Equity Commonwealth (EQC) 10-K 18 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 16, 2016	Jun. 30, 2015
Document and Entity Information
Entity Registrant Name	Equity Commonwealth
Entity Central Index Key	803,649
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		125,925,375
Entity Public Float			$ 3.3

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Real estate properties:
Land	$ 389,410	$ 714,238
Buildings and improvements	3,497,942	5,014,205
Total real estate properties, at cost, gross	3,887,352	5,728,443
Accumulated depreciation	(898,939)	(1,030,445)
Total real estate properties, at cost, net	2,988,413	4,697,998
Acquired real estate leases, net	88,760	198,287
Cash and cash equivalents	1,802,729	364,516
Restricted cash	32,245	32,257
Rents receivable, net of allowance for doubtful accounts of $7,715 and $6,565, respectively	174,676	248,101
Other assets, net	157,549	220,480
Total assets	5,244,372	5,761,639
LIABILITIES AND SHAREHOLDERS’ EQUITY
Senior unsecured debt, net	1,460,592	1,598,416
Mortgage notes payable, net	249,732	609,249
Accounts payable and accrued expenses	123,587	162,204
Assumed real estate lease obligations, net	4,296	26,784
Rent collected in advance	27,340	31,359
Security deposits	10,338	14,044
Total liabilities	$ 1,875,885	$ 2,442,056
Commitments and Contingencies
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Common shares of beneficial interest, $0.01 par value: 350,000,000 shares authorized; 126,349,914 and 129,607,279 shares issued and outstanding, respectively	$ 1,263	$ 1,296
Additional paid in capital	4,414,611	4,487,133
Cumulative net income	2,333,709	2,233,852
Cumulative other comprehensive loss	(3,687)	(53,216)
Cumulative common distributions	(3,111,868)	(3,111,868)
Cumulative preferred distributions	(650,195)	(622,271)
Total shareholders’ equity	3,368,487	3,319,583
Total liabilities and shareholders’ equity	5,244,372	5,761,639
Series D
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Series D preferred shares; 6 1/2% cumulative convertible; 4,915,196 and 4,915,497 shares issued and outstanding, respectively, aggregate liquidation preference of $122,880 and $122,887, respectively	119,263	119,266
Total shareholders’ equity	119,263	119,266
Series E
Preferred shares of beneficial interest, $0.01 par value: 50,000,000 shares authorized;
Series E preferred shares; 7 1/4% cumulative redeemable on or after May 15, 2016; 11,000,000 shares issued and outstanding, aggregate liquidation preference $275,000	265,391	265,391
Total shareholders’ equity	$ 265,391	$ 265,391

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Rents receivable, allowance for doubtful accounts	$ 7,715	$ 6,565
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)	126,349,914	129,607,279
Common shares of beneficial interest, shares outstanding (in shares)	126,349,914	129,607,279
Series D
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	4,915,497
Preferred shares, of beneficial interest, shares outstanding (in shares)	4,915,196	4,915,497
Preferred shares, aggregate liquidation preference	$ 122,880	$ 122,887
Common shares of beneficial interest, shares issued (in shares)	4,915,196	4,915,497
Series E
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	7.25%	7.25%
Preferred shares of beneficial interest, shares issued (in shares)	11,000,000	11,000,000
Preferred shares, of beneficial interest, shares outstanding (in shares)	11,000,000	11,000,000
Preferred shares, aggregate liquidation preference	$ 275,000	$ 275,000
Common shares of beneficial interest, shares issued (in shares)	11,000,000	11,000,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Rental income	$ 570,382	$ 691,699	$ 763,262
Tenant reimbursements and other income	144,509	170,158	189,767
Total revenues	714,891	861,857	953,029
Expenses:
Operating expenses	324,948	387,982	410,045
Depreciation and amortization	194,001	227,532	234,402
General and administrative	57,457	113,155	80,504
Loss on asset impairment	17,162	185,067	124,253
Acquisition related costs	0	5	318
Total expenses	593,568	913,741	849,522
Operating income (loss)	121,323	(51,884)	103,507
Interest and other income	5,989	1,561	1,229
Interest expense (including net amortization of debt discounts, premiums and deferred financing fees of $1,028, $(549), and $9, respectively)	(107,316)	(143,230)	(173,011)
Gain (loss) on early extinguishment of debt	6,661	4,909	(60,052)
Gain on sale of equity investment	0	171,561	66,293
Gain on issuance of shares by an equity investee	0	17,020	0
Foreign currency exchange loss	(8,857)	0	0
Gain on sale of properties	84,421	0	1,596
Income (loss) from continuing operations before income taxes and equity in earnings of investees	102,221	(63)	(60,438)
Income tax expense	(2,364)	(3,191)	(2,634)
Equity in earnings of investees	0	24,460	25,754
Income (loss) from continuing operations	99,857	21,206	(37,318)
Discontinued operations:
Income from discontinued operations	0	8,389	6,393
Loss on asset impairment from discontinued operations	0	(2,238)	(102,869)
Loss on early extinguishment of debt from discontinued operations	0	(3,345)	(1,011)
Net loss on sale of properties from discontinued operations	0	0	(22,162)
Net income attributable to noncontrolling interest in consolidated subsidiary	0	0	(20,093)
Net income (loss) attributable to Equity Commonwealth	99,857	24,012	(177,060)
Net income (loss)	99,857	24,012	(156,967)
Preferred distributions	(27,924)	(32,095)	(44,604)
Excess fair value of consideration over carrying value of preferred shares	0	(16,205)	0
Numerator for net income (loss) per share - basic	71,933	(24,288)	(221,664)
Amounts attributable to Equity Commonwealth common shareholders:
Income (loss) from continuing operations	71,933	(27,094)	(102,015)
Income from discontinued operations	0	8,389	6,393
Loss on asset impairment from discontinued operations	0	(2,238)	(102,869)
Loss on early extinguishment of debt from discontinued operations	0	(3,345)	(1,011)
Numerator for net income (loss) per share - basic	$ 71,933	$ (24,288)	$ (221,664)
Weighted average common shares outstanding — basic (in shares)	128,621	125,163	112,378
Weighted average common shares outstanding — diluted (in shares)	129,437	125,163	112,378
Basic earnings per common share attributable to Equity Commonwealth common shareholders:
Income (loss) from continuing operations (in dollars per share)	$ 0.56	$ (0.21)	$ (0.91)
Income (loss) from discontinued operations (in dollars per share)	0	0.02	(1.06)
Net income (loss) (in dollars per share)	0.56	(0.19)	(1.97)
Diluted earnings per common share attributable to Equity Commonwealth common shareholders:
Income (loss) from continuing operations (in dollars per share)	0.56	(0.21)	(0.91)
Income (loss) from discontinued operations (in dollars per share)	0	0.02	(1.06)
Net income (loss) (in dollars per share)	$ 0.56	$ (0.19)	$ (1.97)

CONSOLIDATED STATEMENTS OF OPE5

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Debt discounts, premiums and deferred financing fees	$ 1,028	$ (549)	$ 9

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 99,857	$ 24,012	$ (156,967)
Other comprehensive income (loss), net of tax:
Unrealized gain on derivative instruments and other assets	612	7,407	4,918
Foreign currency translation adjustments	48,917	(22,270)	(43,718)
Equity in unrealized loss of an investee	0	(22)	(132)
Total comprehensive income (loss)	149,386	9,127	(195,899)
Less: comprehensive income attributable to noncontrolling interest in consolidated subsidiary	0	0	(20,057)
Comprehensive income (loss) attributable to Equity Commonwealth	$ 149,386	$ 9,127	$ (215,956)

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Series D	Series E	Cumulative Preferred Distributions	Common Stock	Cumulative Common Distributions	Additional Paid-in Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Noncontrolling Interest in Consolidated Subsidiary
Net income (loss)	$ (156,967)							$ (177,060)		$ 20,093
Balance at Dec. 31, 2012	3,501,468	$ 368,270	$ 265,391	$ (529,367)	$ 838	$ (2,972,569)	$ 3,585,400	2,386,900	$ 565	396,040
Balance (in shares) at Dec. 31, 2012		15,180,000	11,000,000		83,804,068
Comprehensive income (loss):
Unrealized loss on derivative instrument	4,918								4,918
Foreign currency translation adjustments	(43,718)								(43,718)
Equity in unrealized income of an investee	(132)								(96)	(36)
Total comprehensive income (loss)	(195,899)
Issuance of shares, net	626,809				$ 345		626,506			(42)
Issuance of shares, net (in shares)					34,500,000
Share grants	1,821				$ 1		1,536			284
Share grants (in shares)					82,850
Adjustments to noncontrolling interest resulting from changes in ownership of a subsidiary	0						32			(32)
Distributions	(169,169)			(44,604)		(109,702)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	(14,863)
Deconsolidation of a subsidiary	(401,444)									(401,444)
Balance at Dec. 31, 2013	3,363,586	$ 368,270	$ 265,391	(573,971)	$ 1,184	(3,082,271)	4,213,474	2,209,840	(38,331)	0
Balance (in shares) at Dec. 31, 2013		15,180,000	11,000,000		118,386,918
Net income (loss)	24,012							24,012		0
Comprehensive income (loss):
Unrealized loss on derivative instrument	7,407								7,407
Foreign currency translation adjustments	(22,270)								(22,270)
Equity in unrealized income of an investee	(22)								(22)	0
Total comprehensive income (loss)	9,127
Issuance of shares, net	2,402				$ 0		2,402			0
Issuance of shares, net (in shares)					90,135
Share grants	6,160				$ 8		6,152
Share grants (in shares)					717,727
Distributions	(61,692)			(32,095)		(29,597)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Redemption of shares	0	$ (249,004)		(16,205)	$ 104		265,105
Redemption of shares (in shares)		10,264,503			10,412,499
Balance at Dec. 31, 2014	$ 3,319,583	$ 119,266	$ 265,391	(622,271)	$ 1,296	(3,111,868)	4,487,133	2,233,852	(53,216)	0
Balance (in shares) at Dec. 31, 2014	129,607,279	4,915,497	11,000,000		129,607,279
Net income (loss)	$ 99,857							99,857		0
Comprehensive income (loss):
Unrealized loss on derivative instrument	612								612
Foreign currency translation adjustments	48,917								48,917
Equity in unrealized income of an investee	0
Total comprehensive income (loss)	149,386
Issuance of shares, net	0				$ 0		0			0
Stock Repurchased During Period, Shares					(3,410,300)
Stock Repurchased During Period, Value	(87,983)				$ (35)		(87,948)
Issuance of shares, net (in shares)					0
Share grants	15,425				$ 2		15,423
Share grants (in shares)					152,791
Distributions	(27,924)			(27,924)		0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders	0
Redemption of shares	0	$ (3)		0	$ 0		3
Redemption of shares (in shares)		301			144
Balance at Dec. 31, 2015	$ 3,368,487	$ 119,263	$ 265,391	$ (650,195)	$ 1,263	$ (3,111,868)	$ 4,414,611	$ 2,333,709	$ (3,687)	$ 0
Balance (in shares) at Dec. 31, 2015	126,349,914	4,915,196	11,000,000		126,349,914

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 99,857	$ 24,012	$ (156,967)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation	145,888	166,076	178,353
Net amortization of debt discounts, premiums and deferred financing fees	1,028	(552)	81
Straight line rental income	(5,255)	(12,759)	(31,229)
Amortization of acquired real estate leases	34,277	51,140	59,274
Other amortization	21,309	20,931	18,850
Share-based compensation	15,425	5,733	0
Loss on asset impairment	17,162	187,305	227,122
(Gain) loss on early extinguishment of debt	(6,661)	(1,564)	61,063
Equity in earnings of investees	0	(24,460)	(25,754)
Gain on sale of equity investments	0	(171,561)	(66,293)
Gain on issuance of shares by an equity investee	0	(17,020)	0
Distributions of earnings from investees	0	20,680	23,911
Foreign currency exchange loss	8,857	0	0
Net (gain) loss on sale of properties	(84,421)	0	20,566
Other non-cash expenses	0	2,402	0
Change in assets and liabilities:
Restricted cash	(6,570)	3,486	(1,832)
Rents receivable and other assets	(47,472)	(30,785)	(57,039)
Accounts payable and accrued expenses	(4,643)	10,389	(14,333)
Rent collected in advance	(8,462)	(229)	125
Security deposits	1,225	433	611
Due to related persons	0	(9,277)	(1,858)
Cash provided by operating activities	181,544	224,380	234,651
CASH FLOWS FROM INVESTING ACTIVITIES:
Real estate acquisitions	0	0	(154,370)
Real estate improvements	(70,633)	(99,651)	(114,451)
Principal payments received from direct financing lease	7,352	7,311	6,970
Principal payments received from real estate mortgages receivable	0	0	1,000
Proceeds from sale of properties, net	1,691,831	185,299	224,976
Purchase of securities	0	23,988	0
Proceeds from sale of securities	27,068	0	0
Proceeds from sale of equity investments, net	0	710,492	239,576
Distributions in excess of earnings from investees	0	0	168
Increase in restricted cash	(6,725)	(8,225)	(9,102)
Deconsolidation of a subsidiary	0	0	(12,286)
Cash provided by investing activities	1,648,893	771,238	182,481
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common shares, net	0	0	626,809
Purchase and retirement of common shares	(87,983)	0	0
Repurchase and retirement of outstanding debt securities	0	0	(728,021)
Proceeds from borrowings	0	0	1,036,000
Payments on borrowings	(259,672)	(785,316)	(1,065,432)
Deferred financing fees	(7,143)	0	(1,204)
Distributions to common shareholders	0	(29,597)	(109,702)
Distributions to preferred shareholders	(27,924)	(32,095)	(44,604)
Distributions to noncontrolling interest in consolidated subsidiary	0	0	(14,863)
Cash used in financing activities	(382,722)	(847,008)	(301,017)
Effect of exchange rate changes on cash	(9,502)	(1,126)	(1,302)
Increase in cash and cash equivalents	1,438,213	147,484	114,813
Cash and cash equivalents at beginning of period	364,516	217,032	102,219
Cash and cash equivalents at end of period	1,802,729	364,516	217,032
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid	111,324	146,265	192,010
Taxes paid	6,028	2,732	1,303
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Investment in real estate mortgage receivable	0	0	(7,688)
Net assets transferred to Select Income REIT	0	0	492,736
(Decrease) increase in capital expenditures recorded as liabilities	(13,528)	7,690	(8,475)
Mortgage note payable and interest payable transferred in consensual foreclosure	$ 43,255	$ 0	$ 0

Organization

Organization	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Equity Commonwealth is a real estate investment trust, or REIT, formed in 1986 under the laws of the State of Maryland. Our primary business is the ownership and operation of real estate, primarily office buildings, throughout the United States. All number of properties, number of buildings and square feet are unaudited. At December 31, 2015 , our portfolio included the following (square feet in thousands): Number of Properties Number of Buildings Square Feet Total portfolio 65 127 23,952 From July 2, 2013 through July 9, 2014 we also owned 22,000,000 common shares of Select Income REIT and its consolidated subsidiaries (SIR), and accounted for our investment in SIR under the equity method. On July 9, 2014, we sold our entire stake of 22,000,000 common shares of SIR. SIR was a 100% owned subsidiary of ours until March 12, 2012, on which date SIR completed an initial public offering of 9,200,000 of its common shares (SIR IPO), and became a publicly owned company with shares listed on the New York Stock Exchange (NYSE). On July 2, 2013, SIR issued and sold to the public 10,500,000 of its common shares. Prior to the completion of this offering, our 22,000,000 common shares of SIR represented approximately 56.0% of SIR's outstanding common shares, and SIR was one of our consolidated subsidiaries. Following the completion of this offering, our 22,000,000 common shares of SIR represented approximately 44.2% of SIR's outstanding common shares, and SIR ceased to be our consolidated subsidiary. See Notes 7 and 19 for additional information regarding SIR. Until March 15, 2013, we also owned 9,950,000 , or approximately 18.2% , of the common shares of Government Properties Income Trust (GOV). GOV was our wholly owned subsidiary until its initial public offering in June 2009, when it became a publicly owned company with shares listed on the NYSE. On March 15, 2013, we sold all shares that we owned of GOV. See Notes 7 and 19 for additional information regarding GOV.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
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, 2015 , unless the context indicates otherwise. The portion of a consolidated subsidiary that is not controlled by us, or the noncontrolling interest, is presented as a separate component of equity in our consolidated balance sheets. In addition, net income attributable to the noncontrolling interest is presented separately in our consolidated statements of operations. All intercompany transactions and balances have been eliminated. We account for our investments in 50% or less owned companies, including our investments in SIR (beginning on July 2, 2013 when SIR ceased to be our consolidated subsidiary through the sale date on July 9, 2014), GOV (until March 15, 2013, when we sold all of our GOV common shares) and Affiliates Insurance Company, or AIC (until May 9, 2014, when we sold all of our AIC shares), over which we can exercise influence, but do not control, using the equity method of accounting. We used the income statement method to account for issuance of common shares of beneficial interest by SIR and GOV, and shares of common stock by AIC. Under this method, gains and losses reflecting changes in the value of our investments at the date of issuance of additional common shares by SIR and GOV, or common stock by AIC, are recognized in our income statement. 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 capital or operating lease. The classification of a lease as capital 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 FASB Accounting Standards Codification ™ , or the Codification, 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 to 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 (presented in our consolidated balance sheets as acquired real estate leases) as a reduction to rental income over the remaining terms of the respective leases. We amortize capitalized below market lease values (presented in our consolidated balance sheets as assumed real estate lease obligations) 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 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, cash flow or liquidity, our decision to dispose of an asset before the end of its estimated useful life. 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, 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) recently quoted market prices, (ii) market prices for comparable properties, or (iii) the present value of future cash flows. During the years ended December 31, 2015 and 2014, we recorded a loss on asset impairment in continuing operations totaling $17.2 million and $185.1 million , respectively, to reduce the carrying value of properties to their estimated fair values (see Note 16). 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. During the year ended December 31, 2013, we recorded a loss on asset impairment of $79.8 million in discontinued operations and a loss on asset impairment of $124.3 million in continuing operations to reduce the carrying value of 39 properties ( 93 buildings) classified as held for sale to their estimated fair value less costs to sell. In addition, we recorded losses on asset impairment for properties sold during 2013 totaling $23.1 million . 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, and we have no current plans to remove any such asbestos. 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 at any of our properties that have a material adverse effect on us. However, no assurances can be given that such conditions are not present in our properties or that other costs we incur to remediate contamination will not have a material adverse effect on our business or financial condition. As of December 31, 2015, we did not have any accrued environmental remediation costs. As of December 31, 2014, accrued environmental remediation costs by us totaling $0.5 million were included in accounts payable and accrued expenses in our consolidated balance sheets. Cash and Cash Equivalents. Our cash and cash equivalents consists of cash maintained in time deposits, depository accounts and money market accounts. From time-to-time we may also invest in various U.S. government securities. We continually 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. Restricted Cash. Restricted cash consists of amounts escrowed for future real estate taxes, insurance, leasing costs, capital expenditures and debt service, as required by some of our mortgage debts, as well as security deposits paid to us by some of our tenants. Other Assets, Net. Other assets consist principally of deferred financing fees, deferred leasing costs, capitalized lease incentives and prepaid property operating expenses. Deferred financing fees include issuance costs related to borrowings and are capitalized and amortized over the terms of the respective loans. Deferred leasing costs include brokerage, legal and other fees associated with the successful negotiation of leases and 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. Accounting Policy for Derivative Instruments. The Derivatives and Hedging Topic of the Codification requires companies to recognize all their derivative instruments as either assets or liabilities in the statement of financial position at fair value. The accounting for changes in the fair value of a derivative instrument depends on whether such instrument has been designated and qualifies as part of a hedging relationship and, further, on the type of hedging relationship. For those derivative instruments that are designated and qualify as hedging instruments, we must designate the hedging instrument, based upon the exposure being hedged, as a fair value hedge, cash flow hedge or a hedge of a net investment in a foreign operation. In December 2009, we entered into interest rate swap agreements that qualify as cash flow hedges. We are exposed to certain risks relating to our ongoing business operations. The primary risk managed by using derivative instruments is interest rate risk. Interest rate swaps are entered into to manage interest rate risk associated with our floating rate borrowings. We designate interest rate swaps as cash flow hedges of floating rate borrowings. Revenue Recognition. Rental income from operating leases, which includes rent concessions (including free rent and other lease incentives) and scheduled increases in rental rates during the lease term, 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. Tenant reimbursements and other income includes property level operating expenses reimbursed by our tenants, as well as other incidental revenues, which are recorded as expenses are incurred. Allowance for Doubtful Accounts. We maintain an allowance for doubtful accounts for estimated losses resulting from the inability or unwillingness of certain tenants to make payments required under their leases. The computation of the allowance is based on the tenants' payment histories and current credit profiles, as well as other considerations. Share-Based Compensation. All share-based compensation is measured at fair value on the grant date or date of modification, as applicable, and recognized in earnings over the requisite service period. Depending upon the settlement terms of the awards, all or a portion of the fair value of share-based awards may be presented as a liability or as equity in the consolidated balance sheets. 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 or our restricted share units (RSUs) were converted into our common shares, which could result in a lower EPS amount. The effect of our series D convertible preferred shares on income from continuing operations and net income attributable to common shareholders is anti-dilutive for all periods presented. Reclassifications. Reclassifications have been made to the prior years' financial statements and notes to conform to the current year's presentation. 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 real estate investment trust. However, we are subject to certain state and local taxes without regard to our REIT status. The Income Taxes Topic of the Codification 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. Foreign Operations. During the year ended December 31, 2015, we sold our Australian properties (Note 4) and as of December 31, 2015, we do not have any foreign operations. The U.S. dollar was the functional currency for our consolidated subsidiaries operating in the United States prior to the sale of the Australian portfolio. The functional currency for our consolidated subsidiaries in countries other than the United States was the principal currency in which the entity's assets, liabilities, income and expenses were denominated. The functional currency of our consolidated subsidiary that operated in Australia was the Australian dollar. We translated our Australian subsidiary's financial statements into U.S. dollars when we consolidated that subsidiary's financial statements on a quarterly basis. Generally, we translated assets and liabilities at the exchange rate in effect as of the balance sheet date. The resulting translation adjustments were included in cumulative other comprehensive loss in our consolidated balance sheets. We translated income statement accounts using the average exchange rate for the period and income statement accounts that include significant non-recurring transactions at the rate in effect as of the date of the transaction. We were subject to foreign currency risk due to potential fluctuations in exchange rates between Australian and U.S. currencies. Subsequent to the disposition of the Australian properties, we recognized a foreign currency exchange loss of $8.9 million in our consolidated statement of operations for the year ended December 31, 2015. The foreign currency exchange loss for the year ended December 31, 2015 relates to the change in foreign currency rates resulting in losses on cash proceeds from the Australian portfolio disposition maintained in an Australian bank account prior to the transfer of cash from our Australian subsidiary to our U.S bank accounts. As of December 31, 2015, we did no t have any cumulative foreign currency translation adjustments as the cumulative foreign currency translation adjustment of $63.2 million was reclassified from other comprehensive loss to earnings upon disposition of the Australian properties. As of December 31, 2014, cumulative foreign currency translation adjustments were $(48.9) million . New Accounting Pronouncements. In April 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, or ASU 2014-08. ASU 2014-08 changes the criteria for reporting a discontinued operation. Under the new pronouncement, a disposal of a part of an organization that has a major effect on its operations and financial results is a discontinued operation. We adopted ASU 2014-08 on January 1, 2015, and determined that our 2015 dispositions do not individually represent a strategic shift, as defined by the standard, that has or will have a major effect on our operations and financial results. As a result, the 2015 dispositions have not been presented as discontinued operations in the 2015 statements of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which provides guidance for revenue recognition. This update is effective for interim and annual reporting periods beginning after December 15, 2017. We are currently in the process of evaluating the impact, if any, the adoption of this ASU will have on our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. This standard amends existing guidance to require the presentation of debt issuance costs in the balance sheet as a deduction from the carrying amount of the related debt liability instead of as a deferred charge. It is effective for annual reporting periods beginning after December 15, 2015, but early adoption is permitted. We do not expect that the adoption of this standard will have a material impact on our consolidated financial statements.

Board of Trustees

Board of Trustees	12 Months Ended
	Dec. 31, 2015
Board of Trustees
Board of Trustees	Board of Trustees On March 18, 2014, Related Fund Management, LLC (Related) and Corvex Management LP (Corvex) together, (Related/Corvex), delivered written consents which they represented were from a sufficient number of holders of our outstanding common shares to remove all of our then Trustees (former Trustees) and any other person or persons elected or appointed to our Board of Trustees prior to the effective time of the Related/Corvex removal proposal. After inspection, our then Board of Trustees determined that holders of more than two-thirds of our outstanding common shares as of the February 18, 2014, record date consented to the Related/Corvex proposal, reaching the threshold required to remove all of our then Trustees and any other person or persons appointed as a Trustee prior to the effective time of the Related/Corvex removal proposal. Accordingly, on March 25, 2014, all of our former Trustees certified their removal as Trustees of EQC. On May 23, 2014, at a special meeting of our shareholders (Special Meeting), the following seven individuals were elected to serve on our Board of Trustees: Sam Zell, who serves as the Chairman of the new Board of Trustees, James S. Corl, Edward A. Glickman, David A. Helfand, Peter Linneman, James L. Lozier, Jr. and Kenneth Shea. Each of the foregoing individuals was nominated to serve on the new Board of Trustees by Related/Corvex. On July 31, 2014, our shareholders re-elected the seven individuals listed above and elected Martin L. Edelman, Mary Jane Robertson, Gerald A. Spector and James A. Star to serve on our Board of Trustees, bringing our total number of Trustees to eleven (new Board of Trustees). At the 2015 annual meeting of shareholders held on June 16, 2015, our shareholders re-elected each of our eleven Trustees to serve on our Board of Trustees for the 2015-2016 term.

Real Estate Properties

Real Estate Properties	12 Months Ended
	Dec. 31, 2015
Real Estate [Abstract]
Real Estate Properties	Real Estate Properties The information presented in this Note 4 excludes information related to SIR and its consolidated subsidiaries, unless the context indicates otherwise. We did not make any acquisitions during the years ended December 31, 2015 , or 2014 . During the years ended December 31, 2015 , 2014 , and 2013 , we made improvements, excluding tenant-funded improvements, to our properties totaling $75.7 million , $ 91.6 million and $122.9 million , respectively. Improvements made during the year ended December 31, 2013, include improvements made by SIR to its properties for the period that SIR was our consolidated subsidiary until July 2, 2013. We committed $156.4 million for expenditures related to 4,900,000 square feet of leases executed during 2015 . Committed but unspent tenant related obligations, including leasing commissions and tenant improvements, based on existing leases as of December 31, 2015 , were $118.9 million . Properties Held For Sale: We classify all properties that meet the criteria outlined in the Property, Plant and Equipment Topic of the FASB Accounting Standards Codification (Codification) as held for sale on our consolidated balance sheets. During March 2014, the former management team ceased to actively market 31 properties ( 67 buildings) with a combined 5,641,450 square feet that we had previously classified as held for sale as of December 31, 2013. These properties were not under agreement for sale when our former Trustees were removed in March 2014. These properties were reclassified to properties held and used in operations because they no longer met the requirements under GAAP for classification as held for sale. Operating results for these properties were reclassified from discontinued operations to continuing operations for all periods presented herein. In connection with this reclassification, we reversed previously recorded impairment losses totaling $4.8 million , which included the elimination of estimated costs to sell. As of December 31, 2015, and 2014, we had no properties classified as held for sale. Property Dispositions: During the year ended December 31, 2015 , we disposed of the following properties (dollars in thousands): Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale Properties 11350 North Meridian Street January 2015 1 1 72,264 $ 4,200 $ 766 333 Laurel Oak Drive (1) March 2015 — 1 27,164 2,450 251 1921 E. Alton Avenue March 2015 1 1 67,846 14,533 4,851 46 Inverness Center Parkway April 2015 — — — 2,000 1,857 225 Water Street (2) May 2015 1 1 318,997 — — Sorrento Valley Business Park June 2015 1 4 105,003 23,500 11,896 Illinois Center August 2015 1 2 2,090,162 376,000 26,956 16th and Race Street August 2015 1 1 608,625 43,000 7,922 185 Asylum Street September 2015 1 1 868,395 113,250 17,619 One South Church Avenue October 2015 1 1 240,811 32,000 4,282 775 Ridge Lake Boulevard October 2015 1 1 120,678 16,300 (360 ) One Park Square October 2015 1 6 259,737 34,300 9,512 Arizona Center December 2015 1 4 1,070,724 126,000 22,838 4 South 84th Avenue December 2015 1 1 236,007 18,000 8,393 Portfolio of properties 7450 Campus Drive May 2015 1 1 77,411 129 Worthington Ridge Road May 2015 1 1 227,500 599 Research Parkway May 2015 1 1 48,249 181 Marsh Hill Road May 2015 1 1 162,036 101 Barnes Road May 2015 1 1 45,755 15 Sterling Drive May 2015 1 1 173,015 35 Thorpe Avenue May 2015 1 1 79,862 50 Barnes Industrial Road North May 2015 1 1 154,255 5-9 Barnes Industrial Road May 2015 1 1 38,006 860 North Main Street May 2015 1 1 31,165 One Barnes Industrial Road South May 2015 1 1 30,170 Village Lane May 2015 1 2 58,185 100 Northfield Drive May 2015 1 1 116,986 905 Meridian Lake Drive May 2015 1 1 74,652 1717 Deerfield Road May 2015 1 1 141,186 1955 West Field Court May 2015 1 1 59,130 5015 S. Water Circle May 2015 1 1 113,524 Adams Place May 2015 1 2 230,259 Cabot Business Park May 2015 1 2 252,755 2300 Crown Colony Drive May 2015 1 1 45,974 Myles Standish Industrial Park May 2015 1 2 74,800 340 Thompson Road May 2015 1 1 25,000 100 South Charles Street May 2015 1 1 159,616 6710 Oxon Hill May 2015 1 1 118,336 8800 Queen Avenue South May 2015 1 1 280,822 Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale 9800 Sherlard Parkway May 2015 1 1 46,765 Rosedale Corporate Plaza May 2015 1 3 149,116 1000 Shelard Parkway May 2015 1 1 62,499 525 Park Street May 2015 1 1 75,636 1900 Meyer Drury Drive May 2015 1 1 65,225 131-165 West Ninth Street May 2015 1 1 75,517 7-9 Vreeland Road May 2015 1 1 155,891 5 Paragon Drive May 2015 1 1 119,089 1000 Voorhees Drive and 400 Laurel Oak Drive (1) May 2015 1 2 125,415 1601 Veterans Highway May 2015 1 1 63,608 Two Corporate Center Drive May 2015 1 1 291,230 11311 Cornell Park Drive May 2015 1 1 93,413 5300 Kings Island Drive May 2015 1 1 159,421 3 Crown Point Court May 2015 1 1 73,987 515 Pennsylvania Avenue May 2015 1 1 82,000 443 Gulph Road May 2015 1 1 21,000 4350 Northern Pike May 2015 1 1 503,885 Thunderbolt Place May 2015 1 2 100,505 6160 Kempsville Circle May 2015 1 1 129,565 448 Viking Drive May 2015 1 1 75,374 Portfolio of small office and industrial assets 45 53 5,287,790 $ 376,000 $ (8,160 ) 2501 20th Place South June 2015 1 1 125,722 420 20th Street North June 2015 1 1 514,893 Inverness Center June 2015 1 4 475,882 701 Poydras Street June 2015 1 1 1,256,971 300 North Greene Street June 2015 1 1 324,305 1320 Main Street June 2015 1 1 334,075 AL, LA, NC, SC office portfolio 6 9 3,031,848 $ 417,450 $ 41,596 12655 Olive Boulevard June 2015 1 1 98,588 1285 Fern Ridge Parkway June 2015 1 1 66,510 St. Louis portfolio (3) 2 2 165,098 $ 14,300 $ (2,349 ) 310-314 Invermay Road (4) April 2015 1 1 47,480 253-293 George Town Road (4) April 2015 1 1 143,914 7 Modal Crescent June 2015 1 1 164,160 71-93 Whiteside Road June 2015 1 1 303,488 9-13 Titanium Court June 2015 1 1 69,664 16 Rodborough Road June 2015 1 1 90,525 22 Rodborough Road June 2015 1 1 43,427 127-161 Cherry Lane June 2015 1 1 278,570 310-320 Pitt Street June 2015 1 1 313,865 Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale 44-46 Mandarin Street June 2015 1 1 226,718 19 Leadership Way June 2015 1 1 76,714 Australia portfolio (5) 11 11 1,758,525 $ 232,955 $ (47,872 ) Widewaters Parkway August 2015 1 8 514,241 5062 Brittonfield Parkway August 2015 1 1 40,162 Woodcliff Drive August 2015 1 6 516,760 Interstate Place August 2015 1 2 61,399 1000 Pittsford - Victor Road August 2015 1 1 73,358 1200 Pittsford - Victor Road August 2015 1 1 18,900 Corporate Crossing August 2015 1 5 216,126 Canal View Boulevard August 2015 1 3 118,375 14 Classic Street August 2015 1 1 37,084 110 W Fayette Street August 2015 1 1 304,906 251 Salina Meadows Parkway August 2015 1 1 65,617 Upstate New York portfolio (3) 11 30 1,966,928 $ 104,625 $ (12,518 ) 9040 Roswell Road October 2015 1 1 178,941 The Exchange October 2015 1 2 187,632 3920 Arkwright Road October 2015 1 1 196,156 1775 West Oak Commons Court October 2015 1 1 79,854 Georgia portfolio (3) 4 5 642,583 $ 48,550 $ (3,059 ) 91 135 18,939,185 $ 1,999,413 $ 84,421 (1) This property contains three buildings. We sold one building in March 2015 and two buildings in May 2015. (2) Title to this property was transferred to the lender pursuant to a consensual foreclosure in full satisfaction of the mortgage debt with a principal balance of $40.1 million , resulting in a gain on early extinguishment of debt of $17.3 million for the year ended December 31, 2015. See Note 9 for additional information. (3) Prior to the disposition of these properties, we recorded a total impairment charge of $17.2 million during the year ended December 31, 2015, based upon updated market information in accordance with our impairment analysis procedures. (4) These properties were sold in a separate transaction to a different buyer than other Australian properties. (5) The loss on sale includes a $63.2 million cumulative foreign currency translation adjustment reclassified from cumulative other comprehensive loss due to the disposition of the Australian portfolio. During the years ended December 31, 2014 and 2013, we sold the following properties (dollars in thousands): Date Sold Number of Number of Square Footage Sales Price Gain (Loss) on Sale Sales of properties resulting in gains and losses December 2013 3 40 1,670,104 $ 89,000 $ (25,521 ) June 2013 (6) — — — 2,551 1,765 June 2013 1 1 30,105 1,600 317 March 2013 (6) — — — 1,806 1,596 January 2013 (7) 3 18 1,060,026 10,250 1,277 7 59 2,760,235 $ 105,207 $ (20,566 ) Sales of properties with previously recorded asset impairment losses: June 2014 (8) 14 43 2,784,098 $ 215,900 December 2013 2 2 77,394 $ 2,020 November 2013 18 21 2,125,278 50,500 October 2013 1 2 199,418 4,000 October 2013 1 1 665,545 13,900 October 2013 9 41 1,211,536 43,000 August 2013 1 3 129,452 4,100 June 2013 1 1 143,802 5,250 June 2013 1 2 356,045 16,300 May 2013 1 1 57,250 4,025 April 2013 1 1 618,000 830 36 75 5,583,720 $ 143,925 (6) We sold a land parcel. (7) We provided mortgage financing to the buyer, an unrelated third party, totaling $7.7 million at 6.0% per annum (Note 8). (8) In connection with this transaction, we recognized a loss on asset impairment of $2.2 million and a loss on early extinguishment of debt of $3.3 million for the year ended December 31, 2014. The sales price excludes mortgage debt repayments. These properties are included in income from discontinued operations for all years presented. Results of operations for properties sold prior to December 31, 2014, are included in discontinued operations in our consolidated statements of operations. Summarized income statement information for properties included in discontinued operations is as follows (in thousands): Year Ended December 31, 2014 2013 Rental income $ 14,243 $ 55,073 Tenant reimbursements and other income 1,900 6,842 Total revenues 16,143 61,915 Operating expenses 7,138 37,027 Depreciation and amortization — 12,550 General and administrative 10 4,268 Total expenses 7,148 53,845 Operating income 8,995 8,070 Interest and other income 2 65 Interest expense (608 ) (1,742 ) Income from discontinued operations $ 8,389 $ 6,393 Lease Payments Our real estate properties are generally leased on gross lease, modified gross lease or triple net lease bases pursuant to non-cancelable, fixed term operating leases expiring between 2016 and 2033. Our triple net leases generally require the lessee to pay all property operating costs. Our 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, 2015 are as follows (in thousands): 2016 $ 400,987 2017 380,501 2018 353,286 2019 313,563 2020 275,406 Thereafter 1,175,661 $ 2,899,404 One of our real estate properties, 111 River Street in Hoboken, New Jersey, is subject to a ground lease. The land on this property is leased pursuant to a non-cancelable, fixed term operating ground lease that expires in 2098. The future minimum lease payments scheduled to be paid by us during the current terms of this ground lease under which we are the lessee, as of December 31, 2015 , are as follows (in thousands): 2016 $ 1,477 2017 1,477 2018 1,483 2019 1,503 2020 1,503 Thereafter 128,491 $ 135,934 The amount of ground lease expense included in operating expenses during the years ended December 31, 2015 , 2014 and 2013 , totaled $1.8 million , $1.8 million and $1.9 million , respectively. Ground lease expense includes percentage rent.

