordinary income 100.00 % 100.00 % — % Return of capital — % — % 100.00 % Capital gain — % — % — % Unrecaptured Section 1250 gain — % — % — % 100.0 % 100.0 % 100.00 %

Noncontrolling Interest (Tables

Noncontrolling Interest (Tables)	12 Months Ended
Noncontrolling Interest (Tables)	Dec. 31, 2023
Noncontrolling Interest [Abstract]
Schedule of Issued and Outstanding Common Shares	The following table presents the changes in Equity Commonwealth’s issued and outstanding common shares and units for the year ended December 31, 2023: Common Shares OP Units and LTIP Units Total Outstanding at January 1, 2023 109,428,252 279,892 109,708,144 Repurchase and surrender of shares (3,152,604) — (3,152,604) OP Unit redemption 135,392 (135,392) — Share-based compensation grants and vesting, net of forfeitures 436,398 81,518 517,916 Outstanding at December 31, 2023 106,847,438 226,018 107,073,456 Noncontrolling ownership interest in the Operating Trust 0.21 %
Schedule of Issued and Outstanding Units	The following table presents the changes in Equity Commonwealth’s issued and outstanding common shares and units for the year ended December 31, 2023: Common Shares OP Units and LTIP Units Total Outstanding at January 1, 2023 109,428,252 279,892 109,708,144 Repurchase and surrender of shares (3,152,604) — (3,152,604) OP Unit redemption 135,392 (135,392) — Share-based compensation grants and vesting, net of forfeitures 436,398 81,518 517,916 Outstanding at December 31, 2023 106,847,438 226,018 107,073,456 Noncontrolling ownership interest in the Operating Trust 0.21 % The table below presents a summary of restricted share, RSU and LTIP Unit activity for the years ended December 31, 2023, 2022 and 2021: Number Weighted Number Weighted Outstanding at December 31, 2020 385,688 $ 31.52 1,964,918 $ 15.65 Granted 144,672 28.06 619,750 15.19 Vested (188,990) 30.99 (605,096) 15.31 Not earned (1) — — — — Forfeited — — — — Outstanding at December 31, 2021 341,370 $ 30.35 1,979,572 $ 15.61 Granted 143,268 25.84 615,585 14.09 Vested (125,958) 30.15 (382,993) 15.46 Not earned (1) — — (358,692) 15.91 Forfeited — — — — Outstanding at December 31, 2022 358,680 $ 28.62 1,853,472 $ 15.13 Granted 167,432 24.61 672,000 14.65 Vested (195,521) 29.07 (350,484) 16.07 Not earned (1) — — (136,212) 16.12 Forfeited — — — — Outstanding at December 31, 2023 330,591 $ 26.32 2,038,776 $ 14.74

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Provision for Income Taxes	Our provision for income taxes consists of the following (in thousands): Year Ended December 31, 2023 2022 2021 Current: State and local $ (50) $ (103) $ (120) Federal (1,816) (350) — Income tax expense $ (1,866) $ (453) $ (120)
Schedule of Reconciliation of Effective Tax Rate and the U.S. Federal Statutory Income Tax Rate	A reconciliation of our effective tax rate and the U.S. Federal statutory income tax rate is as follows: Year Ended December 31, 2023 2022 2021 Taxes at statutory U.S. federal income tax rate 21.00 % 21.00 % 21.00 % Dividends paid deduction and net operating loss utilization (21.00) % (21.00) % (21.00) % Federal taxes 1.95 % 0.93 % — % State and local income taxes 0.05 % 0.27 % (0.74) % Effective tax rate 2.00 % 1.20 % (0.74) %

