Equity Commonwealth (EQC) 10-K 19 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 18, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	Equity Commonwealth
Entity Central Index Key	803649
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$3.40
Entity Common Stock, Shares Outstanding		129,733,598
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Real estate properties:
Land	$714,238	$699,135
Buildings and improvements	5,014,205	4,838,030
Total real estate properties, at cost, gross	5,728,443	5,537,165
Accumulated depreciation	-1,030,445	-895,059
Total real estate properties, at cost, net	4,697,998	4,642,106
Properties held for sale	0	573,531
Acquired real estate leases, net	198,287	255,812
Equity investments	0	517,991
Cash and cash equivalents	379,058	222,449
Restricted cash	17,715	22,101
Rents receivable, net of allowance for doubtful accounts of $6,565 and $7,885, respectively	248,101	223,769
Other assets, net	220,480	188,675
Total assets	5,761,639	6,646,434
LIABILITIES AND SHAREHOLDERS' EQUITY
Revolving credit facility	0	235,000
Senior unsecured debt, net	1,598,416	1,855,900
Mortgage notes payable, net	609,249	914,510
Liabilities related to properties held for sale	0	28,734
Accounts payable and accrued expenses	162,204	165,855
Assumed real estate lease obligations, net	26,784	33,935
Rent collected in advance	31,359	27,553
Security deposits	14,044	11,976
Due to related persons	0	9,385
Total liabilities	2,442,056	3,282,848
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; 129,607,279 and 118,386,918 shares issued and outstanding, respectively (including 710,182 and 130,914 unvested restricted shares)	1,296	1,184
Additional paid in capital	4,487,133	4,213,474
Cumulative net income	2,233,852	2,209,840
Cumulative other comprehensive loss	-53,216	-38,331
Cumulative common distributions	-3,111,868	-3,082,271
Cumulative preferred distributions	-622,271	-573,971
Total shareholders' equity	3,319,583	3,363,586
Total liabilities and shareholders' equity	5,761,639	6,646,434
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; 4,915,497 and 15,180,000 shares issued and outstanding, respectively, aggregate liquidation preference of $122,887 and $379,500, respectively	119,266	368,270
Total shareholders' equity	119,266	368,270
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 $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Rents receivable, allowance for doubtful accounts	$6,565,000	$7,885,000
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)	129,607,279	118,386,918
Common shares of beneficial interest, shares outstanding (in shares)	129,607,279	118,386,918
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)	4,915,497	15,180,000
Preferred shares of beneficial interest, shares outstanding (in shares)	4,915,497	15,180,000
Preferred shares, aggregate liquidation preference	122,887,000	379,500,000
Common shares of beneficial interest, shares issued (in shares)	4,915,497	15,180,000
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	$275,000,000	$275,000,000
Common shares of beneficial interest, shares issued (in shares)	11,000,000	11,000,000
Unvested restricted shares
Common shares of beneficial interest, shares outstanding (in shares)	710,182	130,914

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Rental income	$691,699	$763,262	$774,600
Tenant reimbursements and other income	170,158	189,767	186,487
Total revenues	861,857	953,029	961,087
Expenses:
Operating expenses	387,982	410,045	397,673
Depreciation and amortization	227,532	234,402	230,284
General and administrative	113,155	80,504	49,312
Loss on asset impairment	185,067	124,253	0
Acquisition related costs	5	318	5,648
Total expenses	913,741	849,522	682,917
Operating (loss) income	-51,884	103,507	278,170
Interest and other income	1,561	1,229	1,410
Interest expense (including net amortization of debt discounts, premiums and deferred financing fees of $(549), $9 and $3,296, respectively)	-143,230	-173,011	-202,055
Gain (loss) on early extinguishment of debt	4,909	-60,052	-287
Gain on sale of equity investment	171,561	66,293	0
Gain on issuance of shares by an equity investee	17,020	0	7,246
(Loss) income from continuing operations before income tax expense and equity in earnings of investees	-63	-62,034	84,484
Income tax expense	-3,191	-2,634	-3,207
Equity in earnings of investees	24,460	25,754	11,420
Income (loss) from continuing operations	21,206	-38,914	92,697
Discontinued operations:
Income (loss) from discontinued operations	8,389	6,393	-4,341
Loss on asset impairment from discontinued operations	-2,238	-102,869	-168,632
Loss on early extinguishment of debt from discontinued operations	-3,345	-1,011	-1,608
Net (loss) gain on sale of properties from discontinued operations	0	-22,162	2,039
Income (loss) before gain on sale of properties	24,012	-158,563	-79,845
Gain on sale of properties	0	1,596	0
Net income (loss)	24,012	-156,967	-79,845
Net income attributable to noncontrolling interest in consolidated subsidiary	0	-20,093	-15,576
Net income (loss) attributable to Equity Commonwealth	24,012	-177,060	-95,421
Preferred distributions	-32,095	-44,604	-51,552
Excess redemption price paid over carrying value of preferred shares	-16,205	0	-4,985
Net loss attributable to Equity Commonwealth common shareholders	-24,288	-221,664	-151,958
Amounts attributable to Equity Commonwealth common shareholders:
(Loss) income from continuing operations	-27,094	-102,015	20,584
Income (loss) from discontinued operations	8,389	6,393	-4,341
Loss on asset impairment from discontinued operations	-2,238	-102,869	-168,632
Loss on early extinguishment of debt from discontinued operations	-3,345	-1,011	-1,608
Net (loss) gain on sale of properties from discontinued operations	0	-22,162	2,039
Net loss attributable to Equity Commonwealth common shareholders	($24,288)	($221,664)	($151,958)
Weighted average number of common shares outstanding - basic and diluted	125,163	112,378	83,750
Basic and diluted earnings per common share attributable to Equity Commonwealth common shareholders:
(Loss) income from continuing operations (in dollars per share)	($0.21)	($0.91)	$0.25
Income (loss) from discontinued operations (in dollars per share)	$0.02	($1.06)	($2.06)
Net loss (in dollars per share)	($0.19)	($1.97)	($1.81)

CONSOLIDATED_STATEMENTS_OF_OPE1

CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Amortization of debt discounts, premiums and deferred financing fees	($549)	$9	$3,296

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$24,012	($156,967)	($79,845)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on derivative instruments and other assets	7,407	4,918	-828
Foreign currency translation adjustments	-22,270	-43,718	6,062
Equity in unrealized (loss) income of an investee	-22	-132	47
Total comprehensive income (loss)	9,127	-195,899	-74,564
Less: comprehensive income attributable to noncontrolling interest in consolidated subsidiary	0	-20,057	-15,583
Comprehensive income (loss) attributable to Equity Commonwealth	$9,127	($215,956)	($90,147)