Lease Intangibles

Lease Intangibles	12 Months Ended
	Dec. 31, 2015
Leases [Abstract]
Leases Intangibles	Lease Intangibles The following table summarizes the carrying amounts for our acquired real estate leases and assumed real estate lease obligations as of December 31, 2015 , and 2014 , and (in thousands): December 31, 2015 2014 Acquired in-place leases $ 147,056 $ 272,077 Acquired above market leases 78,210 121,969 Acquired real estate leases 225,266 394,046 Accumulated amortization, acquired in-place leases (91,301 ) (136,089 ) Accumulated amortization, acquired above market leases (45,205 ) (59,670 ) Acquired real estate leases, net $ 88,760 $ 198,287 Acquired below market leases 19,742 56,541 Accumulated amortization (15,446 ) (29,757 ) Assumed real estate lease obligations, net $ 4,296 $ 26,784 Amortization of the lease intangibles for the years ended December 31, 2015 , 2014 , and 2013 , is as follows (in thousands): December 31, Income Statement Location 2015 2014 2013 Amortization of acquired in-place leases Depreciation and amortization $ 26,787 $ 40,493 $ 48,023 Amortization of acquired in-place leases Discontinued operations — — 1,720 Amortization of above and below market leases Increase (decrease) to rental income (7,515 ) (10,650 ) (10,310 ) Amortization of above and below market leases Discontinued operations — — 775 Future amortization of net intangible lease assets and liabilities to be recognized by us during the current terms of our leases as of December 31, 2015 , are approximately (in thousands): 2016 $ 18,054 2017 15,213 2018 12,619 2019 8,778 2020 7,535 Thereafter 22,265 $ 84,464

Investment in Direct Financing

Investment in Direct Financing Lease	12 Months Ended
	Dec. 31, 2015
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Investment in Direct Financing Lease	Investment in Direct Financing Lease We had an investment in a direct financing lease that related to a lease with a term that exceeded 75% of the useful life of an office tower located within a mixed use property in Phoenix, AZ. In December 2015, we sold this property. Prior to the sale of the property, we recognized income using the effective interest method to produce a level yield on funds not yet recovered. The carrying amount of our net investment of $12.5 million as of December 31, 2014, is included in other assets in our consolidated balance sheets. We monitored the payment history and credit profile of the tenant and have determined that no allowance for losses related to our direct financing lease was necessary at December 31, 2014.

Equity Investments

Equity Investments	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	Equity Investments At December 31, 2015 , and 2014 , we did not have any ownership interests in equity investments. For the years ended December 31, 2014, and 2013, equity in earnings is as follows (in thousands): Year Ended December 31, 2014 2013 SIR $ 24,516 $ 21,153 GOV — 4,111 AIC (56 ) 490 $ 24,460 $ 25,754 Investment in SIR SIR was one of our consolidated subsidiaries until July 2, 2013 and was an unconsolidated equity investment from July 2, 2013 until July 9, 2014. On July 9, 2014, we sold our entire stake of 22,000,000 common shares of SIR. We received $704.8 million in cash representing $32.04 per share and recognized a gain on sale of equity investment of $171.8 million in our consolidated statement of operations. Proceeds from this sale were used to repay our revolving credit facility and certain mortgage loans (Note 9). As a result of this sale, we no longer hold any interest in SIR. During the second quarter of 2014, SIR issued 10,000,000 common shares in a public offering for $29.00 per common share, raising net proceeds (after deducting underwriters’ discounts and commissions and expenses) of approximately $277.4 million . We recognized a gain on this sale by an equity investee of $16.9 million as a result of the per share sales price of this transaction being above our per share carrying value. Our ownership percentage in SIR was reduced to 36.7% as a result of the transaction. On July 2, 2013, SIR issued and sold to the public 10,500,000 of its common shares for $28.25 per common share. Prior to the completion of this offering, our 22,000,000 common shares of SIR represented approximately 56.0% of SIR's outstanding common shares, and SIR was one of our consolidated subsidiaries. Following the completion of this offering, our 22,000,000 common shares of SIR represented approximately 44.2% of SIR's outstanding common shares and SIR ceased to be our consolidated subsidiary. Accordingly, after the completion of this offering on July 2, 2013, we no longer consolidated our investment in SIR, but instead accounted for this investment under the equity method. Under the equity method, we recorded our percentage share of net earnings of SIR in our consolidated statements of operations. Prior to July 2, 2013, the operating results and investments of SIR were included in our consolidated results of operations and financial position. On July 2, 2013, our share of the underlying equity of SIR exceeded our carrying value by $17.6 million . As required under GAAP, we amortized this difference to equity in earnings of investees over a 34 year period, which approximates the average remaining useful lives of the buildings owned by SIR as of July 2, 2013. See Notes 1 and 19 for additional information regarding SIR. For the period from January 1, 2014, through July 9, 2014, we received cash distributions from SIR totaling $20.7 million . For the period from July 2, 2013, through December 31, 2013, we received cash distributions from SIR totaling $19.8 million . The following unaudited summarized income statement information of SIR for the period from January 1, 2014, through July 9, 2014, and for the year ended December 31, 2013, is as follows (in thousands, except per share data): For the Period from January 1, 2014 through July 9, 2014 Year Ended December 31, 2013 Rental income 98,226 $ 159,011 Tenant reimbursements and other income 16,980 29,312 Total revenues 115,206 188,323 Operating expenses 20,982 36,382 Depreciation and amortization 20,832 31,091 Acquisition related costs 374 2,002 General and administrative 7,731 12,423 Total expenses 49,919 81,898 Operating income 65,287 106,425 Interest expense (7,287 ) (13,763 ) Gain on early extinguishment of debt 243 — Income before income tax expense and equity in earnings of an investee 58,243 92,662 Income tax expense (90 ) 96 Equity in earnings of an investee 32 334 Net income $ 58,185 $ 93,092 Weighted average common shares outstanding 52,394 44,565 Net income per common share $ 1.11 $ 2.09 Investment in GOV On March 15, 2013, we sold all 9,950,000 common shares that we owned of GOV in a public offering for $25.20 per common share, raising gross proceeds of $250.7 million ( $239.6 million after deducting underwriters' discounts and commissions and expenses). We recognized a gain on this sale of an equity investment of $66.3 million as a result of the per share sales price of this transaction being above our per share carrying value. GOV was our wholly owned subsidiary until its initial public offering in June 2009 when it became a separate public entity. During the year ended December 31, 2013, we received cash distributions from GOV totaling $4.3 million . We no longer own any interest in GOV. Investment in AIC As of May 9, 2014, we had a net investment of $5.8 million in AIC, an insurance company that was owned in equal proportion by us, our former manager Reit Management & Research LLC (RMR), SIR and five other companies to which RMR provides management services. On May 9, 2014, as a result of the removal of the former Trustees and in accordance with the terms of the shareholder agreement between us and the other AIC shareholders, the other AIC shareholders exercised their right to purchase all of the 20,000 shares of AIC we then owned. We received $5.8 million in aggregate proceeds from this sale. We no longer own any interest in AIC. Our participation in the AIC property insurance program expired in June 2014. See Note 19 for additional information about our investment in AIC.

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2015
Other Assets [Abstract]
Other Assets	Other Assets Real Estate Mortgages Receivable As of December 31, 2015 , and 2014 , we had total real estate mortgages receivable with an aggregate carrying value of $8.1 million included in other assets in our consolidated balance sheets. We provided mortgage financing totaling $7.7 million at 6.0% per annum in connection with our sale of three properties ( 18 buildings) in January 2013 in Dearborn, MI; this real estate mortgage requires monthly interest payments and matures on January 24, 2023 . We also provided mortgage financing totaling $0.4 million at 6.0% per annum in connection with our sale of a property in Salina, NY in April 2012. This real estate mortgage requires monthly interest payments and matures on April 30, 2019 . In addition, in September 2013, another buyer of a property we sold prepaid to us in full a $1.0 million real estate mortgage that was scheduled to mature on July 1, 2017. We monitor the payment history of the borrowers and have determined that no allowance for losses related to these real estate mortgages receivable were necessary at December 31, 2015 , and 2014 . Deferred Financing Fees, Deferred Leasing Costs and Capitalized Lease Incentives The following table summarizes our deferred financing fees, deferred leasing costs and capitalized lease incentives as of December 31, 2015 , and 2014 (in thousands): December 31, 2015 2014 Deferred financing fees $ 43,346 $ 41,339 Accumulated amortization (25,158 ) (24,478 ) Deferred financing fees, net $ 18,188 $ 16,861 Deferred leasing costs $ 166,390 $ 184,600 Accumulated amortization (56,162 ) (58,348 ) Deferred leasing costs, net $ 110,228 $ 126,252 Capitalized lease incentives $ 11,623 $ 22,650 Accumulated amortization (2,498 ) (7,459 ) Capitalized lease incentives, net $ 9,125 $ 15,191 Future amortization of deferred leasing costs and capitalized lease incentives to be recognized by us during the current terms of our leases as of December 31, 2015 are approximately (in thousands): Deferred Leasing Costs Capitalized Lease Incentives 2016 $ 15,933 $ 1,528 2017 14,870 1,477 2018 13,369 779 2019 12,246 704 2020 10,324 608 Thereafter 43,486 4,029 $ 110,228 $ 9,125

Indebtedness

Indebtedness	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Indebtedness	Indebtedness At December 31, 2015 and 2014 , our outstanding indebtedness included the following (in thousands): December 31, Interest Rate at December 31, 2015 Maturity Date 2015 2014 Unsecured revolving credit facility, at LIBOR plus a premium 1.68 % 1/28/2019 $ — $ — 5-year unsecured term loan, at LIBOR plus a premium 1.83 % 1/28/2020 200,000 — 7-year unsecured term loan, at LIBOR plus a premium 2.23 % 1/28/2022 200,000 — Unsecured term loan, at LIBOR plus a premium — % — — 400,000 Unsecured floating rate debt 2.03 % (1) $ 400,000 $ 400,000 5.75% Senior Unsecured Notes due 2015 — % — $ — $ 138,773 6.25% Senior Unsecured Notes due 2016 6.25 % 8/15/2016 139,104 139,104 6.25% Senior Unsecured Notes due 2017 6.25 % 6/15/2017 250,000 250,000 6.65% Senior Unsecured Notes due 2018 6.65 % 1/15/2018 250,000 250,000 5.875% Senior Unsecured Notes due 2020 5.88 % 9/15/2020 250,000 250,000 5.75% Senior Unsecured Notes due 2042 5.75 % 8/1/2042 175,000 175,000 Unsecured fixed rate debt 6.17 % (1) $ 1,064,104 $ 1,202,877 111 Monument Circle — % — $ — $ 116,000 225 Water Street — % — — 40,059 111 East Wacker Drive — % — — 142,666 2501 20th Place South — % — — 10,267 Parkshore Plaza 5.67 % 5/1/2017 41,275 41,275 1735 Market Street (2) 5.66 % 12/2/2019 169,612 171,498 206 East 9th Street 5.69 % 1/5/2021 27,515 27,965 1320 Main Street — % — — 38,979 33 Stiles Lane 6.75 % 3/1/2022 2,785 3,132 97 Newberry Road 5.71 % 3/1/2026 6,375 6,819 Secured fixed rate debt 5.68 % (1) $ 247,562 $ 598,660 $ 1,711,666 $ 2,201,537 Unamortized net premiums and discounts (1,342 ) 6,128 $ 1,710,324 $ 2,207,665 (1) Represents weighted average interest rate at December 31, 2015 . (2) Interest on this loan is payable at LIBOR plus 2.625% but has been fixed for the first seven years to December 1, 2016 by a cash flow hedge which sets the rate at approximately 5.66% . Unsecured Revolving Credit Facility and Term Loan: Prior to January 29, 2015, we had a $750.0 million unsecured revolving credit facility. The unsecured revolving credit facility was set to mature on October 19, 2015, and had an interest rate of LIBOR plus a spread, which was 150 basis points as of December 31, 2014. We paid a facility fee of 35 basis points per annum on the total amount of lending commitments under our revolving credit facility. Prior to January 29, 2015, we also had a $500.0 million unsecured term loan that was set to mature on December 15, 2016. Our term loan had an interest rate of LIBOR plus a spread, which was 185 basis points as of December 31, 2014. On December 5, 2014, we paid $100.0 million of our unsecured term loan, reducing our term loan borrowings to $400.0 million . On January 29, 2015, we entered into a new credit agreement, pursuant to which the lenders agreed to provide (i) a $750.0 million unsecured revolving credit facility, (ii) a $200.0 million 5 -year term loan facility and (iii) a $200.0 million 7 -year term loan facility. The new agreement replaced our prior credit agreement, dated as of August 9, 2010, and our prior term loan agreement, dated as of December 16, 2010. In connection with the new agreement, we recognized a loss on early extinguishment of debt of $0.4 million from the write-off of unamortized deferred financing fees for the year ended December 31, 2015 . The revolving credit facility has a scheduled maturity date of January 28, 2019, which maturity date may be extended for up to two additional periods of six months at our option subject to satisfaction of certain conditions and the payment of an extension fee of 0.075% of the aggregate amount available under the revolving credit facility. The 5-year term loan and the 7-year term loan have scheduled maturity dates of January 28, 2020 and January 28, 2022, respectively. We used the proceeds of borrowings under the credit agreement to repay all amounts outstanding and due under the previous term loan agreement. The credit agreement permits us to utilize up to $100.0 million of the revolving credit facility for the issuance of letters of credit. Amounts outstanding under the credit agreement generally may be prepaid at any time without premium or penalty, subject to certain exceptions. We have the right to request increases in the aggregate maximum amount of borrowings available under the revolving credit facility and term loans up to an additional $1.15 billion , subject to certain conditions. Borrowings under the 5-year term loan and 7-year term loan will, subject to certain exceptions, bear interest at a LIBOR rate plus a margin of 90 to 180 basis points for the 5-year term loan and 140 to 235 basis points for the 7-year term loan, in each case depending on our credit rating. Borrowings under the revolving credit facility will, subject to certain exceptions, bear interest at a rate equal to, at our option, either a LIBOR rate or a base rate plus a margin of 87.5 to 155 basis points for LIBOR rate advances and 0 to 55 basis points for base rate advances, in each case depending on our credit rating. In addition, we are required to pay a facility fee of 12.5 to 30 basis points, depending on our credit rating, on the borrowings available under the revolving credit facility, whether or not utilized. Borrowings under our revolving credit facility currently bear interest at LIBOR plus a spread, which was 125 basis points as of December 31, 2015 . As of December 31, 2015 , the interest rate payable on borrowings under our revolving credit facility was 1.68% . As of December 31, 2015 , we had no balance outstanding and $750.0 million available under our revolving credit facility. Our term loans currently bear interest at a rate of LIBOR plus a spread, which was 140 and 180 basis points for the 5-year and 7-year term loan, respectively, as of December 31, 2015 . As of December 31, 2015 , the interest rates for the amounts outstanding under our 5-year term loan and 7-year term loan were 1.83% and 2.23% , respectively. As of December 31, 2015 , we had $200.0 million outstanding under each of our 5-year and 7-year term loans. Debt Covenants: Our public debt indenture and related supplements, our revolving credit facility agreement and our term loan agreement contain a number of financial and other covenants, including covenants that restrict our ability to incur indebtedness or to make distributions under certain circumstances and require us to maintain financial ratios and a minimum net worth. At December 31, 2015 , we believe we were in compliance with all of our respective covenants under our public debt indenture and related supplements, our revolving credit facility and our term loan agreements. Senior Unsecured Notes: On May 1, 2015, we redeemed at par $138.8 million of our 5.75% senior unsecured notes due 2015 and recognized a loss on early extinguishment of debt of $0.1 million from the write-off of an unamortized discount and unamortized deferred financing fees. On November 17, 2014, we redeemed at par $125.0 million of our 7.50% unsecured senior notes due 2019 and recognized a loss on early extinguishment of debt of $1.8 million from the write-off of an unamortized discount and deferred financing fees. On September 15, 2014, we redeemed at par $33.4 million of our 6.40% unsecured senior notes due 2015. In March 2013, we purchased a total of $670.3 million of the outstanding principal amount of senior notes for $726.2 million , excluding transaction costs, pursuant to a tender offer. In connection with the purchase of these senior notes, we recognized a combined loss on early extinguishment of debt totaling $60.0 million , which includes the write-off of unamortized discounts and deferred financing fees and expenses. Mortgage Notes Payable: At December 31, 2015 , five of our properties ( 8 buildings) with an aggregate net book value of $287.5 million had secured mortgage notes totaling $249.7 million (including net premiums and discounts) maturing from 2017 through 2026. On December 1, 2015, we repaid at par $116.0 million of 5.24% mortgage debt at 111 Monument Circle and recognized a gain on early extinguishment of debt of $0.6 million for the year ended December 31, 2015 from the write-off of an unamortized premium, net of the write-off of unamortized deferred financing fees. In accordance with the agreement to sell Illinois Center, we were required to deliver the property unencumbered. On August 3, 2015, prior to the sale, we defeased the outstanding $141.4 million balance of the mortgage loan secured by 111 East Wacker Drive, one of the buildings included in Illinois Center. The defeasance costs and write off of the unamortized deferred financing costs, net of the write off of the unamortized premium, resulted in a net loss on early extinguishment of debt of $3.9 million for the year ended December 31, 2015 . In accordance with the agreement to sell 2501 20th Place South, we were required to deliver the property unencumbered. On June 5, 2015, we prepaid $10.0 million of 7.36% mortgage debt at 2501 20th Place South and recognized a loss on early extinguishment of debt totaling $0.6 million for the year ended December 31, 2015 , which consisted of a prepayment premium and the write off of unamortized deferred financing fees, net of the write off of an unamortized premium. In accordance with the agreement to sell 1320 Main Street, we were required to deliver the property unencumbered. On June 3, 2015, prior to the sale, we defeased the $38.7 million outstanding balance of the mortgage loan secured by 1320 Main Street. The defeasance costs and write off of the unamortized deferred financing costs, net of the write off of the unamortized premium, resulted in a net loss on early extinguishment of debt of $6.2 million for the year ended December 31, 2015 . During the quarter ended June 30, 2014, we made the decision to cease making loan servicing payments on 225 Water Street in Jacksonville, Florida. The first payment we determined not to make for this property was due on June 11, 2014. The property was secured by a non-recourse mortgage loan. On October 10, 2014, we were notified by the lender that our decision to cease making loan servicing payments created an event of default effective July 11, 2014, and the lender exercised its option to accelerate the maturity of the unpaid balance of the loan. Beginning July 11, 2014, we accrued interest on this loan at 10.03% , to include the 4.0% of default interest. The lender filed a suit of foreclosure for this property and we cooperated with the lender to allow for a consensual foreclosure process. On May 22, 2015, title to 225 Water Street was transferred to the lender pursuant to the consensual foreclosure in full satisfaction of the mortgage debt, with a principal balance of $40.1 million . The transaction resulted in a gain on early extinguishment of debt of $17.3 million for the excess of the debt principal balance over the net book value of the property for the year ended December 31, 2015 . On October 31, 2014, we rep aid at par the $7.8 million mortgage loan encumbering 6200 Glenn Carlson Drive. On August 1, 2014, we prepaid at par the $265.0 million of 5.68% mortgage debt at 600 West Chicago Avenue and recognized a net gain on early extinguishment of debt of $6.7 million from the write-off of an unamortized premium, net of the write-off of unamortized deferred financing fees. On June 27, 2014, we repaid $11.2 million of 6.14% mortgage debt and $8.5 million of 5.78% mortgage debt in connection with the sale of the related properties and recognized a loss on early extinguishment of debt of $3.3 million , included in loss on early extinguishment of debt from discontinued operations, from prepayment penalties and the write-off of unamortized discounts and deferred financing fees. On March 11, 2014, we prepaid at par the $12.0 million of 4.95% mortgage debt at 3920 Arkwright Road. Required Principal Payments: The required principal payments due during the next five years and thereafter under all of our outstanding debt at December 31, 2015 are as follows (in thousands): 2016 $ 142,450 2017 294,865 2018 253,847 2019 164,613 2020 451,674 Thereafter 404,217 $ 1,711,666

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity Common Share Issuances: During the year ended December 31, 2015 , we issued 144 common shares to holders of 301 of our series D cumulative convertible preferred shares (series D preferred shares) who elected to convert their series D preferred shares into our common shares. During the year ended December 31, 2014, we issued 10,412,499 common shares to holders of 10,264,503 of our series D preferred shares who converted their series D preferred shares into our common shares. During the year ended December 31, 2014, we issued 90,135 common shares to RMR pursuant to the amended and restated business management agreement. See Note 19 for further information regarding this agreement. See Note 14 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 plan, which authorizes the repurchase of up to $100.0 million of our outstanding common shares over the twelve month period following the date of authorization. On September 14, 2015, our Board of Trustees authorized the repurchase of up to an additional $100.0 million of our outstanding common shares over the twelve month period following the date of authorization. During the year ended December 31, 2015 , we purchased and retired 3,410,300 of our common shares at a weighted average price of $25.76 per share. Common Share Distributions: In January 2014, we declared a distribution of $0.25 per common share, or $29.6 million , which we paid on February 21, 2014 to shareholders of record on January 13, 2014. Our revolving credit facility agreement and term loan agreement contain a number of financial and other covenants, including a covenant which restricts our ability to make distributions under certain circumstances. See Note 9 for additional information regarding our revolving credit facility agreement and term loan agreement. The following characterizes distributions paid per common share for the years ended December 31, 2015 , 2014 , and 2013 : Year Ended December 31, 2015 2014 2013 Ordinary income — % — % — % Return of capital — % — % 100.00 % Capital gain — % 100.00 % — % 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 an initial conversion rate of 0.480775 common shares per series D preferred share, which is equivalent to an initial conversion price of $52.00 per common share, or 2,363,103 additional common shares at December 31, 2015. On or after November 20, 2011, 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 of us 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 income from continuing operations attributable to Equity Commonwealth common shareholders per share for future periods. The removal of our former Trustees on March 25, 2014, triggered a Fundamental Change Conversion Right of the series D preferred shares, as defined in our Articles Supplementary dated October 10, 2006, setting forth the terms of the series D preferred shares. Pursuant to such right, the holders of series D preferred shares had the option to elect to convert all or any portion of their series D preferred shares at any time from April 9, 2014 until the close of business on May 14, 2014 into a number of common shares per $25.00 liquidation preference of the series D preferred shares equal to the sum of such $25.00 liquidation preference plus accrued and unpaid dividends to, but not including, May 14, 2014, divided by 98% of the average of the closing sale prices of the common shares for the five consecutive trading days ending on May 9, 2014, or the Fundamental Change Conversion Rate. Holders of 10,263,003 series D preferred shares elected to exercise their Fundamental Change Conversion Right and converted their series D preferred shares into 10,411,779 of our common shares. As a result of this transaction, we recognized a non-cash preferred distribution of $16.2 million , for the excess of the market value of the common shares issued above the carrying value of the series D preferred shares redeemed. As of December 31, 2015 , we had 4,915,196 outstanding series D preferred shares that were convertible into 2,363,103 of our common shares. Series E Preferred Shares: Each of our 11,000,000 series E preferred shares has a liquidation preference of $25.00 and requires dividends of $1.8125 , or 7.25% per annum of the liquidation amount, payable in equal quarterly payments. The series E preferred shares are redeemable at our option for $25.00 each plus accrued and unpaid distributions at any time on or after May 15, 2016 or if a change of control occurs which results in our common shares (or the common securities of an acquiring or surviving entity) not being listed or quoted on the NYSE or certain other exchanges or quotation systems. Also, upon the occurrence of such a change of control, holders of series E preferred shares that we do not elect to redeem may at their option convert those series E preferred shares into our common shares (or certain alternative consideration) at a conversion rate generally based on their $25.00 liquidation preference per share, plus accrued and unpaid distributions, and the market price of our common shares at the time of conversion, subject to a cap. Preferred Share Distributions: In 2015, our Board of Trustees declared distributions on our series D preferred shares and series E cumulative redeemable preferred shares to date as follows: Declaration Date Record Date Payment Date Series D Dividend Per Share Series E Dividend Per Share January 16, 2015 February 2, 2015 February 17, 2015 $ 0.40625 $ 0.453125 April 8, 2015 May 1, 2015 May 15, 2015 $ 0.40625 $ 0.453125 July 9, 2015 July 31, 2015 August 17, 2015 $ 0.40625 $ 0.453125 October 9, 2015 November 2, 2015 November 16, 2015 $ 0.40625 $ 0.453125 Under our governing documents and Maryland law, distributions to our shareholders are to be authorized and declared by our Board of Trustees. Additionally, the removal of our former Trustees, which occurred on March 25, 2014, constituted an event of default under our term loan and revolving credit facility agreements, under which we generally are prevented from making any distributions or paying any dividends during the pendency of an event of default. As a result of the foregoing, we were unable to declare and pay dividends between March 25, 2014, and June 6, 2014, the date on which we obtained waivers of the aforementioned events of default from our lenders. Alternative Minimum Tax: Alternative minimum tax adjustments are to be apportioned between a REIT and its shareholders under Internal Revenue Code Section 59(d). Although regulations have not yet been issued under that provision, based on regulations issued pursuant to a similar provision of prior law and the legislative history of the current provision, it appears that such alternative minimum tax adjustments are to be apportioned to a REIT’s shareholders to the extent that the REIT distributes its regular taxable income. It is our policy to distribute all of our regular taxable income and accordingly, all of our alternative minimum tax adjustments are being apportioned to our shareholders. We have determined that 0% , 15.41% and 0% of each distribution to our shareholders for the tax years ended December 31, 2015, 2014 , and 2013, respectively, consists of an alternative minimum tax adjustment.

Cumulative Other Comprehensive

Cumulative Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Cumulative Other Comprehensive Loss	Cumulative Other Comprehensive Loss The following tables present the amounts recognized in cumulative other comprehensive loss by component for the year ended December 31, 2015 (in thousands): Year Ended December 31, 2015 Unrealized Loss on Derivative Instruments and Other Assets Foreign Currency Translation Adjustments Total Balances as of January 1, 2015 $ (4,299 ) $ (48,917 ) $ (53,216 ) Other comprehensive loss before reclassifications (1,232 ) (14,290 ) (15,522 ) Amounts reclassified from cumulative other comprehensive loss to net income 1,844 63,207 65,051 Net current period other comprehensive income 612 48,917 49,529 Balances as of December 31, 2015 $ (3,687 ) $ — $ (3,687 ) The following tables present reclassifications out of cumulative other comprehensive loss for the year ended December 31, 2015 (in thousands): Year Ended December 31, 2015 Details about Cumulative Other Comprehensive Loss Components Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income Affected Line Items in the Statement of Operations Interest rate swap contracts $ 4,924 Interest expense Foreign currency translation adjustment activity 63,207 Gain on sale of properties Realized gain on available for sale securities (3,080 ) Interest and other income $ 65,051

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Our provision for income taxes consists of the following (in thousands): Year Ended December 31, 2015 2014 2013 Current: State $ 270 $ 350 $ 519 Federal 513 — — Foreign 2,336 2,772 2,572 3,119 3,122 3,091 Deferred: Foreign (755 ) 69 (457 ) (755 ) 69 (457 ) Income tax expense $ 2,364 $ 3,191 $ 2,634 Federal income tax expense for the year ended December 31, 2015 relates to taxes incurred as a result of a taxable built-in gain triggered by the sale of a property that was previously owned by a C corporation. As a result of the disposition of the Australian properties, we incurred net income tax expense of $1.6 million for the year ended December 31, 2015. A reconciliation of our effective tax rate and the U.S. Federal statutory income tax rate is as follows: Year Ended December 31, 2015 2014 2013 Taxes at statutory U.S. federal income tax rate 35.00 % 35.00 % 35.00 % Dividends paid deduction and net operating loss utilization (35.00 )% (35.00 )% (35.00 )% Federal taxes on built-in gain 0.50 % — % — % State, local, and foreign income taxes 1.81 % 11.73 % (1.71 )% Effective tax rate 2.31 % 11.73 % (1.71 )% Deferred income tax assets and liabilities, net of a valuation allowance, represent the tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes, and are determined using tax rates expected to be in effect when the deferred income tax assets and liabilities are anticipated to be paid or recovered. At December 31, 2014, we had deferred tax assets of $2.4 million , net of a valuation allowance of $0.6 million , and deferred tax liabilities of $3.1 million , which primarily relate to different carrying amounts for financial reporting and for Australian income tax purposes related to our properties and operations in Australia. The deferred tax assets primarily relate to depreciation differences and the deferred tax liabilities primarily relate to straight line rent adjustments. During the year ended December 31, 2015, we sold our Australian properties (Note 4) and as of December 31, 2015, we do not have any deferred tax assets or liabilities related to our Australian properties. We generated significant net operating losses through the 2015 property sales and we have fully reserved the associated deferred tax assets due to the uncertainty of our ability to utilize the net operating losses in the future.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments Risk Management Objective of Using Derivatives We are exposed to certain risks relating to our ongoing business operations, including the effect of changes in interest rates. The only risk we currently manage by using derivative instruments is a part of our interest rate risk. We may use derivative financial instruments, including interest rate swaps, caps, options, floors and other interest rate derivative contracts, to hedge all or a portion of the interest rate risk associated with our borrowings. The principal objective of such arrangements is to minimize the risks and/or costs associated with our operating and financial structure as well as to hedge specific anticipated transactions. We do not intend to utilize derivatives for speculative or other purposes other than interest rate risk management. The use of derivative financial instruments carries certain risks, including the risk that the counterparties to these contractual arrangements are not able to perform under the agreements. To mitigate this risk, we only enter into derivative financial instruments with counterparties with high credit ratings and with major financial institutions with which we and our affiliates may also have other financial relationships. We do not anticipate that any of the counterparties will fail to meet their obligations. Cash Flow Hedges of Interest Rate Risk Our objectives in using interest rate derivatives are to add stability to interest expense and to manage our exposure to interest rate movements. To accomplish this objective, we periodically use interest rate swaps, caps, or other similar instruments as part of our interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable-rate amounts from a counterparty in exchange for us making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount. The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in cumulative other comprehensive income (loss) and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During 2015, such derivatives were used to hedge the variable cash flows associated with variable-rate debt. The ineffective portion of the change in fair value of the derivatives is recognized directly in earnings. Amounts reported in cumulative other comprehensive loss related to derivatives will be reclassified to interest expense as interest payments are made on our variable-rate debt. During the next twelve months, we estimate that an additional $3.7 million will be reclassified from cumulative other comprehensive loss as an increase to interest expense. We have interest rate swap agreements to manage our interest rate risk exposure on $169.6 million of mortgage debt due 2019, which require interest at a spread over LIBOR . The interest rate swap agreements utilized by us qualify as cash flow hedges and effectively modify our exposure to interest rate risk by converting our floating interest rate debt to a fixed interest rate basis for this loan through December 1, 2016, thus reducing the impact of interest rate changes on future interest expense. As of December 31, 2015 , we had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk: Interest Rate Derivative Number of Instruments Notional Amount (in thousands) Interest rate swap 2 $169,612 The table below presents the fair value of our derivative financial instruments as well as their classification on the consolidated balance sheets as of December 31, 2015 , and 2014 (amounts in thousands): Fair Value as of December 31, Interest Rate Derivative Designated as Hedging Instrument Balance Sheet Location 2015 2014 Pay-fixed swaps Accounts payable and accrued expenses $ 3,687 $ 7,462 The table below details the location in the financial statements of the gain or loss recognized on interest rate derivatives designated as cash flow hedges for the years ended December 31, 2015 , 2014 , and 2013 (amounts in thousands): Year Ended December 31, 2015 2014 2013 Balance at beginning of period $ (7,462 ) $ (11,706 ) $ (16,624 ) Amount of loss recognized in cumulative other comprehensive loss (1,149 ) (776 ) (103 ) Amount of loss reclassified from cumulative other comprehensive loss into interest expense 4,924 5,020 5,021 Unrealized gain on derivative instruments 3,775 4,244 4,918 Balance at end of period $ (3,687 ) $ (7,462 ) $ (11,706 ) Credit-risk-related Contingent Features We have agreements with each of our derivative counterparties that contain a provision where if we either default or are capable of being declared in default on any of our indebtedness, then we could also be declared in default on our derivative obligations. As of December 31, 2015 , the fair value of derivatives in a net liability position including accrued interest but excluding any adjustment for nonperformance risk related to these agreements was $4.1 million . As of December 31, 2015 , we have not posted any collateral related to these agreements and were not in breach of any agreement provisions. If we had breached any of these provisions, we could have been required to settle our obligations under the agreements at their aggregate termination value of $4.1 million at December 31, 2015 .