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
Share-Based Compensation (Tables)	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Restricted Share and Restricted Stock Unit Activity	The following table presents the changes in Equity Commonwealth’s issued and outstanding common shares and units for the year ended December 31, 2023: Common Shares OP Units and LTIP Units Total Outstanding at January 1, 2023 109,428,252 279,892 109,708,144 Repurchase and surrender of shares (3,152,604) — (3,152,604) OP Unit redemption 135,392 (135,392) — Share-based compensation grants and vesting, net of forfeitures 436,398 81,518 517,916 Outstanding at December 31, 2023 106,847,438 226,018 107,073,456 Noncontrolling ownership interest in the Operating Trust 0.21 % The table below presents a summary of restricted share, RSU and LTIP Unit activity for the years ended December 31, 2023, 2022 and 2021: Number Weighted Number Weighted Outstanding at December 31, 2020 385,688 $ 31.52 1,964,918 $ 15.65 Granted 144,672 28.06 619,750 15.19 Vested (188,990) 30.99 (605,096) 15.31 Not earned (1) — — — — Forfeited — — — — Outstanding at December 31, 2021 341,370 $ 30.35 1,979,572 $ 15.61 Granted 143,268 25.84 615,585 14.09 Vested (125,958) 30.15 (382,993) 15.46 Not earned (1) — — (358,692) 15.91 Forfeited — — — — Outstanding at December 31, 2022 358,680 $ 28.62 1,853,472 $ 15.13 Granted 167,432 24.61 672,000 14.65 Vested (195,521) 29.07 (350,484) 16.07 Not earned (1) — — (136,212) 16.12 Forfeited — — — — Outstanding at December 31, 2023 330,591 $ 26.32 2,038,776 $ 14.74
Summary of Assumptions and Fair Values for Restricted Stock Units Granted in the Period	The assumptions and fair values for the RSUs and market-based LTIP Units granted for the years ended December 31, 2023, 2022 and 2021 are included in the following table on a per share and unit basis. 2023 2022 2021 Fair value of RSUs and market-based LTIP Units granted at the target amount $ 36.51 $ 35.11 $ 37.87 Fair value of RSUs and market-based LTIP Units granted at the maximum amount $ 14.65 $ 14.09 $ 15.19 Expected term (years) 4 4 4 Expected volatility 18.47 % 17.04 % 16.99 % Expected dividend yield — % — % — % Risk-free rate 3.84 % 1.39 % 0.17 %

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
Earnings Per Common Share (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share (amounts in thousands except per share amounts): Year Ended December 31, 2023 2022 2021 Numerator for earnings per common share - basic: Net income (loss) $ 91,445 $ 37,357 $ (16,429) Net (income) loss attributable to noncontrolling interest (281) (94) 33 Preferred distributions (7,988) (7,988) (7,988) Numerator for net income (loss) per share - basic $ 83,176 $ 29,275 $ (24,384) Numerator for earnings per common share - diluted: Net income (loss) $ 91,445 $ 37,357 $ (16,429) Net (income) loss attributable to noncontrolling interest (281) (94) 33 Preferred distributions (7,988) (7,988) (7,988) Numerator for net income (loss) per share - diluted $ 83,176 $ 29,275 $ (24,384) Denominator for earnings per common share - basic and diluted: Weighted average number of common shares outstanding - basic (1) 108,841 111,674 121,411 RSUs (2) 1,224 970 — LTIP Units (3) 120 181 — Weighted average number of common shares outstanding - diluted 110,185 112,825 121,411 Net income (loss) per common share attributable to Equity Commonwealth common shareholders: Basic $ 0.76 $ 0.26 $ (0.20) Diluted $ 0.75 $ 0.26 $ (0.20) Anti-dilutive securities (4) : Effect of Series D preferred shares; 6.50% cumulative convertible 4,032 3,365 3,237 Effect of RSUs (2) — — 549 Effect of LTIP Units (3) — — 47 Effect of OP Units and time-based LTIP Units (5) 335 276 245 (1) The years ended December 31, 2023, 2022 and 2021, include 127, 105, and 256 weighted-average, unvested, earned RSUs, respectively. (2) Represents the weighted-average number of common shares that would have been issued if the year-end was the measurement date for unvested, unearned RSUs. (3) Represents the weighted-average dilutive shares issuable from market-based LTIP Units if the year-end was the measurement date for the periods shown. (4) These securities are excluded from the diluted earnings per share calculation for one or more of the years presented because including them results in anti-dilution. (5) Beneficial interests in the Operating Trust.