CONSOLIDATED_STATEMENTS_OF_SHA

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)	Total	Series C	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
In Thousands, except Share data, unless otherwise specified
Balance at Dec. 31, 2011	$3,568,517	$145,015	$368,270	$265,391	($476,657)	$837	($2,826,030)	$3,614,079	$2,482,321	($4,709)	$0
Balance (in shares) at Dec. 31, 2011		6,000,000	15,180,000	11,000,000		83,721,736
Comprehensive income (loss):
Net income (loss)	-79,845								-95,421		15,576
Unrealized gain (loss) on derivative instruments and other assets	-828									-828
Foreign currency translation adjustments	6,062									6,062
Equity in unrealized income of an investee	47									40	7
Total comprehensive income (loss)	-74,564
Issuance of shares of subsidiary, net	363,657										363,657
Adjustments to noncontrolling interest from changes in ownership of a subsidiary	0							-24,817			24,817
Redemption of shares	-150,000	-145,015						-4,985
Redemption of shares (in shares)		-6,000,000
Share grants	1,493					1		1,123			369
Share grants (in shares)						82,332
Distributions	-207,635				-52,710		-146,539				-8,386
Balance at Dec. 31, 2012	3,501,468	0	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		0	15,180,000	11,000,000		83,804,068
Comprehensive income (loss):
Net income (loss)	-156,967								-177,060		20,093
Unrealized gain (loss) on derivative instruments and other assets	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
Adjustments to noncontrolling interest from changes in ownership of a subsidiary	0							32			-32
Share grants	1,821					1		1,536			284
Share grants (in shares)						82,850
Distributions	-169,169				-44,604		-109,702				-14,863
Deconsolidation of a subsidiary	-401,444										-401,444
Balance at Dec. 31, 2013	3,363,586	0	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	118,386,918	0	15,180,000	11,000,000		118,386,918
Comprehensive income (loss):
Net income (loss)	24,012								24,012
Unrealized gain (loss) on derivative instruments and other assets	7,407									7,407
Foreign currency translation adjustments	-22,270									-22,270
Equity in unrealized income of an investee	-22									-22
Total comprehensive income (loss)	9,127
Issuance of shares, net	2,402							2,402
Issuance of shares, net (in shares)						90,135
Redemption of shares	0		-249,004		-16,205	104		265,105
Redemption of shares (in shares)			-10,264,503			10,412,499
Share grants	6,160					8		6,152
Share grants (in shares)						717,727
Distributions	-61,692				-32,095		-29,597
Balance at Dec. 31, 2014	$3,319,583	$0	$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	0	4,915,497	11,000,000		129,607,279

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$24,012	($156,967)	($79,845)
Adjustments to reconcile net income (loss) to cash provided by operating activities:
Depreciation	166,076	178,353	188,123
Net amortization of debt discounts, premiums and deferred financing fees	-552	81	3,405
Straight line rental income	-12,759	-31,229	-38,812
Amortization of acquired real estate leases	51,140	59,274	60,176
Other amortization	20,931	18,850	19,955
Loss on asset impairment	187,305	227,122	168,632
Loss on early extinguishment of debt	-1,564	61,063	1,895
Equity in earnings of investees	-24,460	-25,754	-11,420
Gain on issuance of shares by an equity investee	-17,020	0	-7,246
Gain on sale of equity investment	-171,561	-66,293	0
Distributions of earnings from investees	20,680	23,911	10,835
Net loss (gain) on sale of properties	0	20,566	-2,039
Other non-cash expenses	8,135	0	0
Change in assets and liabilities:
Restricted cash	3,486	-1,832	-6,216
Rents receivable and other assets	-54,773	-57,039	-38,801
Accounts payable and accrued expenses	10,389	-14,333	6,034
Rent collected in advance	-229	125	-1,104
Security deposits	433	611	1,548
Due to related persons	-9,277	-1,858	1,663
Cash provided by operating activities	200,392	234,651	276,783
CASH FLOWS FROM INVESTING ACTIVITIES:
Real estate acquisitions	0	-154,370	-631,279
Real estate improvements	-99,651	-114,451	-131,300
Principal payments received from direct financing lease	7,311	6,970	6,645
Principal payments received from real estate mortgages receivable	0	1,000	0
Proceeds from sale of properties, net	185,299	224,976	9,643
Proceeds from sale of equity investment, net	710,492	239,576	0
Distributions in excess of earnings from investees	0	168	5,981
Investment in Affiliates Insurance Company	0	0	-5,335
Decrease (increase) in restricted cash	900	-3,685	-2,541
Deconsolidation of a subsidiary	0	-12,286	0
Cash provided by (used in) investing activities	804,351	187,898	-748,186
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common shares, net	0	626,809	363,657
Redemption of preferred shares	0	0	-150,000
Repurchase and retirement of outstanding debt securities	0	-728,021	0
Proceeds from borrowings	0	1,036,000	1,702,500
Payments on borrowings	-785,316	-1,065,432	-1,312,982
Deferred financing fees	0	-1,204	-15,117
Distributions to common shareholders	-29,597	-109,702	-146,539
Distributions to preferred shareholders	-32,095	-44,604	-52,710
Distributions to noncontrolling interest in consolidated subsidiary	0	-14,863	-8,386
Cash (used in) provided by financing activities	-847,008	-301,017	380,423
Effect of exchange rate changes on cash	-1,126	-1,302	436
Increase (decrease) in cash and cash equivalents	156,609	120,230	-90,544
Cash and cash equivalents at beginning of year	222,449	102,219	192,763
Cash and cash equivalents at end of year	379,058	222,449	102,219
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid	146,265	192,010	204,772
Taxes paid	2,732	1,303	779
NON-CASH INVESTING ACTIVITIES:
Real estate acquisitions	0	0	-370,139
Investment in real estate mortgages receivable	0	-7,688	-1,419
Net assets transferred to Select Income REIT	0	492,736	0
Increase (decrease) in capital expenditures recorded as liabilities	7,690	-8,475	-4,501
NON-CASH FINANCING ACTIVITIES:
Assumption of mortgage notes payable	0	0	359,213
Liabilities assumed	$0	$0	$10,926

Organization

Organization	12 Months Ended
	Dec. 31, 2014
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 in central business districts (CBD) and suburban locations throughout the United States. As of December 31, 2014, we also own eleven properties (11 buildings) with a combined 1,759,000 square feet in Australia. All number of properties, number of buildings and square feet are unaudited.
	At December 31, 2014, our portfolio included the following (square feet in thousands):
		Number of Properties	Number of Buildings	Square Feet
	CBD locations	40	53	21,892
	Suburban locations	116	209	21,027
	Total portfolio	156	262	42,919
	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. SIR is a REIT that primarily owns and invests in net leased, single tenant office and industrial properties throughout the United States and leased lands in Hawaii. 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, a REIT that primarily owns properties located throughout the United States that are majority leased to government tenants, 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_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
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, 2014, 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 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 amount 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 year ended December 31, 2014, we recorded a loss on asset impairment in continuing operations totaling $185.1 million 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, 2014 and 2013, accrued environmental remediation costs by us totaling $0.5 million and $0.4 million, respectively, were included in accounts payable and accrued expenses in our consolidated balance sheets.
	Cash and Cash Equivalents.    We carry cash and short term investments with original maturities of three months or less at the date of purchase at cost plus accrued interest.
	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 were converted into our common shares or our restricted share units (RSUs), which could result in a lower EPS amount. The effect of our series D convertible preferred shares and RSUs 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, local and Australian 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.    The U.S. dollar is the functional currency for our consolidated subsidiaries operating in the United States. The functional currency for our consolidated subsidiaries in countries other than the United States is the principal currency in which the entity's assets, liabilities, income and expenses are denominated. The functional currency of our consolidated subsidiary that operates in Australia is the Australian dollar. We translate our Australian subsidiary's financial statements into U.S. dollars when we consolidate that subsidiary's financial statements on a quarterly basis. Generally, we translate assets and liabilities at the exchange rate in effect as of the balance sheet date. The resulting translation adjustments are included in cumulative other comprehensive loss in our consolidated balance sheets. We translate 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 are subject to foreign currency risk due to potential fluctuations in exchange rates between Australian and U.S. currencies. A significant change in the value of Australian currency compared to U.S. currency would have an effect on future reported results of operations and financial position. We do not currently borrow in Australian dollars or enter currency derivative contracts to mitigate foreign currency risk. As of December 31, 2014 and 2013, cumulative foreign currency translation adjustments were $(48.9) million and $(26.6) million, respectively.
	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 are required to adopt ASU 2014-08 prospectively for all disposals of components of our business classified as held for sale during fiscal periods beginning after December 15, 2014 and are currently evaluating what impact, if any, its adoption will have to the presentation of our consolidated financial statements.
	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, 2016.  We are currently in the process of evaluating the impact, if any, the adoption of this ASU will have on our consolidated financial statements.