Share-Based Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation Equity Commonwealth 2015 Omnibus Incentive Plan On June 16, 2015, at our 2015 annual meeting of shareholders, our shareholders approved the Equity Commonwealth 2015 Omnibus Incentive Plan (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). 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 3,250,000 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, the Company’s unvested restricted shareholders are eligible to receive dividend payments on their shares at the same rate and on the same date as any other common shareholder. Recipients of the Company’s restricted stock units (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 ordinary cash dividends that would have been paid in respect of 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. 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. 2015 Equity Award Activity On June 16, 2015, in accordance with the Company’s compensation plan for independent Trustees, the Committee awarded each of the nine independent Trustees $0.1 million in restricted shares as part of their compensation for the 2015-2016 year of service on the Board of Trustees. These awards equated to 3,843 shares per Trustee, for a total of 34,587 shares, valued at $26.02 per share, the closing price of our common shares on the NYSE on that day. These shares vest one year after the date of the award. On January 28, 2015, the Committee approved a grant of 126,319 restricted common shares and 639,250 RSUs at target to the Company’s officers, certain employees and to Mr. Zell, the Chairman of our Board of Trustees, as part of their compensation for fiscal year 2014. The restricted shares are service based awards and vest over a four -year period. The restricted shares were granted on January 28, 2015 and were valued at $26.58 per share, the closing price of our common shares on the NYSE on that day. The 776,456 unvested restricted shares as of December 31, 2015 are scheduled to vest as follows: 188,879 shares in 2016, 185,467 shares in 2017, 339,759 shares in 2018 and 62,351 shares in 2019. As of December 31, 2015 , the estimated future compensation expense for all unvested restricted share grants was $14.6 million . Compensation expense for the restricted share awards 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 is approximately 2.8 years. The RSUs are market based awards with a service condition and grant recipients may earn the RSU grants based on the Company’s total shareholder return (TSR) relative to the TSR's for the constituent REITs that comprise the NAREIT Office Index for the performance period of January 28, 2015 - January 28, 2018. Following the end of the performance period on January 28, 2018, the number of earned awards will be determined. The earned awards vest in two tranches with 50% of the earned award vesting on January 28, 2018 and the remaining 50% of the earned award vesting on January 28, 2019, subject to the grant recipient’s continued employment. Recipients of the Company’s RSUs are entitled to receive dividends with respect to the common shares underlying the RSUs if and when the RSUs are earned. To the extent that an award does not vest, the dividends will be forfeited. Compensation expense for the RSU awards was determined using a Monte Carlo simulation model and is being recognized ratably from the grant date to the vesting date of each tranche. 2014 Equity Award Activity On October 28, 2014, the Committee approved the one-time grant of restricted common shares and restricted share units under the 2012 Plan to certain of the Company’s officers and employees and to Mr. Zell, the Chairman of our Board of Trustees. The Committee also approved the one-time grant of restricted common shares under the 2012 Plan to our independent Trustees, a grant of restricted common shares to each independent Trustee as annual compensation for his or her service as a Trustee, and a pro-rata grant of fully vested common shares for five of our independent Trustees for their service from May 23, 2014 through July 31, 2014. Outstanding Equity Awards The table below presents a summary of restricted share and RSU activity under the 2015 Incentive Plan and the 2012 Plan for the years ended December 31, 2015 , and 2014 , excluding restricted shares granted to our former Trustees, former officers and certain employees of RMR under the terms of our 2012 Plan (which grants are further described below): Number Weighted Number Weighted Outstanding at December 31, 2013 — $ — — $ — Granted 713,727 26.66 1,266,237 15.99 Vested (3,545 ) 26.66 — — Outstanding at December 31, 2014 710,182 1,266,237 Granted 160,906 26.46 639,250 15.47 Vested (86,517 ) 26.02 — — Forfeited (8,115 ) 26.64 (21,377 ) 15.80 Outstanding at December 31, 2015 776,456 1,884,110 The RSUs are market based awards with a service condition and grant recipients may earn between 0% - 100% of the RSU grant based on the Company’s TSR relative to the TSR for the NAREIT Office Index for the period from October 28, 2014 - October 28, 2017. Following the end of the performance period on October 28, 2017, the number of earned awards will be determined. The earned awards vest in two tranches with 50% of the earned award vesting on October 28, 2017 and the remaining 50% of the earned award vesting on October 28, 2018 subject to the grant recipient’s continued employment. As of December 31, 2015 , the estimated future compensation expense for all unvested RSUs was $20.3 million . The weighted average period over which the future compensation expense will be recorded for the RSUs is approximately 2.4 years. The assumptions and fair values for the RSUs granted for the years ended December 31, 2015 , and 2014 are included in the following table on a per share basis. 2015 2014 Fair value of RSUs granted $ 15.47 $ 15.99 Expected term (years) 4 4 Expected volatility — — Expected dividend yield 1.88 % 1.88 % Risk-free rate 0.81 % 0.84 % During the years ended December 31, 2015 and 2014 , we recorded $15.4 million and $2.6 million , respectively, of compensation expense, net of forfeitures, in general and administrative expense for grants to our Board of Trustees and the Company's employees related to our Plan. At December 31, 2015 , 3,215,413 common shares remain available for issuance under the Plan. 2012 Equity Compensation Plan Prior to the adoption of the 2015 Incentive Plan, we had common shares available for issuance under the 2012 Plan. The 2012 Plan was adopted in May 2012 and replaced our 2003 Incentive Share Award Plan, or the 2003 Plan. We awarded common shares to our former officers and certain employees of RMR pursuant to both of these plans. On January 28, 2014, we granted 2,000 common shares of beneficial interest, par value $0.01 per share, valued at $23.46 per share, the closing price of our common shares on the New York Stock Exchange, or NYSE, on that day, to two of our former Trustees as part of their then annual compensation. We also awarded each of our former Trustees 2,000 common shares in 2013 with an aggregate market value of $0.2 million on the date of grant, as part of their annual compensation. The common shares awarded to our former Trustees vested immediately. We include the value of awarded shares in general and administrative expenses at the time the awards vest. See Note 19 for further information regarding grants of restricted shares we made to our former officers and certain employees of RMR. On October 28, 2014, the Board of Trustees approved an amendment to the 2012 Plan to permit the Company to issue RSUs. Additionally, on October 28, 2014, the Committee approved new forms of Restricted Share and Restricted Share Unit Agreements to be used for grants of restricted common shares to members of the Board of Trustees, as well as grants of restricted common shares and restricted share units to officers and employees of the Company. The 2015 Incentive Plan replaced the 2012 Plan. No future grants will be made under the 2012 Plan, although the terms and conditions of the 2012 Plan will continue to govern any outstanding awards granted under the 2012 Plan. A summary of shares granted and vested to our former Trustees, former officers and certain employees of RMR under the terms of our 2012 Plan and our 2003 Plan for the years ended December 31, 2014, and 2013, is as follows: Number Weighted Unvested shares at December 31, 2012 114,703 19.39 Granted 83,450 23.29 Vested (66,639 ) 23.06 Forfeited (600 ) 22.49 Unvested shares at December 31, 2013 130,914 20.70 Granted 4,000 23.46 Vested (134,914 ) 25.79 Unvested shares at December 31, 2014 — — As a result of the removal of our former Trustees on March 25, 2014, the vesting of 130,914 common shares previously issued to our former officers and certain employees of RMR pursuant to our equity compensation plans accelerated in accordance with the terms of their governing share grants. During the year ended December 31, 2014 , we recorded $3.4 million of general and administrative expense related to the vesting of these shares. During the years ended December 31, 2014, and 2013, we recorded $3.4 million and $1.8 million , respectively, of compensation expense for former Trustees, former officers and certain employees of RMR under the terms of our 2012 Plan and our 2003 Plan. In addition, during the period that SIR was our consolidated subsidiary, we recorded compensation expense related to SIR's equity compensation plan of $0.4 million for the year ended December 31, 2013.

Defined Contribution Plan (Note

Defined Contribution Plan (Notes)	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Defined Contribution Plan	Defined Contribution Plan We have a defined contribution plan that covers employees meeting eligibility requirements. We match 100% of the first 3% of compensation that an employee elects to defer plus 50% of compensation that an employee elects to defer exceeding 3% but not exceeding 5% , subject to a maximum of $8,000 . The Company’s matching contribution vests immediately. The Company's contributions were $0.3 million for the year ended December 31, 2015.

Fair Value of Assets and Liabil

Fair Value of Assets and Liabilities	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Assets and Liabilities	Fair Value of Assets and Liabilities The table below presents certain of our assets and liabilities measured at fair value during 2015 and 2014 , categorized by the level of inputs used in the valuation of each asset and liability (dollars in thousands): Fair Value at December 31, 2015 Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Description Total (Level 1) (Level 2) (Level 3) Recurring Fair Value Measurements: Effective portion of interest rate swap contracts $ (3,687 ) $ — $ (3,687 ) $ — Derivative liability (7,219 ) — — (7,219 ) Fair Value at December 31, 2014 Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Description Total (Level 1) (Level 2) (Level 3) Recurring Fair Value Measurements: Effective portion of interest rate swap contracts $ (7,462 ) $ — $ (7,462 ) $ — Derivative liability (6,658 ) — — (6,658 ) Effective Portion of Interest Rate Swap Contracts The fair value of our interest rate swap contracts is determined using the net discounted cash flows of each derivative based on the market based interest rate curve (level 2 inputs) and adjusted for our credit spread and the actual and estimated credit spreads of the counterparties (level 3 inputs). Although we have determined that the majority of the inputs used to value our derivatives fall within level 2 of the fair value hierarchy, the credit valuation adjustments associated with our derivatives utilize level 3 inputs, such as estimates of current credit spreads, to evaluate the likelihood of default by us and the counterparties. As of December 31, 2015 , we have assessed the significance of the impact of the credit valuation adjustments on the overall valuation of our derivative positions and have determined that the credit valuation adjustments are not significant to the overall valuation of our derivatives. As a result, we have determined that our derivative valuations in their entirety are classified as level 2 inputs in the fair value hierarchy. Derivative Liability On July 31, 2014, our shareholders voted to approve the reimbursement of expenses incurred by Related/Corvex (Note 17). Approximately $8.4 million was to be reimbursed only if the average closing price of our common shares was at least $26.00 (as adjusted for any share splits or share dividends) during the one year period after the date on which the reimbursement was approved by shareholders, and the remaining approximately $8.4 million will be reimbursed only if the average closing price of our common shares is at least $26.00 (as adjusted for any share splits or share dividends) during the one year period between the first and second anniversaries of the date on which the reimbursement was approved by shareholders. The average closing price of our common shares was at least $26.00 during the first one year period after the date on which the reimbursement was approved by shareholders, and in August 2015, we paid $8.4 million to Related/Corvex. The potential future reimbursement represents a derivative instrument as codified in ASC 815 Derivatives and Hedging which requires the potential future reimbursement to be recorded at fair value at each reporting date. We recognized expense of $9.0 million for the year ended December 31, 2015, which was recorded in general and administrative expenses in our consolidated statement of operations for the year ended December 31, 2015 . The valuation techniques and significant unobservable inputs used for our level 3 fair value measurement at December 31, 2015 , and 2014 were as follows: Description Fair Value at December 31, 2015 Primary Valuation Technique Unobservable Inputs Rate Derivative liability $ 7,219 Monte Carlo simulation Risk-free rate 0.52% Volatility 20.0% Description Fair Value at December 31, 2014 Primary Valuation Technique Unobservable Inputs Rate Derivative liability $ 6,658 Monte Carlo simulation Risk-free rate 0.50% Volatility 20.0% Properties Held and Used As part of our disposition plan, and pursuant to our accounting policy, in 2015, we evaluated the recoverability of the carrying values of each of the real estate assets that comprised our portfolio and determined that due to the shortening of the expected periods of ownership as a result of the disposition plan, it was necessary to reduce the net book value of a portion of the real estate assets in our portfolio to reduce the assets to their estimated fair values. During the year ended December 31, 2015, we recorded an impairment charge of $17.2 million in accordance with our impairment analysis procedures. In 2014, we ceased to actively market 31 properties with a combined 5.6 million square feet which we had previously classified as held for sale as of December 31, 2013, which were not under agreement for sale when our former Trustees were removed. These properties were reclassified to properties held and used in operations because they no longer meet the requirements for classification as held for sale. Operating results for these properties were reclassified from discontinued operations to continuing operations for all periods presented herein. In connection with this reclassification, we reversed previously recorded impairment losses totaling $4.8 million in 2014, which includes the elimination of estimated costs to sell. In connection with the internalization of management, we developed a disposition plan in the fourth quarter of 2014. Through this plan, we expect to dispose of many of our assets in the coming years. Pursuant to our accounting policy, we evaluated the recoverability of the carrying values of each of the real estate assets that comprised our portfolio and determined that due to the shortening of the expected periods of ownership, as a result of the disposition plan, that it was necessary to reduce the net book value of a portion of the real estate assets in our portfolio. As a result, we recorded a loss on asset impairment for 34 properties of $167.1 million in 2014, to reflect the estimated fair values of those real estate assets in our portfolio that failed the recoverability test because the net book values exceeded their fair values. We reduced the aggregate carrying value of these properties from $581.7 million to their estimated fair value of $414.6 million , reflected in the table below. The fair value measurements used in the evaluation of our real estate assets are considered to be Level 3 valuations within the fair value hierarchy outlined above, as there are significant unobservable inputs. Examples of inputs that were utilized in the fair value calculations include estimated holding periods, discount rates, market capitalization rates, expected lease rental rates, and third party broker information. The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at December 31, 2014 were as follows: Description Fair Value at December 31, 2014 Primary Valuation Techniques Unobservable Inputs Weighted Average(1) Properties held and used on which we recognized impairment losses $ 414,625 Discounted cash flows Discount rate 10.2% Exit capitalization rate 9.1% (1) Calculated as a weighted average based on the fair value at December 31, 2014. In 2014, we made the decision to cease making loan servicing payments on 225 Water Steet in Jacksonville, Florida (Note 9). As a result of the decision to discontinue making loan servicing payments on this property, we recorded a loss on asset impairment totaling $22.7 million to reduce the aggregate carrying value of this property from $42.3 million to its estimated fair value of $19.6 million . We used discounted cash flow analysis and third party broker information (level 3 inputs) in determining the fair value of this property. The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at June 30, 2014 were as follows: Description Fair Value at June 30, 2014 Primary Valuation Techniques Unobservable Inputs Rate 225 Water Street $ 19,589 Discounted cash flows Discount rate 8% Exit capitalization rate 8% Financial Instruments In addition to the assets and liabilities described in the above table, our financial instruments include our cash and cash equivalents, real estate mortgages receivable, restricted cash, senior unsecured debt and mortgage notes payable. At December 31, 2015 and 2014 , the fair value of these additional financial instruments were not materially different from their carrying values, except as follows (in thousands): December 31, 2015 December 31, 2014 Carrying Amount Fair Value Carrying Amount Fair Value Senior unsecured debt and mortgage notes payable, net $ 1,710,324 $ 1,749,211 $ 2,207,665 $ 2,263,535 The fair values of our senior notes and mortgage notes payable are based on estimates using discounted cash flow analyses and currently prevailing interest rates adjusted by credit risk spreads (level 3 inputs). Other financial instruments that potentially subject us to concentrations of credit risk consist principally of rents receivable; however, as of December 31, 2015 , no single tenant of ours is responsible for more than 4% of our total annualized rents. Our derivative financial instruments, including interest rate swaps, are entered with major financial institutions and we monitor the amount of credit exposure to any one counterparty.

Earnings Per Common Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2015
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, 2015 2014 2013 Numerator for earnings per common share - basic and diluted: Income (loss) from continuing operations $ 99,857 $ 21,206 $ (37,318 ) Net income attributable to noncontrolling interest in consolidated subsidiary — — (20,093 ) Preferred distributions (27,924 ) (32,095 ) (44,604 ) Excess fair value of consideration over carrying vale of preferred shares — (16,205 ) — Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders 71,933 (27,094 ) (102,015 ) Discontinued operations — 2,806 (119,649 ) Numerator for net income (loss) per share - basic and diluted $ 71,933 $ (24,288 ) $ (221,664 ) Denominator for earnings per common share - basic and diluted: Weighted average number of common shares outstanding - basic 128,621 125,163 112,378 Weighted average number of common shares outstanding - diluted (1) 129,437 125,163 112,378 Earnings per share - basic: Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders $ 0.56 $ (0.21 ) $ (0.91 ) Discontinued operations — 0.02 (1.06 ) Net income (loss) per share - basic $ 0.56 $ (0.19 ) $ (1.97 ) Earnings per share - diluted: Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders $ 0.56 $ (0.21 ) $ (0.91 ) Discontinued operations — 0.02 (1.06 ) Net income (loss) per share - diluted $ 0.56 $ (0.19 ) $ (1.97 ) Anti-dilutive securities: Effect of Series D preferred shares; 6 1/2% cumulative convertible (2) 2,363 4,175 7,298 (1) As of December 31, 2015 , we had granted RSUs to certain employees, officers, and the chairman of the Board of Trustees. The RSUs contain both service and market-based vesting components. None of the RSUs have vested. If the market-based vesting component was measured as of December 31, 2015 , 1,143 common shares would be issued to the RSU holders, and no shares would have been issued for the other periods presented. Using a weighted average basis, 816 common shares are reflected in diluted earnings per share for the year ended ended December 31, 2015 . (2) The Series D preferred shares are excluded from the diluted earnings per share calculation because including the Series D preferred shares would also require that the preferred distributions be added back to net income, resulting in anti-dilution during the periods presented.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information Our primary business is the ownership and operation of office properties. Due to significant dispositions during 2015, during the fourth quarter of 2015 we changed the composition of our operating segments from two reportable segments (central business district properties and suburban properties) to one reportable segment. This change was made based on the financial information reviewed and used by the chief operating decision maker to make operating decisions, assess performance, develop strategy and allocate capital resources. More than 90% of our revenues are from office properties.

Related Person Transactions

Related Person Transactions	12 Months Ended
	Dec. 31, 2015
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, 2015 , 2014 and 2013 . Certain of these related person transactions, and their approvals, occurred prior to the election of our new Board of Trustees at the Special Meeting and the appointment of our current executive officers following the Special Meeting. The disclosure below under “—Transactions with Prior Related Persons” describes our transactions and approvals with our prior related persons. Related Person Transactions Following the Special Meeting: Equity Group Investments and associated entities: Effective February 1, 2016, we entered into a lease with Two North Riverside Plaza Joint Venture Limited Partnership, an entity associated with Mr. Zell, our Chairman, for storage space in the basement of the building. The lease expires December 31, 2020, provided each party has the right to terminate on 30 days' prior written notice, and the payment is nominal. This lease was approved by the Audit Committee of the Board of Trustees. Effective July 20, 2015, we entered into a lease with Two North Riverside Plaza Joint Venture Limited Partnership, an entity associated with Mr. Zell, our Chairman, to occupy office space on the twentieth and twenty-first floors of Two North Riverside Plaza in Chicago, Illinois. The initial term of the lease is approximately five years, with one 5 -year renewal option. The lease payment is approximately $0.5 million for the initial year beginning in 2016, and $0.8 million annually thereafter. This lease was approved by the Audit Committee of the Board of Trustees on June 16, 2015. Effective June 1, 2014, we entered into a one -year license agreement with Equity Group Investments, a private investment firm (Equity Group), to use office space on the sixth floor at Two North Riverside Plaza in Chicago, Illinois. The license fee was $0.2 million for the initial year. The license fee includes the non-exclusive use of additional areas on the sixth floor (such as conference rooms and common areas), certain administrative services (such as mail room services and reception desk staffing), office equipment, office furniture, supplies, licensee’s share of building operating expenses and real estate taxes and access to one parking space. Mr. Zell, our Chairman, is the Chairman and Chief Executive Officer of Equity Group, and Mr. Helfand, our President and Chief Executive Officer, is the Co-President of Equity Group. This license agreement was approved by the Audit Committee of the Board of Trustees and was scheduled to expire on May 31, 2015. On May 4, 2015, the Audit Committee of the Board of Trustees approved an agreement to extend the term of the license agreement through November 30, 2015. The license fee payment is approximately $0.1 million for the extended term. On November 2, 2015, the Audit Committee of the Board of Trustees approved an agreement to extend the term of the license agreement through January 31, 2016, for a maximum license fee payment of approximately $0.1 million . The extension of the license agreement was terminated as of December 30, 2015. Effective June 1, 2014, we entered into a one -year lease with one 3 -month renewal option with Two North Riverside Plaza Joint Venture Limited Partnership, an entity associated with Mr. Zell, our Chairman, to occupy office space on the fourteenth floor at Two North Riverside Plaza in Chicago, Illinois. The lease payment was $0.2 million for the initial term. This lease was terminated, effective January 31, 2015. This lease was approved by the Audit Committee of the Board of Trustees. Effective July 31, 2014, we entered into a sublease with Equity Residential Management, L.L.C. to occupy office space on the tenth floor of Two North Riverside Plaza in Chicago, Illinois. Equity Residential Management, L.L.C. leases the space from Two North Riverside Plaza Joint Venture Limited Partnership, an entity associated with Mr. Zell, our Chairman. The initial term of the sublease was approximately seven months commencing on or about October 22, 2014, expiring on May 31, 2015, with one 3 -month renewal option. The sublease payment was approximately $0.2 million for the initial term. This sublease was approved by the Audit Committee of the Board of Trustees. On May 4, 2015, the Audit Committee of the Board of Trustees approved an agreement to extend the term of the sublease through November 30, 2015. The sublease payment is approximately $0.2 million for the extended term. On November 2, 2015, the Audit Committee of the Board of Trustees approved an agreement to extend the term of the sublease through January 31, 2016, for a maximum sublease payment of approximately $0.1 million . The extension of the sublease was terminated as of December 30, 2015. Related/Corvex: On July 31, 2014, at the reconvened session of our 2014 annual meeting of shareholders, our shareholders voted to approve the reimbursement of approximately $33.5 million of expenses incurred by Related/Corvex in connection with their consent solicitations to remove our former Trustees and elect the new Board of Trustees and to engage in related litigation. Approximately $16.7 million was paid during the year ended December 31, 2014. Approximately $8.4 million was to be reimbursed only if the average closing price of our common shares is at least $26.00 (as adjusted for any share splits or share dividends) during the one year period after the date on which the reimbursement was approved by shareholders, and the remaining approximately $8.4 million will be reimbursed only if the average closing price of our common shares is at least $26.00 (as adjusted for any share splits or share dividends) during the one year period between the first and second anniversaries of the date on which the reimbursement was approved by shareholders. The average closing price of our common shares was at least $26.00 during the first one year period after the date on which the reimbursement was approved by shareholders, and in August 2015, we paid $8.4 million to Related/Corvex. Transactions with Prior Related Persons: RMR : Prior to entering into the Termination and Cooperation Agreement with RMR, as further described below, we had three primary agreements with RMR and its affiliates to provide management and administrative services to us: (i) a business management agreement, which relates to our business generally, (ii) a property management agreement, which relates to our property level operations, and (iii) an Australia business and property management agreement, which relates to our Australian properties. During the time we were externally managed by RMR, one of our former Managing Trustees, Mr. Barry Portnoy, was Chairman, majority owner and an employee of RMR. Another former Managing Trustee and our former President, Mr. Adam Portnoy, is the son of Mr. Barry Portnoy, and was an owner, President, Chief Executive Officer and a director of RMR. Mr. John Popeo, our former Treasurer and Chief Financial Officer, and Mr. David Lepore, our former Chief Operating Officer, were also officers of RMR. Two of our former independent Trustees served as independent directors or independent trustees of other public companies to which RMR provided management services. Mr. Barry Portnoy served as a managing director or managing trustee of a majority of the public companies to which RMR or its affiliate provided management services and Mr. Adam Portnoy served as a managing trustee of a majority of those companies. In addition, officers of RMR served as officers of those companies. As a result of the removal, effective March 25, 2014, of Mr. Barry Portnoy and Mr. Adam Portnoy as Trustees of the Company and the resignation on May 23, 2014, of Mr. Adam D. Portnoy, Mr. John C. Popeo, Mr. David M. Lepore and other officers of RMR from their respective positions as officers of the Company, they, RMR, RMR Australia Asset Management Pty Limited, or RMR Australia, GOV, SIR and AIC have ceased to be related persons of the Company. Therefore, we only present related person transactions with these entities through June 30, 2014. On December 19, 2013, we and RMR entered into an amended and restated business management agreement, effective with respect to services performed on and after January 1, 2014. Under the terms of this amended and restated business management agreement: • The annual amount of the base management fee which was to be paid to RMR by us for each applicable period was to be equal to the lesser of: • the sum of (a) 0.7% of the average historical cost of our real estate investments during such period up to $250.0 million , plus (b) 1.0% of the average historical cost of our real estate investments located outside the United States, Puerto Rico and Canada during such period, plus (c) 0.5% of the average historical cost of our real estate investments during such period exceeding $250.0 million and the average historical cost of our real estate investments located outside the United States, Puerto Rico and Canada combined; and • the sum of (a) 0.7% of the average closing price per share of our common shares on the NYSE, during such period, multiplied by the average number of our common shares outstanding during such period, plus the daily weighted average of the aggregate liquidation preference of each class of our preferred shares outstanding during such period, plus the daily weighted average of the aggregate principal amount of our consolidated indebtedness during such period, or, together, our Average Market Capitalization, up to $250.0 million , plus (b) 1.0% of the average historical cost of our real estate investments located outside the United States, Puerto Rico and Canada during such period, plus (c) 0.5% of our Average Market Capitalization exceeding $250.0 million and the average historical cost of our real estate investments located outside the United States, Puerto Rico and Canada during such period combined. The average historical cost of our real estate investments will include our consolidated assets invested, directly or indirectly, in equity interests in or loans secured by real estate and personal property owned in connection with such real estate (including acquisition related costs and costs which may be allocated to intangibles or are unallocated), all before reserves for depreciation, amortization, impairment charges or bad debts or other similar noncash reserves. Our investment in SIR (or in any other company which has a management agreement with RMR) is not counted for purposes of calculating the fees payable by us to RMR. • Although the fee calculation is stated in annual percentages, the base management fee is paid monthly to RMR, ninety percent ( 90% ) in cash and ten percent ( 10% ) in our common shares, which shall be fully-vested when issued. The number of our common shares to be issued in payment of the base management fee for each month is equal to the value of 10.0% of the total base management fee for that month divided by the average daily closing price of our common shares during that month. • The incentive management fee which may be earned by RMR for an annual period will be an amount, subject to a cap based on the value of our outstanding common shares, equal to 12.0% of the product of (a) our equity market capitalization on the last trading day on the year immediately prior to the relevant measurement period, and (b) the amount (expressed as a percentage) by which the total returns per share realized by the holders of our common shares (i.e., share price appreciation plus dividends) exceeds the total shareholder return of the SNL Office REIT Index (in each case subject to certain adjustments) for the relevant measurement period. The measurement periods are generally three -year periods ending with the year for which the incentive management fee is being calculated, with shorter periods applicable in the case of the calculation of the incentive management fee for 2014 ( one year ) and 2015 ( two years ). • The incentive management fee is payable in our common shares, with one-third of our common shares issued in payment of an incentive management fee vested on the date of issuance, and the remaining two-thirds vesting thereafter in two equal annual installments. If the issuance of common shares in payment of a portion of the base management fee or incentive management fee would be limited by applicable law and regulations, such portion of the applicable fee will instead be paid in cash. • RMR and certain eligible transferees of our common shares issued in payment of the base management fee or incentive management fee are entitled to demand registration rights, exercisable not more frequently than twice per year, and to "piggy-back" registration rights, with certain expenses to be paid by us. We and applicable selling shareholders also have agreed to indemnify each other (and their officers, trustees, directors and controlling persons) against certain liabilities, including liabilities under the Securities Act in connection with any such registration. Pursuant to our business management agreement with RMR as described above, we recognized business management fee expense of $31.7 million for the six months ended June 30, 2014. The fees for the six months ended June 30, 2014, include estimated 2014 incentive fees payable in common shares based on our common share total return. These amounts are included in general and administrative expenses, in our consolidated financial statements. In accordance with the terms of our business management agreement, as amended in December 2013, we issued 68,206 of our common shares to RMR for the six months ended June 30, 2014 as payment for 10% of the base business management fee we recognized for such period. For 2013, our business management agreement provided for the base business management fee to be paid to RMR at an annual rate equal to (a) 0.7% of the historical cost of our real estate investments, as described in the business management agreement, located in the United States, Puerto Rico or Canada, for the first $250.0 million of such investments, and 0.5% thereafter, plus (b) 1.0% of the historical cost of our real estate investments located outside the United States, Puerto Rico and Canada. In addition, for 2013, our business management agreement provided for RMR to be paid an incentive fee equal to 15.0% of the product of (i) the weighted average of our common shares outstanding on a fully diluted basis during a fiscal year and (ii) the excess, if any, of the FFO Per Share, as defined in the business management agreement, for such fiscal year over the FFO Per Share for the preceding fiscal year. Our investments in GOV and SIR, which are described below, were not counted for purposes of determining the business management fees payable by us to RMR; however, we reported the business management fees payable to RMR by SIR in our consolidated 2013 results until we deconsolidated our investment in SIR on July 2, 2013. The business management fees, we and SIR (while SIR was a consolidated subsidiary of ours) recognized on a consolidated basis were $43.3 million for 2013. This amount is included in general and administrative expenses and income from discontinued operations, as appropriate, in our consolidated financial statements. No incentive fees were paid by us to RMR for 2013. Our property management agreement with RMR provided for management fees equal to 3.0% of gross collected rents and construction supervision fees for construction equal to 5.0% of construction costs. The aggregate property management and construction supervision fees we and SIR (while SIR was a consolidated subsidiary of ours) recognized on a consolidated basis were $13.8 million for the six months ended June 30, 2014, and $32.5 million for 2013. These amounts are included in operating expenses and income from discontinued operations or have been capitalized, as appropriate, in our consolidated financial statements. MacarthurCook Fund Management Limited (MacarthurCook) previously provided us with business and property management services related to our Australian properties. Our contract with MacarthurCook terminated on January 31, 2013, and on that date we entered into a business and property management agreement (Australia Management Agreement) with RMR Australia for the benefit of CWH Australia Trust, a subsidiary of ours (CWHAT). RMR Australia is owned by two of our former Trustees and our former President and it has been granted an Australian financial services license by the Australian Securities & Investments Commission. The Australia Management Agreement provides for compensation to RMR Australia for business management and real estate investment services at an annual rate equal to 0.5% of the average historical cost of CWHAT's real estate investments, as described in the Australia Management Agreement. The Australia Management Agreement also provides for additional compensation to RMR Australia (i) for property management services at an annual rate equal to 50% of the difference between 3.0% of collected gross rents and the aggregate of all amounts paid or payable by or on behalf of CWHAT to third party property managers, and (ii) for construction supervision services at an annual rate equal to 50% of the difference between 5.0% of constructions costs and any amounts paid to third parties for construction management and/or supervision. Similar to our prior arrangement with respect to fees we paid to MacarthurCook, RMR has agreed to waive half of the fees payable by us under our property management agreement with RMR and half of the business management fees otherwise payable by us under our business management agreement with RMR related to real estate investments that are subject to the Australia Management Agreement for so long as the Australia Management Agreement is in effect and we or any of our subsidiaries are paying the fees under that agreement. The aggregate business and property management fees we recognized pursuant to the Australia Management Agreement were $0.9 million for the six months ended June 30, 2014, which amounts are equal to the fees waived by RMR and excluded from the amount that was payable to RMR during the six months ended June 30, 2014. Pursuant to the Australia Management Agreement, we recognized aggregate business and property management fees of $1.6 million for the year ended December 31, 2013, which amount is equal to the fees waived by RMR and excluded from the amounts that were payable to RMR during 2013. For January 2013, with respect to our investments in Australia, RMR agreed to waive half of the fees payable by us under our property management agreement and half of the business management fees related to real estate investments located outside of the United States, Puerto Rico and Canada, so long as our business and property management agreement with MacarthurCook, with respect to those investments, was in effect and we or any of our subsidiaries were paying fees under that agreement. MacarthurCook earned $0.2 million in January 2013, with respect to our Australian properties, which amounts are equal to the fees waived by RMR and excluded from the amounts that were payable to RMR during those periods. RMR also provided internal audit services to us in return for our share of the total internal audit costs incurred by RMR for us and other publicly owned companies managed by RMR and its affiliates, which amounts were subject to approval by our former Compensation Committee. Our former Audit Committee appointed our Director of Internal Audit. Our and SIR's (while SIR was a consolidated subsidiary of ours) share of RMR's costs of providing this internal audit function was, on a consolidated basis, approximately $0.3 million for 2013, which amounts are included in general and administrative expenses in our consolidated financial statements. These allocated costs are in addition to the business and property management fees we and SIR paid to RMR. RMR also leased from us office space for eleven of its regional offices. We earned approximately $0.4 million for the six months ended June 30, 2014 and $0.8 million in rental income from RMR in 2013, with respect to approximately 36,500 square feet of office space, which we believe was commercially reasonable rent for this office space, not all of which was leased to RMR for the entire three -year period. These leases were terminated when our management agreements with RMR terminated. Under our share award plans, we granted restricted shares to certain employees of RMR, some of whom are our former officers. We granted a total of 73,450 restricted shares with an aggregate value of $1.7 million to such persons in 2013, based on upon the closing price of our common shares on the NYSE on the dates of grants. One fifth of those restricted shares vested on the grant dates and one fifth vests on each of the next four anniversaries of the grant dates. These share grants to RMR employees were in addition to the fees we pay to RMR. On occasion, we have entered into arrangements with former employees of RMR in connection with the termination of their employment with RMR, providing for the acceleration of vesting of restricted shares previously granted to them under our share award plan. Additionally, each of our former President, former Treasurer and former Chief Financial Officer and former Senior Vice President and former Chief Operating Officer received grants of restricted shares of other companies to which RMR provides management services in their capacities as officers of RMR. As a result of the removal of our former Trustees on March 25, 2014, the vesting of common shares previously issued to our former officers and certain employees of RMR pursuant to our equity compensation plans accelerated in accordance with the terms of their governing share grants (Note 14). Termination and Cooperation Agreement: On September 30, 2014, we entered into a termination and cooperation agreement (Cooperation Agreement) with RMR and RMR Australia (together, Manager). Under the terms of the agreement, the existing business and property management agreements with RMR terminated effective September 30, 2014. Pursuant to the Cooperation Agreement, through February 28, 2015, Manager agreed to use best efforts to assist us in the transition of our management and operations. We paid Manager $1.2 million per month for transition services from October 1, 2014 to February 28, 2015, which included continued management and other services for the Australian assets pursuant to the Australian Management Agreement. Beginning March 1, 2015, we agreed to pay Manager $0.1 million per month until we no longer required such services or until the Australia Management Agreement was terminated, which was terminated in the third quarter of 2015, effective October 31, 2015. There is no future obligation to pay any fees to Manager. RMR is responsible for any severance payments to its employees. We paid accrued vacation benefits for any of Manager’s employees that were terminated as a result of the transition and we paid Manager the $15.3 million pro-rata portion of the current year’s incentive fee under the existing business management agreement for the period from January 1, 2014 to September 30, 2014. This incentive fee relates to the business management agreement entered into prior to the election of our new Board of Trustees on May 23, 2014. There is no future obligation to pay an incentive fee to RMR. GOV: GOV was formerly our 100% owned subsidiary. In 2009, GOV completed an initial public offering pursuant to which GOV ceased to be a majority owned subsidiary of ours. To facilitate this offering, we and GOV entered into a transaction agreement that governs our separation from and relationship with GOV. Pursuant to this transaction agreement and subject to certain conditions, among other things, we granted GOV the right of first purchase to acquire any property owned by us that we determine to divest (including sale, mortgage or other financing), if the property is then, or is reasonably expected within twelve ( 12 ) months to be, majority leased to a government tenant, which right of first purchase will also apply in the event of an indirect sale of any such properties as a result of a change of control of us. On July 23, 2014, we and GOV entered into a letter agreement whereby GOV irrevocably waived and released us from the right of first purchase described above. Additionally, pursuant to the letter agreement we and GOV each agreed to waive certain consent rights over the other party’s investments in certain categories of properties. During the time we were externally managed by RMR, RMR provided management services to both us and GOV, two of our former Trustees and our former President were managing trustees of GOV and GOV’s executive officers were officers of RMR. On March 15, 2013, we sold all of our 9,950,000 common shares of GOV in a public offering for net proceeds (after deducting underwriters' discounts and commissions and expenses) of $239.6 million and we realized a gain of $66.3 million . In connection with this public offering, on March 11, 2013, we entered into a registration agreement with GOV under which we agreed to pay all expenses incurred by GOV relating to the registration and sale of our GOV common shares. We incurred and paid $0.3 million of reimbursements to GOV pursuant to this agreement during 2013. In addition, under the registration agreement, GOV agreed to indemnify us and our officers, Trustees and controlling persons, and we agreed to indemnify GOV and its officers, trustees and controlling persons, against certain liabilities related to the public offering, including liabilities under the Securities Act of 1933, as amended, (Securities Act). SIR : SIR was formerly our 100% owned subsidiary. In March 2012, SIR completed an initial public offering, or the SIR IPO. As of June 30, 2014, we owned 22,000,000 common shares of SIR, which represented approximately 36.7% of SIR’s outstanding common shares. Two of our former Trustees and our former President were managing trustees of SIR and our former Treasurer and Chief Financial Officer served as the treasurer and chief financial officer of SIR and SIR’s executive officers were officers of RMR. In addition, one of our former independent Trustees was an independent trustee of SIR. In March 2012, SIR completed an initial public offering pursuant to which it issued 9,200,000 of its common shares for net proceeds (after deducting underwriters' discounts and commissions and expenses) of $180.8 million . SIR applied those net proceeds, along with proceeds from drawings under SIR's revolving credit facility, to repay in full a $400.0 million demand promissory note that we received from SIR on February 16, 2012, along with 22,000,000 SIR common shares (including SIR common shares that had been previously issued to us in connection with SIR's formation), in exchange for our transfer to SIR of 79 properties ( 251 separate buildings or land parcels with a combined approximately 21,400,000 rentable square feet). SIR also reimbursed us for costs that we incurred in connection with SIR's organization and preparation for the SIR IPO. In March 2013, we entered into a registration agreement with SIR, pursuant to which SIR agreed to, among other things, file a registration statement with respect to an offering of up to all of the 22,000,000 common shares of SIR that we owned, and SIR filed a registration statement on Form S-3 to permit the resale by us of some or all of the common shares of SIR we owned. Under the registration agreement, we agreed to pay all expenses incurred by SIR relating to the registration and sale of the shares in an offering. We incurred and paid $0.6 million of reimbursements to SIR pursuant to this agreement. By letter dated March 31, 2014, SIR notified us that, effective that same day, SIR had elected to terminate the registration agreement with us as a result of the removal of all the former Trustees effective March 25, 2014, which constituted a change of control of us as provided in that agreement. The letter also noted that SIR would welcome the opportunity to meet with our new Board of Trustees to discuss mutually beneficial arrangements regarding the registration of the shares of SIR owned by EQC. On July 9, 2014, we sold our entire stake of 22,000,000 common shares of SIR, for $32.04 per share, raising aggregate gross proceeds of $704.8 million . As a result of this sale, we no longer hold any interest in SIR. AIC : We previously owned 12.5% of AIC, an Indiana insurance company, and, as of May 9, 2014, had invested $5.2 million in AIC since we became an equity owner of AIC in 2009. RMR, GOV, SIR and four other companies to which RMR provides management services also own shares of AIC. During the time we were externally managed by RMR, RMR provided management and administrative services to AIC pursuant to a management and administrative services agreement with AIC and a majority of the former Trustees, our former President and most of the trustees and directors of the other AIC shareholders served on the board of directors of AIC. On March 25, 2014, as a result of the removal of the former Trustees, we underwent a change in control, as defined in the shareholders’ agreement among us, the other shareholders of AIC and AIC. As a result of that change in control and in accordance with the terms of the shareholders agreement, the other shareholders of AIC, on May 9, 2014, exercised their right to purchase the 20,000 shares of AIC we then owned. We received $5.8 million in aggregate proceeds from this sale and we no longer own any interest in AIC. We previously purchased property insurance providing $500.0 million of coverage pursuant to an insurance program arranged by AIC and with respect to which AIC was a reinsurer of certain coverage amounts. This program expired in June 2014. We paid AIC a premium, including taxes and fees, of approximately $6.0 million in connection with that policy. Indemnification : Pursuant to our declaration of trust and separate indemnification agreements, we have advanced amounts incurred for legal fees and costs on behalf of certain of the former Trustees and officers with respect to the legal proceedings described in Part I, Item 3, “Legal Proceedings” in this Annual Report on Form 10-K. Pursuant to indemnification provisions in our business and property management agreements with RMR, we have also incurred legal fees and costs on behalf of RMR for claims brought against RMR in its capacity as our business and property manager with respect to certain legal proceedings described in Part I, Item 3, “Legal Proceedings” in this Annual Report on Form 10-K. For the six months ended June 30, 2014, we incurred approximately $5.4 million in such legal fees and costs, and for the year ended December 31, 2013, we incurred approximately $30.4 million in such legal fees and costs, including our costs. Settlement of Certain Tenant Litigation : On March 1, 2014, pursuant to mediation, we and an affiliate of RMR agreed to terms of a settlement of a long running litigation with an unrelated third party that was a tenant, or the Tenant, of two separate properties: one property owned by us and one property owned by the RMR affiliate. This litigation arose as a result of flooding in 1999 and 2001 at both of these properties. After the flooding, the Tenant filed a complaint seeking declaratory and injunctive relief providing that Tenant was no longer obligated to pay rent at the two properties in question and brought claims against EQC and the RMR affiliate, as landlords, for, among other things, breach of the covenants of quiet enjoyment and habitability. We and RMR counterclaimed, seeking damages based in part upon Tenant’s failure to pay rent and make repairs. The settlement agreement regarding this litigation provides for a payment by Tenant of $12.0 million to EQC and the RMR affiliate, payable in three installments ( $6.0 million on June 30, 2014 and $3.0 million on each of September 30, 2014 and December 31, 2014), split pro-rata between EQC and the RMR affiliate based upon the balance of the rent due under each lease. The total rent due under the EQC lease was approximately $9.2 million ; the total rent due under the lease with the RMR affiliate was approximately $1.1 million . This settlement was approved by the court on May 6, 2014.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following is a summary of our unaudited quarterly results of operations for 2015 and 2014 (dollars in thousands): 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 213,055 $ 203,694 $ 159,208 $ 138,934 Net income attributable to Equity Commonwealth common shareholders 6,649 5,635 23,485 36,164 Net income attributable to Equity Commonwealth common shareholders per share—basic 0.05 0.04 0.18 0.29 Net income attributable to Equity Commonwealth common shareholders per share—diluted 0.05 0.04 0.18 0.28 The decrease in the third and fourth quarter 2015 total revenues and net income attributable to Equity Commonwealth common shareholders was primarily attributable to properties sold in the second, third and fourth quarters of 2015. 2014 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 217,260 $ 215,194 $ 216,595 $ 212,808 Net income (loss) attributable to Equity Commonwealth common shareholders 9,297 (17,802 ) 149,759 (165,542 ) Net income (loss) attributable to Equity Commonwealth common shareholders per share—basic 0.08 (0.14 ) 1.16 (1.28 ) Net income (loss) attributable to Equity Commonwealth common shareholders per share—diluted 0.08 (0.14 ) 1.16 (1.28 ) Common distributions declared 0.25 — — — The decrease in the second quarter 2014 net loss attributable to Equity Commonwealth common shareholders was primarily attributable to a loss on asset impairment of $22.7 million . The increase in third quarter 2014 net income attributable to Equity Commonwealth common shareholders was largely attributable to the gain on equity investment in SIR of $171.8 million . The decrease in the fourth quarter 2014 net loss attributable to Equity Commonwealth common shareholders was impacted by a loss on asset impairment of $167.1 million .