Organization (Details)

Organization (Details) $ in Thousands, ft² in Millions	12 Months Ended
Organization (Details) $ in Thousands, ft² in Millions	Dec. 31, 2023 USD ($) ft² property building	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Aug. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 2,160,535	$ 2,582,222
General and administrative	$ 36,974	$ 30,378	$ 37,444
Monmouth Real Estate Investment Corporation
Segment Reporting Information [Line Items]
Business acquisition, transaction costs				$ 10,000
General and administrative			$ 100
Consolidated portfolio
Segment Reporting Information [Line Items]
Number of properties \| property	4
Number of buildings \| building	8
Property square feet (in sqft) \| ft²	1.5
EQC Operating Trust
Segment Reporting Information [Line Items]
Noncontrolling interest, ownership percentage by parent	99.79%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	12 Months Ended
Summary of Significant Accounting Policies (Details)	Dec. 31, 2023 USD ($) property	Dec. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($)
Property, Plant and Equipment [Line Items]
Percentage of investments in subsidiaries	100%
Asset impairment charges \| $	$ 0	$ 0	$ 0
Minimum percentage of likelihood of realization of tax benefits (greater than)	50%
Disposal Group, Held-for-sale, Not Discontinued Operations
Property, Plant and Equipment [Line Items]
Number of properties \| property	0	0
Buildings and improvements \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
Personal property \| Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life	12 years

Real Estate Properties - Narrat

Real Estate Properties - Narrative (Details) ft² in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) ft² property	Dec. 31, 2022 USD ($) property	Dec. 31, 2021 USD ($) property
Real Estate [Abstract]
Real estate property improvements	$ 7.6	$ 4	$ 6.3
Committed expenditures on leases executed during period	$ 9.6
Square feet of leases committed for expenditures during the period (in sqft) \| ft²	0.2
Committed but unspent tenant related obligations based on existing leases	$ 13.1
Number of real estate properties sold \| property	0	0	0

Real Estate Properties - Schedu

Real Estate Properties - Schedule of Future Minimum Lease Payments, Excluding Tenant Reimbursement Revenue, Scheduled to be Received (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Lessor, Operating Lease, Payments, Fiscal Year Maturity [Abstract]
2024	$ 34,544
2025	32,955
2026	30,033
2027	25,066
2028	20,031
Thereafter	46,434
Total	$ 189,063

Real Estate Properties - Rental

Real Estate Properties - Rental Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Real Estate [Abstract]
Lease payments	$ 36,008	$ 37,846	$ 36,461
Variable lease payments	19,328	20,917	18,466
Rental revenue	$ 55,336	$ 58,763	$ 54,927

Other Assets - Summary of Defer

Other Assets - Summary of Deferred Financing Fees, Deferred Leasing Costs and Capitalized Lease Incentives (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Other Assets [Abstract]
Deferred leasing costs	$ 21,356	$ 22,034
Accumulated amortization	(10,540)	(11,320)
Deferred leasing costs, net	10,816	10,714
Capitalized lease incentives	3,471	3,352
Accumulated amortization	(2,278)	(1,873)
Capitalized lease incentives, net	$ 1,193	$ 1,479

Other Assets - Summary of Futur

Other Assets - Summary of Future Amortization of Deferred Leasing Costs and Capitalized Lease Incentives (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred Leasing Costs
2024	$ 2,548
2025	1,833
2026	1,811
2027	1,411
2028	1,098
Thereafter	2,115
Deferred leasing costs, net	10,816	$ 10,714
Capitalized Lease Incentives
2024	283
2025	222
2026	216
2027	170
2028	107
Thereafter	195
Capitalized lease incentives, net	$ 1,193	$ 1,479