Board_of_Trustees

Board of Trustees	12 Months Ended
	Dec. 31, 2014
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 to us written consents which they represented were from a sufficient number of holders of our outstanding common shares to remove all of our then 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 then Trustees (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 (new 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 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.

Real_Estate_Properties

Real Estate Properties	12 Months Ended
	Dec. 31, 2014
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, 2014 or 2013.
	During the years ended December 31, 2014, 2013 and 2012 we made improvements totaling $91.6 million, $122.9 million and $134.6 million, respectively, to our properties. 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 $88.6 million for expenditures related to 4,792,000 square feet of leases executed during 2014. Committed but unspent tenant related obligations based on existing leases as of December 31, 2014, were $99.9 million.
	Property Sales:
	During the years ended December 31, 2014, 2013 and 2012 , we sold the following (dollars in thousands):
	Asset		Date Sold		Number of			Number of		Square		Sales Price		Gain
					Properties			Buildings		Footage				(Loss) on
														Sale
	Sales of properties resulting in gains and losses
	Suburban properties		Dec-13		3			40		1,670,104		$	89,000	$	(25,521	)
	Land parcel		Jun-13		—			—		—		2,551		1,765
	Suburban property		Jun-13		1			1		30,105		1,600		317
	Land parcel adjacent to CBD property		Mar-13		—			—		—		1,806		1,596
	Suburban office and industrial properties(1)		Jan-13		3			18		1,060,026		10,250		1,277
					7			59		2,760,235		$	105,207	$	(20,566	)
	Suburban property		Sep-12		1			—		208,850		$	9,900	$	1,689
	Suburban property(2)		Jun-12		1			—		76,978		1,250		192
	Suburban property (3)		Apr-12		1			—		12,934		575		158
					3			—		298,762		$	11,725	$	2,039
	Sales of properties with previously recorded asset impairment losses:
	CBD and suburban properties(4)		Jun-14		14			43		2,784,098		$	215,900	$	—
	Suburban properties		Dec-13		2			2		77,394		$	2,020	$	—
	CBD and suburban properties		Nov-13		18			21		2,125,278		50,500		—
	Suburban property		Oct-13		1			2		199,418		4,000		—
	Suburban property		Oct-13		1			1		665,545		13,900		—
	Suburban properties		Oct-13		9			41		1,211,536		43,000		—
	Suburban property		Aug-13		1			3		129,452		4,100		—
	Suburban property		Jun-13		1			1		143,802		5,250		—
	Suburban property		Jun-13		1			2		356,045		16,300		—
	Suburban property		May-13		1			1		57,250		4,025		—
	Suburban property		Apr-13		1			1		618,000		830		—
					36			75		5,583,720		$	143,925	$	—
	(1) We provided mortgage financing to the buyer, an unrelated third party, totaling $7.7 million at 6.0% per annum (Note 8).
	(2) We provided mortgage financing to the buyer, an unrelated third party, totaling $1.0 million at 5.0% per annum. In September 2013, this mortgage note was prepaid in full (Note 8).
	(3) We provided mortgage financing to the buyer, an unrelated third party, totaling $0.4 million at 6.0% per annum (Note 8).
	(4) 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 were previously classified as held for sale as of December 31, 2013 and are included in income from discontinued operations for all years presented.
	We classify all properties that meet the criteria outlined in the Property, Plant and Equipment Topic of the FASB Accounting Standards Codification™, or the Codification, as held for sale, as such on our consolidated balance sheets. As of December 31, 2013, we had three CBD properties (four buildings) and 42 suburban properties (106 buildings) with a combined 8,425,548 square feet held for sale. During March 2014, the former management team ceased to actively market two CBD properties (two buildings) and 29 suburban properties (65 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 meet 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 includes the elimination of estimated costs to sell.
	Results of operations for properties sold or held for sale are included in discontinued operations in our consolidated statements of operations once the criteria for discontinued operations in the Presentation of Financial Statements Topic of the Codification are met.
	Summarized balance sheet information for all properties classified as held for sale and income statement information for properties held for sale or sold is as follows (in thousands):
			December 31,
			2013
	Real estate properties		$	536,552
	Acquired real estate leases		6,937
	Rents receivable		14,180
	Other assets, net		15,862
	Properties held for sale		$	573,531
	Mortgage notes payable, net		$	20,018
	Assumed real estate lease obligations		2,070
	Rent collected in advance		4,043
	Security deposits		2,603
	Liabilities related to properties held for sale		$	28,734
		Year Ended December 31,
		2014				2013			2012
	Rental income	$	14,243			$	55,073		$	69,752
	Tenant reimbursements and other income	1,900				6,842			8,156
	Total revenues	16,143				61,915			77,908
	Operating expenses	7,138				37,027			46,705
	Depreciation and amortization	—				12,550			28,008
	General and administrative	10				4,268			5,420
	Total expenses	7,148				53,845			80,133
	Operating income	8,995				8,070			(2,225		)
	Interest and other income	2				65			73
Interest expense	(608		)		(1,742		)	(2,189		)
Income from discontinued operations	$	8,389			$	6,393		$	(4,341	)
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 2015 and 2045. 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.
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, 2014 are as follows (in thousands):
2015	$	640,967
2016	576,172
2017	513,445
2018	459,290
2019	392,832
Thereafter	1,404,960
	$	3,987,666
One of our real estate properties 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, 2014, are as follows (in thousands):
2015	$	1,477
2016	1,477
2017	1,477
2018	1,483
2019	1,503
Thereafter	129,994
	$	137,411
The amount of ground lease expense included in operating expenses during the years ended December 31, 2014, 2013 and 2012, totaled $1.8 million, $1.9 million and $1.8 million, respectively.