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 16, 2016, we redeemed at par $139.1 million of our 6.25% senior unsecured notes due 2016. On February 16, 2016, we sold Executive Park ( 9 buildings), with 427,443 square feet for $50.9 million . From January 1, 2016 through February 16, 2016, share buyback activity has totaled 861,162 common shares at a weighted average price of $25.94 per share.

SCHEDULE II VALUATION AND QUALI

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Schedule II Valuation and Qualifying Accounts	Description Balance at Charged to Deductions Balance at Year Ended December 31, 2013: Allowance for doubtful accounts $ 9,962 $ 818 $ (2,895 ) $ 7,885 Year Ended December 31, 2014: Allowance for doubtful accounts $ 7,885 $ 2,196 $ (3,516 ) $ 6,565 Year Ended December 31, 2015: Allowance for doubtful accounts $ 6,565 $ 4,533 $ (3,383 ) $ 7,715

SCHEDULE III REAL ESTATE AND AC

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION	12 Months Ended
	Dec. 31, 2015
SEC Schedule III, 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 Encumbrances(1) Land Buildings and Improvements Costs Impairment/Write Downs Land Buildings and Improvements Total(2) Accumulated Depreciation(3) Date Acquired Original Construction Date 785 Schilinger Road South Mobile AL — 1,540 9,732 (3 ) — 1,540 9,729 11,269 1,990 10/22/2007 1998 Parkshore Plaza Folsom CA 41,275 4,370 41,749 3,063 (3 ) 4,370 44,809 49,179 5,086 6/16/2011 1999 Leased Land Gonzalez CA — 18,941 9,060 3,967 — 18,940 13,028 31,968 2,862 8/31/2010 - Sky Park Centre San Diego CA — 936 8,094 756 — 936 8,850 9,786 3,308 6/24/2002 1986 9110 East Nichols Avenue Centennial CO — 1,708 14,616 4,002 — 1,708 18,618 20,326 6,438 11/2/2001 1984 1225 Seventeenth Street Denver CO — 22,400 110,090 17,269 — 22,400 127,359 149,759 21,595 6/24/2009 1982 5073, 5075, & 5085 S. Syracuse Street Denver CO — 4,720 58,890 — — 4,720 58,890 63,610 8,343 4/16/2010 2007 1601 Dry Creek Drive Longmont CO — 3,714 24,397 5,535 — 3,715 29,931 33,646 9,165 10/26/2004 1982 97 Newberry Road East Windsor CT 6,375 2,960 12,360 30 — 2,943 12,407 15,350 2,865 10/24/2006 1989 33 Stiles Lane North Haven CT 2,785 2,090 9,141 216 (1,654 ) 1,799 7,994 9,793 2,161 10/24/2006 1970 1250 H Street, NW Washington DC — 5,975 53,778 10,947 (2 ) 5,975 64,723 70,698 26,030 6/23/1998 1992 Georgetown-Green and Harris Buildings Washington DC — 24,000 35,979 44 — 24,000 36,023 60,023 5,700 9/3/2009 1960;1975 802 Delaware Avenue Wilmington DE — 4,409 39,681 10,533 (11,156 ) 3,390 40,077 43,467 23,091 7/23/1998 1986 6600 North Military Trail Boca Raton FL — 15,900 129,790 123 — 15,900 129,913 145,813 16,224 1/11/2011 2008 Executive Park Atlanta GA — 13,729 78,032 6,776 (54,313 ) 10,954 33,270 44,224 14,859 7/16/2004; 7/26/2007 1972 633 Ahua Street Honolulu HI — 1,256 3 18,054 (2,912 ) 1,100 15,301 16,401 3,765 12/5/2003 2006 625 Crane Street Aurora IL — 1,180 3,411 (2 ) (2,978 ) 533 1,078 1,611 87 4/2/2007 1977 1200 Lakeside Drive Bannockburn IL — 5,846 48,568 14,768 (7,610 ) 5,858 55,714 61,572 12,601 12/29/2005 1999 600 West Chicago Avenue Chicago IL — 34,980 315,643 12,058 — 34,980 327,701 362,681 35,679 8/10/2011 1908 8750 Bryn Mawr Avenue Chicago IL — 6,600 77,764 7,400 (170 ) 6,600 84,994 91,594 11,705 10/28/2010 1985 101-115 W. Washington Street Indianapolis IN — 7,495 60,465 23,210 — 7,496 83,674 91,170 23,976 5/10/2005 1977 111 Monument Circle Indianapolis IN — 9,670 158,085 8,556 — 9,670 166,641 176,311 13,115 10/22/2012 1959;1990 109 Brookline Avenue Boston MA — 3,168 30,397 12,684 — 3,168 43,081 46,249 18,718 9/28/1995 1915 Cabot Business Park Land Mansfield MA — 1,033 — — — 1,033 — 1,033 — 8/1/2003 - 111 Market Place Baltimore MD — 6,328 54,645 16,152 — 6,328 70,797 77,125 24,753 1/28/2003 1990 25 S. Charles Street Baltimore MD — 2,830 22,996 12,678 — 2,830 35,674 38,504 12,479 7/16/2004 1972 820 W. Diamond Gaithersburg MD — 4,381 18,798 10,538 (35 ) 4,461 29,221 33,682 11,487 3/31/1997 1995 Danac Stiles Business Park Rockville MD — 7,638 62,572 6,329 (10,975 ) 6,595 58,969 65,564 18,984 7/20/2004 2002 Initial Cost to Company Cost Amount Carried at Close of Period Property City State Encumbrances(1) Land Buildings and Improvements Costs Impairment/Write Downs Land Buildings and Improvements Total(2) Accumulated Depreciation(3) Date Acquired Original Construction Date East Eisenhower Parkway Ann Arbor MI — 6,760 46,988 1,513 — 6,760 48,501 55,261 6,836 6/15/2010 1975;2006 2250 Pilot Knob Road Mendota Heights MN — 533 4,795 1,202 — 533 5,997 6,530 2,643 3/19/1998 1995 411 Farwell Avenue South St. Paul MN — 1,303 10,451 4,603 — 1,304 15,053 16,357 3,526 6/2/2004 1970 6200 Glenn Carlson Drive St. Cloud MN — 1,950 13,803 — — 1,950 13,803 15,753 2,156 10/15/2009 1999 4700 Belleview Avenue Kansas City MO — 1,165 3,097 2,895 — 1,165 5,992 7,157 1,029 7/17/2008 1986 111 River Street (4) Hoboken NJ — — 134,199 1,871 — — 136,070 136,070 21,630 8/11/2009 2002 North Point Office Complex Cleveland OH — 12,000 94,448 18,136 — 12,000 112,584 124,584 22,363 2/12/2008 1985;1989;1990 Raintree Industrial Park Solon OH — 1,808 16,620 2,270 (8,387 ) 1,339 10,972 12,311 858 7/16/2004 1975 401 Vine Street Delmont PA — 1,575 5,542 — — 1,575 5,542 7,117 1,130 10/22/2007 1999 Cherrington Corporate Center Moon Township PA — 11,369 39,892 28,367 (5,454 ) 11,164 63,010 74,174 21,480 9/14/1998; 8/23/1999 1987;1988; 1989;1990; 1500 Market Street Philadelphia PA — 18,758 167,487 104,542 (388 ) 18,758 271,641 290,399 78,551 10/10/2002 1974 1525 Locust Street Philadelphia PA — 931 8,377 1,902 — 930 10,280 11,210 4,122 6/11/1999 1987 1600 Market Street Philadelphia PA — 3,462 111,946 18,259 — 3,462 130,205 133,667 55,534 3/30/1998 1983 1735 Market Street Philadelphia PA 169,612 24,753 222,775 52,107 — 24,747 274,888 299,635 121,238 6/30/1998 1990 Foster Plaza Pittsburgh PA — 6,168 51,588 17,969 — 6,171 69,554 75,725 19,771 9/16/2005 1987;1990; 1994; 128 Crews Drive Columbia SC — 2,420 4,017 1,322 (4,012 ) 1,024 2,723 3,747 489 4/2/2007 1968 111 Southchase Boulevard Fountain Inn SC — 520 6,822 1,734 (2,912 ) 390 5,774 6,164 1,531 5/23/2007 1987 1043 Global Avenue Graniteville SC — 720 15,552 603 — 720 16,155 16,875 3,537 4/2/2007 1998 633 Frazier Drive Franklin TN — 5,800 13,190 (10 ) — 5,800 13,180 18,980 2,711 10/22/2007 1999 1601 Rio Grande Street Austin TX — 688 6,192 1,539 (23 ) 697 7,699 8,396 3,106 6/3/1999 1985 206 East 9th Street Austin TX 27,515 7,900 38,533 2,166 — 7,900 40,699 48,599 3,702 5/31/2012 1984 4515 Seton Center Parkway Austin TX — 2,038 18,338 2,731 — 2,037 21,070 23,107 9,110 10/8/1999 1997 4516 Seton Center Parkway Austin TX — 2,028 18,251 3,022 — 2,027 21,274 23,301 9,681 10/8/1999 1985 7800 Shoal Creek Boulevard Austin TX — 1,731 14,921 4,614 (14 ) 1,731 19,521 21,252 7,672 6/30/1999 1974 812 San Antonio Street Austin TX — 626 5,636 2,564 — 621 8,205 8,826 3,115 8/18/1999 1987 8701 N Mopac Austin TX — 1,574 14,168 2,677 — 1,573 16,846 18,419 6,751 8/3/1999 1982 Bridgepoint Parkway Austin TX — 7,784 70,526 10,214 (97 ) 7,785 80,642 88,427 37,559 12/5/1997 1986;1996;1997 Initial Cost to Company Cost Amount Carried at Close of Period Property City State Encumbrances(1) Land Buildings and Improvements Costs Impairment/Write Downs Land Buildings and Improvements Total(2) Accumulated Depreciation(3) Date Acquired Original Construction Date Lakewood on the Park Austin TX — 3,548 31,936 1,704 (77 ) 3,548 33,563 37,111 14,554 10/20/1998 1998 Research Park Austin TX — 15,859 60,175 14,601 — 18,411 72,224 90,635 29,564 10/7/1998 1968;1998; 2001 9840 Gateway Boulevard North El Paso TX — 1,700 9,736 (4 ) — 1,700 9,732 11,432 1,996 10/22/2007 1999 3003 South Expressway 281 Hidalgo TX — 1,480 15,533 (9 ) — 1,480 15,524 17,004 3,193 10/22/2007 1999 3330 N Washington Boulevard Arlington VA — 810 7,289 724 — 811 8,012 8,823 3,304 8/26/1998 1987 333 108th Avenue NE Bellevue WA — 14,400 136,412 1,745 — 14,400 138,157 152,557 22,060 11/12/2009 2008 600 108th Avenue NE Bellevue WA — 3,555 30,244 14,252 — 3,555 44,496 48,051 11,904 7/16/2004 1980 1331 North Center Parkway Kennewick WA — 1,850 7,339 (2 ) — 1,850 7,337 9,187 1,506 10/22/2007 1999 100 East Wisconsin Avenue Milwaukee WI — 3,150 72,113 7,733 — 3,150 79,846 82,996 11,433 8/11/2010 1989 111 East Kilbourn Avenue Milwaukee WI — 2,400 47,562 5,143 — 2,400 52,705 55,105 10,528 6/12/2008 1988 $ 247,562 $ 394,913 $ 3,065,229 $ 540,382 $ (113,172 ) $ 389,410 $ 3,497,942 $ 3,887,352 $ 898,939 Analysis of the carrying amount of real estate properties and accumulated depreciation: Real Estate Accumulated Balance at January 1, 2013 $ 7,829,409 $ 1,007,606 Additions(5) 231,485 176,777 Loss on asset impairment (384,141 ) (185,795 ) Deconsolidation of SIR (1,446,781 ) (56,023 ) Properties reclassified to discontinued operations (552,024 ) (15,471 ) Disposals (140,783 ) (32,035 ) Balance at December 31, 2013 5,537,165 895,059 Additions(5) 70,963 164,815 Loss on asset impairment (191,490 ) (6,423 ) Properties reclassified to continuing operations 341,024 5,724 Disposals (29,219 ) (28,730 ) Balance at December 31, 2014 5,728,443 1,030,445 Additions(5) 68,118 144,844 Loss on asset impairment (17,162 ) — Disposals (1,892,047 ) (276,350 ) Balance at December 31, 2015 $ 3,887,352 $ 898,939 (1) Excludes net unamortized premiums and discounts. (2) Excludes value of real estate intangibles. Aggregate cost for federal income tax purposes is approximately $4,160,805 . (3) 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. (4) Property is subject to a ground lease. (5) Includes adjustments to real estate properties additions of $(13,217) , $(20,445) and $(40,020) , and adjustments to accumulated depreciation additions of $(887) , $(1,279) and $(1,528) , related to changes in foreign currency exchange rates during 2015 , 2014 and 2013 , respectively.

SCHEDULE IV MORTGAGE LOANS ON R

SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE (Schedule)	12 Months Ended
	Dec. 31, 2015
Mortgage Loans on Real Estate [Abstract]
Schedule IV Mortgage Loans on Real Estate	Location Interest Rate Final Periodic Payment Terms Face Carrying Principal Amount of Salina, NY 6.00% 4/30/2019 Interest payable monthly in arrears. $419 due at maturity. $ 419 399 $ — Dearborn, MI 6.00% 1/24/2023 Interest payable monthly in arrears. $7,688 due at maturity. 7,688 7,688 — $ 8,107 $ 8,087 $ — Reconciliation of the carrying amount of mortgage loans at the beginning of the period: Balance at January 1, 2013 $ 1,419 New mortgage loans 7,688 Collections of principal (1,000 ) Balance at December 31, 2013 $ 8,107 Balance at December 31, 2014 $ 8,107 Balance at December 31, 2015 $ 8,107 (1) Also represents cost for federal income tax purposes.

Summary of Significant Accoun33

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
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, 2015 , unless the context indicates otherwise. The portion of a consolidated subsidiary that is not controlled by us, or the noncontrolling interest, is presented as a separate component of equity in our consolidated balance sheets. In addition, net income attributable to the noncontrolling interest is presented separately in our consolidated statements of operations. All intercompany transactions and balances have been eliminated. We account for our investments in 50% or less owned companies, including our investments in SIR (beginning on July 2, 2013 when SIR ceased to be our consolidated subsidiary through the sale date on July 9, 2014), GOV (until March 15, 2013, when we sold all of our GOV common shares) and Affiliates Insurance Company, or AIC (until May 9, 2014, when we sold all of our AIC shares), over which we can exercise influence, but do not control, using the equity method of accounting. We used the income statement method to account for issuance of common shares of beneficial interest by SIR and GOV, and shares of common stock by AIC. Under this method, gains and losses reflecting changes in the value of our investments at the date of issuance of additional common shares by SIR and GOV, or common stock by AIC, are recognized in our income statement.
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 capital or operating lease. The classification of a lease as capital 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 FASB Accounting Standards Codification ™ , or the Codification, 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 to 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 (presented in our consolidated balance sheets as acquired real estate leases) as a reduction to rental income over the remaining terms of the respective leases. We amortize capitalized below market lease values (presented in our consolidated balance sheets as assumed real estate lease obligations) 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 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, cash flow or liquidity, our decision to dispose of an asset before the end of its estimated useful life. 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, 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) recently quoted market prices, (ii) market prices for comparable properties, or (iii) the present value of future cash flows. During the years ended December 31, 2015 and 2014, we recorded a loss on asset impairment in continuing operations totaling $17.2 million and $185.1 million , respectively, to reduce the carrying value of properties to their estimated fair values (see Note 16). 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. During the year ended December 31, 2013, we recorded a loss on asset impairment of $79.8 million in discontinued operations and a loss on asset impairment of $124.3 million in continuing operations to reduce the carrying value of 39 properties ( 93 buildings) classified as held for sale to their estimated fair value less costs to sell. In addition, we recorded losses on asset impairment for properties sold during 2013 totaling $23.1 million . 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, and we have no current plans to remove any such asbestos. 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 at any of our properties that have a material adverse effect on us. However, no assurances can be given that such conditions are not present in our properties or that other costs we incur to remediate contamination will not have a material adverse effect on our business or financial condition. As of December 31, 2015, we did not have any accrued environmental remediation costs. As of December 31, 2014, accrued environmental remediation costs by us totaling $0.5 million were included in accounts payable and accrued expenses in our consolidated balance sheets.
Cash and Cash Equivalents	Cash and Cash Equivalents. Our cash and cash equivalents consists of cash maintained in time deposits, depository accounts and money market accounts. From time-to-time we may also invest in various U.S. government securities. We continually 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.
Restricted Cash	Restricted Cash. Restricted cash consists of amounts escrowed for future real estate taxes, insurance, leasing costs, capital expenditures and debt service, as required by some of our mortgage debts, as well as security deposits paid to us by some of our tenants.
Other Assets, Net	Other Assets, Net. Other assets consist principally of deferred financing fees, deferred leasing costs, capitalized lease incentives and prepaid property operating expenses. Deferred financing fees include issuance costs related to borrowings and are capitalized and amortized over the terms of the respective loans. Deferred leasing costs include brokerage, legal and other fees associated with the successful negotiation of leases and 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.
Accounting Policy for Derivative Instruments	Accounting Policy for Derivative Instruments. The Derivatives and Hedging Topic of the Codification requires companies to recognize all their derivative instruments as either assets or liabilities in the statement of financial position at fair value. The accounting for changes in the fair value of a derivative instrument depends on whether such instrument has been designated and qualifies as part of a hedging relationship and, further, on the type of hedging relationship. For those derivative instruments that are designated and qualify as hedging instruments, we must designate the hedging instrument, based upon the exposure being hedged, as a fair value hedge, cash flow hedge or a hedge of a net investment in a foreign operation. In December 2009, we entered into interest rate swap agreements that qualify as cash flow hedges. We are exposed to certain risks relating to our ongoing business operations. The primary risk managed by using derivative instruments is interest rate risk. Interest rate swaps are entered into to manage interest rate risk associated with our floating rate borrowings. We designate interest rate swaps as cash flow hedges of floating rate borrowings.
Revenue Recognition	Revenue Recognition. Rental income from operating leases, which includes rent concessions (including free rent and other lease incentives) and scheduled increases in rental rates during the lease term, 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. Tenant reimbursements and other income includes property level operating expenses reimbursed by our tenants, as well as other incidental revenues, which are recorded as expenses are incurred.
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts. We maintain an allowance for doubtful accounts for estimated losses resulting from the inability or unwillingness of certain tenants to make payments required under their leases. The computation of the allowance is based on the tenants' payment histories and current credit profiles, as well as other considerations.
Share-Based Compensation	Share-Based Compensation. All share-based compensation is measured at fair value on the grant date or date of modification, as applicable, and recognized in earnings over the requisite service period. Depending upon the settlement terms of the awards, all or a portion of the fair value of share-based awards may be presented as a liability or as equity in the consolidated balance sheets.
Earnings Per Common Share	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 or our restricted share units (RSUs) were converted into our common shares, which could result in a lower EPS amount. The effect of our series D convertible preferred shares on income from continuing operations and net income attributable to common shareholders is anti-dilutive for all periods presented.
Reclassifications	Reclassifications. Reclassifications have been made to the prior years' financial statements and notes to conform to the current year's presentation.
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 real estate investment trust. However, we are subject to certain state and local taxes without regard to our REIT status. The Income Taxes Topic of the Codification 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.
Foreign Operations	Foreign Operations. During the year ended December 31, 2015, we sold our Australian properties (Note 4) and as of December 31, 2015, we do not have any foreign operations. The U.S. dollar was the functional currency for our consolidated subsidiaries operating in the United States prior to the sale of the Australian portfolio. The functional currency for our consolidated subsidiaries in countries other than the United States was the principal currency in which the entity's assets, liabilities, income and expenses were denominated. The functional currency of our consolidated subsidiary that operated in Australia was the Australian dollar. We translated our Australian subsidiary's financial statements into U.S. dollars when we consolidated that subsidiary's financial statements on a quarterly basis. Generally, we translated assets and liabilities at the exchange rate in effect as of the balance sheet date. The resulting translation adjustments were included in cumulative other comprehensive loss in our consolidated balance sheets. We translated income statement accounts using the average exchange rate for the period and income statement accounts that include significant non-recurring transactions at the rate in effect as of the date of the transaction. We were subject to foreign currency risk due to potential fluctuations in exchange rates between Australian and U.S. currencies. Subsequent to the disposition of the Australian properties, we recognized a foreign currency exchange loss of $8.9 million in our consolidated statement of operations for the year ended December 31, 2015. The foreign currency exchange loss for the year ended December 31, 2015 relates to the change in foreign currency rates resulting in losses on cash proceeds from the Australian portfolio disposition maintained in an Australian bank account prior to the transfer of cash from our Australian subsidiary to our U.S bank accounts. As of December 31, 2015, we did no t have any cumulative foreign currency translation adjustments as the cumulative foreign currency translation adjustment of $63.2 million was reclassified from other comprehensive loss to earnings upon disposition of the Australian properties. As of December 31, 2014, cumulative foreign currency translation adjustments were $(48.9) million .
New Accounting Pronouncements	New Accounting Pronouncements. In April 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity, or ASU 2014-08. ASU 2014-08 changes the criteria for reporting a discontinued operation. Under the new pronouncement, a disposal of a part of an organization that has a major effect on its operations and financial results is a discontinued operation. We adopted ASU 2014-08 on January 1, 2015, and determined that our 2015 dispositions do not individually represent a strategic shift, as defined by the standard, that has or will have a major effect on our operations and financial results. As a result, the 2015 dispositions have not been presented as discontinued operations in the 2015 statements of operations. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers, which provides guidance for revenue recognition. This update is effective for interim and annual reporting periods beginning after December 15, 2017. We are currently in the process of evaluating the impact, if any, the adoption of this ASU will have on our consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Simplifying the Presentation of Debt Issuance Costs. This standard amends existing guidance to require the presentation of debt issuance costs in the balance sheet as a deduction from the carrying amount of the related debt liability instead of as a deferred charge. It is effective for annual reporting periods beginning after December 15, 2015, but early adoption is permitted. We do not expect that the adoption of this standard will have a material impact on our consolidated financial statements.