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) $ / shares in Units, $ in Thousands						1 Months Ended			12 Months Ended
	Mar. 09, 2023 USD ($)	Feb. 13, 2023 $ / shares	Oct. 18, 2022 USD ($) $ / shares	Sep. 08, 2022 $ / shares	Oct. 20, 2020 $ / shares	Feb. 28, 2023 USD ($)	Feb. 28, 2022 USD ($)	Feb. 28, 2021 USD ($)	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Jul. 01, 2023 USD ($)	Sep. 29, 2022	Mar. 15, 2022 USD ($)	Dec. 14, 2021 USD ($)	Mar. 01, 2021 USD ($)	Oct. 02, 2020	Oct. 01, 2020
Class of Stock [Line Items]
Repurchase of shares \| $									$ 56,803	$ 155,710	$ 174,407
Distributions declared per common share (in dollars per share) \| $ / shares		$ 4.25	$ 1	$ 1
Distributions paid per common share (in dollars per share) \| $ / shares			$ 1		$ 4.25
Payments of capital distribution \| $	$ 468,300		$ 111,000			$ 1,800	$ 1,500	$ 6,000	$ 468,232	$ 112,199	$ 6,024
Preferred shares, of beneficial interest, shares outstanding (in shares)									4,915,196	4,915,196
Preferred shares, dividend yield									6.50%	6.50%
Common Shares
Class of Stock [Line Items]
Stock repurchase program, authorized amount (up to) \| $												$ 150,000		$ 150,000	$ 150,000	$ 150,000
Number of shares repurchased (in shares)										6,110,646
Average cost per share (in dollars per share) \| $ / shares									$ 18.78	$ 24.64	$ 25.85
Repurchase of shares \| $									$ 56,700	$ 155,500	$ 174,100
Repurchase of shares (in shares)									3,018,411		6,735,810
Stock repurchase program, remaining authorized repurchase amount \| $									$ 93,300
Surrender of shares for tax withholding (in shares)									134,193	160,506	245,560
Common shares from conversion of preferred shares (in shares)									4,032,427
Series D Preferred Stock
Class of Stock [Line Items]
Preferred shares dividend (in dollars per share) \| $ / shares									$ 1.625
Preferred shares, dividend yield									6.50%	6.50%	6.50%
Initial conversion rate									0.8204				0.6585				0.8204	0.6846
Initial conversion price per share (in dollars per share) \| $ / shares									$ 30.47
Additional common shares (in shares)									4,032,427
Liquidation preference (in dollars per share) \| $ / shares									$ 25
Percentage of average closing market price of the entity's common stock based on which ratio for conversion of preferred shares into common shares is determined									98%
Purchase price as a percentage of liquidation preference									100%
Common shares from conversion of preferred shares (in shares)									4,915,196

Shareholders' Equity - Schedule

Shareholders' Equity - Schedule of Distributions Paid Per Share (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Common Share
Ordinary income	63.91%	99.07%	0%
Return of capital	36.09%	0.93%	0%
Capital gain	0%	0%	0%
Unrecaptured Section 1250 gain	0%	0%	0%
Common share, distributions paid	100%	100%	0%

Shareholders' Equity - Schedu_2

Shareholders' Equity - Schedule of Declared Distributions (Details) - $ / shares									12 Months Ended
	Nov. 15, 2023	Oct. 16, 2023	Aug. 15, 2023	Jul. 14, 2023	May 15, 2023	Apr. 13, 2023	Feb. 15, 2023	Jan. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Ordinary income									100%	100%	0%
Return of capital									0%	0%	100%
Capital gain									0%	0%	0%
Unrecaptured Section 1250 gain									0%	0%	0%
Preferred stock, dividends, distribution percentage									100%	100%	100%
Series D Preferred Stock
Class of Stock [Line Items]
Dividend declared (in dollars per share)		$ 0.40625		$ 0.40625		$ 0.40625		$ 0.40625
Dividends paid (in dollars per share)	$ 0.40625		$ 0.40625		$ 0.40625		$ 0.40625