Lease_Intangibles

Lease Intangibles	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 and (in thousands):
		December 31,								31-Dec-13
										Properties Held for
		2014				2013				Sale
	Acquired in-place leases	$	272,077			$	282,754			$	9,351
	Acquired above market leases	121,969				127,944				2,047
	Acquired real estate leases	394,046				410,698				11,398
	Accumulated amortization, acquired in-place leases	(136,089		)		(106,045		)		(4,461		)
	Accumulated amortization, acquired above market leases	(59,670		)		(48,841		)		—
	Acquired real estate leases, net	$	198,287			$	255,812			$	6,937
	Acquired below market leases	56,541				56,815				4,996
	Accumulated amortization	(29,757		)		(22,880		)		(2,926		)
	Assumed real estate lease obligations, net	$	26,784			$	33,935			$	2,070
	Amortization of the lease intangibles for the years ended December 31, 2014, 2013 and 2012 is as follows (in thousands):
				December 31,
		Income Statement Location		2014				2013				2012
	Amortization of acquired in-place leases	Depreciation and amortization		$	40,493			$	48,023			$	46,306
	Amortization of acquired in-place leases	Discontinued operations		—				1,720				3,909
	Amortization of above and below market leases	Rental income		(10,650		)		(10,310		)		(10,621		)
	Amortization of above and below market leases	Discontinued operations		—				775				659
	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, 2014 are approximately (in thousands):
	2015	$	39,533
	2016	31,702
	2017	24,151
	2018	20,066
	2019	14,765
	Thereafter	41,286
		$	171,503

Investment_in_Direct_Financing

Investment in Direct Financing Lease	12 Months Ended
	Dec. 31, 2014
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Investment in Direct Financing Lease	Investment in Direct Financing Lease
	We have an investment in a direct financing lease that relates to a lease with a term that exceeds 75% of the useful life of an office tower located within a mixed use property in Phoenix, AZ. We recognize 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 and $19.8 million as of December 31, 2014 and 2013, respectively, is included in other assets in our consolidated balance sheets.
	We monitor 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 and 2013.
	Our direct financing lease has an expiration date in 2045. Future minimum rentals receivable on this direct financing lease as of December 31, 2014 are as follows:
	2015	$	8,098
	2016	226
	2017	226
	2018	226
	2019	226
	Thereafter	5,887
		$	14,889

Equity_Investments

Equity Investments	12 Months Ended
	Dec. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]
Equity Investments	Equity Investments
	At December 31, 2014 and 2013, we had the following equity investments (in thousands):
		Ownership Percentage						Equity Investments						Equity in Earnings
		December 31,						December 31,						Year Ended December 31,
		2014			2013			2014				2013		2014			2013		2012
	SIR	—	%		44.2	%		$	—			$	512,078	$	24,516		$	21,153	$	—
	GOV	—	%		—	%		—				—		—			4,111		10,836
	AIC	—	%		12.5	%		—				5,913		(56		)	490		584
								$	—			$	517,991	$	24,460		$	25,754	$	11,420
	Investment in SIR
	SIR is a REIT that is primarily focused on owning and investing in net leased, single tenant properties. 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. At December 31, 2013, we owned 22,000,000, or approximately 44.2%, of the common shares of beneficial interest of SIR, with a carrying value of $512.1 million and a market value, based on quoted market prices, of $588.3 million ($26.74 per share). 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 $171.6 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, since the completion of this offering on July 2, 2013, we no longer consolidated our investment in SIR, but instead account 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 July 2, 2013 through December 31, 2013, we received cash distributions from SIR totaling $19.8 million. For the period from January 1, 2014 through July 9, 2014, we received cash distributions from SIR totaling $20.7 million.
	The following summarized financial data of SIR as reported in SIR's Annual Report on Form 10-K for the year ended December 31, 2013, or the SIR Annual Report, includes the financial position and results of operations for periods prior to July 2, 2013 (the date SIR ceased to be our consolidated subsidiary), which are included in our consolidated results of operations when SIR was our consolidated subsidiary. References in our financial statements to the SIR Annual Report are included as references to the source of the data only, and the information in the SIR Annual Report is not incorporated by reference into our financial statements. Summarized balance sheet information of SIR as of July 9, 2014, the date of sale, and December 31, 2013 and income statement information through July 9, 2014 is as follows (in thousands, except per share data):
		9-Jul-14				31-Dec-13
	Real estate properties, net	$	1,772,684			$	1,579,234
	Acquired real estate leases, net	125,163				129,426
	Cash and cash equivalents	27,531				20,025
	Rents receivable, net	60,474				55,335
	Other assets, net	17,698				17,839
	Total assets	$	2,003,550			$	1,801,859
	Revolving credit facility	$	74,000			$	159,000
	Term loan	350,000				350,000
	Mortgage notes payable	19,069				27,147
	Assumed real estate lease obligations, net	26,945				26,966
	Other liabilities	44,225				40,055
	Shareholders' equity	1,489,311				1,198,691
	Total liabilities and shareholders' equity	$	2,003,550			$	1,801,859
		For the Period from				Year Ended December 31,
		1-Jan-14
		through July 9, 2014				2013				2012
	Rental income	$	98,226			$	159,011			$	105,559
	Tenant reimbursements and other income	16,980				29,312				17,231
	Total revenues	115,206				188,323				122,790
	Operating expenses	20,982				36,382				23,796
	Depreciation and amortization	20,832				31,091				14,860
	Acquisition related costs	374				2,002				2,470
	General and administrative	7,731				12,423				8,203
	Total expenses	49,919				81,898				49,329
	Operating income	65,287				106,425				73,461
	Interest expense	(7,287		)		(13,763		)		(7,565		)
	Gain on early extinguishment of debt	243				—				—
	Income before income tax expense and equity in earnings of an investee	58,243				92,662				65,896
	Income tax (expense) benefit	(90		)		96				(290		)
	Equity in earnings of an investee	32				334				269
	Net income	$	58,185			$	93,092			$	65,875
	Weighted average common shares outstanding	52,394				44,565				27,122
	Net income per common share	$	1.11			$	2.09			$	2.43
	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 is a REIT which primarily owns properties that are majority leased to government tenants and was our wholly owned subsidiary until its initial public offering in June 2009 when it became a separate public entity.
	During the years ended December 31, 2013 and 2012, we received cash distributions from GOV totaling $4.3 million and $16.8 million, respectively.
	The following summarized financial data of GOV for the year ended December 31, 2012, is as reported in GOV's Annual Report on Form 10-K for the year ended December 31, 2013, or the GOV Annual Report. References in our financial statements to the GOV Annual Report are included as references to the source of the data only, and the information in the GOV Annual Report is not incorporated by reference into our financial statements. Summarized income statement information for the year ended December 31, 2012 is as follows (in thousands, except per share data):
		Year Ended
		December 31, 2012
	Rental income	$	203,700
	Operating expenses	75,326
	Depreciation and amortization	49,070
	Acquisition related costs	1,614
	General and administrative	11,924
	Total expenses	137,934
	Operating income	65,766
	Interest and other income	29
Interest expense	(16,892		)
Income from continuing operations before income tax expense and equity in earnings of an investee	48,903
Income tax expense	(159		)
Equity in earnings of an investee	316
Income from continuing operations	49,060
Income from discontinued operations	900
Net income	$	49,960
Weighted average common shares outstanding	48,617
Per common share:
Income from continuing operations	$	1.01
Income from discontinued operations	$	0.02
Net income	$	1.03
Investment in AIC
As of May 9, 2014, we had a net investment of $5.8 million in AIC, an insurance company owned in equal proportion until May 9, 2014 by us, our former manager RMR, GOV, SIR and four 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 shareholders 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, 2014
Other Assets [Abstract]
Real Estate Mortgages Receivable	Other Assets
	Real Estate Mortgages Receivable
	As of December 31, 2014 and 2013, we had total real estate mortgages receivable with an aggregate carrying value of $8.1 million and $8.1 million, respectively, 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 suburban office and industrial 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 suburban office 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 and credit profiles of the borrowers and have determined that no allowance for losses related to these real estate mortgages receivable were necessary at December 31, 2014 and 2013.
	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, 2014 and 2013 and (in thousands):
		December 31,						31-Dec-13
								Properties Held for
		2014			2013			Sale
	Deferred financing fees	$	41,339		$	45,985		$	272
	Accumulated amortization	(24,478		)	(21,455		)	(132		)
	Deferred financing fees, net	$	16,861		$	24,530		$	140
	Deferred leasing costs	$	184,600		$	146,996		$	13,769
	Accumulated amortization	(58,348		)	(46,228		)	(987		)
	Deferred leasing costs, net	$	126,252		$	100,768		$	12,782
	Capitalized lease incentives	$	22,650		$	20,651		$	590
	Accumulated amortization	(7,459		)	(5,392		)	(40		)
	Capitalized lease incentives, net	$	15,191		$	15,259		$	550
	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, 2014 are approximately (in thousands):
		Deferred Leasing Costs			Capitalized Lease Incentives
	2015	$	22,515		$	2,514
	2016	18,867			2,471
	2017	16,745			2,386
	2018	14,380			2,292
	2019	12,287			2,121
	Thereafter	41,458			3,407
		$	126,252		$	15,191