Organization (Tables)

Organization (Tables)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Portfolio	At December 31, 2015 , our portfolio included the following (square feet in thousands): Number of Properties Number of Buildings Square Feet Total portfolio 65 127 23,952

Real Estate Properties (Tables)

Real Estate Properties (Tables)	12 Months Ended
	Dec. 31, 2015
Real Estate [Abstract]
Summary of Properties Disposed and Income Statement Information for Properties Included in Discontinued Operations	Summarized income statement information for properties included in discontinued operations is as follows (in thousands): Year Ended December 31, 2014 2013 Rental income $ 14,243 $ 55,073 Tenant reimbursements and other income 1,900 6,842 Total revenues 16,143 61,915 Operating expenses 7,138 37,027 Depreciation and amortization — 12,550 General and administrative 10 4,268 Total expenses 7,148 53,845 Operating income 8,995 8,070 Interest and other income 2 65 Interest expense (608 ) (1,742 ) Income from discontinued operations $ 8,389 $ 6,393 During the year ended December 31, 2015 , we disposed of the following properties (dollars in thousands): Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale Properties 11350 North Meridian Street January 2015 1 1 72,264 $ 4,200 $ 766 333 Laurel Oak Drive (1) March 2015 — 1 27,164 2,450 251 1921 E. Alton Avenue March 2015 1 1 67,846 14,533 4,851 46 Inverness Center Parkway April 2015 — — — 2,000 1,857 225 Water Street (2) May 2015 1 1 318,997 — — Sorrento Valley Business Park June 2015 1 4 105,003 23,500 11,896 Illinois Center August 2015 1 2 2,090,162 376,000 26,956 16th and Race Street August 2015 1 1 608,625 43,000 7,922 185 Asylum Street September 2015 1 1 868,395 113,250 17,619 One South Church Avenue October 2015 1 1 240,811 32,000 4,282 775 Ridge Lake Boulevard October 2015 1 1 120,678 16,300 (360 ) One Park Square October 2015 1 6 259,737 34,300 9,512 Arizona Center December 2015 1 4 1,070,724 126,000 22,838 4 South 84th Avenue December 2015 1 1 236,007 18,000 8,393 Portfolio of properties 7450 Campus Drive May 2015 1 1 77,411 129 Worthington Ridge Road May 2015 1 1 227,500 599 Research Parkway May 2015 1 1 48,249 181 Marsh Hill Road May 2015 1 1 162,036 101 Barnes Road May 2015 1 1 45,755 15 Sterling Drive May 2015 1 1 173,015 35 Thorpe Avenue May 2015 1 1 79,862 50 Barnes Industrial Road North May 2015 1 1 154,255 5-9 Barnes Industrial Road May 2015 1 1 38,006 860 North Main Street May 2015 1 1 31,165 One Barnes Industrial Road South May 2015 1 1 30,170 Village Lane May 2015 1 2 58,185 100 Northfield Drive May 2015 1 1 116,986 905 Meridian Lake Drive May 2015 1 1 74,652 1717 Deerfield Road May 2015 1 1 141,186 1955 West Field Court May 2015 1 1 59,130 5015 S. Water Circle May 2015 1 1 113,524 Adams Place May 2015 1 2 230,259 Cabot Business Park May 2015 1 2 252,755 2300 Crown Colony Drive May 2015 1 1 45,974 Myles Standish Industrial Park May 2015 1 2 74,800 340 Thompson Road May 2015 1 1 25,000 100 South Charles Street May 2015 1 1 159,616 6710 Oxon Hill May 2015 1 1 118,336 8800 Queen Avenue South May 2015 1 1 280,822 Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale 9800 Sherlard Parkway May 2015 1 1 46,765 Rosedale Corporate Plaza May 2015 1 3 149,116 1000 Shelard Parkway May 2015 1 1 62,499 525 Park Street May 2015 1 1 75,636 1900 Meyer Drury Drive May 2015 1 1 65,225 131-165 West Ninth Street May 2015 1 1 75,517 7-9 Vreeland Road May 2015 1 1 155,891 5 Paragon Drive May 2015 1 1 119,089 1000 Voorhees Drive and 400 Laurel Oak Drive (1) May 2015 1 2 125,415 1601 Veterans Highway May 2015 1 1 63,608 Two Corporate Center Drive May 2015 1 1 291,230 11311 Cornell Park Drive May 2015 1 1 93,413 5300 Kings Island Drive May 2015 1 1 159,421 3 Crown Point Court May 2015 1 1 73,987 515 Pennsylvania Avenue May 2015 1 1 82,000 443 Gulph Road May 2015 1 1 21,000 4350 Northern Pike May 2015 1 1 503,885 Thunderbolt Place May 2015 1 2 100,505 6160 Kempsville Circle May 2015 1 1 129,565 448 Viking Drive May 2015 1 1 75,374 Portfolio of small office and industrial assets 45 53 5,287,790 $ 376,000 $ (8,160 ) 2501 20th Place South June 2015 1 1 125,722 420 20th Street North June 2015 1 1 514,893 Inverness Center June 2015 1 4 475,882 701 Poydras Street June 2015 1 1 1,256,971 300 North Greene Street June 2015 1 1 324,305 1320 Main Street June 2015 1 1 334,075 AL, LA, NC, SC office portfolio 6 9 3,031,848 $ 417,450 $ 41,596 12655 Olive Boulevard June 2015 1 1 98,588 1285 Fern Ridge Parkway June 2015 1 1 66,510 St. Louis portfolio (3) 2 2 165,098 $ 14,300 $ (2,349 ) 310-314 Invermay Road (4) April 2015 1 1 47,480 253-293 George Town Road (4) April 2015 1 1 143,914 7 Modal Crescent June 2015 1 1 164,160 71-93 Whiteside Road June 2015 1 1 303,488 9-13 Titanium Court June 2015 1 1 69,664 16 Rodborough Road June 2015 1 1 90,525 22 Rodborough Road June 2015 1 1 43,427 127-161 Cherry Lane June 2015 1 1 278,570 310-320 Pitt Street June 2015 1 1 313,865 Asset Date Disposed Number of Number of Square Footage Gross Sales Price Gain (Loss) on Sale 44-46 Mandarin Street June 2015 1 1 226,718 19 Leadership Way June 2015 1 1 76,714 Australia portfolio (5) 11 11 1,758,525 $ 232,955 $ (47,872 ) Widewaters Parkway August 2015 1 8 514,241 5062 Brittonfield Parkway August 2015 1 1 40,162 Woodcliff Drive August 2015 1 6 516,760 Interstate Place August 2015 1 2 61,399 1000 Pittsford - Victor Road August 2015 1 1 73,358 1200 Pittsford - Victor Road August 2015 1 1 18,900 Corporate Crossing August 2015 1 5 216,126 Canal View Boulevard August 2015 1 3 118,375 14 Classic Street August 2015 1 1 37,084 110 W Fayette Street August 2015 1 1 304,906 251 Salina Meadows Parkway August 2015 1 1 65,617 Upstate New York portfolio (3) 11 30 1,966,928 $ 104,625 $ (12,518 ) 9040 Roswell Road October 2015 1 1 178,941 The Exchange October 2015 1 2 187,632 3920 Arkwright Road October 2015 1 1 196,156 1775 West Oak Commons Court October 2015 1 1 79,854 Georgia portfolio (3) 4 5 642,583 $ 48,550 $ (3,059 ) 91 135 18,939,185 $ 1,999,413 $ 84,421 (1) This property contains three buildings. We sold one building in March 2015 and two buildings in May 2015. (2) Title to this property was transferred to the lender pursuant to a consensual foreclosure in full satisfaction of the mortgage debt with a principal balance of $40.1 million , resulting in a gain on early extinguishment of debt of $17.3 million for the year ended December 31, 2015. See Note 9 for additional information. (3) Prior to the disposition of these properties, we recorded a total impairment charge of $17.2 million during the year ended December 31, 2015, based upon updated market information in accordance with our impairment analysis procedures. (4) These properties were sold in a separate transaction to a different buyer than other Australian properties. (5) The loss on sale includes a $63.2 million cumulative foreign currency translation adjustment reclassified from cumulative other comprehensive loss due to the disposition of the Australian portfolio. During the years ended December 31, 2014 and 2013, we sold the following properties (dollars in thousands): Date Sold Number of Number of Square Footage Sales Price Gain (Loss) on Sale Sales of properties resulting in gains and losses December 2013 3 40 1,670,104 $ 89,000 $ (25,521 ) June 2013 (6) — — — 2,551 1,765 June 2013 1 1 30,105 1,600 317 March 2013 (6) — — — 1,806 1,596 January 2013 (7) 3 18 1,060,026 10,250 1,277 7 59 2,760,235 $ 105,207 $ (20,566 ) Sales of properties with previously recorded asset impairment losses: June 2014 (8) 14 43 2,784,098 $ 215,900 December 2013 2 2 77,394 $ 2,020 November 2013 18 21 2,125,278 50,500 October 2013 1 2 199,418 4,000 October 2013 1 1 665,545 13,900 October 2013 9 41 1,211,536 43,000 August 2013 1 3 129,452 4,100 June 2013 1 1 143,802 5,250 June 2013 1 2 356,045 16,300 May 2013 1 1 57,250 4,025 April 2013 1 1 618,000 830 36 75 5,583,720 $ 143,925 (6) We sold a land parcel. (7) We provided mortgage financing to the buyer, an unrelated third party, totaling $7.7 million at 6.0% per annum (Note 8). (8) In connection with this transaction, we recognized a loss on asset impairment of $2.2 million and a loss on early extinguishment of debt of $3.3 million for the year ended December 31, 2014. The sales price excludes mortgage debt repayments. These properties are included in income from discontinued operations for all years presented.
Schedule of Future Minimum Lease Payments	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, 2015 are as follows (in thousands): 2016 $ 400,987 2017 380,501 2018 353,286 2019 313,563 2020 275,406 Thereafter 1,175,661 $ 2,899,404
Schedule of Future Minimum Lease Payment Receivables	The future minimum lease payments scheduled to be paid by us during the current terms of this ground lease under which we are the lessee, as of December 31, 2015 , are as follows (in thousands): 2016 $ 1,477 2017 1,477 2018 1,483 2019 1,503 2020 1,503 Thereafter 128,491 $ 135,934

Lease Intangibles (Tables)

Lease Intangibles (Tables)	12 Months Ended
	Dec. 31, 2015
Leases [Abstract]
Summary of the Carrying Amounts for Acquired Real Estate Leases and Assumed Real Estate Lease Obligations	The following table summarizes the carrying amounts for our acquired real estate leases and assumed real estate lease obligations as of December 31, 2015 , and 2014 , and (in thousands): December 31, 2015 2014 Acquired in-place leases $ 147,056 $ 272,077 Acquired above market leases 78,210 121,969 Acquired real estate leases 225,266 394,046 Accumulated amortization, acquired in-place leases (91,301 ) (136,089 ) Accumulated amortization, acquired above market leases (45,205 ) (59,670 ) Acquired real estate leases, net $ 88,760 $ 198,287 Acquired below market leases 19,742 56,541 Accumulated amortization (15,446 ) (29,757 ) Assumed real estate lease obligations, net $ 4,296 $ 26,784
Schedule of Amortization of Lease Intangibles	Amortization of the lease intangibles for the years ended December 31, 2015 , 2014 , and 2013 , is as follows (in thousands): December 31, Income Statement Location 2015 2014 2013 Amortization of acquired in-place leases Depreciation and amortization $ 26,787 $ 40,493 $ 48,023 Amortization of acquired in-place leases Discontinued operations — — 1,720 Amortization of above and below market leases Increase (decrease) to rental income (7,515 ) (10,650 ) (10,310 ) Amortization of above and below market leases Discontinued operations — — 775
Schedule of Future Amortization of Net Intangible Lease Assets and Liabilities	Future amortization of net intangible lease assets and liabilities to be recognized by us during the current terms of our leases as of December 31, 2015 , are approximately (in thousands): 2016 $ 18,054 2017 15,213 2018 12,619 2019 8,778 2020 7,535 Thereafter 22,265 $ 84,464

Equity Investments (Tables)

Equity Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Investments	At December 31, 2015 , and 2014 , we did not have any ownership interests in equity investments. For the years ended December 31, 2014, and 2013, equity in earnings is as follows (in thousands): Year Ended December 31, 2014 2013 SIR $ 24,516 $ 21,153 GOV — 4,111 AIC (56 ) 490 $ 24,460 $ 25,754
Summary of Unaudited Income Statement Information of Equity Method Investee	The following unaudited summarized income statement information of SIR for the period from January 1, 2014, through July 9, 2014, and for the year ended December 31, 2013, is as follows (in thousands, except per share data): For the Period from January 1, 2014 through July 9, 2014 Year Ended December 31, 2013 Rental income 98,226 $ 159,011 Tenant reimbursements and other income 16,980 29,312 Total revenues 115,206 188,323 Operating expenses 20,982 36,382 Depreciation and amortization 20,832 31,091 Acquisition related costs 374 2,002 General and administrative 7,731 12,423 Total expenses 49,919 81,898 Operating income 65,287 106,425 Interest expense (7,287 ) (13,763 ) Gain on early extinguishment of debt 243 — Income before income tax expense and equity in earnings of an investee 58,243 92,662 Income tax expense (90 ) 96 Equity in earnings of an investee 32 334 Net income $ 58,185 $ 93,092 Weighted average common shares outstanding 52,394 44,565 Net income per common share $ 1.11 $ 2.09

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Other Assets [Abstract]
Summary of Deferred Financing Fees, Deferred Leasing Costs and Capitalized Lease Incentives	The following table summarizes our deferred financing fees, deferred leasing costs and capitalized lease incentives as of December 31, 2015 , and 2014 (in thousands): December 31, 2015 2014 Deferred financing fees $ 43,346 $ 41,339 Accumulated amortization (25,158 ) (24,478 ) Deferred financing fees, net $ 18,188 $ 16,861 Deferred leasing costs $ 166,390 $ 184,600 Accumulated amortization (56,162 ) (58,348 ) Deferred leasing costs, net $ 110,228 $ 126,252 Capitalized lease incentives $ 11,623 $ 22,650 Accumulated amortization (2,498 ) (7,459 ) Capitalized lease incentives, net $ 9,125 $ 15,191
Summary of Future Amortization of Deferred Leasing Costs and Capitalized Lease Incentives	Future amortization of deferred leasing costs and capitalized lease incentives to be recognized by us during the current terms of our leases as of December 31, 2015 are approximately (in thousands): Deferred Leasing Costs Capitalized Lease Incentives 2016 $ 15,933 $ 1,528 2017 14,870 1,477 2018 13,369 779 2019 12,246 704 2020 10,324 608 Thereafter 43,486 4,029 $ 110,228 $ 9,125

Indebtedness (Tables)

Indebtedness (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of Outstanding Indebtedness	At December 31, 2015 and 2014 , our outstanding indebtedness included the following (in thousands): December 31, Interest Rate at December 31, 2015 Maturity Date 2015 2014 Unsecured revolving credit facility, at LIBOR plus a premium 1.68 % 1/28/2019 $ — $ — 5-year unsecured term loan, at LIBOR plus a premium 1.83 % 1/28/2020 200,000 — 7-year unsecured term loan, at LIBOR plus a premium 2.23 % 1/28/2022 200,000 — Unsecured term loan, at LIBOR plus a premium — % — — 400,000 Unsecured floating rate debt 2.03 % (1) $ 400,000 $ 400,000 5.75% Senior Unsecured Notes due 2015 — % — $ — $ 138,773 6.25% Senior Unsecured Notes due 2016 6.25 % 8/15/2016 139,104 139,104 6.25% Senior Unsecured Notes due 2017 6.25 % 6/15/2017 250,000 250,000 6.65% Senior Unsecured Notes due 2018 6.65 % 1/15/2018 250,000 250,000 5.875% Senior Unsecured Notes due 2020 5.88 % 9/15/2020 250,000 250,000 5.75% Senior Unsecured Notes due 2042 5.75 % 8/1/2042 175,000 175,000 Unsecured fixed rate debt 6.17 % (1) $ 1,064,104 $ 1,202,877 111 Monument Circle — % — $ — $ 116,000 225 Water Street — % — — 40,059 111 East Wacker Drive — % — — 142,666 2501 20th Place South — % — — 10,267 Parkshore Plaza 5.67 % 5/1/2017 41,275 41,275 1735 Market Street (2) 5.66 % 12/2/2019 169,612 171,498 206 East 9th Street 5.69 % 1/5/2021 27,515 27,965 1320 Main Street — % — — 38,979 33 Stiles Lane 6.75 % 3/1/2022 2,785 3,132 97 Newberry Road 5.71 % 3/1/2026 6,375 6,819 Secured fixed rate debt 5.68 % (1) $ 247,562 $ 598,660 $ 1,711,666 $ 2,201,537 Unamortized net premiums and discounts (1,342 ) 6,128 $ 1,710,324 $ 2,207,665 (1) Represents weighted average interest rate at December 31, 2015 . (2) Interest on this loan is payable at LIBOR plus 2.625% but has been fixed for the first seven years to December 1, 2016 by a cash flow hedge which sets the rate at approximately 5.66% .
Schedule of Required Principal Payments on Outstanding Debt	The required principal payments due during the next five years and thereafter under all of our outstanding debt at December 31, 2015 are as follows (in thousands): 2016 $ 142,450 2017 294,865 2018 253,847 2019 164,613 2020 451,674 Thereafter 404,217 $ 1,711,666

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Schedule of Declared Distributions	The following characterizes distributions paid per common share for the years ended December 31, 2015 , 2014 , and 2013 : Year Ended December 31, 2015 2014 2013 Ordinary income — % — % — % Return of capital — % — % 100.00 % Capital gain — % 100.00 % — % Unrecaptured Section 1250 gain — % — % — % — % 100.00 % 100.00 % In 2015, our Board of Trustees declared distributions on our series D preferred shares and series E cumulative redeemable preferred shares to date as follows: Declaration Date Record Date Payment Date Series D Dividend Per Share Series E Dividend Per Share January 16, 2015 February 2, 2015 February 17, 2015 $ 0.40625 $ 0.453125 April 8, 2015 May 1, 2015 May 15, 2015 $ 0.40625 $ 0.453125 July 9, 2015 July 31, 2015 August 17, 2015 $ 0.40625 $ 0.453125 October 9, 2015 November 2, 2015 November 16, 2015 $ 0.40625 $ 0.453125

Cumulative Other Comprehensiv41

Cumulative Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Amounts Recognized in Cumulative Other Comprehensive Loss	The following tables present the amounts recognized in cumulative other comprehensive loss by component for the year ended December 31, 2015 (in thousands): Year Ended December 31, 2015 Unrealized Loss on Derivative Instruments and Other Assets Foreign Currency Translation Adjustments Total Balances as of January 1, 2015 $ (4,299 ) $ (48,917 ) $ (53,216 ) Other comprehensive loss before reclassifications (1,232 ) (14,290 ) (15,522 ) Amounts reclassified from cumulative other comprehensive loss to net income 1,844 63,207 65,051 Net current period other comprehensive income 612 48,917 49,529 Balances as of December 31, 2015 $ (3,687 ) $ — $ (3,687 )
Schedule of Reclassifications Out of Cumulative Other Comprehensive Loss	The following tables present reclassifications out of cumulative other comprehensive loss for the year ended December 31, 2015 (in thousands): Year Ended December 31, 2015 Details about Cumulative Other Comprehensive Loss Components Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income Affected Line Items in the Statement of Operations Interest rate swap contracts $ 4,924 Interest expense Foreign currency translation adjustment activity 63,207 Gain on sale of properties Realized gain on available for sale securities (3,080 ) Interest and other income $ 65,051

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 2014 2013 Current: State $ 270 $ 350 $ 519 Federal 513 — — Foreign 2,336 2,772 2,572 3,119 3,122 3,091 Deferred: Foreign (755 ) 69 (457 ) (755 ) 69 (457 ) Income tax expense $ 2,364 $ 3,191 $ 2,634
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, 2015 2014 2013 Taxes at statutory U.S. federal income tax rate 35.00 % 35.00 % 35.00 % Dividends paid deduction and net operating loss utilization (35.00 )% (35.00 )% (35.00 )% Federal taxes on built-in gain 0.50 % — % — % State, local, and foreign income taxes 1.81 % 11.73 % (1.71 )% Effective tax rate 2.31 % 11.73 % (1.71 )%

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Outstanding Interest Rate Derivatives Designated as Cash Flow Hedges of Interest Rate Risk	As of December 31, 2015 , we had the following outstanding interest rate derivatives that were designated as cash flow hedges of interest rate risk: Interest Rate Derivative Number of Instruments Notional Amount (in thousands) Interest rate swap 2 $169,612
Schedule of Fair Value of Derivative Financial Instruments	The table below presents the fair value of our derivative financial instruments as well as their classification on the consolidated balance sheets as of December 31, 2015 , and 2014 (amounts in thousands): Fair Value as of December 31, Interest Rate Derivative Designated as Hedging Instrument Balance Sheet Location 2015 2014 Pay-fixed swaps Accounts payable and accrued expenses $ 3,687 $ 7,462
Schedule of Gain or Loss Recognized on Interest Rate Derivatives Designated as Cash Flow Hedges	The table below details the location in the financial statements of the gain or loss recognized on interest rate derivatives designated as cash flow hedges for the years ended December 31, 2015 , 2014 , and 2013 (amounts in thousands): Year Ended December 31, 2015 2014 2013 Balance at beginning of period $ (7,462 ) $ (11,706 ) $ (16,624 ) Amount of loss recognized in cumulative other comprehensive loss (1,149 ) (776 ) (103 ) Amount of loss reclassified from cumulative other comprehensive loss into interest expense 4,924 5,020 5,021 Unrealized gain on derivative instruments 3,775 4,244 4,918 Balance at end of period $ (3,687 ) $ (7,462 ) $ (11,706 )

Share-Based Compensation (Table

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Restricted Share and Restricted Stock Unit Activity	The table below presents a summary of restricted share and RSU activity under the 2015 Incentive Plan and the 2012 Plan for the years ended December 31, 2015 , and 2014 , excluding restricted shares granted to our former Trustees, former officers and certain employees of RMR under the terms of our 2012 Plan (which grants are further described below): Number Weighted Number Weighted Outstanding at December 31, 2013 — $ — — $ — Granted 713,727 26.66 1,266,237 15.99 Vested (3,545 ) 26.66 — — Outstanding at December 31, 2014 710,182 1,266,237 Granted 160,906 26.46 639,250 15.47 Vested (86,517 ) 26.02 — — Forfeited (8,115 ) 26.64 (21,377 ) 15.80 Outstanding at December 31, 2015 776,456 1,884,110
Summary of Assumptions and Fair Values for Restricted Stock Units Granted in the Period	The assumptions and fair values for the RSUs granted for the years ended December 31, 2015 , and 2014 are included in the following table on a per share basis. 2015 2014 Fair value of RSUs granted $ 15.47 $ 15.99 Expected term (years) 4 4 Expected volatility — — Expected dividend yield 1.88 % 1.88 % Risk-free rate 0.81 % 0.84 %
Schedule of Shares Granted and Vested	A summary of shares granted and vested to our former Trustees, former officers and certain employees of RMR under the terms of our 2012 Plan and our 2003 Plan for the years ended December 31, 2014, and 2013, is as follows: Number Weighted Unvested shares at December 31, 2012 114,703 19.39 Granted 83,450 23.29 Vested (66,639 ) 23.06 Forfeited (600 ) 22.49 Unvested shares at December 31, 2013 130,914 20.70 Granted 4,000 23.46 Vested (134,914 ) 25.79 Unvested shares at December 31, 2014 — —

Fair Value of Assets and Liab45

Fair Value of Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value	The table below presents certain of our assets and liabilities measured at fair value during 2015 and 2014 , categorized by the level of inputs used in the valuation of each asset and liability (dollars in thousands): Fair Value at December 31, 2015 Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Description Total (Level 1) (Level 2) (Level 3) Recurring Fair Value Measurements: Effective portion of interest rate swap contracts $ (3,687 ) $ — $ (3,687 ) $ — Derivative liability (7,219 ) — — (7,219 ) Fair Value at December 31, 2014 Using Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Significant Unobservable Inputs Description Total (Level 1) (Level 2) (Level 3) Recurring Fair Value Measurements: Effective portion of interest rate swap contracts $ (7,462 ) $ — $ (7,462 ) $ — Derivative liability (6,658 ) — — (6,658 )
Schedule of Valuation Techniques and Significant Unobservable Inputs used for Level 3 Fair Value Measurements	The valuation techniques and significant unobservable inputs used for our level 3 fair value measurement at December 31, 2015 , and 2014 were as follows: Description Fair Value at December 31, 2015 Primary Valuation Technique Unobservable Inputs Rate Derivative liability $ 7,219 Monte Carlo simulation Risk-free rate 0.52% Volatility 20.0% Description Fair Value at December 31, 2014 Primary Valuation Technique Unobservable Inputs Rate Derivative liability $ 6,658 Monte Carlo simulation Risk-free rate 0.50% Volatility 20.0% The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at June 30, 2014 were as follows: Description Fair Value at June 30, 2014 Primary Valuation Techniques Unobservable Inputs Rate 225 Water Street $ 19,589 Discounted cash flows Discount rate 8% Exit capitalization rate 8% The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at December 31, 2014 were as follows: Description Fair Value at December 31, 2014 Primary Valuation Techniques Unobservable Inputs Weighted Average(1) Properties held and used on which we recognized impairment losses $ 414,625 Discounted cash flows Discount rate 10.2% Exit capitalization rate 9.1% (1) Calculated as a weighted average based on the fair value at December 31, 2014.
Schedule of Fair Value and Carrying Value of Financial Instruments	At December 31, 2015 and 2014 , the fair value of these additional financial instruments were not materially different from their carrying values, except as follows (in thousands): December 31, 2015 December 31, 2014 Carrying Amount Fair Value Carrying Amount Fair Value Senior unsecured debt and mortgage notes payable, net $ 1,710,324 $ 1,749,211 $ 2,207,665 $ 2,263,535

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2015
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, 2015 2014 2013 Numerator for earnings per common share - basic and diluted: Income (loss) from continuing operations $ 99,857 $ 21,206 $ (37,318 ) Net income attributable to noncontrolling interest in consolidated subsidiary — — (20,093 ) Preferred distributions (27,924 ) (32,095 ) (44,604 ) Excess fair value of consideration over carrying vale of preferred shares — (16,205 ) — Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders 71,933 (27,094 ) (102,015 ) Discontinued operations — 2,806 (119,649 ) Numerator for net income (loss) per share - basic and diluted $ 71,933 $ (24,288 ) $ (221,664 ) Denominator for earnings per common share - basic and diluted: Weighted average number of common shares outstanding - basic 128,621 125,163 112,378 Weighted average number of common shares outstanding - diluted (1) 129,437 125,163 112,378 Earnings per share - basic: Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders $ 0.56 $ (0.21 ) $ (0.91 ) Discontinued operations — 0.02 (1.06 ) Net income (loss) per share - basic $ 0.56 $ (0.19 ) $ (1.97 ) Earnings per share - diluted: Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders $ 0.56 $ (0.21 ) $ (0.91 ) Discontinued operations — 0.02 (1.06 ) Net income (loss) per share - diluted $ 0.56 $ (0.19 ) $ (1.97 ) Anti-dilutive securities: Effect of Series D preferred shares; 6 1/2% cumulative convertible (2) 2,363 4,175 7,298 (1) As of December 31, 2015 , we had granted RSUs to certain employees, officers, and the chairman of the Board of Trustees. The RSUs contain both service and market-based vesting components. None of the RSUs have vested. If the market-based vesting component was measured as of December 31, 2015 , 1,143 common shares would be issued to the RSU holders, and no shares would have been issued for the other periods presented. Using a weighted average basis, 816 common shares are reflected in diluted earnings per share for the year ended ended December 31, 2015 . (2) The Series D preferred shares are excluded from the diluted earnings per share calculation because including the Series D preferred shares would also require that the preferred distributions be added back to net income, resulting in anti-dilution during the periods presented.

Selected Quarterly Financial 47

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Unaudited Quarterly Results of Operations	The following is a summary of our unaudited quarterly results of operations for 2015 and 2014 (dollars in thousands): 2015 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 213,055 $ 203,694 $ 159,208 $ 138,934 Net income attributable to Equity Commonwealth common shareholders 6,649 5,635 23,485 36,164 Net income attributable to Equity Commonwealth common shareholders per share—basic 0.05 0.04 0.18 0.29 Net income attributable to Equity Commonwealth common shareholders per share—diluted 0.05 0.04 0.18 0.28 The decrease in the third and fourth quarter 2015 total revenues and net income attributable to Equity Commonwealth common shareholders was primarily attributable to properties sold in the second, third and fourth quarters of 2015. 2014 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 217,260 $ 215,194 $ 216,595 $ 212,808 Net income (loss) attributable to Equity Commonwealth common shareholders 9,297 (17,802 ) 149,759 (165,542 ) Net income (loss) attributable to Equity Commonwealth common shareholders per share—basic 0.08 (0.14 ) 1.16 (1.28 ) Net income (loss) attributable to Equity Commonwealth common shareholders per share—diluted 0.08 (0.14 ) 1.16 (1.28 ) Common distributions declared 0.25 — — —

Organization - Schedule of Port

Organization - Schedule of Portfolio (Details)	Dec. 31, 2015ft²buildingproperty	Dec. 31, 2014ft²property	Mar. 31, 2014ft²
Segment Reporting Information [Line Items]
Number of Properties | property		31
Square Footage | ft²		5,600,000	5,641,450
Consolidated portfolio
Segment Reporting Information [Line Items]
Number of Properties | property	65
Number of Buildings | building	127
Square Footage | ft²	23,952,000

Organization - Narrative (Detai

Organization - Narrative (Details) - shares	Jul. 09, 2014	Jul. 02, 2013	Mar. 12, 2012	Feb. 29, 2012	Mar. 31, 2012	Jun. 30, 2014	Jul. 03, 2013	Jul. 01, 2013	Mar. 15, 2013
SIR
Organization
Equity investments, number of shares sold (in shares)	22,000,000
Issuance of shares, net (in shares)		10,500,000				10,000,000
Ownership percentage							44.20%
Ownership Percentage	0.00%	56.00%				36.70%
Equity investments, common shares owned (in shares)		22,000,000					22,000,000
GOV
Organization
Ownership Percentage									18.20%
Equity investments, common shares owned (in shares)									9,950,000
SIR
Organization
Less than wholly owned subsidiary, common shares owned (in shares)	22,000,000					22,000,000		22,000,000
Equity investments, number of shares sold (in shares)	22,000,000
Ownership percentage prior to initial public offering			100.00%	100.00%
Issuance of shares, net (in shares)		10,500,000	9,200,000		9,200,000
Ownership Percentage	0.00%	44.20%				36.70%
SIR | Previously reported
Organization
Ownership percentage								56.00%

Summary of Significant Accoun50

Summary of Significant Accounting Policies - Narrative (Details)	1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 30, 2014USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)property
Property, Plant and Equipment [Line Items]
Foreign Currency Transaction Gain (Loss), before Tax				$ 8,857,000	$ 0	$ 0
Percentage of investments in subsidiaries				100.00%
Loss on asset impairment		$ 167,100,000	$ 22,700,000	$ 17,162,000	185,067,000	124,253,000
Loss on asset impairment in discontinuing operations						$ 79,800,000
Number of properties impaired | property						39
Number of buildings impaired | property						93
Losses on asset impairment for properties sold						$ 23,100,000
Accrued environmental remediation costs		500,000			$ 500,000
Minimum percentage of likelihood of realization of tax benefits					50.00%
Foreign currency translation adjustments		$ (48,900,000)		0	$ (48,900,000)
Total amounts reclassified				$ (65,051,000)
Maximum
Property, Plant and Equipment [Line Items]
Maximum percentage of investment accounted for under equity method of accounting				50.00%
Maximum | Buildings and improvements
Property, Plant and Equipment [Line Items]
Maximum estimated useful life				40 years
Maximum | Personal property
Property, Plant and Equipment [Line Items]
Maximum estimated useful life				12 years
Foreign Currency Translation Adjustments
Property, Plant and Equipment [Line Items]
Total amounts reclassified				$ (63,207,000)
Foreign Currency Translation Adjustments | Australia Portfolio
Property, Plant and Equipment [Line Items]
Total amounts reclassified	$ 63,200,000

Board of Trustees - Narrative (

Board of Trustees - Narrative (Details) - trustee	Jun. 16, 2015	Jul. 31, 2014	May. 23, 2014	Feb. 18, 2014
Board of Trustees
Number of trustees elected		7	7
Total number of trustees	11	11
Minimum holders of outstanding common shares consented to the proposal, reaching the required threshold (as a percent)				66.67%

Real Estate Properties - Narrat

Real Estate Properties - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2014USD ($)ft²buildingproperty	Dec. 31, 2014USD ($)ft²property	Jun. 30, 2014USD ($)	Dec. 31, 2015USD ($)ft²property	Dec. 31, 2014USD ($)ft²property	Dec. 31, 2013USD ($)
Real Estate Properties [Line Items]
Loss on asset impairment		$ 167,100	$ 22,700	$ 17,162	$ 185,067	$ 124,253
Real estate property improvements				75,700	$ 91,600	122,900
Committed expenditures on leases executed during period				$ 156,400
Square feet of leases committed for expenditures during the period | ft²				4,900,000
Committed but unspent tenant related obligations based on existing leases				$ 118,900
Number of real estate properties held for use | property	31
Number of buildings held for use | building	67
Property square feet | ft²	5,641,450	5,600,000			5,600,000
Reversal of previously recorded impairment losses	$ 4,800
Number of real estate properties held for sale | property		0		0	0
Ground lease expenses				$ 1,800	$ 1,800	$ 1,900
Disposed of by Sale
Real Estate Properties [Line Items]
Property square feet | ft²				18,939,185

Real Estate Properties - Summar

Real Estate Properties - Summary of Properties Held for Sale (Details)	Dec. 31, 2015property	Dec. 31, 2014ft²property	Mar. 31, 2014ft²
Real Estate [Abstract]
Number of Real Estate Properties Held for Sale | property	0	0
Square Footage | ft²		5,600,000	5,641,450