Noncontrolling Interest - Addit

Noncontrolling Interest - Additional Information (Details)	12 Months Ended
Noncontrolling Interest - Additional Information (Details)	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Noncontrolling Interest [Abstract]
Common stock, conversion term	6 months
Common stock, conversion basis	1
EQC Operating Trust
Noncontrolling Interest [Line Items]
Noncontrolling interest, weighted average ownership percentage by parent	99.69%	99.75%	99.80%

Noncontrolling Interest - Commo

Noncontrolling Interest - Common Shares and Units Activity (Details)	12 Months Ended
	Dec. 31, 2023 shares
Equity Commonwealth
Increase (Decrease) in Stockholders' Equity
Noncontrolling ownership interest in the Operating Trust	0.21%
Common Shares, OP Units and LTIP Units
Increase (Decrease) in Stockholders' Equity
Beginning balance (in shares)	109,708,144
Redemption and surrender of shares (in shares)	(3,152,604)
OP Unit Redemption (in shares)	0
Share-based compensation grants and vesting, net of forfeitures (in shares)	517,916
Ending balance (in shares)	107,073,456
Common Shares
Increase (Decrease) in Stockholders' Equity
Beginning balance (in shares)	109,428,252
Redemption and surrender of shares (in shares)	(3,152,604)
OP Unit Redemption (in shares)	135,392
Share-based compensation grants and vesting, net of forfeitures (in shares)	436,398
Ending balance (in shares)	106,847,438
OP Units and LTIP Units \| Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Beginning balance (in shares)	279,892
Redemption and surrender of shares (in shares)	0
OP Unit Redemption (in shares)	(135,392)
Share-based compensation grants and vesting, net of forfeitures (in shares)	81,518
Ending balance (in shares)	226,018

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current:
State and local	$ (50)	$ (103)	$ (120)
Federal	(1,816)	(350)	0
Income tax expense	$ (1,866)	$ (453)	$ (120)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Uncertain tax position as part of income tax provision	$ 0.1	$ 0	$ 0.1
Taxable Gain	200	82
Net operating loss carryforwards	29	$ 29
Net operating loss carryforwards, expiring in 2037	18
Tax credit carryforward, no expiration date	$ 11

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Effective Tax Rate and the U.S. Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Taxes at statutory U.S. federal income tax rate	21%	21%	21%
Dividends paid deduction and net operating loss utilization	(21.00%)	(21.00%)	(21.00%)
Federal taxes	1.95%	0.93%	0%
State and local income taxes	0.05%	0.27%	(0.74%)
Effective tax rate	2%	1.20%	(0.74%)