Indebtedness

Indebtedness	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Indebtedness	Indebtedness
	At December 31, 2014 and 2013, our outstanding indebtedness included the following (in thousands):
								December 31,
		Interest Rate at December 31, 2014			Maturity Date			2014		2013
	Unsecured revolving credit facility, at LIBOR plus a premium	1.669	%		10/19/15			$	—	$	235,000
	Unsecured term loan, at LIBOR plus a premium	2.019	%		12/15/16			400,000		500,000
	Unsecured floating rate debt	2.019	%	-1				$	400,000	$	735,000
	6.40% Senior Unsecured Notes due 2015	—	%		—			$	—	$	33,440
	5.75% Senior Unsecured Notes due 2015	5.75	%		11/1/15			138,773		138,773
	6.25% Senior Unsecured Notes due 2016	6.25	%		8/15/16			139,104		139,104
	6.25% Senior Unsecured Notes due 2017	6.25	%		6/15/17			250,000		250,000
	6.65% Senior Unsecured Notes due 2018	6.65	%		1/15/18			250,000		250,000
	7.50% Senior Unsecured Notes due 2019	—	%		—			—		125,000
	5.875% Senior Unsecured Notes due 2020	5.875	%		9/15/20			250,000		250,000
	5.75% Senior Unsecured Notes due 2042	5.75	%		8/1/42			175,000		175,000
	Unsecured fixed rate debt	6.125	%	-1				$	1,202,877	$	1,361,317
	3920 Arkwright Road	—	%		—			$	—	$	12,040
	6200 Glenn Carlson Drive	—	%		—			—		7,987
	111 Monument Circle	5.235	%		3/1/16			116,000		116,000
	225 Water Street(2)	6.03	%		5/11/16			40,059		40,334
	111 East Wacker Drive	6.29	%		7/11/16			142,666		144,522
	2501 20th Place South	7.36	%		8/1/16			10,267		10,804
	Parkshore Plaza	5.67	%		5/1/17			41,275		41,275
	600 West Chicago Avenue	—	%		—			—		265,000
	1735 Market Street(3)	5.66	%		12/2/19			171,498		173,247
	206 East 9th Street	5.69	%		1/5/21			27,965		28,391
	1320 Main Street	5.3	%		6/1/21			38,979		39,598
	33 Stiles Lane	6.75	%		3/1/22			3,132		3,456
	97 Newberry Road	5.71	%		3/1/26			6,819		7,240
	Secured fixed rate debt	5.767	%	-1				$	598,660	$	889,894
								$	2,201,537	$	2,986,211
	Unamortized net premiums and discounts							6,128		19,199
								$	2,207,665	$	3,005,410
	-1	Represents weighted average interest rate at December 31, 2014.
	-2	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 is secured by a non-recourse mortgage loan, with a current principal balance of $40.1 million. 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 has exercised its option to accelerate the maturity of the unpaid balance of the loan. The lender has filed a suit of foreclosure for this property. Since July 11, 2014, we have accrued interest on this loan at 10.03%, to include the 4.0% of default interest.
	-3	Interest on this loan is payable at a spread over LIBOR 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 Unsecured Term Loan:
	We have a $750.0 million unsecured revolving credit facility that is available for general business purposes, including acquisitions. The maturity date of our revolving credit facility is October 19, 2015 and, subject to the payment of an extension fee and meeting certain other conditions, includes an option for us to extend the stated maturity date of our revolving credit facility by one year to October 19, 2016. Borrowings under our revolving credit facility bear interest at LIBOR plus a premium, which was 150 basis points as of December 31, 2014 and 2013. We also pay a facility fee of 35 basis points per annum on the total amount of lending commitments under our revolving credit facility. Both the interest rate premium and the facility fee are subject to adjustment based upon changes to our credit ratings. As of December 31, 2014 and 2013, the interest rate payable on borrowings under our revolving credit facility was 1.7%. As of December 31, 2014, we had no balance outstanding and $750.0 million available under our revolving credit facility.
	We also have an unsecured term loan that matures in December 2016 and is prepayable without penalty at any time. Our term loan includes a feature under which maximum borrowings may be increased to up to $1.0 billion in certain circumstances. Our term loan bears interest at a rate of LIBOR plus a premium, which was 185 basis points as of December 31, 2014 and 2013. The interest rate premium is subject to adjustment based upon changes to our credit ratings. As of December 31, 2014 and 2013, the interest rate for the amount outstanding under our term loan was 2.0% and 2.0%, respectively. On December 5, 2014, we paid $100.0 million of our unsecured term loan, reducing our term loan borrowings to $400.0 million.
	Our revolving credit facility agreement and our term loan agreement provide for a right to accelerate payment of all amounts due thereunder upon the occurrence and continuation of certain events of default. The removal of our former Trustees on March 25, 2014 constituted an event of default under our revolving credit facility and term loan agreements. As a consequence, the lenders under each of these agreements became entitled to exercise certain remedies, including the right to accelerate their loans and to require that their loans bear interest at the post-default rate. Effective as of April 11, 2014, we entered into separate forbearance agreements regarding our revolving credit facility and term loan agreements. Pursuant to each forbearance agreement, the applicable lenders agreed, on and subject to the terms and conditions set forth therein, to forbear during the period (which period would have expired on June 13, 2014, but for the waivers and amendments described below) from exercising certain of their rights and remedies under the revolving credit facility or term loan, as applicable, including, without limitation, their right to accelerate repayment of the loans thereunder and to require that the loans bear interest at the post-default rate. Following the election of our new Board of Trustees on May 23, 2014, we requested that the lenders provide waivers of these events of default. Effective as of June 6, 2014, we obtained such waivers and amended the revolving credit facility and term loan agreements. Pursuant to these amendments and waivers, the lenders waived the events of default arising from the removal of our former Trustees, and each of the revolving credit facility and term loan agreements was amended to:
	•	remove as “Material Contracts” (i) the Business Management Agreement, dated as of June 8, 2009, as amended, by and between us and RMR, and (ii) the Amended and Restated Property Management Agreement, dated as of January 21, 2010, by and between us and RMR;
	•	revise the change of control Event of Default (as defined in each of the revolving credit facility and term loan agreements) so that failure of RMR to act as sole business and property manager no longer constitutes a change of control thereunder; and
	•	revise the change of control Event of Default to increase from 25% to 35% the level of voting power with respect to the Company’s shares that constitutes a change of control if acquired by any person or group.
	In addition, the forbearance agreements were deemed to be terminated upon effectiveness of these amendments and waivers, other than certain provisions thereof relating to the release of claims against, and confirming no waivers by, the lenders.
	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 replaces our prior credit agreement, dated as of August 9, 2010, and our prior term loan agreement, dated as of December 16, 2010.  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.
	Unsecured Senior Notes:
	On November 17, 2014, we prepaid 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 prepaid at par $33.4 million of our 6.40% unsecured senior notes due 2015.
	In October 2013, we prepaid at par all $99.0 million of our 5.75% unsecured senior notes due 2014, using borrowings under our revolving credit facility.
	In March 2013, we purchased a total of $670.3 million of the outstanding principal amount of the following senior notes for $726.2 million, excluding transaction costs, pursuant to a tender offer:
	Senior Note	Principal				Purchase
						Price
	5.75% Senior Notes due February 15, 2014	$	145,612			$	148,746
	6.40% Senior Notes due February 15, 2015	152,560				164,140
	5.75% Senior Notes due November 1, 2015	111,227				121,047
	6.25% Senior Notes due August 15, 2016	260,896				292,218
		$	670,295			$	726,151
	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, 2014, 10 of our properties (14 buildings) with an aggregate net book value of $705.3 million had secured mortgage notes totaling $609.2 million (including net premiums and discounts) maturing from 2015 through 2026.
	On October 31, 2014 we repaid 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 using cash on hand.
In addition, we prepaid $7.1 million of 5.76% mortgage debt in December 2013, in connection with the sale of the related property. In connection with the prepayment of mortgage debt, we recorded a loss on early extinguishment of debt totaling $1.0 million from a prepayment premium and the write off of unamortized discount.
Credit Facility and Term Loan 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, 2014, 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.
Required Principal Payments:
The required principal payments due during the next five years and thereafter under all of our outstanding debt at December 31, 2014 are as follows (in thousands):
2015	$	145,973
2016	848,708
2017	295,592
2018	254,614
2019	165,422
Thereafter	491,228
	$	2,201,537