Real Estate Properties - Summ54

Real Estate Properties - Summary of Properties Disposed (Details) $ in Thousands	1 Months Ended										3 Months Ended		12 Months Ended
	Dec. 31, 2015USD ($)ft²buildingproperty	Oct. 31, 2015USD ($)ft²buildingproperty	Sep. 30, 2015USD ($)ft²buildingproperty	Aug. 31, 2015USD ($)ft²buildingproperty	Jun. 30, 2015USD ($)ft²buildingproperty	May. 31, 2015USD ($)ft²buildingproperty	Apr. 30, 2015USD ($)ft²buildingproperty	Mar. 31, 2015USD ($)ft²buildingproperty	Jan. 31, 2015USD ($)ft²buildingproperty	Jan. 31, 2013building	Jun. 30, 2015USD ($)ft²buildingproperty	May. 31, 2015ft²building	Dec. 31, 2015USD ($)ft²buildingproperty	Dec. 31, 2014USD ($)ft²	Dec. 31, 2013USD ($)	Mar. 31, 2014ft²
Real Estate Properties [Line Items]
Number of Buildings										18
Square Footage | ft²														5,600,000		5,641,450
Gain (Loss) on Sale | $													$ 84,421	$ 0	$ 1,596
333 Laurel Oak Drive
Real Estate Properties [Line Items]
Number of Buildings												3
Disposed of by Sale
Real Estate Properties [Line Items]
Number of Properties | property													91
Number of Buildings													135
Square Footage | ft²	18,939,185												18,939,185
Gross Sales Price | $													$ 1,999,413
Gain (Loss) on Sale | $													$ 84,421
Disposed of by Sale | 11350 North Meridian Street
Real Estate Properties [Line Items]
Number of Properties | property									1
Number of Buildings									1
Square Footage | ft²									72,264
Gross Sales Price | $									$ 4,200
Gain (Loss) on Sale | $									$ 766
Disposed of by Sale | 333 Laurel Oak Drive
Real Estate Properties [Line Items]
Number of Properties | property								0
Number of Buildings						2		1
Square Footage | ft²								27,164
Gross Sales Price | $								$ 2,450
Gain (Loss) on Sale | $								$ 251
Disposed of by Sale | 1921 E. Alton Avenue
Real Estate Properties [Line Items]
Number of Properties | property								1
Number of Buildings								1
Square Footage | ft²								67,846
Gross Sales Price | $								$ 14,533
Gain (Loss) on Sale | $								$ 4,851
Disposed of by Sale | 46 Inverness Center Parkway
Real Estate Properties [Line Items]
Number of Properties | property							0
Number of Buildings							0
Square Footage | ft²							0
Gross Sales Price | $							$ 2,000
Gain (Loss) on Sale | $							$ 1,857
Disposed of by Sale | Sorrento Valley Business Park
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					4
Square Footage | ft²					105,003						105,003
Gross Sales Price | $					$ 23,500
Gain (Loss) on Sale | $					$ 11,896
Disposed of by Sale | Illinois Center
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				2
Square Footage | ft²				2,090,162
Gross Sales Price | $				$ 376,000
Gain (Loss) on Sale | $				$ 26,956
Disposed of by Sale | 16th and Race Street
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				608,625
Gross Sales Price | $				$ 43,000
Gain (Loss) on Sale | $				$ 7,922
Disposed of by Sale | 185 Asylum Street
Real Estate Properties [Line Items]
Number of Properties | property			1
Number of Buildings			1
Square Footage | ft²			868,395
Gross Sales Price | $			$ 113,250
Gain (Loss) on Sale | $			$ 17,619
Disposed of by Sale | One South Church Avenue
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		1
Square Footage | ft²		240,811
Gross Sales Price | $		$ 32,000
Gain (Loss) on Sale | $		$ 4,282
Disposed of by Sale | 775 Ridge Lake Boulevard
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		1
Square Footage | ft²		120,678
Gross Sales Price | $		$ 16,300
Gain (Loss) on Sale | $		$ (360)
Disposed of by Sale | One Park Square
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		6
Square Footage | ft²		259,737
Gross Sales Price | $		$ 34,300
Gain (Loss) on Sale | $		$ 9,512
Disposed of by Sale | Arizona Center
Real Estate Properties [Line Items]
Number of Properties | property	1
Number of Buildings	4
Square Footage | ft²	1,070,724												1,070,724
Gross Sales Price | $	$ 126,000
Gain (Loss) on Sale | $	$ 22,838
Disposed of by Sale | 4 South 84th Avenue
Real Estate Properties [Line Items]
Number of Properties | property	1
Number of Buildings	1
Square Footage | ft²	236,007												236,007
Gross Sales Price | $	$ 18,000
Gain (Loss) on Sale | $	$ 8,393
Disposed of by Sale | 7450 Campus Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						77,411						77,411
Disposed of by Sale | 129 Worthington Ridge Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						227,500						227,500
Disposed of by Sale | 599 Research Parkway
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						48,249						48,249
Disposed of by Sale | 181 Marsh Hill Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						162,036						162,036
Disposed of by Sale | 101 Barnes Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						45,755						45,755
Disposed of by Sale | 15 Sterling Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						173,015						173,015
Disposed of by Sale | 35 Thorpe Avenue
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						79,862						79,862
Disposed of by Sale | 50 Barnes Industrial Road North
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						154,255						154,255
Disposed of by Sale | 5-9 Barnes Industrial Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						38,006						38,006
Disposed of by Sale | 860 North Main Street
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						31,165						31,165
Disposed of by Sale | One Barnes Industrial Road South
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						30,170						30,170
Disposed of by Sale | Village Lane
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						58,185						58,185
Disposed of by Sale | 100 Northfield Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						116,986						116,986
Disposed of by Sale | 905 Meridian Lake Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						74,652						74,652
Disposed of by Sale | 1717 Deerfield Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						141,186						141,186
Disposed of by Sale | 1955 West Field Court
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						59,130						59,130
Disposed of by Sale | 5015 S. Water Circle
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						113,524						113,524
Disposed of by Sale | Adams Place
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						230,259						230,259
Disposed of by Sale | Cabot Business Park
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						252,755						252,755
Disposed of by Sale | 2300 Crown Colony Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						45,974						45,974
Disposed of by Sale | Myles Standish Industrial Park
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						74,800						74,800
Disposed of by Sale | 340 Thompson Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						25,000						25,000
Disposed of by Sale | 100 South Charles Street
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						159,616						159,616
Disposed of by Sale | 6710 Oxon Hill
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						118,336						118,336
Disposed of by Sale | 8800 Queen Avenue South
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						280,822						280,822
Disposed of by Sale | 9800 Sherlard Parkway
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						46,765						46,765
Disposed of by Sale | Rosedale Corporate Plaza
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						3
Square Footage | ft²						149,116						149,116
Disposed of by Sale | 1000 Shelard Parkway
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						62,499						62,499
Disposed of by Sale | 525 Park Street
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						75,636						75,636
Disposed of by Sale | 1900 Meyer Drury Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						65,225						65,225
Disposed of by Sale | 131-165 West Ninth Street
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						75,517						75,517
Disposed of by Sale | 7-9 Vreeland Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						155,891						155,891
Disposed of by Sale | 5 Paragon Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						119,089						119,089
Disposed of by Sale | 1000 Voorhees Drive and 400 Laurel Oak Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						125,415						125,415
Disposed of by Sale | 1601 Veterans Highway
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						63,608						63,608
Disposed of by Sale | Two Corporate Center Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						291,230						291,230
Disposed of by Sale | 11311 Cornell Center Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						93,413						93,413
Disposed of by Sale | 5300 Kings Island Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						159,421						159,421
Disposed of by Sale | 3 Crown Point Court
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						73,987						73,987
Disposed of by Sale | 515 Pennsylvania Avenue
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						82,000						82,000
Disposed of by Sale | 443 Gulph Road
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						21,000						21,000
Disposed of by Sale | 4350 Northern Pike
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						503,885						503,885
Disposed of by Sale | Thunderbolt Place
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						2
Square Footage | ft²						100,505						100,505
Disposed of by Sale | 6160 Kempsville Circle
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						129,565						129,565
Disposed of by Sale | 448 Viking Drive
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						75,374						75,374
Disposed of by Sale | Portfolio of Small Office and Industrial Assets
Real Estate Properties [Line Items]
Number of Properties | property						45
Number of Buildings						53
Square Footage | ft²						5,287,790						5,287,790
Gross Sales Price | $						$ 376,000
Gain (Loss) on Sale | $						$ (8,160)
Disposed of by Sale | 2501 20th Place South
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					125,722						125,722
Disposed of by Sale | 420 20th Street North
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					514,893						514,893
Disposed of by Sale | Inverness Center
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					4
Square Footage | ft²					475,882						475,882
Disposed of by Sale | 701 Poydras Street
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					1,256,971						1,256,971
Disposed of by Sale | 300 North Greene Street
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					324,305						324,305
Disposed of by Sale | 1320 Main Street
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					334,075						334,075
Disposed of by Sale | AL, LA, NC, SC Office Portfolio
Real Estate Properties [Line Items]
Number of Properties | property					6
Number of Buildings					9
Square Footage | ft²					3,031,848						3,031,848
Gross Sales Price | $					$ 417,450
Gain (Loss) on Sale | $					$ 41,596
Disposed of by Sale | 12655 Olive Boulevard
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					98,588						98,588
Disposed of by Sale | 1285 Fern Ridge Parkway
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					66,510						66,510
Disposed of by Sale | St. Louis Portfolio
Real Estate Properties [Line Items]
Number of Properties | property					2
Number of Buildings					2
Square Footage | ft²					165,098						165,098
Gross Sales Price | $					$ 14,300
Gain (Loss) on Sale | $					$ (2,349)
Disposed of by Sale | 310-314 Invermay Road
Real Estate Properties [Line Items]
Number of Properties | property							1
Number of Buildings							1
Square Footage | ft²							47,480
Disposed of by Sale | 253-293 George Town Road
Real Estate Properties [Line Items]
Number of Properties | property							1
Number of Buildings							1
Square Footage | ft²							143,914
Disposed of by Sale | 7 Modal Crescent
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					164,160						164,160
Disposed of by Sale | 71-93 Whiteside Road
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					303,488						303,488
Disposed of by Sale | 9-13 Titanium Court
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					69,664						69,664
Disposed of by Sale | 16 Rodborough Road
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					90,525						90,525
Disposed of by Sale | 22 Rodborough Road
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					43,427						43,427
Disposed of by Sale | 127-161 Cherry Lane
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					278,570						278,570
Disposed of by Sale | 310-320 Pitt Street
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					313,865						313,865
Disposed of by Sale | 44-46 Mandarin Street
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					226,718						226,718
Disposed of by Sale | 19 Leadership Way
Real Estate Properties [Line Items]
Number of Properties | property					1
Number of Buildings					1
Square Footage | ft²					76,714						76,714
Disposed of by Sale | Australia Portfolio
Real Estate Properties [Line Items]
Number of Properties | property											11
Number of Buildings											11
Square Footage | ft²					1,758,525						1,758,525
Gross Sales Price | $											$ 232,955
Gain (Loss) on Sale | $											$ (47,872)
Disposed of by Sale | Widewaters Parkway
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				8
Square Footage | ft²				514,241
Disposed of by Sale | 5062 Brittonfield Parkway
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				40,162
Disposed of by Sale | Woodcliff Drive
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				6
Square Footage | ft²				516,760
Disposed of by Sale | Interstate Place
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				2
Square Footage | ft²				61,399
Disposed of by Sale | 1000 Pittsford - Victor Road
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				73,358
Disposed of by Sale | 1200 Pittsford - Victor Road
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				18,900
Disposed of by Sale | Corporate Crossing
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				5
Square Footage | ft²				216,126
Disposed of by Sale | Canal View Boulevard
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				3
Square Footage | ft²				118,375
Disposed of by Sale | 14 Classic Street
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				37,084
Disposed of by Sale | 110 W Fayette Street
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				304,906
Disposed of by Sale | 251 Salina Meadows Parkway
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings				1
Square Footage | ft²				65,617
Disposed of by Sale | Upstate New York Portfolio
Real Estate Properties [Line Items]
Number of Properties | property				11
Number of Buildings				30
Square Footage | ft²				1,966,928
Gross Sales Price | $				$ 104,625
Gain (Loss) on Sale | $				$ (12,518)
Disposed of by Sale | 9040 Roswell Road
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		1
Square Footage | ft²		178,941
Disposed of by Sale | The Exchange
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		2
Square Footage | ft²		187,632
Disposed of by Sale | 3920 Arkwright Road
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		1
Square Footage | ft²		196,156
Disposed of by Sale | 1775 West Oak Commons Court
Real Estate Properties [Line Items]
Number of Properties | property		1
Number of Buildings		1
Square Footage | ft²		79,854
Disposed of by Sale | Georgia Portfolio
Real Estate Properties [Line Items]
Number of Properties | property		4
Number of Buildings		5
Square Footage | ft²		642,583
Gross Sales Price | $		$ 48,550
Gain (Loss) on Sale | $		$ (3,059)
Foreclosure | 225 Water Street
Real Estate Properties [Line Items]
Number of Properties | property						1
Number of Buildings						1
Square Footage | ft²						318,997						318,997
Gross Sales Price | $						$ 0
Gain (Loss) on Sale | $						$ 0

Real Estate Properties - Summ55

Real Estate Properties - Summary of Properties Disposed (Footnote) (Details) $ in Thousands

1 Months Ended

3 Months Ended

12 Months Ended

Jun. 30, 2015USD ($)

May. 31, 2015USD ($)building

Mar. 31, 2015building

Mar. 31, 2013USD ($)

Jan. 31, 2013building

Jun. 30, 2015building

May. 31, 2015USD ($)building

Dec. 31, 2014USD ($)

Jun. 30, 2014USD ($)

Dec. 31, 2015USD ($)building

Dec. 31, 2014USD ($)

Dec. 31, 2013USD ($)

Real Estate Properties [Line Items]

Number of buildings sold | building

18

Principal balance

$ 2,201,537

$ 1,711,666

$ 2,201,537

Gain (loss) on early extinguishment of debt

$ (60,000)

6,661

4,909

$ (60,052)

Loss on asset impairment

$ 167,100

$ 22,700

17,162

$ 185,067

$ 124,253

Amounts reclassified from cumulative other comprehensive loss to net income

(65,051)

Foreign Currency Translation Adjustments

Real Estate Properties [Line Items]

Amounts reclassified from cumulative other comprehensive loss to net income

$ (63,207)

Disposed of by Sale

Real Estate Properties [Line Items]

Number of buildings sold | building

135

333 Laurel Oak Drive

Real Estate Properties [Line Items]

Number of buildings sold | building

3

333 Laurel Oak Drive | Disposed of by Sale

Real Estate Properties [Line Items]

Number of buildings sold | building

2

1

225 Water Street | Mortgage notes

Real Estate Properties [Line Items]

Principal balance

$ 40,100

$ 40,100

Gain (loss) on early extinguishment of debt

$ 17,300

Australia Portfolio | Foreign Currency Translation Adjustments

Real Estate Properties [Line Items]

Amounts reclassified from cumulative other comprehensive loss to net income

$ 63,200

Australia Portfolio | Disposed of by Sale

Real Estate Properties [Line Items]

Number of buildings sold | building

11

Real Estate Properties - Summ56

Real Estate Properties - Summary of Properties Sold (Details) $ in Thousands	1 Months Ended										12 Months Ended
	Jun. 30, 2014USD ($)ft²property	Dec. 31, 2013USD ($)ft²buildingproperty	Nov. 30, 2013USD ($)ft²buildingproperty	Oct. 31, 2013USD ($)ft²buildingproperty	Aug. 31, 2013USD ($)ft²buildingproperty	Jun. 30, 2013USD ($)ft²buildingproperty	May. 31, 2013USD ($)ft²buildingproperty	Apr. 30, 2013USD ($)ft²buildingproperty	Mar. 31, 2013USD ($)ft²buildingproperty	Jan. 31, 2013USD ($)ft²buildingproperty	Dec. 31, 2015USD ($)ft²building	Dec. 31, 2014USD ($)ft²	Dec. 31, 2013USD ($)ft²buildingproperty	Mar. 31, 2014ft²
Real Estate Properties [Line Items]
Number of Properties | property										3
Number of Buildings | building										18
Square Footage | ft²												5,600,000		5,641,450
Gain (Loss) on Sale											$ 84,421	$ 0	$ 1,596
Disposed of by Sale
Real Estate Properties [Line Items]
Number of Buildings | building											135
Square Footage | ft²											18,939,185
Sales Price											$ 1,999,413
Gain (Loss) on Sale											$ 84,421
Disposed of by Sale | Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Number of Properties | property						1				3			7
Number of Buildings | building						1				18			59
Square Footage | ft²		2,760,235				30,105				1,060,026			2,760,235
Sales Price						$ 1,600				$ 10,250			$ 105,207
Gain (Loss) on Sale						$ 317				$ 1,277			$ (20,566)
Disposed of by Sale | Sales of properties with previously recorded asset impairment losses:
Real Estate Properties [Line Items]
Number of Properties | property	14		18	9	1	1	1	1					36
Number of Buildings	43		21	41	3	2	1	1					75
Square Footage | ft²	2,784,098	5,583,720	2,125,278	1,211,536	129,452	356,045	57,250	618,000					5,583,720
Sales Price	$ 215,900		$ 50,500	$ 43,000	$ 4,100	$ 16,300	$ 4,025	$ 830					$ 143,925
Gain (Loss) on Sale
Disposed of by Sale | Properties Sold in December | Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Number of Properties | property		3
Number of Buildings | building		40
Square Footage | ft²		1,670,104											1,670,104
Sales Price		$ 89,000
Gain (Loss) on Sale		$ (25,521)
Disposed of by Sale | Properties Sold in December | Sales of properties with previously recorded asset impairment losses:
Real Estate Properties [Line Items]
Number of Properties | property		2
Number of Buildings | building		2
Square Footage | ft²		77,394											77,394
Sales Price		$ 2,020
Disposed of by Sale | Land parcel | Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Number of Properties | property						0			0
Number of Buildings | building						0			0
Square Footage | ft²						0			0
Sales Price						$ 2,551			$ 1,806
Gain (Loss) on Sale						$ 1,765			$ 1,596
Disposed of by Sale | Properties Sold in October | Sales of properties with previously recorded asset impairment losses:
Real Estate Properties [Line Items]
Number of Properties | property				1
Number of Buildings | building				2
Square Footage | ft²				199,418
Sales Price				$ 4,000
Disposed of by Sale | Other Properties | Sales of properties with previously recorded asset impairment losses:
Real Estate Properties [Line Items]
Number of Properties | property				1		1
Number of Buildings | building				1		1
Square Footage | ft²				665,545		143,802
Sales Price				$ 13,900		$ 5,250

Real Estate Properties - Summ57

Real Estate Properties - Summary of Properties Sold (Footnote) (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jun. 30, 2014	Jan. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Real Estate Properties [Line Items]
Mortgage financing related to property sold					$ 7,688
Loss on asset impairment from discontinued operations			$ 0	$ (2,238)	(102,869)
Loss on early extinguishment of debt from discontinued operations			$ 0	$ (3,345)	$ (1,011)
Disposed of by Sale | Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Mortgage financing related to property sold		$ 7,700
Interest rate on real estate mortgage receivable		6.00%
Disposed of by Sale | Sales of properties with previously recorded asset impairment losses:
Real Estate Properties [Line Items]
Loss on asset impairment from discontinued operations	$ 2,200
Loss on early extinguishment of debt from discontinued operations	$ 3,300

Real Estate Properties - Summ58

Real Estate Properties - Summary of Income Statement Information for Properties Included in Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statements of Operations:
Rental income									$ 570,382	$ 691,699	$ 763,262
Tenant reimbursements and other income									144,509	170,158	189,767
Total revenues	$ 138,934	$ 159,208	$ 203,694	$ 213,055	$ 212,808	$ 216,595	$ 215,194	$ 217,260	714,891	861,857	953,029
Operating expenses									324,948	387,982	410,045
Depreciation and amortization									194,001	227,532	234,402
General and administrative									57,457	113,155	80,504
Total expenses									593,568	913,741	849,522
Operating income (loss)									121,323	(51,884)	103,507
Interest and other income									5,989	1,561	1,229
Interest expense									(107,316)	(143,230)	(173,011)
Income from discontinued operations									$ 0	8,389	6,393
Discontinued operations, properties sold
Statements of Operations:
Rental income										14,243	55,073
Tenant reimbursements and other income										1,900	6,842
Total revenues										16,143	61,915
Operating expenses										7,138	37,027
Depreciation and amortization										0	12,550
General and administrative										10	4,268
Total expenses										7,148	53,845
Operating income (loss)										8,995	8,070
Interest and other income										2	65
Interest expense										(608)	(1,742)
Income from discontinued operations										$ 8,389	$ 6,393

Real Estate Properties - Schedu

Real Estate Properties - Schedule of Future Minimum Lease Payment Receivables and Payments (Details) $ in Thousands	Dec. 31, 2015USD ($)
Future minimum lease payments receivable:
2,016	$ 400,987
2,017	380,501
2,018	353,286
2,019	313,563
2,020	275,406
Thereafter	1,175,661
Total	2,899,404
Future minimum lease payments:
2,016	1,477
2,017	1,477
2,018	1,483
2,019	1,503
2,020	1,503
Thereafter	128,491
Total	$ 135,934

Lease Intangibles - Summary of

Lease Intangibles - Summary of the Carrying Amounts for Acquired Real Estate Leases and Assumed Real Estate Lease Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	$ 225,266	$ 394,046
Acquired real estate leases, net	88,760	198,287
Assumed real estate lease obligations, net	4,296	26,784
Leases, Acquired-in-Place
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	147,056	272,077
Accumulated amortization	(91,301)	(136,089)
Leases Acquired-in-Place, Above Market Lease
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	78,210	121,969
Accumulated amortization	(45,205)	(59,670)
Leases Acquired-in-Place, Below Market Lease
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	19,742	56,541
Accumulated amortization	$ (15,446)	$ (29,757)

Lease Intangibles - Schedule of

Lease Intangibles - Schedule of Amortization of Lease Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Leases [Abstract]
Amortization of acquired in-place leases, Depreciation and amortization	$ 26,787	$ 40,493	$ 48,023
Amortization of acquired in-place leases, Discontinued operations	0	0	1,720
Amortization of above and below market leases, Increase (decrease) to rental income	(7,515)	(10,650)	(10,310)
Amortization of above and below market leases, Discontinued operations	$ 0	$ 0	$ 775

Lease Intangibles - Schedule 62

Lease Intangibles - Schedule of Future Amortization of Net Intangible Lease Assets and Liabilities (Details) $ in Thousands	Dec. 31, 2015USD ($)
Leases [Abstract]
2,016	$ 18,054
2,017	15,213
2,018	12,619
2,019	8,778
2,020	7,535
Thereafter	22,265
Total	$ 84,464

Investment in Direct Financin63

Investment in Direct Financing Lease - Narrative (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Percentage of term exceeding useful life of one office tower	75.00%
Carrying amount of net investment in direct financing lease		$ 12,500,000
Allowance for losses related to our direct financing lease		$ 0

Equity Investments - Schedule o

Equity Investments - Schedule of Equity Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Equity in earnings of investees	$ 0	$ 24,460	$ 25,754
SIR
Schedule of Equity Method Investments [Line Items]
Equity in earnings of investees		24,516	21,153
GOV
Schedule of Equity Method Investments [Line Items]
Equity in earnings of investees		0	4,111
AIC
Schedule of Equity Method Investments [Line Items]
Equity in earnings of investees		$ (56)	$ 490

Equity Investments - Narrative

Equity Investments - Narrative (Details) $ / shares in Units, $ in Thousands	Jul. 09, 2014USD ($)$ / sharesshares	May. 09, 2014USD ($)companyshares	Jul. 02, 2013USD ($)$ / sharesshares	Mar. 15, 2013USD ($)$ / sharesshares	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)$ / sharesshares	Jul. 09, 2014USD ($)$ / shares	Dec. 31, 2013USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jul. 03, 2013shares
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity investment									$ 0	$ 171,561	$ 66,293
Proceeds from issuance of common shares, net									0	0	626,809
Gain on issuance of shares by an equity investee									$ 0	$ 17,020	0
AIC
Schedule of Equity Method Investments [Line Items]
Equity investments, number of shares sold (in shares) | shares		20,000
Equity investments, proceeds from sale		$ 5,800
Ownership Percentage		0.00%
Amount invested in equity investee		$ 5,800
Number of other companies which are shareholders of related party | company		5
SIR
Schedule of Equity Method Investments [Line Items]
Equity investments, number of shares sold (in shares) | shares	22,000,000
Equity investments, proceeds from sale	$ 704,800
Price per common share (in dollars per share) | $ / shares	$ 32.04						$ 32.04
Gain on sale of equity investment	$ 171,800				$ 171,800
Ownership Percentage	0.00%		56.00%			36.70%	0.00%
Issuance of shares, net (in shares) | shares			10,500,000			10,000,000
Common stock price per share (in dollars per share) | $ / shares			$ 28.25			$ 29
Proceeds from issuance of common shares, net						$ 277,400
Gain on issuance of shares by an equity investee						$ 16,900
Equity investments, common shares owned (in shares) | shares			22,000,000									22,000,000
Less than wholly owned subsidiary, parent ownership interest percentage												44.20%
Market value of common shares exceeding carrying value			$ 17,600
Amortization of the difference between carrying value and share of underlying equity			34 years
Cash distributions							$ 20,700	$ 19,800
GOV
Schedule of Equity Method Investments [Line Items]
Ownership Percentage				18.20%
Common stock price per share (in dollars per share) | $ / shares				$ 25.20
Gain on issuance of shares by an equity investee				$ 66,300
Equity investments, common shares owned (in shares) | shares				9,950,000
Cash distributions											$ 4,300
Gross proceeds received on issuance or sale of common stock				$ 250,700
Net proceeds received on issuance or sale of common shares				$ 239,600

Equity Investments - Summary of

Equity Investments - Summary of Unaudited Income Statement Information of Equity Method Investee (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended								6 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jul. 09, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statements:
Rental income											$ 570,382	$ 691,699	$ 763,262
Tenant reimbursements and other income											144,509	170,158	189,767
Total revenues		$ 138,934	$ 159,208	$ 203,694	$ 213,055	$ 212,808	$ 216,595	$ 215,194	$ 217,260		714,891	861,857	953,029
Operating expenses											324,948	387,982	410,045
General and administrative											57,457	113,155	80,504
Total expenses											593,568	913,741	849,522
Operating income (loss)											121,323	(51,884)	103,507
Interest expense											(107,316)	(143,230)	(173,011)
Gain (loss) on early extinguishment of debt	$ (60,000)										6,661	4,909	(60,052)
Income (loss) from continuing operations before income taxes and equity in earnings of investees											102,221	(63)	(60,438)
Income tax expense											(2,364)	(3,191)	(2,634)
Equity in earnings of investees											0	24,460	25,754
Net income (loss)											$ 99,857	$ 24,012	$ (156,967)
Weighted average common shares outstanding (in shares)											128,621	125,163	112,378
Net income per common share (in dollars per share)		$ 0.29	$ 0.18	$ 0.04	$ 0.05	$ (1.28)	$ 1.16	$ (0.14)	$ 0.08		$ 0.56	$ (0.19)	$ (1.97)
SIR
Income Statements:
Rental income										$ 98,226			$ 159,011
Tenant reimbursements and other income										16,980			29,312
Total revenues										115,206			188,323
Operating expenses										20,982			36,382
Depreciation and amortization										20,832			31,091
Acquisition related costs										374			2,002
General and administrative										7,731			12,423
Total expenses										49,919			81,898
Operating income (loss)										65,287			106,425
Interest expense										(7,287)			(13,763)
Gain (loss) on early extinguishment of debt										243			0
Income (loss) from continuing operations before income taxes and equity in earnings of investees										58,243			92,662
Income tax expense										(90)			96
Equity in earnings of investees										32			334
Net income (loss)										$ 58,185			$ 93,092
Weighted average common shares outstanding (in shares)										52,394			44,565
Net income per common share (in dollars per share)										$ 1.11			$ 2.09

Other Assets - Narrative (Detai

Other Assets - Narrative (Details)	1 Months Ended					12 Months Ended
	Dec. 31, 2013buildingproperty	Sep. 30, 2013USD ($)	Jun. 30, 2013buildingproperty	Jan. 31, 2013USD ($)buildingproperty	Apr. 30, 2012USD ($)	Dec. 31, 2015USD ($)building	Dec. 31, 2013USD ($)buildingproperty	Dec. 31, 2014USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total real estate mortgage receivable included in other assets, carrying value						$ 8,087,000
Mortgage financing related to property sold							$ 7,688,000
Number of properties sold or agreed to be sold | property				3
Number of buildings sold | building				18
Real estate mortgages receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for losses related to real estate mortgages receivable						$ 0		$ 0
Sales of properties resulting in gains and losses | Properties Sold in December
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage financing related to property sold		$ 1,000,000			$ 400,000
Interest rate on real estate mortgage receivable					6.00%
Disposed of by Sale
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of buildings sold | building						135
Disposed of by Sale | Sales of properties resulting in gains and losses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage financing related to property sold				$ 7,700,000
Interest rate on real estate mortgage receivable				6.00%
Number of properties sold or agreed to be sold | property			1	3			7
Number of buildings sold | building			1	18			59
Disposed of by Sale | Sales of properties resulting in gains and losses | Properties Sold in December
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of properties sold or agreed to be sold | property	3
Number of buildings sold | building	40

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, 2015	Dec. 31, 2014
Deferred Finance Costs [Abstract]
Deferred financing fees	$ 43,346	$ 41,339
Accumulated amortization	(25,158)	(24,478)
Deferred financing fees, net	18,188	16,861
Deferred Costs, Leasing, Net [Abstract]
Deferred leasing costs	166,390	184,600
Accumulated amortization	(56,162)	(58,348)
Deferred leasing costs, net	110,228	126,252
Capital Lease Incentives, Net [Abstract]
Capitalized lease incentives	11,623	22,650
Accumulated amortization	(2,498)	(7,459)
Capitalized lease incentives, net	$ 9,125	$ 15,191

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, 2015	Dec. 31, 2014
Deferred Costs, Leasing, Amortization Expense, Fiscal Year Maturity [Abstract]
2,016	$ 15,933
2,017	14,870
2,018	13,369
2,019	12,246
2,020	10,324
Thereafter	43,486
Deferred leasing costs, net	110,228	$ 126,252
Capitalized Lease Incentives, Amortization Expense, Fiscal Year Maturity [Abstract]
2,016	1,528
2,017	1,477
2,018	779
2,019	704
2,020	608
Thereafter	4,029
Capitalized lease incentives, net	$ 9,125	$ 15,191

Indebtedness - Schedule of Outs

Indebtedness - Schedule of Outstanding Indebtedness (Details) - USD ($)	Dec. 31, 2015	May. 01, 2015	Jan. 29, 2015	Jan. 28, 2015	Dec. 31, 2014	Dec. 05, 2014
Debt Instrument [Line Items]
Outstanding indebtedness	$ 1,711,666,000				$ 2,201,537,000
Unamortized net premiums and discounts	(1,342,000)				6,128,000
Total	$ 1,710,324,000				2,207,665,000
Unsecured revolving credit facility, at LIBOR plus a premium
Debt Instrument [Line Items]
Interest rate stated percentage	1.6795%
Outstanding indebtedness	$ 0				0
5-year unsecured term loan, at LIBOR plus a premium
Debt Instrument [Line Items]
Interest rate stated percentage	1.8295%
Outstanding indebtedness	$ 200,000,000				0
Total	$ 200,000,000		$ 200,000,000
7-year unsecured term loan, at LIBOR plus a premium
Debt Instrument [Line Items]
Interest rate stated percentage	2.2295%
Outstanding indebtedness	$ 200,000,000				0
Total	$ 200,000,000		$ 200,000,000
Unsecured term loan, at LIBOR plus a premium
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0			$ 500,000,000	400,000,000	$ 400,000,000
Unsecured floating rate debt
Debt Instrument [Line Items]
Interest rate stated percentage	2.03%
Outstanding indebtedness	$ 400,000,000				400,000,000
5.75% Senior Unsecured Notes due 2015
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%	5.75%
Outstanding indebtedness	$ 0				138,773,000
6.25% Senior Unsecured Notes due 2016
Debt Instrument [Line Items]
Interest rate stated percentage	6.25%
Outstanding indebtedness	$ 139,104,000				139,104,000
6.25% Senior Unsecured Notes due 2017
Debt Instrument [Line Items]
Interest rate stated percentage	6.25%
Outstanding indebtedness	$ 250,000,000				250,000,000
6.65% Senior Unsecured Notes due 2018
Debt Instrument [Line Items]
Interest rate stated percentage	6.65%
Outstanding indebtedness	$ 250,000,000				250,000,000
5.875% Senior Unsecured Notes due 2020
Debt Instrument [Line Items]
Interest rate stated percentage	5.875%
Outstanding indebtedness	$ 250,000,000				250,000,000
5.75% Senior Unsecured Notes due 2042
Debt Instrument [Line Items]
Interest rate stated percentage	5.75%
Outstanding indebtedness	$ 175,000,000				175,000,000
Unsecured fixed rate debt
Debt Instrument [Line Items]
Interest rate stated percentage	6.17%
Outstanding indebtedness	$ 1,064,104,000				1,202,877,000
Mortgage Notes Payable Encumbering 111 Monument Circle
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0				116,000,000
Mortgage Notes Payable Encumbering 225 Water Street
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0				40,059,000
Mortgage Notes Payable Encumbering 111 East Wacker Drive
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0				142,666,000
Mortgage Notes Payable Encumbering 2501 20th Place South
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0				10,267,000
Mortgage Notes Payable Encumbering Parkshore Plaza
Debt Instrument [Line Items]
Interest rate stated percentage	5.67%
Outstanding indebtedness	$ 41,275,000				41,275,000
Mortgage Notes Payable Encumbering 1735 Market Street
Debt Instrument [Line Items]
Interest rate stated percentage	5.66%
Outstanding indebtedness	$ 169,612,000				171,498,000
Mortgage Notes Payable Encumbering 206 East 9th Street
Debt Instrument [Line Items]
Interest rate stated percentage	5.69%
Outstanding indebtedness	$ 27,515,000				27,965,000
Mortgage Notes Payable Encumbering 1320 Main Street
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	$ 0				38,979,000
Mortgage Notes Payable Encumbering 33 Stiles Lane
Debt Instrument [Line Items]
Interest rate stated percentage	6.75%
Outstanding indebtedness	$ 2,785,000				3,132,000
Mortgage Notes Payable Encumbering 97 Newberry Road
Debt Instrument [Line Items]
Interest rate stated percentage	5.71%
Outstanding indebtedness	$ 6,375,000				6,819,000
Secured Fixed Rate Debt
Debt Instrument [Line Items]
Interest rate stated percentage	5.68%
Outstanding indebtedness	$ 247,562,000				$ 598,660,000