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) $ / shares in Units, $ in Millions								12 Months Ended
	Jun. 13, 2023 USD ($) trustee $ / shares shares	Jan. 26, 2023 $ / shares shares	Jun. 21, 2022 USD ($) trustee $ / shares shares	Jan. 26, 2022 $ / shares shares	Jun. 23, 2021 USD ($) trustee $ / shares shares	Jan. 25, 2021 $ / shares shares	Jun. 16, 2015	Dec. 31, 2027 shares	Dec. 31, 2026 shares	Dec. 31, 2025 shares	Dec. 31, 2024 shares	Dec. 31, 2023 USD ($) tranche $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 shares	Jun. 20, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	1,650,000
Common shares available for issuance (in shares)												2,073,350
Number of independent trustees \| trustee	6		6		6
Common stock issued (in shares)												106,847,438	109,428,252
Compensation expense, accelerated vesting due to a staffing reduction \| $												$ 5.2	$ 0.4	$ 3.5
Equity Commonwealth 2015 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)																2,500,000
Share-based compensation arrangement, plan term							10 years
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense \| $												$ 16	$ 11.9	$ 15.4
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)		132,794	18,020	92,573	18,505	122,466
Granted (in dollars per share) \| $ / shares		$ 25.61		$ 25.50		$ 28.25
Common stock issued (in shares)														523,662
Restricted shares \| Independent Trustee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)	28,865
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period												3 years
Number of tranches \| tranche												2
Vested (in shares)												274,739	382,993	523,662
Common stock issued (in shares)												274,739
RSUs \| Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage												50%
RSUs \| Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period												1 year
Vesting percentage												50%
RSUs, target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)		269,609		187,951		248,646
RSUs, maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)		672,000		468,468		619,750
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity award, conversion basis												1
Number of equity awards granted (in shares)	5,773
Time-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)			3,604	29,071	3,701
Market-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares)														81,434
Conversion of equity instruments (in shares)														81,434
Market-Based LTIP Units, target
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)				59,024
Market-Based LTIP Units At Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)				147,117
OP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of equity instruments (in shares)														81,434
Restricted Shares and Time-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)	5,773											167,432	143,268	144,672
Granted (in dollars per share) \| $ / shares												$ 24.61	$ 25.84	$ 28.06
Share based compensation amount \| $	$ 0.1		$ 0.1		$ 0.1
Price per share (in dollars per share) \| $ / shares	$ 20.79		$ 27.75		$ 27.02
Vested (in shares)												195,521	125,958	188,990
Unvested (in shares)												330,591	358,680	341,370	385,688
Estimated future compensation expense for unvested shares \| $												$ 4.3
Weighted average period over which compensation expense will be recorded												2 years 3 months 18 days
Restricted Shares and Time-Based LTIP Units \| Independent Trustee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)			3,604		3,701
Restricted Shares and Time-Based LTIP Units \| Scenario, Forecast
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested (in shares)								53,503	73,427	90,554	113,107
RSUs and Market-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity awards granted (in shares)												672,000	615,585	619,750
Granted (in dollars per share) \| $ / shares												$ 14.65	$ 14.09	$ 15.19
Vested (in shares)												350,484	382,993	605,096
Unvested (in shares)												2,038,776	1,853,472	1,979,572	1,964,918
Estimated future compensation expense for unvested shares \| $												$ 9.7
Weighted average period over which compensation expense will be recorded												2 years 2 months 12 days
Common Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued (in shares)													382,993
Maximum \| Equity Commonwealth 2015 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares available for issuance (in shares)												7,400,000

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Restricted Share and Restricted Stock Unit Activity (Details) - $ / shares		12 Months Ended
	Jun. 13, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restricted Shares and Time-Based LTIP Units
Number of Shares
Beginning balance (in shares)		358,680	341,370	385,688
Granted (in shares)	5,773	167,432	143,268	144,672
Vested (in shares)		(195,521)	(125,958)	(188,990)
Not earned (in shares)		0	0	0
Forfeited (in shares)		0	0	0
Ending balance (in shares)		330,591	358,680	341,370
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)		$ 28.62	$ 30.35	$ 31.52
Granted (in dollars per share)		24.61	25.84	28.06
Vested (in dollars per share)		29.07	30.15	30.99
Not earned (in dollars per share)		0	0	0
Forfeited (in dollars per share)		0	0	0
Ending balance (in dollars per share)		$ 26.32	$ 28.62	$ 30.35
RSUs and Market-Based LTIP Units
Number of Shares
Beginning balance (in shares)		1,853,472	1,979,572	1,964,918
Granted (in shares)		672,000	615,585	619,750
Vested (in shares)		(350,484)	(382,993)	(605,096)
Not earned (in shares)		(136,212)	(358,692)	0
Forfeited (in shares)		0	0	0
Ending balance (in shares)		2,038,776	1,853,472	1,979,572
Weighted Average Grant Date Fair Value
Beginning balance (in dollars per share)		$ 15.13	$ 15.61	$ 15.65
Granted (in dollars per share)		14.65	14.09	15.19
Vested (in dollars per share)		16.07	15.46	15.31
Not earned (in dollars per share)		16.12	15.91	0
Forfeited (in dollars per share)		0	0	0
Ending balance (in dollars per share)		$ 14.74	$ 15.13	$ 15.61