Shareholders_Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders' Equity
	Common Share Issuances:
	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.
	During the year ended December 31, 2014, we issued 10,412,499 common shares to holders of 10,264,503 of our series D cumulative convertible preferred shares (series D preferred shares) who converted their series D preferred shares into our common shares.
	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, 2014, 2013 and 2012:
		Year Ended December 31,
		2014		2013		2012
	Ordinary income	—	%	—	%	61.72	%
	Return of capital	—	%	100	%	38.28	%
	Capital gain	100	%	—	%	—	%
	Unrecaptured Section 1250 gain	—	%	—	%	—	%
		100	%	100	%	100	%
	Series D Preferred Shares:
	Each of our 4,915,497 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 2,363,248 additional common shares at December 31, 2014. 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.  We calculated the Fundamental Change Conversion Rate as 1.0145 common shares per $25.00 liquidation preference.  May 14, 2014 was the last day upon which holders of the series D preferred shares could exercise their Fundamental Change Conversion Right.  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 recorded a 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, 2014, we had 4,915,497 outstanding series D preferred shares that were convertible into 2,363,248 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
	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.
	On July 25, 2014, our Board of Trustees declared a dividend of $0.81250 per series D preferred share to be paid on August 15, 2014 to shareholders of record on August 5, 2014. This dividend includes the accrued dividend of $0.40625 per share for the period from February 15, 2014 to May 14, 2014 and the accrued dividend of $0.40625 per share for the period from May 15, 2014 to August 14, 2014. On July 25, 2014, our Board of Trustees also declared a dividend of $0.90625 per series E preferred share to be paid on August 15, 2014 to shareholders of record on August 5, 2014. This dividend includes the accrued dividend of $0.453125 per share for the period from February 15, 2014 to May 14, 2014 and the accrued dividend of $0.453125 per share for the period from May 15, 2014 to August 14, 2014. The aggregate amounts of $0.81250 and $0.90625 paid to the holders of series D preferred shares and series E preferred shares, respectively, represent the full amounts of accrued and unpaid dividends under the series D preferred shares and the series E preferred shares, respectively.
	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 15.41% of each distribution to our shareholders for the tax year ended December 31, 2014 consists of an alternative minimum tax adjustment.

Cumulative_Other_Comprehensive

Cumulative Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Cumulative Other Comprehensive Loss	Cumulative Other Comprehensive Loss
	The following table presents a roll forward of amounts recognized in cumulative other comprehensive loss by component for the year ended December 31, 2014:
		Year Ended December 31, 2014
		Unrealized			Foreign			Equity in			Total
		Gain (Loss)			Currency			Unrealized
		on Derivative			Translation			Gain (Loss) of
		Instruments and Other Assets			Adjustments			an Investee
	Balances as of December 31, 2013	$	(11,706	)	$	(26,647	)	$	22		$	(38,331	)
	Other comprehensive income (loss) before reclassifications	2,387			(22,270		)	42			(19,841		)
	Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	5,020			—			(64		)	4,956
	Net current period other comprehensive income (loss)	7,407			(22,270		)	(22		)	(14,885		)
	Balances as of December 31, 2014	$	(4,299	)	$	(48,917	)	$	—		$	(53,216	)
	The following table presents reclassifications out of cumulative other comprehensive loss for the year ended December 31, 2014:
		Year Ended December 31, 2014
	Details about Cumulative Other Comprehensive Loss Components	Amounts Reclassified from			Affected Line Items in the
		Cumulative Other Comprehensive			Statement of Operations
		Loss to Net Income (Loss)
	Interest rate swap contracts	$	5,020		Interest expense
	Realized gains and losses on available for sale securities	(64		)	Equity in earnings of investees
		$	4,956