Indebtedness - Schedule of Ou71

Indebtedness - Schedule of Outstanding Indebtedness (Footnote) (Details)	12 Months Ended
	Dec. 31, 2015
Mortgage Notes Payable Encumbering 1735 Market Street
Debt Instrument [Line Items]
Variable rate basis	LIBOR
Period for which interest on loan payable is fixed by a cash flow hedge	7 years
Interest accrual rate	5.66%
LIBOR
Debt Instrument [Line Items]
Basis points on variable rate	2.625%

Indebtedness - Narrative (Detai

Indebtedness - Narrative (Details)	Dec. 01, 2015USD ($)	Aug. 03, 2015USD ($)	Jun. 05, 2015USD ($)	Jun. 03, 2015USD ($)	May. 01, 2015USD ($)	Jan. 29, 2015USD ($)option	Dec. 05, 2014USD ($)	Nov. 17, 2014USD ($)	Oct. 31, 2014USD ($)	Sep. 15, 2014USD ($)	Aug. 01, 2014USD ($)	Jun. 27, 2014USD ($)	Mar. 11, 2014USD ($)	Mar. 31, 2013USD ($)	Dec. 31, 2015USD ($)buildingproperty	May. 22, 2015	Dec. 31, 2015USD ($)buildingproperty	Dec. 31, 2015USD ($)buildingproperty	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	May. 31, 2015USD ($)	Jan. 28, 2015USD ($)
Debt Instrument [Line Items]
Outstanding indebtedness															$ 1,711,666,000		$ 1,711,666,000	$ 1,711,666,000	$ 2,201,537,000
Term loan amount outstanding															1,710,324,000		1,710,324,000	1,710,324,000	2,207,665,000
Gain (loss) on early extinguishment of debt														$ (60,000,000)				6,661,000	4,909,000	$ (60,052,000)
Outstanding principal														670,300,000
Purchase price														$ 726,200,000
Real estate properties, net															2,988,413,000		2,988,413,000	2,988,413,000	4,697,998,000
Mortgage notes payable, net															249,732,000		249,732,000	$ 249,732,000	$ 609,249,000
LIBOR
Debt Instrument [Line Items]
Basis points on variable rate																		2.625%
Revolving credit facility
Debt Instrument [Line Items]
Interest rate payable percentage																		1.68%
Revolving credit facility															0		$ 0	$ 0
Revolving credit facility | Minimum
Debt Instrument [Line Items]
Commitment fee percentage																	0.125%
Revolving credit facility | Maximum
Debt Instrument [Line Items]
Commitment fee percentage																	0.30%
Revolving credit facility | LIBOR
Debt Instrument [Line Items]
Basis points on variable rate																	1.25%
Revolving credit facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis points on variable rate																	0.875%
Revolving credit facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis points on variable rate																	1.55%
Revolving credit facility | Base rate | Minimum
Debt Instrument [Line Items]
Basis points on variable rate																	0.00%
Revolving credit facility | Base rate | Maximum
Debt Instrument [Line Items]
Basis points on variable rate																	0.55%
Unsecured revolving credit facility | Revolving credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 750,000,000																$ 750,000,000
Gain (loss) on early extinguishment of debt																		(400,000)
Number of extension options | option						2
Extension option term						6 months
Extension option fee, percent						0.075%
Amount available for borrowing															750,000,000		$ 750,000,000	750,000,000
Basis points on variable rate																			1.50%
Commitment fee percentage																			0.35%
Unsecured revolving credit facility | Letter of credit
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 100,000,000
Unsecured term loan, due December 2016
Debt Instrument [Line Items]
Repayments of debt							$ 100,000,000
Outstanding indebtedness							$ 400,000,000								$ 0		$ 0	$ 0	$ 400,000,000			$ 500,000,000
Interest rate stated percentage															0.00%		0.00%	0.00%
Basis points on variable rate																			1.85%
Loan facility, 5-year term
Debt Instrument [Line Items]
Outstanding indebtedness															$ 200,000,000		$ 200,000,000	$ 200,000,000	$ 0
Term loan amount outstanding						$ 200,000,000									$ 200,000,000		$ 200,000,000	$ 200,000,000
Interest accrual rate																		1.83%
Interest rate stated percentage															1.8295%		1.8295%	1.8295%
Loan facility, 5-year term | LIBOR
Debt Instrument [Line Items]
Basis points on variable rate																	1.40%
Loan facility, 5-year term | LIBOR | Minimum
Debt Instrument [Line Items]
Basis points on variable rate																	0.90%
Loan facility, 5-year term | LIBOR | Maximum
Debt Instrument [Line Items]
Basis points on variable rate																	1.80%
Loan facility, 5-year term | Revolving credit facility
Debt Instrument [Line Items]
Debt instrument, term						5 years
Loan facility, 7-year term
Debt Instrument [Line Items]
Outstanding indebtedness															$ 200,000,000		$ 200,000,000	$ 200,000,000	0
Term loan amount outstanding						$ 200,000,000									$ 200,000,000		$ 200,000,000	$ 200,000,000
Interest accrual rate																		2.23%
Interest rate stated percentage															2.2295%		2.2295%	2.2295%
Loan facility, 7-year term | LIBOR
Debt Instrument [Line Items]
Basis points on variable rate																	1.80%
Loan facility, 7-year term | LIBOR | Minimum
Debt Instrument [Line Items]
Basis points on variable rate																	1.40%
Loan facility, 7-year term | LIBOR | Maximum
Debt Instrument [Line Items]
Basis points on variable rate																	2.35%
Loan facility, 7-year term | Revolving credit facility
Debt Instrument [Line Items]
Debt instrument, term						7 years
Revolving credit facility and term loans
Debt Instrument [Line Items]
Additional increases in maximum amount of borrowings available						$ 1,150,000,000
5.75% Senior Unsecured Notes due 2015
Debt Instrument [Line Items]
Outstanding indebtedness															$ 0		$ 0	$ 0	138,773,000
Gain (loss) on early extinguishment of debt					$ (100,000)
Amount of debt, redeemed, defeased, or prepaid					$ 138,800,000
Interest rate stated percentage					5.75%										0.00%		0.00%	0.00%
Senior Notes 7.50% Due 2019 | Mortgage notes
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt								$ (1,800,000)
Amount of debt, redeemed, defeased, or prepaid								$ 125,000,000
Interest rate stated percentage								7.50%
Senior Notes 6.40% Due 2015 | Mortgage notes
Debt Instrument [Line Items]
Amount of debt, redeemed, defeased, or prepaid										$ 33,400,000
Interest rate stated percentage										6.40%
Mortgage notes
Debt Instrument [Line Items]
Number of real estate properties secured by mortgage | property															5		5	5
Number of buildings secured by mortgage | building															8		8	8
Real estate properties, net															$ 287,500,000		$ 287,500,000	$ 287,500,000
Mortgage notes payable, net															249,700,000		249,700,000	249,700,000
Mortgage notes | 111 East Wacker Drive
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt															(3,900,000)
Amount of debt, redeemed, defeased, or prepaid		$ 141,400,000
Mortgage notes | 1320 Main Street
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt																		(6,200,000)
Amount of debt, redeemed, defeased, or prepaid				$ 38,700,000
Mortgage notes | 225 Water Street in Jacksonville, Florida
Debt Instrument [Line Items]
Outstanding indebtedness																					$ 40,100,000
Gain (loss) on early extinguishment of debt																		17,300,000
Interest accrual rate																10.03%
Default interest																4.00%
Mortgage notes | Mortgage notes
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt												$ (3,300,000)
Mortgage Notes Payable Encumbering 111 Monument Circle
Debt Instrument [Line Items]
Outstanding indebtedness															$ 0		$ 0	$ 0	$ 116,000,000
Interest rate stated percentage															0.00%		0.00%	0.00%
Mortgage Notes Payable Encumbering 111 Monument Circle | Mortgage notes
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt	$ 600,000
Amount of debt, redeemed, defeased, or prepaid	$ 116,000,000
Interest rate stated percentage	5.24%
7.36% Mortgage Debt | Mortgage notes | 2501 20th Place South
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt																		$ (600,000)
Amount of debt, redeemed, defeased, or prepaid			$ 10,000,000
Interest rate stated percentage			7.36%
Mortgage Notes Payable Encumbering 6200 Glenn Carlson Drive | Mortgage notes
Debt Instrument [Line Items]
Repayments of debt									$ 7,800,000
Mortgage Notes Payable Encumbering 600 West Chicago Avenue | Mortgage notes
Debt Instrument [Line Items]
Gain (loss) on early extinguishment of debt											$ 6,700,000
Amount of debt, redeemed, defeased, or prepaid											$ 265,000,000
Interest rate stated percentage											5.68%
Mortgage Notes Payable Six Point One Four Percent Due in 2023 | Mortgage notes
Debt Instrument [Line Items]
Amount of debt, redeemed, defeased, or prepaid												$ 11,200,000
Interest rate stated percentage												6.14%
Mortgage Notes Payable 5.78% Due in 2015 | Mortgage notes
Debt Instrument [Line Items]
Amount of debt, redeemed, defeased, or prepaid												$ 8,500,000
Interest rate stated percentage												5.78%
Mortgage Notes Payable Encumbering 3920 Arkwright Road | Mortgage notes
Debt Instrument [Line Items]
Amount of debt, redeemed, defeased, or prepaid													$ 12,000,000
Interest rate stated percentage													4.95%

Indebtedness - Schedule of Requ

Indebtedness - Schedule of Required Principal Payments on Outstanding Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
2,016	$ 142,450
2,017	294,865
2,018	253,847
2,019	164,613
2,020	451,674
Thereafter	404,217
Total	$ 1,711,666	$ 2,201,537

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details)	Mar. 25, 2014USD ($)$ / sharesshares	Jan. 31, 2014USD ($)$ / shares	Dec. 31, 2014$ / sharesshares	Sep. 30, 2014$ / shares	Jun. 30, 2014$ / shares	Mar. 31, 2014$ / shares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)	Sep. 14, 2015USD ($)	Aug. 24, 2015USD ($)
Class of Stock [Line Items]
Distributions on common stock declared (in dollars per share) | $ / shares		$ 0.25	$ 0	$ 0	$ 0	$ 0.25
Distributions paid or declared on common shares | $		$ 29,600,000
Distribution for the excess of the market value of common shares issued above carrying value of series D preferred shares redeemed | $							$ 0	$ 16,205,000	$ 0
Distribution percentage to shareholders consisting of an alternative minimum tax adjustment							0.00%	15.41%	0.00%
Common Shares
Class of Stock [Line Items]
Common shares issued to holders of preferred shares (in shares)							144	10,412,499
Stock repurchase program, authorized amount | $											$ 100,000,000
Stock repurchase program, additional authorized amount | $										$ 100,000,000
Number of shares repurchased (in shares)							3,410,300
Price per common share (in dollars per share) | $ / shares							$ 25.76
Common shares from conversion of preferred shares (in shares)							2,363,103
Common Shares | Fundamental change conversion right
Class of Stock [Line Items]
Preferred shares converted into common shares (in shares)	10,411,779
Series D
Class of Stock [Line Items]
Number of shares repurchased (in shares)							301	10,264,503
Preferred shares, of beneficial interest, shares outstanding (in shares)			4,915,497				4,915,196	4,915,497
Preferred shares dividend (in dollars per share) | $ / shares							$ 1.625
Preferred shares, dividend yield							6.50%	6.50%
Initial conversion rate							0.480775
Initial conversion price per share (in dollars per share) | $ / shares							$ 52
Additional common shares (in shares)							2,363,103
Liquidation preference (in dollars per share) | $ / shares	$ 25						$ 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	98.00%						98.00%
Purchase price as a percentage of liquidation preference							100.00%
Number of consecutive trading days for calculating the average closing sale price of common shares	5 days
Common shares from conversion of preferred shares (in shares)							4,915,196
Series D | Fundamental change conversion right
Class of Stock [Line Items]
Preferred shares converted into common shares (in shares)	10,263,003
Distribution for the excess of the market value of common shares issued above carrying value of series D preferred shares redeemed | $	$ 16,200,000
Series E
Class of Stock [Line Items]
Preferred shares, of beneficial interest, shares outstanding (in shares)			11,000,000				11,000,000	11,000,000
Preferred shares dividend (in dollars per share) | $ / shares							$ 1.8125
Preferred shares, dividend yield							7.25%	7.25%
Liquidation preference (in dollars per share) | $ / shares							$ 25
Redemption price (in dollars per share) | $ / shares							$ 25
RMR
Class of Stock [Line Items]
Common shares issued (in shares)								90,135

Shareholders' Equity - Schedule

Shareholders' Equity - Schedule of Distributions Paid Per Common Share (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Abstract]
Ordinary income	0.00%	0.00%	0.00%
Return of capital	0.00%	0.00%	100.00%
Capital gain	0.00%	100.00%	0.00%
Unrecaptured Section 1250 gain	0.00%	0.00%	0.00%
Common share, distributions paid	0.00%	100.00%	100.00%

Shareholders' Equity - Schedu76

Shareholders' Equity - Schedule of Declared Distributions (Details) - $ / shares	Oct. 09, 2015	Jul. 09, 2015	Apr. 08, 2015	Jan. 16, 2015
Series D
Class of Stock [Line Items]
Dividend declared (in dollars per share)	$ 0.40625	$ 0.40625	$ 0.40625	$ 0.40625
Series E
Class of Stock [Line Items]
Dividend declared (in dollars per share)	$ 0.453125	$ 0.453125	$ 0.453125	$ 0.453125

Cumulative Other Comprehensiv77

Cumulative Other Comprehensive Loss - Schedule of Amounts Recognized in Cumulative Other Comprehensive Loss (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balances as of January 1, 2015	$ (53,216)
Other comprehensive loss before reclassifications	(15,522)
Amounts reclassified from cumulative other comprehensive loss to net income	65,051
Net current period other comprehensive income	49,529
Balances as of December 31, 2015	(3,687)
Unrealized Loss on Derivative Instruments and Other Assets
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balances as of January 1, 2015	(4,299)
Other comprehensive loss before reclassifications	(1,232)
Amounts reclassified from cumulative other comprehensive loss to net income	1,844
Net current period other comprehensive income	612
Balances as of December 31, 2015	(3,687)
Foreign Currency Translation Adjustments
Amounts recognized in cumulative other comprehensive income (Loss) by component
Balances as of January 1, 2015	(48,917)
Other comprehensive loss before reclassifications	(14,290)
Amounts reclassified from cumulative other comprehensive loss to net income	63,207
Net current period other comprehensive income	48,917
Balances as of December 31, 2015	$ 0

Cumulative Other Comprehensiv78

Cumulative Other Comprehensive Loss - Schedule of Reclassifications Out of Cumulative Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassifications out of cumulative other comprehensive income (Loss)
Interest expense	$ 107,316	$ 143,230	$ 173,011
Gain on sale of properties	84,421	0	1,596
Interest and other income	(5,989)	$ (1,561)	$ (1,229)
Total amounts reclassified	(65,051)
Foreign currency translation adjustment activity
Reclassifications out of cumulative other comprehensive income (Loss)
Total amounts reclassified	(63,207)
Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income
Reclassifications out of cumulative other comprehensive income (Loss)
Total amounts reclassified	65,051
Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income | Foreign currency translation adjustment activity
Reclassifications out of cumulative other comprehensive income (Loss)
Gain on sale of properties	63,207
Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income | Realized gain on available for sale securities
Reclassifications out of cumulative other comprehensive income (Loss)
Interest and other income	(3,080)
Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income | Interest rate swap contracts
Reclassifications out of cumulative other comprehensive income (Loss)
Interest expense	$ 4,924

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
State	$ 270	$ 350	$ 519
Federal	513	0	0
Foreign	2,336	2,772	2,572
Current income tax expense (benefit)	3,119	3,122	3,091
Deferred:
Foreign	(755)	69	(457)
Deferred income tax expense (benefit)	(755)	69	(457)
Income tax expense	$ 2,364	$ 3,191	$ 2,634

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, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Taxes at statutory U.S. federal income tax rate	35.00%	35.00%	35.00%
Dividends paid deduction and net operating loss utilization	(35.00%)	(35.00%)	(35.00%)
Federal taxes on built-in gain	0.50%	0.00%	0.00%
State, local, and foreign income taxes	1.81%	11.73%	(1.71%)
Effective tax rate	2.31%	11.73%	(1.71%)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Real Estate Properties [Line Items]
Deferred tax assets		$ 2.4
Valuation allowance		0.6
Deferred tax liabilities		$ 3.1
Australian Properties
Real Estate Properties [Line Items]
Income Tax Expense (Benefit)	$ 1.6

Derivative Instruments - Narrat

Derivative Instruments - Narrative (Details)	12 Months Ended
	Dec. 31, 2015USD ($)
Derivative [Line Items]
Aggregate termination value	$ 4,100,000
Interest rate swap
Derivative [Line Items]
Fair value of derivatives in a net liability position	4,100,000
Cash flow hedging | Designated as hedging instrument
Derivative [Line Items]
Estimated gain (loss) reclassification from OCI to income	3,700,000
Cash flow hedging | Designated as hedging instrument | Interest rate swap
Derivative [Line Items]
Amount of hedged item	$ 169,600,000
Derivative, variable interest rate	LIBOR

Derivative Instruments - Schedu

Derivative Instruments - Schedule of Outstanding Interest Rate Derivatives Designated as Cash Flow Hedges of Interest Rate Risk (Details) - Interest rate swap - Cash flow hedging - Designated as hedging instrument $ in Thousands	Dec. 31, 2015USD ($)financial_instrument
Derivative [Line Items]
Number of Instruments | financial_instrument	2
Notional Amount (in thousands) | $	$ 169,612

Derivative Instruments - Sche84

Derivative Instruments - Schedule of Fair Value of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Interest rate swap | Cash flow hedging | Designated as hedging instrument | Accounts payable and accrued expenses
Derivatives, Fair Value [Line Items]
Pay-fixed swaps	$ 3,687	$ 7,462

Derivative Instruments - Sche85

Derivative Instruments - Schedule of Gain or Loss Recognized on Interest Rate Derivatives Designated as Cash Flow Hedges (Details) - Cash flow hedging - Designated as hedging instrument - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Rate Cash Flow Hedges [Roll Forward]
Balance at beginning of period	$ (7,462)	$ (11,706)	$ (16,624)
Amount of loss recognized in cumulative other comprehensive loss	(1,149)	(776)	(103)
Amount of loss reclassified from cumulative other comprehensive loss into interest expense	4,924	5,020	5,021
Unrealized gain on derivative instruments	3,775	4,244	4,918
Balance at end of period	$ (3,687)	$ (7,462)	$ (11,706)

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) $ / shares in Units, $ in Millions

Jun. 16, 2015USD ($)trustee$ / sharesshares

Jan. 28, 2015tranche$ / sharesshares

Oct. 28, 2014

Mar. 25, 2014shares

Jan. 28, 2014trustee$ / sharesshares

Jun. 30, 2014

Dec. 31, 2019shares

Dec. 31, 2018shares

Dec. 31, 2017shares

Dec. 31, 2016shares

Dec. 31, 2015USD ($)tranche$ / sharesshares

Dec. 31, 2014USD ($)$ / sharesshares

Dec. 31, 2013USD ($)$ / sharesshares

Jul. 31, 2014trustee

Jul. 09, 2014$ / shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of independent trustees | trustee

11

11

Number of equity awards granted (in shares)

4,000

83,450

Granted (in dollars per share) | $ / shares

$ 23.46

$ 23.29

Unvested Number of Shares, Ending (in shares)

0

130,914

Vested (in shares)

134,914

66,639

Number of independent trustees | trustee

5

Common shares of beneficial interest, par value (in dollars per share) | $ / shares

$ 0.01

$ 0.01

SIR

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation expense | $

$ 0.4

Price per common share (in dollars per share) | $ / shares

$ 32.04

Common Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Price per common share (in dollars per share) | $ / shares

$ 25.76

Vesting on January 28, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percent

20.00%

Vesting on January 28, 2019

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percent

20.00%

Trustees | Common Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common shares granted in period (in shares)

2,000

Common shares of beneficial interest, par value (in dollars per share) | $ / shares

$ 0.01

Price per common share (in dollars per share) | $ / shares

$ 23.46

Number of trustees | trustee

2

Officers and Employees | Employee Stock | RMR

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation expense | $

$ 3.4

Officers and Employees | Employee Stock | Common Stock | RMR

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common shares issued (in shares)

130,914

Restricted shares

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of independent trustees | trustee

9

Share based compensation amount | $

$ 0.1

Number of equity awards granted (in shares)

34,587

126,319

160,906

713,727

Price per share (in dollars per share) | $ / shares

$ 26.02

Vesting period

1 year

4 years

Granted (in dollars per share) | $ / shares

$ 26.58

$ 26.46

$ 26.66

Unvested Number of Shares, Ending (in shares)

776,456

710,182

0

Vested (in shares)

86,517

3,545

Estimated future compensation expense for unvested shares | $

$ 14.6

Weighted average period over which compensation expense will be recorded

2 years 9 months 18 days

Restricted shares | RMR

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of equity awards granted (in shares)

73,450

Vesting period

4 years

Restricted shares | Scenario, Forecast

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vested (in shares)

62,351

339,759

185,467

188,879

Restricted shares | Independent Trustee

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of equity awards granted (in shares)

3,843

Restricted stock units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected term of incentive plan after effective date (in years)

4 years

4 years

Number of equity awards granted (in shares)

639,250

639,250

1,266,237

Granted (in dollars per share) | $ / shares

$ 15.47

$ 15.99

Unvested Number of Shares, Ending (in shares)

1,884,110

1,266,237

0

Vested (in shares)

0

0

Estimated future compensation expense for unvested shares | $

$ 20.3

Weighted average period over which compensation expense will be recorded

2 years 4 months 24 days

Number of tranches | tranche

2

2

Restricted stock units | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percent of RSU grants grant recipients may earn

0.00%

Restricted stock units | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Percent of RSU grants grant recipients may earn

100.00%

Restricted stock units | Vesting on January 28, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percent

50.00%

50.00%

Restricted stock units | Vesting on January 28, 2019

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Vesting percent

50.00%

50.00%

2015 Incentive Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Expected term of incentive plan after effective date (in years)

10 years

2015 Incentive Plan | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common shares available for issuance (in shares)

3,250,000

Share award plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common shares available for issuance (in shares)

3,215,413

Compensation expense | $

$ 3.4

$ 1.8

Share award plan | General and administrative expense

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation expense | $

$ 15.4

$ 2.6

Share award plan | Trustees

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of equity awards granted (in shares)

2,000

Aggregate market value of shares awarded | $

$ 0.2

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Restricted Share and Restricted Stock Unit Activity (Details) - $ / shares	Jun. 16, 2015	Jan. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Unvested Number of Shares, Beginning (in shares)			0	130,914	114,703
Granted (in shares)				4,000	83,450
Vested (in shares)				(134,914)	(66,639)
Forfeited (in shares)					(600)
Unvested Number of Shares, Ending (in shares)				0	130,914
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)			$ 0	$ 20.70	$ 19.39
Granted (in dollars per share)				23.46	23.29
Vested (in dollars per share)				25.79	23.06
Forfeited (in dollars per share)					22.49
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)				$ 0	$ 20.70
Restricted shares
Number of Shares
Unvested Number of Shares, Beginning (in shares)			710,182	0
Granted (in shares)	34,587	126,319	160,906	713,727
Vested (in shares)			(86,517)	(3,545)
Forfeited (in shares)			(8,115)
Unvested Number of Shares, Ending (in shares)			776,456	710,182	0
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)				$ 0
Granted (in dollars per share)		$ 26.58	$ 26.46	26.66
Vested (in dollars per share)			26.02	$ 26.66
Forfeited (in dollars per share)			$ 26.64
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)					$ 0
Restricted stock units
Number of Shares
Unvested Number of Shares, Beginning (in shares)			1,266,237	0
Granted (in shares)		639,250	639,250	1,266,237
Vested (in shares)			0	0
Forfeited (in shares)			(21,377)
Unvested Number of Shares, Ending (in shares)			1,884,110	1,266,237	0
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)				$ 0
Granted (in dollars per share)			$ 15.47	15.99
Vested (in dollars per share)			0	$ 0
Forfeited (in dollars per share)			$ 15.80
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)					$ 0

Share-Based Compensation - Su88

Share-Based Compensation - Summary of Assumptions and Fair Values for Restricted Stock Units Granted in the Period (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Fair value of RSUs granted (in dollars per share)		$ 23.46	$ 23.29
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Fair value of RSUs granted (in dollars per share)	$ 15.47	$ 15.99
Expected term (years)	4 years	4 years
Expected volatility	0.00%	0.00%
Expected dividend yield	1.88%	1.88%
Risk-free rate	0.81%	0.84%

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of Shares Granted and Vested (Details) - $ / shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Number of Shares
Unvested Number of Shares, Beginning (in shares)	130,914	114,703
Granted (in shares)	4,000	83,450
Vested (in shares)	(134,914)	(66,639)
Forfeited (in shares)		(600)
Unvested Number of Shares, Ending (in shares)	0	130,914
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)	$ 20.70	$ 19.39
Granted (in dollars per share)	23.46	23.29
Vested (in dollars per share)	25.79	23.06
Forfeited (in dollars per share)		22.49
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$ 0	$ 20.70

Defined Contribution Plan (Deta

Defined Contribution Plan (Details)	12 Months Ended
	Dec. 31, 2015USD ($)
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of match	100.00%
Employer matching contribution, percent of employees' gross pay	3.00%
Employer maximum contribution	$ 8,000
Employer matching contribution in excess of three percent of employee contribution, percent of match	50.00%
Employer contribution amount	$ 300,000
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay	5.00%
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution, percent of employees' gross pay	3.00%

Fair Value of Assets and Liab91

Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measure at Fair Value (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	$ (3,687)	$ (7,462)
Derivative liability	(7,219)	(6,658)
Level 1
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	0	0
Derivative liability	0	0
Level 2
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	(3,687)	(7,462)
Derivative liability	0	0
Level 3
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	0	0
Derivative liability	$ (7,219)	$ (6,658)

Fair Value of Assets and Liab92

Fair Value of Assets and Liabilities - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2015USD ($)	Dec. 31, 2015USD ($)Tenant	Dec. 31, 2014USD ($)ft²property	Jul. 31, 2014USD ($)$ / shares	Mar. 31, 2014ft²
Fair value of assets and liabilities
Impairment of Real Estate		$ 17,200
Number of properties | property			31
Property square feet | ft²			5,600,000		5,641,450
Real estate properties, net		$ 2,988,413	$ 4,697,998
Number of tenants responsible for more than 3% of total annualized rents | Tenant		0
Total rents | Credit concentration
Fair value of assets and liabilities
Concentration risk		4.00%
225 Water Street in Jacksonville, Florida
Fair value of assets and liabilities
Loss on asset impairment			22,700
Level 3 | Real estate properties held for sale | Discounted cash flows
Fair value of assets and liabilities
Fair value of assets			414,625
Carrying Amount | Nonrecurring | 225 Water Street in Jacksonville, Florida
Fair value of assets and liabilities
Real estate properties, net			42,300
Fair value | Nonrecurring | 225 Water Street in Jacksonville, Florida
Fair value of assets and liabilities
Fair value of assets			$ 19,600
Disposition Plan
Fair value of assets and liabilities
Number of properties | property			34
Loss on asset impairment			$ 167,100
Disposition Plan | Carrying Amount | Nonrecurring
Fair value of assets and liabilities
Real estate properties, net			581,700
Previously reported
Fair value of assets and liabilities
Loss on asset impairment			4,800
General and administrative expense
Fair value of assets and liabilities
Change in fair value of derivatives		$ 9,000
Minimum
Fair value of assets and liabilities
Average closing price per common share during one year period after date (in dollars per share) | $ / shares				$ 26
Average closing price per common share during first and second year after date (in dollars per share) | $ / shares				$ 26
Related/Corvex
Fair value of assets and liabilities
Amount of reimbursements payable to related party if specified minimum common share price maintain during the one year period after the date on which the reimbursement is approved by shareholders				$ 8,400
Amount of reimbursements payable to related party if specified minimum common share price maintain during the one year period between the first and second anniversaries of the date on which the reimbursement is approved by shareholders				$ 8,400
Amount of reimbursements payable to related party upon the approval of shareholders	$ 8,400		$ 16,700

Fair Value of Assets and Liab93

Fair Value of Assets and Liabilities - Schedule of Valuation Techniques and Significant Unobservable Inputs Used for Level 3 Fair Value Measurements (Details) - Level 3 - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Real estate properties held for sale | Discounted cash flows
Fair Value of Assets and Liabilities
Fair value of assets			$ 414,625
Discount rate			10.20%
Exit capitalization rate			9.10%
Property, plant and equipment | Discounted cash flows
Fair Value of Assets and Liabilities
Fair value of assets	$ 19,589
Discount rate	8.00%
Exit capitalization rate	8.00%
Derivative liability
Fair Value of Assets and Liabilities
Fair value of liabilities		$ 7,219	$ 6,658
Risk-free rate		0.52%	0.50%
Volatility		20.00%	20.00%

Fair Value of Assets and Liab94

Fair Value of Assets and Liabilities - Schedule of Fair Value and Carrying Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Carrying Amount
Fair value of financial instruments
Senior unsecured debt and mortgage notes payable, net	$ 1,710,324	$ 2,207,665
Fair Value
Fair value of financial instruments
Senior unsecured debt and mortgage notes payable, net	$ 1,749,211	$ 2,263,535

Earnings Per Common Share - Sch

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator for earnings per common share - basic and diluted:
Income (loss) from continuing operations									$ 99,857	$ 21,206	$ (37,318)
Net income attributable to noncontrolling interest in consolidated subsidiary									0	0	(20,093)
Preferred distributions									(27,924)	(32,095)	(44,604)
Excess fair value of consideration over carrying value of preferred shares									0	(16,205)	0
Income (loss) from continuing operations attributable to Equity Commonwealth common shareholders									71,933	(27,094)	(102,015)
Discontinued operations									0	2,806	(119,649)
Numerator for net income (loss) per share - basic and diluted	$ 36,164	$ 23,485	$ 5,635	$ 6,649	$ (165,542)	$ 149,759	$ (17,802)	$ 9,297	$ 71,933	$ (24,288)	$ (221,664)
Denominator for earnings per common share - basic and diluted:
Weighted average common shares outstanding — basic (in shares)									128,621	125,163	112,378
Weighted average common shares outstanding — diluted (in shares)									129,437	125,163	112,378
Earnings per share - basic:
Income from continuing operations attributable to Equity Commonwealth common shareholders (in dollars per share)									$ 0.56	$ (0.21)	$ (0.91)
Discontinued operations (in dollars per share)									0	0.02	(1.06)
Net income (loss) (in dollars per share)	$ 0.29	$ 0.18	$ 0.04	$ 0.05	$ (1.28)	$ 1.16	$ (0.14)	$ 0.08	0.56	(0.19)	(1.97)
Earnings per share - diluted:
Income from continuing operations attributable to Equity Commonwealth common shareholders (in dollars per share)									0.56	(0.21)	(0.91)
Discontinued operations (in dollars per share)									0	0.02	(1.06)
Net income (loss) (in dollars per share)	$ 0.28	$ 0.18	$ 0.04	$ 0.05	$ (1.28)	$ 1.16	$ (0.14)	$ 0.08	$ 0.56	$ (0.19)	$ (1.97)
Effect of Series D preferred shares; 6 1/2% cumulative convertible
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Preferred shares, dividend yield									6.50%	6.50%	6.50%
Anti-dilutive securities:
Anti-dilutive securities (in shares)									2,363	4,175	7,298
Effect of Series D preferred shares; 6 1/2% cumulative convertible
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Preferred shares, dividend yield									6.50%	6.50%

Earnings Per Common Share - S96

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Footnote) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
RSUs vested (in shares)		134,914	66,639
Restricted stock units
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
RSUs vested (in shares)	0	0
Common shares issued (in shares)	1,143,000	0
Weighted average common shares outstanding — diluted (in shares)	816,000

Segment Information - Narrative

Segment Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Percentage of CBD and suburban properties that are office properties (more than)	90.00%