Share-Based Compensation - Su_2

Share-Based Compensation - Summary of Assumptions and Fair Values for Restricted Stock Units Granted in the Period (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
RSUs and Market-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Fair value of RSUs and market-based LTIP Units granted (in dollars per share)	$ 14.65	$ 14.09	$ 15.19
Expected term (years)	4 years	4 years	4 years
Expected volatility	18.47%	17.04%	16.99%
Expected dividend yield	0%	0%	0%
Risk-free rate	3.84%	1.39%	0.17%
RSUs and Market-Based LTIP Units, target
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Fair value of RSUs and market-based LTIP Units granted (in dollars per share)	$ 36.51	$ 35.11	$ 37.87
RSUs and Market-Based LTIP Units, maximum
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology
Fair value of RSUs and market-based LTIP Units granted (in dollars per share)	$ 14.65	$ 14.09	$ 15.19

Fair Value of Assets and Liab_2

Fair Value of Assets and Liabilities - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Fair value of assets and liabilities	$ 0	$ 0

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator for earnings per common share - basic:
Net income (loss)	$ 91,445	$ 37,357	$ (16,429)
Net (income) loss attributable to noncontrolling interest	(281)	(94)	33
Preferred distributions	(7,988)	(7,988)	(7,988)
Net income (loss) attributable to Equity Commonwealth common shareholders	83,176	29,275	(24,384)
Numerator for earnings per common share - diluted:
Net income (loss)	91,445	37,357	(16,429)
Net (income) loss attributable to noncontrolling interest	(281)	(94)	33
Preferred distributions	(7,988)	(7,988)	(7,988)
Numerator for net income (loss) per share - diluted	$ 83,176	$ 29,275	$ (24,384)
Denominator for earnings per common share - basic and diluted:
Weighted average common shares outstanding — basic (in shares)	108,841	111,674	121,411
Weighted average common shares outstanding — diluted (in shares)	110,185	112,825	121,411
Net income (loss) per common share attributable to Equity Commonwealth common shareholders, basic
Basic (in dollars per share)	$ 0.76	$ 0.26	$ (0.20)
Net income (loss) per common share attributable to Equity Commonwealth common shareholders, diluted
Diluted (in dollars per share)	$ 0.75	$ 0.26	$ (0.20)
Anti-dilutive securities(4):
Preferred shares, dividend yield	6.50%	6.50%
Weighted average number of shares, restricted stock units, unvested (in shares)	127	105	256
Series D Preferred Stock
Anti-dilutive securities(4):
Preferred shares, dividend yield	6.50%	6.50%	6.50%
Series D Preferred Stock
Anti-dilutive securities(4):
Effect of anti-dilutive securities (in shares)	4,032	3,365	3,237
RSUs
Anti-dilutive securities(4):
Effect of anti-dilutive securities (in shares)	0	0	549
LTIP Units
Anti-dilutive securities(4):
Effect of anti-dilutive securities (in shares)	0	0	47
Operating Partnership Units and Time-Based LTIP Units
Anti-dilutive securities(4):
Effect of anti-dilutive securities (in shares)	335	276	245
RSUs
Denominator for earnings per common share - basic and diluted:
Weighted average number of common shares outstanding, dilutive adjustment (in shares)	1,224	970	0
LTIP Units
Denominator for earnings per common share - basic and diluted:
Weighted average number of common shares outstanding, dilutive adjustment (in shares)	120	181	0

Segment Information (Details)

Segment Information (Details)	12 Months Ended
Segment Information (Details)	Dec. 31, 2023 segment
Concentration Risk [Line Items]
Number of reportable segments	1
Product Concentration Risk \| Revenue \| Office Properties
Concentration Risk [Line Items]
Concentration risk	100%