Noncontrolling_Interest_in_Con

Noncontrolling Interest in Consolidated Subsidiary	12 Months Ended
	Dec. 31, 2014
Noncontrolling Interest [Abstract]
Noncontrolling Interest in Consolidated Subsidiary	Noncontrolling Interest in Consolidated Subsidiary
	At December 31, 2013 and 2012, we owned 22,000,000, or approximately 44.2% and 56.0%, respectively, of SIR's outstanding common shares. SIR is a REIT that is focused on owning and investing in net leased, single tenant properties and was a 100% owned subsidiary of ours until the SIR IPO in March 2012, when it became a publicly owned company listed on the NYSE. We were SIR's largest shareholder and SIR was one of our consolidated subsidiaries until July 2, 2013. During the time that SIR was our majority owned consolidated subsidiary (from the date of the SIR IPO to July 2, 2013), the portion of SIR's equity that we did not own is reported as noncontrolling interest in our consolidated balance sheets, and the portion of SIR's net income not allocated to us is reported as noncontrolling interest in our consolidated statements of operations. See Note 19 for additional information regarding the SIR IPO and Note 7 for information regarding the deconsolidation of SIR.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes
	Our provision for income taxes consists of the following (amounts in thousands):
		Year Ended December 31,
		2014			2013				2012
	Current:
	State	$	350		$	519			$	765
	Foreign	2,772			2,572				199
		3,122			3,091				964
	Deferred:
	Foreign	69			(457		)		2,243
		69			(457		)		2,243
	Income tax provision	$	3,191		$	2,634			$	3,207
	A reconciliation of our effective tax rate and the U.S. Federal statutory income tax rate is as follows:
		Year Ended December 31,
		2014		2013			2012
	Taxes at statutory U.S. federal income tax rate	35	%	35	%		35	%
	Dividends paid deduction and net operating loss utilization	(35.00	)%	(35.00	)%		(35.00	)%
	State, local, and foreign income taxes, net of federal tax benefit	11.73	%	(1.71	)%		(4.20	)%
	Effective tax rate	11.73	%	(1.71	)%		(4.20	)%
	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 and 2013, we had deferred tax assets of $2.4 million and $2.6 million, respectively, net of valuation allowances of $0.6 million and $0.5 million, respectively, and deferred tax liabilities of $3.1 million and $3.3 million, respectively, which primarily relate to different carrying amounts for financial reporting and for Australian income tax purposes related to our properties and operations in Australia. Because we are uncertain of our ability to realize the future benefit of certain Australian loss carry forwards, we have reduced our net deferred income tax assets by a valuation allowance, as noted above. The deferred tax assets primarily relate to depreciation differences and the deferred tax liabilities primarily relate to straight line rent adjustments.

Derivative_Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2014
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 foreign currency exchange rates and interest rates.  The only risk we currently manage by using derivative instruments is a part of our interest rate risk.  Although we have not done so as of December 31, 2014, we may manage our Australian currency exchange exposure by borrowing in Australian dollars or using derivative instruments in the future, depending on the relative significance of our business activities in Australia at that time.
	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. Interest rate collars designated as cash flow hedges involve the receipt of variable-rate amounts if interest rates rise above the cap strike rate on the contract and payments of variable-rate amounts if interest rates fall below the floor strike rate on the contract.
	The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. During 2014, 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 accumulated other comprehensive income 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 $4.7 million will be reclassified from other comprehensive income as an increase to interest expense.
	We have interest rate swap agreements to manage our interest rate risk exposure on $171.5 million of mortgage debt due 2019, which require interest at a premium 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, 2014, 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			$171,498
	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, 2014 and 2013 (amounts in thousands):
					Fair Value as of December 31,
	Interest Rate Derivative Designated as Hedging Instrument		Balance Sheet Location		2014				2013
	Pay-fixed swaps		Accounts payable and accrued expenses		$	7,462			$	11,706
	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, 2014, 2013 and 2012 (amounts in thousands):
		Year Ended December 31,
		2014				2013				2012
	Balance at beginning of year	$	(11,706	)		$	(16,624	)		$	(15,796	)
	Amount of loss recognized in cumulative other comprehensive loss	(776		)		(103		)		(5,790		)
	Amount of loss reclassified from cumulative other comprehensive loss into interest expense	5,020				5,021				4,962
	Unrealized gain (loss) on derivative instruments	4,244				4,918				(828		)
	Balance at end of year	$	(7,462	)		$	(11,706	)		$	(16,624	)
	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 its indebtedness, then we could also be declared in default on our derivative obligations.
	As of December 31, 2014, 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 $8.1 million. As of December 31, 2014, 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 $8.1 million at December 31, 2014.

ShareBased_Compensation

Share-Based Compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation
	2012 Equity Compensation Plan
	We have common shares available for issuance under the terms of our 2012 Equity Compensation Plan, or 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 and 2,000 common shares in 2012 with an aggregate market value of $0.2 million on the date of the 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.
	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, 2013 and 2012, is as follows:
		Number			Weighted
		of			Average
		Shares			Grant Date
					Fair Value
	Unvested shares at December 31, 2011	103,615			23.32
	Granted	83,617			15.99
	Vested	(71,244	)		15.75
	Forfeited	(1,285	)		18.74
	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			20.7
	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 compensation expense in general and administrative expense related to the vesting of these shares.
	During the years ended December 31, 2014, 2013 and 2012, we recorded $3.4 million, $1.8 million and $1.2 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 and $0.5 million for the years ended December 31, 2013 and 2012, respectively.
	2012 Plan Amendment
	On October 28, 2014, our Board of Trustees approved an amendment to the 2012 Plan (as amended, the Plan).  This amendment permits us to issue RSUs.  Additionally, on October 28, 2014, our Compensation Committee (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.
	Recipients of the Company’s unvested restricted shares have the same voting rights as any other common share holder. 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 share holder.
	On October 28, 2014, the Committee approved the one-time grant of restricted common shares and restricted share units 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 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.
	A summary of restricted share and RSU activity under the Plan for the year ended December 31, 2014 is as follows:
		Number			Weighted		Number	Weighted
		of			Average		of	Average
		Restricted Shares			Grant Date		RSUs	Grant Date
					Fair Value			Fair Value
	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	$	—
	The restricted shares are service based awards and vest over a four year period. The restricted shares were granted on October 28, 2014 and were valued using $26.66 per share, the closing price of our common shares on the NYSE on that day. The 710,182 unvested restricted shares as of December 31, 2014 are scheduled to vest as follows: 86,517 shares in 2015, 155,916 shares in 2016, 155,916 shares in 2017 and 311,833 shares in 2018. As of December 31, 2014, the estimated future compensation expense for the unvested restricted shares was $17.4 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 compensation expense will be recorded for the restricted shares is approximately 3.5 years.
	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 total shareholder return (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. Dividends on the RSUs will be earned during the vesting period. 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. As of December 31, 2014, the estimated future compensation expense for the unvested RSUs was $19.2 million. The weighted average period over which the compensation expense will be recorded for the RSUs is approximately 3.3 years.
	The assumptions and fair values for the RSUs granted for the year ended December 31, 2014 is included in the following table on a per share basis.
		2014
	Fair value of RSUs granted	$	15.99
	Expected term (years)	4
	Expected volatility	—
	Expected dividend yield	1.88		%
	Risk-free rate	0.84		%
	During the year ended December 31, 2014, we recorded $2.6 million of compensation expense in general and administrative expense for grants to the Trustees and the Company's employees related to our Plan. At December 31, 2014, 849,569 common shares remain available for issuance under the Plan.