Related Person Transactions - N

Related Person Transactions - Narrative (Details)	Jul. 20, 2015USD ($)option	Jun. 16, 2015shares	May. 04, 2015USD ($)	Mar. 01, 2015USD ($)	Jan. 28, 2015shares	Dec. 31, 2014USD ($)ft²property	Sep. 30, 2014USD ($)trustee	Sep. 29, 2014trusteeagreement	Jul. 31, 2014USD ($)option$ / shares	Jul. 09, 2014USD ($)$ / sharesshares	Jun. 30, 2014USD ($)ft²shares	Jun. 01, 2014USD ($)optionparking_space	May. 09, 2014USD ($)companyshares	Mar. 01, 2014property	Dec. 19, 2013USD ($)	Jul. 02, 2013shares	Mar. 15, 2013USD ($)shares	Mar. 12, 2012shares	Feb. 29, 2012	Feb. 16, 2012USD ($)ft²buildingpropertyshares	Jan. 31, 2016USD ($)	Aug. 31, 2015USD ($)	Jan. 31, 2013USD ($)	Mar. 31, 2012USD ($)shares	Jun. 30, 2014ft²officeshares	Feb. 28, 2015USD ($)	Jun. 30, 2014USD ($)ft²shares	Sep. 30, 2014USD ($)	Dec. 31, 2015shares	Dec. 31, 2014USD ($)ft²propertytrusteeinstallmentshares	Dec. 31, 2013USD ($)shares	Dec. 31, 2009	May. 31, 2014USD ($)	May. 08, 2014	Mar. 31, 2014ft²	Jul. 01, 2013shares	Mar. 31, 2013USD ($)
Related Party Transaction [Line Items]
Property square feet | ft²						5,600,000																								5,600,000					5,641,450
Number of equity awards granted (in shares) | shares																														4,000	83,450
Number of properties | property						31																								31
Incentive management fee vesting on the date of issuance, percent															33.33%
Incentive management fee vesting one year from the date of issuance, percent															33.34%
Incentive management fee vesting in two years from the date of issuance, percent															33.33%
Twenty Percent on Grant Date
Related Party Transaction [Line Items]
Vesting percent																													20.00%
Twenty Percent in Year One
Related Party Transaction [Line Items]
Vesting percent																													20.00%
Twenty Percent in Year Two
Related Party Transaction [Line Items]
Vesting percent																													20.00%
Twenty Percent in Year Three
Related Party Transaction [Line Items]
Vesting percent																													20.00%
Twenty Percent in Year Four
Related Party Transaction [Line Items]
Vesting percent																													20.00%
SIR
Related Party Transaction [Line Items]
Amount of reimbursements payable to related party																																					$ 600,000
Number of former independent trustees | trustee																														1
Property square feet | ft²																				21,400,000
Prior ownership percentage																		100.00%	100.00%
Shares sold (in shares) | shares																10,500,000		9,200,000						9,200,000
Less than wholly owned subsidiary, common shares owned (in shares) | shares										22,000,000	22,000,000														22,000,000		22,000,000									22,000,000
Ownership Percentage										0.00%	36.70%					44.20%									36.70%		36.70%
Proceeds from IPO																								$ 180,800,000
Repayment of promissory note																				$ 400,000,000
Common shares consideration received on transfer of properties (in shares) | shares																				22,000,000
Number of properties sold or transferred or agreed to be sold or transferred | property																				79
Number of separate buildings or land parcels sold or transferred or agreed to be sold or transferred | building																				251
Equity investments, number of shares sold (in shares) | shares										22,000,000
Price per common share (in dollars per share) | $ / shares										$ 32.04
Equity investments, proceeds from sale										$ 704,800,000
Parent Company
Related Party Transaction [Line Items]
Number of properties | property														1
Amended Agreement
Related Party Transaction [Line Items]
Base business management fee payable in common shares (as a percent)											10.00%														10.00%		10.00%
Restricted shares
Related Party Transaction [Line Items]
Number of equity awards granted (in shares) | shares		34,587			126,319																								160,906	713,727
Number of anniversaries of the grant date for vesting of restricted shares		1 year			4 years
Minimum
Related Party Transaction [Line Items]
Price per common share during one year period after date (in dollars per share) | $ / shares									$ 26
Price per common share during first and second year after date (in dollars per share) | $ / shares									$ 26
Maximum
Related Party Transaction [Line Items]
Ownership Percentage																													50.00%
Equity Group Investments and associated entities
Related Party Transaction [Line Items]
Initial term	$ 500,000								$ 200,000			$ 200,000
Lease term	5 years								7 months			1 year
Number of renewal options | option	1								1			1
Renewal option term	5 years								3 months			3 months
Lease payment	$ 800,000		$ 200,000
License agreement term												1 year
License fee			$ 100,000									$ 200,000
Number of parking spaces | parking_space												1
Equity Group Investments and associated entities | Subsequent event
Related Party Transaction [Line Items]
Lease payment																					$ 100,000
License fee																					$ 100,000
Related/Corvex
Related Party Transaction [Line Items]
Amount of reimbursements payable to related party									$ 33,500,000
Reimbursement amount paid																						$ 8,400,000								$ 16,700,000
Amount of reimbursements payable to related party if specified minimum common share price maintain during the one year period after the date on which the reimbursement is approved by shareholders									8,400,000
Amount of reimbursements payable to related party if specified minimum common share price maintain during the one year period between the first and second anniversaries of the date on which the reimbursement is approved by shareholders									$ 8,400,000
RMR
Related Party Transaction [Line Items]
Lease term																									3 years
Number of agreements | agreement								3
Number of former managing trustees | trustee								1
Number of former independent trustees | trustee							2
Base management fee payable as a percentage of average historical cost of real estate investments, located outside the United States, Puerto Rico and Canada																															1.00%
Business management fees																											$ 31,700,000
Shares issued (in shares) | shares																											68,206
Base management fee payable as a percentage of average historical cost of real estate investments, located in the United States, Puerto Rico and Canada																															0.70%
Annual business management fee as a percentage of aggregate cost of properties acquired in excess of $250,000																															0.50%
Incentive fee as a percentage of the product of weighted average common shares outstanding on a fully diluted basis and the excess, if any of the Normalized FFO per share for current fiscal year over the preceding fiscal year																															15.00%
Incentive fees paid																															$ 0
Property management fees as a percentage of gross collected rents											3.00%														3.00%		3.00%
Construction supervision fees as a percentage of construction costs											5.00%														5.00%		5.00%
Property management and construction supervision fees																											$ 13,800,000
Payments to MacArthur Cook Fund Management Limited																							$ 200,000
Number of regional offices leased | office																									11
Rental income earned																											$ 400,000				800,000
Property square feet | ft²											36,500														36,500		36,500
Legal fees and costs																											$ 5,400,000				30,400,000
Number of properties | property														2
Total rent due						$ 1,100,000																								$ 1,100,000
RMR | SIR
Related Party Transaction [Line Items]
Business management fees																															43,300,000
Property management and construction supervision fees																															32,500,000
Pro rata share of related party's costs of providing internal audit function																															$ 300,000
RMR | Parent Company
Related Party Transaction [Line Items]
Number of properties acquired or agreed to be acquired | property														1
RMR | Amended Agreement
Related Party Transaction [Line Items]
Base management fee payable as a percentage of average historical cost of real estate investments, up to specified amount															0.70%
Base management fee payable as a percentage of average historical cost of real estate investments, located outside the United States, Puerto Rico and Canada															1.00%
Base management fee payable as a percentage of average historical cost of real estate investments, exceeding specified amount															0.50%
Base management fee payable as a percentage of average closing price per share of common shares on NYSE															0.70%
Base management fee payable as a percentage of average market capitalization exceeding specified amount															0.50%
Base business management fee payable in cash (as a percent)															90.00%
Base business management fee payable in common shares (as a percent)															10.00%
Minimum ownership of outstanding common shares of related party required to engage the same manager or common managing trustees															10.00%
Related Party Transaction Percentage for Limitation and Adjustments of Incentive Management Fee Payable															12.00%
Measurement period of incentive management fee															3 years
RMR | Restricted shares
Related Party Transaction [Line Items]
Number of equity awards granted (in shares) | shares																															73,450
Aggregate value of restricted shares granted																															$ 1,700,000
Number of anniversaries of the grant date for vesting of restricted shares																									4 years
RMR | 2014 | Amended Agreement
Related Party Transaction [Line Items]
Measurement period of incentive management fee																														1 year
RMR | 2015 | Amended Agreement
Related Party Transaction [Line Items]
Measurement period of incentive management fee																													2 years
RMR | Maximum
Related Party Transaction [Line Items]
Threshold amount of real estate investments for payment of base management fee																															250,000,000
RMR | Maximum | Amended Agreement
Related Party Transaction [Line Items]
Threshold amount of real estate investments for payment of base management fee															$ 250,000,000
Base management fee payable, average market capitalization															$ 250,000,000
RMR Australia
Related Party Transaction [Line Items]
Property management fees as a percentage of gross collected rents											3.00%														3.00%		3.00%
Construction supervision fees as a percentage of construction costs											5.00%														5.00%		5.00%
Compensation for business management and real estate investment services as a percentage of average historical cost of CWHAT's real estate investments											0.50%														0.50%		0.50%
Compensation for property management services as a percentage of difference between 3.5% of collected gross rents and the aggregate of all amounts paid or payable by or on behalf of CWHAT to third party property managers											50.00%														50.00%		50.00%
Compensation for construction supervision services as a percentage of difference between 5.0% of construction costs and any amounts paid to third parties for construction management and/or supervision											50.00%														50.00%		50.00%
Business and property management fees																											$ 900,000				1,600,000
RMR and RMR Australia
Related Party Transaction [Line Items]
Monthly management fees				$ 100,000																						$ 1,200,000
Pro rata portion of the current year's incentive fee under the existing business management agreement																												$ 15,300,000
GOV
Related Party Transaction [Line Items]
Amount of reimbursements payable to related party																															$ 300,000
Prior ownership percentage																																100.00%
Shares sold (in shares) | shares																	9,950,000
Net proceeds received on issuance or sale of common shares																	$ 239,600,000
Realized gain on sale of common shares																	$ 66,300,000
AIC
Related Party Transaction [Line Items]
Ownership Percentage													0.00%																					12.50%
Equity investments, number of shares sold (in shares) | shares													20,000
Equity investments, proceeds from sale													$ 5,800,000
Amount invested in equity investee													$ 5,200,000
Number of other companies which are shareholders of related party | company													4
Coverage amount for property insurance																																	$ 500,000,000
Premium for property insurance																											$ 6,000,000
Equity Commonwealth and REIT Management and Research LLC
Related Party Transaction [Line Items]
Settlement receivable						12,000,000																								$ 12,000,000
Number of settlement receivable installments | installment																														3
Settlement receivable installment amount						3,000,000	$ 3,000,000				$ 6,000,000
Equity Commonwealth
Related Party Transaction [Line Items]
Total rent due						$ 9,200,000																								$ 9,200,000

Selected Quarterly Financial 99

Selected Quarterly Financial Data - Summary of Unaudited Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 31, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Total revenues		$ 138,934	$ 159,208	$ 203,694	$ 213,055	$ 212,808	$ 216,595	$ 215,194	$ 217,260	$ 714,891	$ 861,857	$ 953,029
Net income attributable to Equity Commonwealth common shareholders		$ 36,164	$ 23,485	$ 5,635	$ 6,649	$ (165,542)	$ 149,759	$ (17,802)	$ 9,297	$ 71,933	$ (24,288)	$ (221,664)
Net income attributable to Equity Commonwealth common shareholders per share—basic		$ 0.29	$ 0.18	$ 0.04	$ 0.05	$ (1.28)	$ 1.16	$ (0.14)	$ 0.08	$ 0.56	$ (0.19)	$ (1.97)
Net income attributable to Equity Commonwealth common shareholders per share—diluted		$ 0.28	$ 0.18	$ 0.04	$ 0.05	(1.28)	1.16	(0.14)	0.08	$ 0.56	$ (0.19)	$ (1.97)
Common distributions declared	$ 0.25					$ 0	$ 0	$ 0	$ 0.25

Selected Quarterly Financial100

Selected Quarterly Financial Data - Narrative (Details) - USD ($) $ in Thousands	Jul. 09, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Loss on asset impairment		$ 167,100		$ 22,700	$ 17,162	$ 185,067	$ 124,253
Gain on sale of equity investment					$ 0	$ 171,561	$ 66,293
SIR
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity investment	$ 171,800		$ 171,800

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) $ / shares in Units, $ in Millions	Feb. 16, 2016USD ($)$ / shares	Feb. 18, 2016USD ($)ft²building	Jan. 31, 2013building	Feb. 16, 2016$ / sharesshares	Dec. 31, 2015ft²buildingproperty$ / sharesshares	Dec. 31, 2014ft²	Mar. 31, 2014ft²
Subsequent Event [Line Items]
Number of buildings sold | building			18
Property square feet | ft²						5,600,000	5,641,450
6.25% Senior Unsecured Notes due 2016
Subsequent Event [Line Items]
Interest rate stated percentage					6.25%
Disposed of by Sale
Subsequent Event [Line Items]
Number of properties sold or agreed to be sold | property					91
Number of buildings sold | building					135
Property square feet | ft²					18,939,185
Subsequent event
Subsequent Event [Line Items]
Interest rate stated percentage	6.25%			6.25%
Redemption of shares (in shares) | shares				861,162
Subsequent event | Disposed of by Sale
Subsequent Event [Line Items]
Number of buildings sold | building		9
Property square feet | ft²		427,443
Gross proceeds from sale of real estate anticipated | $		$ 50.9
Senior Notes | Subsequent event | 6.25% Senior Unsecured Notes due 2016
Subsequent Event [Line Items]
Repayments of debt | $	$ 139.1
Common Stock
Subsequent Event [Line Items]
Redemption of shares (in shares) | shares					3,410,300
Treasury Stock Acquired, Average Cost Per Share | $ / shares					$ 25.76
Common Stock | Subsequent event
Subsequent Event [Line Items]
Treasury Stock Acquired, Average Cost Per Share | $ / shares	$ 25.94			$ 25.94

SCHEDULE II VALUATION AND QU102

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Movement in valuation and qualifying accounts
Balance at Beginning of Period	$ 6,565	$ 7,885	$ 9,962
Charged to Costs and Expenses	4,533	2,196	818
Deductions	(3,383)	(3,516)	(2,895)
Balance at End of Period	$ 7,715	$ 6,565	$ 7,885

SCHEDULE III REAL ESTATE AND103

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 247,562
Initial Cost to Company
Land	394,913
Buildings and Improvements	3,065,229
Costs Capitalized Subsequent to Acquisition, Net	540,382
Impairment/Write Downs	(113,172)
Cost Amount Carried at Close of Period
Land	389,410
Buildings and Improvements	3,497,942
Total	3,887,352	$ 5,728,443	$ 5,537,165	$ 7,829,409
Accumulated Depreciation	898,939	$ 1,030,445	$ 895,059	$ 1,007,606
785 Schilinger Road South, Mobile, AL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,540
Buildings and Improvements	9,732
Costs Capitalized Subsequent to Acquisition, Net	(3)
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,540
Buildings and Improvements	9,729
Total	11,269
Accumulated Depreciation	1,990
Parkshore Plaza, Folsom, CA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	41,275
Initial Cost to Company
Land	4,370
Buildings and Improvements	41,749
Costs Capitalized Subsequent to Acquisition, Net	3,063
Impairment/Write Downs	(3)
Cost Amount Carried at Close of Period
Land	4,370
Buildings and Improvements	44,809
Total	49,179
Accumulated Depreciation	5,086
Leased Land, Gonzalez, CA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	18,941
Buildings and Improvements	9,060
Costs Capitalized Subsequent to Acquisition, Net	3,967
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	18,940
Buildings and Improvements	13,028
Total	31,968
Accumulated Depreciation	2,862
Sky Park Centre, San Diego, CA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	936
Buildings and Improvements	8,094
Costs Capitalized Subsequent to Acquisition, Net	756
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	936
Buildings and Improvements	8,850
Total	9,786
Accumulated Depreciation	3,308
9110 East Nichols Avenue, Centennial, CO
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,708
Buildings and Improvements	14,616
Costs Capitalized Subsequent to Acquisition, Net	4,002
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,708
Buildings and Improvements	18,618
Total	20,326
Accumulated Depreciation	6,438
1225 Seventeenth Street, Denver, CO
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	22,400
Buildings and Improvements	110,090
Costs Capitalized Subsequent to Acquisition, Net	17,269
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	22,400
Buildings and Improvements	127,359
Total	149,759
Accumulated Depreciation	21,595
5073, 5075, & 5085 S. Syracuse Street, Denver, CO
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,720
Buildings and Improvements	58,890
Costs Capitalized Subsequent to Acquisition, Net	0
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	4,720
Buildings and Improvements	58,890
Total	63,610
Accumulated Depreciation	8,343
1601 Dry Creek Drive, Longmont, CO
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,714
Buildings and Improvements	24,397
Costs Capitalized Subsequent to Acquisition, Net	5,535
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,715
Buildings and Improvements	29,931
Total	33,646
Accumulated Depreciation	9,165
97 Newberry Road, East Windsor, CT
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	6,375
Initial Cost to Company
Land	2,960
Buildings and Improvements	12,360
Costs Capitalized Subsequent to Acquisition, Net	30
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,943
Buildings and Improvements	12,407
Total	15,350
Accumulated Depreciation	2,865
33 Stiles Lane, North Haven, CT
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	2,785
Initial Cost to Company
Land	2,090
Buildings and Improvements	9,141
Costs Capitalized Subsequent to Acquisition, Net	216
Impairment/Write Downs	(1,654)
Cost Amount Carried at Close of Period
Land	1,799
Buildings and Improvements	7,994
Total	9,793
Accumulated Depreciation	2,161
1250 H Street, NW, Washington, DC
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,975
Buildings and Improvements	53,778
Costs Capitalized Subsequent to Acquisition, Net	10,947
Impairment/Write Downs	(2)
Cost Amount Carried at Close of Period
Land	5,975
Buildings and Improvements	64,723
Total	70,698
Accumulated Depreciation	26,030
Georgetown-Green and Harris Buildings, Washington, DC
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	24,000
Buildings and Improvements	35,979
Costs Capitalized Subsequent to Acquisition, Net	44
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	24,000
Buildings and Improvements	36,023
Total	60,023
Accumulated Depreciation	5,700
802 Delaware Avenue, Wilmington, DE
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,409
Buildings and Improvements	39,681
Costs Capitalized Subsequent to Acquisition, Net	10,533
Impairment/Write Downs	(11,156)
Cost Amount Carried at Close of Period
Land	3,390
Buildings and Improvements	40,077
Total	43,467
Accumulated Depreciation	23,091
6600 North Military Trail, Boca Raton, FL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	15,900
Buildings and Improvements	129,790
Costs Capitalized Subsequent to Acquisition, Net	123
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	15,900
Buildings and Improvements	129,913
Total	145,813
Accumulated Depreciation	16,224
Executive Park, Atlanta, GA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	13,729
Buildings and Improvements	78,032
Costs Capitalized Subsequent to Acquisition, Net	6,776
Impairment/Write Downs	(54,313)
Cost Amount Carried at Close of Period
Land	10,954
Buildings and Improvements	33,270
Total	44,224
Accumulated Depreciation	14,859
633 Ahua Street, Honolulu, HI
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,256
Buildings and Improvements	3
Costs Capitalized Subsequent to Acquisition, Net	18,054
Impairment/Write Downs	(2,912)
Cost Amount Carried at Close of Period
Land	1,100
Buildings and Improvements	15,301
Total	16,401
Accumulated Depreciation	3,765
625 Crane Street, Aurora, IL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,180
Buildings and Improvements	3,411
Costs Capitalized Subsequent to Acquisition, Net	(2)
Impairment/Write Downs	(2,978)
Cost Amount Carried at Close of Period
Land	533
Buildings and Improvements	1,078
Total	1,611
Accumulated Depreciation	87
1200 Lakeside Drive, Bannockburn, IL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,846
Buildings and Improvements	48,568
Costs Capitalized Subsequent to Acquisition, Net	14,768
Impairment/Write Downs	(7,610)
Cost Amount Carried at Close of Period
Land	5,858
Buildings and Improvements	55,714
Total	61,572
Accumulated Depreciation	12,601
600 West Chicago Avenue, Chicago, IL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	34,980
Buildings and Improvements	315,643
Costs Capitalized Subsequent to Acquisition, Net	12,058
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	34,980
Buildings and Improvements	327,701
Total	362,681
Accumulated Depreciation	35,679
8750 Bryn Mawr Avenue, Chicago, IL
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,600
Buildings and Improvements	77,764
Costs Capitalized Subsequent to Acquisition, Net	7,400
Impairment/Write Downs	(170)
Cost Amount Carried at Close of Period
Land	6,600
Buildings and Improvements	84,994
Total	91,594
Accumulated Depreciation	11,705
101-115 W. Washington Street, Indianapolis, IN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,495
Buildings and Improvements	60,465
Costs Capitalized Subsequent to Acquisition, Net	23,210
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	7,496
Buildings and Improvements	83,674
Total	91,170
Accumulated Depreciation	23,976
111 Monument Circle, Indianapolis, IN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	9,670
Buildings and Improvements	158,085
Costs Capitalized Subsequent to Acquisition, Net	8,556
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	9,670
Buildings and Improvements	166,641
Total	176,311
Accumulated Depreciation	13,115
109 Brookline Avenue, Boston, MA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,168
Buildings and Improvements	30,397
Costs Capitalized Subsequent to Acquisition, Net	12,684
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,168
Buildings and Improvements	43,081
Total	46,249
Accumulated Depreciation	18,718
Cabot Business Park Land, Mansfield, MA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,033
Buildings and Improvements	0
Costs Capitalized Subsequent to Acquisition, Net	0
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,033
Buildings and Improvements	0
Total	1,033
Accumulated Depreciation	0
111 Market Place, Baltimore, MD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,328
Buildings and Improvements	54,645
Costs Capitalized Subsequent to Acquisition, Net	16,152
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,328
Buildings and Improvements	70,797
Total	77,125
Accumulated Depreciation	24,753
25 S. Charles Street, Baltimore, MD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,830
Buildings and Improvements	22,996
Costs Capitalized Subsequent to Acquisition, Net	12,678
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,830
Buildings and Improvements	35,674
Total	38,504
Accumulated Depreciation	12,479
820 W. Diamond, Gaithersburg, MD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,381
Buildings and Improvements	18,798
Costs Capitalized Subsequent to Acquisition, Net	10,538
Impairment/Write Downs	(35)
Cost Amount Carried at Close of Period
Land	4,461
Buildings and Improvements	29,221
Total	33,682
Accumulated Depreciation	11,487
Danac Stiles Business Park, Rockville, MD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,638
Buildings and Improvements	62,572
Costs Capitalized Subsequent to Acquisition, Net	6,329
Impairment/Write Downs	(10,975)
Cost Amount Carried at Close of Period
Land	6,595
Buildings and Improvements	58,969
Total	65,564
Accumulated Depreciation	18,984
East Eisenhower Parkway, Ann Arbor, MI
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,760
Buildings and Improvements	46,988
Costs Capitalized Subsequent to Acquisition, Net	1,513
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,760
Buildings and Improvements	48,501
Total	55,261
Accumulated Depreciation	6,836
2250 Pilot Knob Road, Mendota Heights, MN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	533
Buildings and Improvements	4,795
Costs Capitalized Subsequent to Acquisition, Net	1,202
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	533
Buildings and Improvements	5,997
Total	6,530
Accumulated Depreciation	2,643
411 Farwell Avenue, South St. Paul, MN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,303
Buildings and Improvements	10,451
Costs Capitalized Subsequent to Acquisition, Net	4,603
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,304
Buildings and Improvements	15,053
Total	16,357
Accumulated Depreciation	3,526
6200 Glenn Carlson Drive, St. Cloud, MN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,950
Buildings and Improvements	13,803
Costs Capitalized Subsequent to Acquisition, Net	0
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,950
Buildings and Improvements	13,803
Total	15,753
Accumulated Depreciation	2,156
4700 Belleview Avenue, Kansas City, MO
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,165
Buildings and Improvements	3,097
Costs Capitalized Subsequent to Acquisition, Net	2,895
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,165
Buildings and Improvements	5,992
Total	7,157
Accumulated Depreciation	1,029
111 River Street, Hoboken, NJ
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	0
Buildings and Improvements	134,199
Costs Capitalized Subsequent to Acquisition, Net	1,871
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	0
Buildings and Improvements	136,070
Total	136,070
Accumulated Depreciation	21,630
North Point Office Complex, Cleveland, OH
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	12,000
Buildings and Improvements	94,448
Costs Capitalized Subsequent to Acquisition, Net	18,136
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	12,000
Buildings and Improvements	112,584
Total	124,584
Accumulated Depreciation	22,363
Raintree Industrial Park, Solon, OH
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,808
Buildings and Improvements	16,620
Costs Capitalized Subsequent to Acquisition, Net	2,270
Impairment/Write Downs	(8,387)
Cost Amount Carried at Close of Period
Land	1,339
Buildings and Improvements	10,972
Total	12,311
Accumulated Depreciation	858
401 Vine Street, Delmont, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,575
Buildings and Improvements	5,542
Costs Capitalized Subsequent to Acquisition, Net	0
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,575
Buildings and Improvements	5,542
Total	7,117
Accumulated Depreciation	1,130
Cherrington Corporate Center Moon, Township, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	11,369
Buildings and Improvements	39,892
Costs Capitalized Subsequent to Acquisition, Net	28,367
Impairment/Write Downs	(5,454)
Cost Amount Carried at Close of Period
Land	11,164
Buildings and Improvements	63,010
Total	74,174
Accumulated Depreciation	21,480
1500 Market Street, Philadelphia, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	18,758
Buildings and Improvements	167,487
Costs Capitalized Subsequent to Acquisition, Net	104,542
Impairment/Write Downs	(388)
Cost Amount Carried at Close of Period
Land	18,758
Buildings and Improvements	271,641
Total	290,399
Accumulated Depreciation	78,551
1525 Locust Street, Philadelphia, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	931
Buildings and Improvements	8,377
Costs Capitalized Subsequent to Acquisition, Net	1,902
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	930
Buildings and Improvements	10,280
Total	11,210
Accumulated Depreciation	4,122
1600 Market Street, Philadelphia, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,462
Buildings and Improvements	111,946
Costs Capitalized Subsequent to Acquisition, Net	18,259
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,462
Buildings and Improvements	130,205
Total	133,667
Accumulated Depreciation	55,534
1735 Market Street, Philadelphia, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	169,612
Initial Cost to Company
Land	24,753
Buildings and Improvements	222,775
Costs Capitalized Subsequent to Acquisition, Net	52,107
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	24,747
Buildings and Improvements	274,888
Total	299,635
Accumulated Depreciation	121,238
Foster Plaza, Pittsburgh, PA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,168
Buildings and Improvements	51,588
Costs Capitalized Subsequent to Acquisition, Net	17,969
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,171
Buildings and Improvements	69,554
Total	75,725
Accumulated Depreciation	19,771
128 Crews Drive, Columbia, SC
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,420
Buildings and Improvements	4,017
Costs Capitalized Subsequent to Acquisition, Net	1,322
Impairment/Write Downs	(4,012)
Cost Amount Carried at Close of Period
Land	1,024
Buildings and Improvements	2,723
Total	3,747
Accumulated Depreciation	489
111 Southchase Boulevard, Fountain Inn, SC
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	520
Buildings and Improvements	6,822
Costs Capitalized Subsequent to Acquisition, Net	1,734
Impairment/Write Downs	(2,912)
Cost Amount Carried at Close of Period
Land	390
Buildings and Improvements	5,774
Total	6,164
Accumulated Depreciation	1,531
1043 Global Avenue, Graniteville, SC
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	720
Buildings and Improvements	15,552
Costs Capitalized Subsequent to Acquisition, Net	603
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	720
Buildings and Improvements	16,155
Total	16,875
Accumulated Depreciation	3,537
633 Frazier Drive, Franklin, TN
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,800
Buildings and Improvements	13,190
Costs Capitalized Subsequent to Acquisition, Net	(10)
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	5,800
Buildings and Improvements	13,180
Total	18,980
Accumulated Depreciation	2,711
1601 Rio Grande Street, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	688
Buildings and Improvements	6,192
Costs Capitalized Subsequent to Acquisition, Net	1,539
Impairment/Write Downs	(23)
Cost Amount Carried at Close of Period
Land	697
Buildings and Improvements	7,699
Total	8,396
Accumulated Depreciation	3,106
206 East 9th Street, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	27,515
Initial Cost to Company
Land	7,900
Buildings and Improvements	38,533
Costs Capitalized Subsequent to Acquisition, Net	2,166
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	7,900
Buildings and Improvements	40,699
Total	48,599
Accumulated Depreciation	3,702
4515 Seton Center Parkway, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,038
Buildings and Improvements	18,338
Costs Capitalized Subsequent to Acquisition, Net	2,731
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,037
Buildings and Improvements	21,070
Total	23,107
Accumulated Depreciation	9,110
4516 Seton Center Parkway, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,028
Buildings and Improvements	18,251
Costs Capitalized Subsequent to Acquisition, Net	3,022
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,027
Buildings and Improvements	21,274
Total	23,301
Accumulated Depreciation	9,681
7800 Shoal Creek Boulevard, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,731
Buildings and Improvements	14,921
Costs Capitalized Subsequent to Acquisition, Net	4,614
Impairment/Write Downs	(14)
Cost Amount Carried at Close of Period
Land	1,731
Buildings and Improvements	19,521
Total	21,252
Accumulated Depreciation	7,672
812 San Antonio Street, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	626
Buildings and Improvements	5,636
Costs Capitalized Subsequent to Acquisition, Net	2,564
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	621
Buildings and Improvements	8,205
Total	8,826
Accumulated Depreciation	3,115
8701 N. Mopac, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,574
Buildings and Improvements	14,168
Costs Capitalized Subsequent to Acquisition, Net	2,677
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,573
Buildings and Improvements	16,846
Total	18,419
Accumulated Depreciation	6,751
Bridgepoint Parkway, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,784
Buildings and Improvements	70,526
Costs Capitalized Subsequent to Acquisition, Net	10,214
Impairment/Write Downs	(97)
Cost Amount Carried at Close of Period
Land	7,785
Buildings and Improvements	80,642
Total	88,427
Accumulated Depreciation	37,559
Lakewood on the Park, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,548
Buildings and Improvements	31,936
Costs Capitalized Subsequent to Acquisition, Net	1,704
Impairment/Write Downs	(77)
Cost Amount Carried at Close of Period
Land	3,548
Buildings and Improvements	33,563
Total	37,111
Accumulated Depreciation	14,554
Research Park, Austin, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	15,859
Buildings and Improvements	60,175
Costs Capitalized Subsequent to Acquisition, Net	14,601
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	18,411
Buildings and Improvements	72,224
Total	90,635
Accumulated Depreciation	29,564
9840 Gateway Boulevard North, El Paso, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,700
Buildings and Improvements	9,736
Costs Capitalized Subsequent to Acquisition, Net	(4)
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,700
Buildings and Improvements	9,732
Total	11,432
Accumulated Depreciation	1,996
3003 South Expressway 281, Hidalgo, TX
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,480
Buildings and Improvements	15,533
Costs Capitalized Subsequent to Acquisition, Net	(9)
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,480
Buildings and Improvements	15,524
Total	17,004
Accumulated Depreciation	3,193
3330 N Washington Boulevard, Arlington, VA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	810
Buildings and Improvements	7,289
Costs Capitalized Subsequent to Acquisition, Net	724
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	811
Buildings and Improvements	8,012
Total	8,823
Accumulated Depreciation	3,304
333 108th Avenue NE, Bellevue, WA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	14,400
Buildings and Improvements	136,412
Costs Capitalized Subsequent to Acquisition, Net	1,745
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	14,400
Buildings and Improvements	138,157
Total	152,557
Accumulated Depreciation	22,060
600 108th Avenue NE, Bellevue, WA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,555
Buildings and Improvements	30,244
Costs Capitalized Subsequent to Acquisition, Net	14,252
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,555
Buildings and Improvements	44,496
Total	48,051
Accumulated Depreciation	11,904
1331 North Center Parkway, Kennewick, WA
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,850
Buildings and Improvements	7,339
Costs Capitalized Subsequent to Acquisition, Net	(2)
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,850
Buildings and Improvements	7,337
Total	9,187
Accumulated Depreciation	1,506
100 East Wisconsin Avenue, Milwaukee, WI
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,150
Buildings and Improvements	72,113
Costs Capitalized Subsequent to Acquisition, Net	7,733
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,150
Buildings and Improvements	79,846
Total	82,996
Accumulated Depreciation	11,433
111 East Kilbourn Avenue, Milwaukee, WI
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,400
Buildings and Improvements	47,562
Costs Capitalized Subsequent to Acquisition, Net	5,143
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,400
Buildings and Improvements	52,705
Total	55,105
Accumulated Depreciation	$ 10,528

SCHEDULE III REAL ESTATE AND104

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Analysis of Carrying Amount of Real Estate Properties and Accumulated Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Real Estate Properties
Balance at the beginning of the year			$ 5,728,443	$ 5,537,165	$ 7,829,409
Additions			68,118	70,963	231,485
Loss on asset impairment	$ (167,100)	$ (22,700)	(17,162)	(185,067)	(124,253)
Deconsolidation of SIR					(1,446,781)
Properties reclassified to discontinued operations					(552,024)
Properties reclassified to continuing operations				341,024
Disposals			(1,892,047)	(29,219)	(140,783)
Balance at the end of the year	5,728,443		3,887,352	5,728,443	5,537,165
Accumulated Depreciation
Balance at the beginning of the year			1,030,445	895,059	1,007,606
Additions			144,844	164,815	176,777
Loss on asset impairment			0	(6,423)	(185,795)
Deconsolidation of SIR					(56,023)
Properties reclassified to discontinued operations					(15,471)
Disposals			(276,350)	(28,730)	(32,035)
Properties reclassified to continuing operations				5,724
Balance at the end of the year	$ 1,030,445		$ 898,939	1,030,445	895,059
Real Estate
Real Estate Properties
Loss on asset impairment				$ (191,490)	$ (384,141)

SCHEDULE III REAL ESTATE AND105

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Analysis of Carrying Amount of Real Estate Properties and Accumulated Depreciation (Footnote) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Aggregate cost of properties for federal income tax purposes	$ 4,160,805
Real estate properties additions due to changes in foreign currency exchange	(13,217)	$ (20,445)	$ (40,020)
Accumulated depreciation additions due to changes in foreign currency exchange	$ (887)	$ (1,279)	$ (1,528)
Maximum | Buildings and improvements
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives	40 years
Maximum | Personal property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Estimated useful lives	12 years

SCHEDULE IV MORTGAGE LOANS O106

SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE
Face Amount of Mortgage			$ 8,107
Carrying Amount of Mortgage			8,087
Principal Amount of Loans Subject to Delinquent Principal or Interest			0
Reconciliation of the carrying amount of mortgage loans at the beginning of the period:
Balance at the beginning of period	$ 8,107	$ 1,419
New mortgage loans		7,688
Collections of principal		(1,000)
Balance at the end of period	8,107	8,107
Balance at the end of period	$ 8,107	$ 1,419	8,107	$ 8,107
Salina, NY
SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE
Interest Rate	6.00%
Periodic Payment Terms				419
Face Amount of Mortgage			419
Carrying Amount of Mortgage			399
Principal Amount of Loans Subject to Delinquent Principal or Interest			0
Dearborn, MI
SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE
Interest Rate	6.00%
Periodic Payment Terms				$ 7,688
Face Amount of Mortgage			7,688
Carrying Amount of Mortgage			7,688
Principal Amount of Loans Subject to Delinquent Principal or Interest			$ 0