Related Person Transactions (De

Related Person Transactions (Details) - Two North Riverside Plaza Joint Venture Limited Partnership	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) option	Dec. 31, 2021 USD ($) option	Aug. 31, 2023 USD ($) option	Dec. 31, 2020 USD ($) option
Related Party Transaction [Line Items]
Renewal term of lease arrangement		1 year	1 year	1 year	1 year
Number of renewal options of lease arrangement \| option		0	0	0	0
Lessee, operating lease, liability, to be paid, year one	$ 400,000	$ 400,000	$ 400,000	$ 400,000	$ 300,000
Operating lease, expense	400,000	400,000	$ 300,000
Accounts payable	$ 0	$ 0

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent event - $ / shares	Feb. 15, 2024	Jan. 16, 2024
Subsequent Event [Line Items]
Dividend declared (in dollars per share)		$ 0.40625
Scenario, Forecast
Subsequent Event [Line Items]
Dividends paid (in dollars per share)	$ 0.40625

SCHEDULE III REAL ESTATE AND _2

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Reconciliation of Carrying Costs (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Initial Cost to Company
Land	$ 44,060
Buildings and Improvements	272,927
Costs Capitalized Subsequent to Acquisition, Net	112,792
Impairment/Write Downs	(17,892)
Cost Amount Carried at Close of Period
Land	44,060
Buildings and Improvements	367,827
Total	411,887
Accumulated Depreciation	180,535	$ 169,530	$ 156,439	$ 143,319
1225 Seventeenth Street
Initial Cost to Company
Land	22,400
Buildings and Improvements	110,090
Costs Capitalized Subsequent to Acquisition, Net	48,374
Impairment/Write Downs	(4,877)
Cost Amount Carried at Close of Period
Land	22,400
Buildings and Improvements	153,587
Total	175,987
Accumulated Depreciation	65,171
1250 H Street, NW
Initial Cost to Company
Land	5,975
Buildings and Improvements	53,778
Costs Capitalized Subsequent to Acquisition, Net	22,316
Impairment/Write Downs	(6,046)
Cost Amount Carried at Close of Period
Land	5,975
Buildings and Improvements	70,048
Total	76,023
Accumulated Depreciation	41,761
206 East 9th Street
Initial Cost to Company
Land	7,900
Buildings and Improvements	38,533
Costs Capitalized Subsequent to Acquisition, Net	9,952
Impairment/Write Downs	(1,710)
Cost Amount Carried at Close of Period
Land	7,900
Buildings and Improvements	46,775
Total	54,675
Accumulated Depreciation	14,003
Bridgepoint Square
Initial Cost to Company
Land	7,785
Buildings and Improvements	70,526
Costs Capitalized Subsequent to Acquisition, Net	32,150
Impairment/Write Downs	(5,259)
Cost Amount Carried at Close of Period
Land	7,785
Buildings and Improvements	97,417
Total	105,202
Accumulated Depreciation	$ 59,600

SCHEDULE III REAL ESTATE AND _3

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Analysis of Carrying Amount of Real Estate Properties and Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Real Estate Properties
Additions	$ 7,600	$ 4,000	$ 6,300
Balance at the end of the year	411,887
Accumulated Depreciation
Balance at the beginning of the year	169,530	156,439	143,319
Additions	14,879	15,072	15,054
Disposals	(3,874)	(1,981)	(1,934)
Balance at the end of the year	180,535	169,530	156,439
Aggregate cost of properties for federal income tax purposes	545,860
Real Estate Properties
Real Estate Properties
Balance at the beginning of the year	408,123	406,102	401,710
Additions	7,638	4,002	6,326
Disposals	(3,874)	(1,981)	(1,934)
Balance at the end of the year	$ 411,887	$ 408,123	$ 406,102
Buildings and improvements \| Maximum
Accumulated Depreciation
Estimated useful lives	40 years
Personal property \| Maximum
Accumulated Depreciation
Estimated useful lives	12 years