Fair_Value_of_Assets_and_Liabi

Fair Value of Assets and Liabilities

12 Months Ended

Dec. 31, 2014

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 2014 and 2013, categorized by the level of inputs used in the valuation of each asset and liability:

Fair Value at December 31, 2014 Using

Description

Total

Quoted Prices in

Significant Other

Significant

Active Markets for

Observable Inputs

Unobservable

Identical Assets

(Level 2)

Inputs

(Level 1)

(Level 3)

Recurring Fair Value Measurements:

Effective portion of interest rate contracts

$

(7,462

)

$

—

$

(7,462

)

$

—

Derivative liability

$

(6,658

)

$

—

$

—

$

(6,658

)

Fair Value at December 31, 2013 Using

Description

Total

Quoted Prices in

Significant Other

Significant

Active Markets for

Observable Inputs

Unobservable

Identical Assets

(Level 2)

Inputs

(Level 1)

(Level 3)

Recurring Fair Value Measurements:

Effective portion of interest rate contracts

$

(11,706

)

$

—

$

(11,706

)

$

—

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, 2014, 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 19). 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 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 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. The valuation techniques and significant unobservable inputs used for our level 3 fair value measurement at December 31, 2014 were as follows:

Description

Fair Value at December 31, 2014

Primary

Unobservable Inputs

Rate

Valuation

Techniques

Derivative liability

$

(6,658

)

Monte Carlo

Risk-free rate

0.50%

simulation

Volatility

20.00%

Properties Held and Used

In 2014, we ceased to actively market two CBD properties and 29 suburban properties with a combined 5,641,450 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, 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

Primary

Unobservable

Weighted Average(1)

31-Dec-14

Valuation

Inputs

Techniques

Properties held and used on which we recognized impairment losses

$

414,625

Discounted cash flows

Discount rate

10.20%

Exit capitalization rate

9.10%

(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

Primary

Unobservable

Rate

June 30, 2014

Valuation

Inputs

Techniques

225 Water Street

$

19,589

Discounted cash flows

Discount rate

8%

Exit capitalization rate

8%

For the period ended December 31, 2013, we recorded a net loss on asset impairment totaling $204.0 million (excluding $23.1 million of asset impairment recorded on properties sold during 2013) for 39 of our properties to reduce the aggregate carrying value of these properties from $668.3 million to their estimated fair value of $471.5 million, reflected in the table below, less costs to sell of $7.2 million, for a net of $464.3 million. All of these properties were classified as held for sale as of December 31, 2013. We used third party broker information, independent appraisals and sales comparables (level 3 inputs), in determining the fair value of these properties. The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at December 31, 2013 were as follows:

Description

Fair Value at

Primary

Unobservable

Weighted Average

31-Dec-13

Valuation

Inputs

Techniques

Properties held for sale on which we recognized impairment losses

$

471,457

Discounted cash flows

Discount rate

10.30%

Exit capitalization rate

8.80%

Financial Instruments

In addition to the assets and liabilities described in the above table, our financial instruments include our cash and cash equivalents, rents receivable, investment in direct financing lease receivable, real estate mortgages receivable, restricted cash, revolving credit facility, senior notes and mortgage notes payable, accounts payable and accrued expenses, rent collected in advance, security deposits and amounts due to related persons. At December 31, 2014 and 2013, the fair values of these additional financial instruments, excluding mortgage debt related to properties held for sale, were not materially different from their carrying values, except as follows (in thousands):

December 31, 2014

December 31, 2013

Carrying

Fair

Carrying

Fair

Amount

Value

Amount

Value

Revolving credit facility, senior unsecured debt and mortgage notes payable, net

$

2,207,665

$

2,263,535

$

3,005,410

$

3,037,649

The fair values of our revolving credit facility, 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, 2014, no single tenant of ours is responsible for more than 3% of our total rents.

Our derivative financial instruments, including interest rate swaps, are entered into 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, 2014
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,
		2014			2013			2012
	Numerator for earnings per common share - basic and diluted:
	Income (loss) from continuing operations	$	21,206		$	(38,914	)	$	92,697
	Gain on sale of properties	—			1,596			—
	Net income attributable to noncontrolling interest in consolidated subsidiary	—			(20,093		)	(15,576		)
	Preferred distributions	(32,095		)	(44,604		)	(51,552		)
	Distribution on conversion of preferred shares	(16,205		)	—			(4,985		)
	(Loss) income from continuing operations attributable to Equity Commonwealth common shareholders	(27,094		)	(102,015		)	20,584
	Discontinued operations	2,806			(119,649		)	(172,542		)
	Numerator for net loss per share - basic and diluted	$	(24,288	)	$	(221,664	)	$	(151,958	)
	Denominator for earnings per common share - basic and diluted:
	Weighted average number of common shares outstanding - basic and diluted	125,163			112,378			83,750
	Earnings per share - basic and diluted:
	(Loss) income from continuing operations attributable to Equity Commonwealth common shareholders	$	(0.21	)	$	(0.91	)	$	0.25
	Discontinued operations	0.02			(1.06		)	(2.06		)
	Net loss per share - basic and diluted	$	(0.19	)	$	(1.97	)	$	(1.81	)
	Anti-dilutive securities:
	Effect of Series D preferred shares; 6 1/2% cumulative convertible(1)	4,175			7,298			7,298
	Effect of RSUs(2)	—			—			—
	(1) The Series D preferred shares are anti-dilutive as the Company reported a net loss for the year ended December 31, 2014.
	(2) As of December 31, 2014, the Company's performance criteria detailed in the Plan would have resulted in zero RSU's being issued.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Segment Information	Segment Information
	Our primary business is the ownership and operation of office properties. We account for each of our individual properties as a separate operating segment. We have aggregated our separate operating segments into two reportable segments based on our primary method of internal reporting: CBD properties and suburban properties. More than 90% of our CBD and suburban properties are office properties. Each of our reportable segments includes properties with similar operating and economic characteristics that are subject to unique supply and demand conditions. Our operating segments (i.e., our individual properties) are managed and operated consistently in accordance with our standard operating procedures. We use property net operating income, or NOI, and cash yield to evaluate the performance of our operating segments. We define NOI as income from our real estate including lease termination fees received from tenants less our property operating expenses, which include property marketing costs. NOI excludes amortization of capitalized tenant improvement costs and leasing commissions.
	As of December 31, 2014, we owned 40 CBD properties (53 buildings) and 116 suburban properties (209 buildings). Prior periods have been restated to reflect properties reclassified from discontinued operations to continuing operations during 2014.
	Property level information by operating segment as of December 31, 2014 and 2013, excluding assets held for sale as of December 31, 2013, and for the years ended December 31, 2014, 2013 and 2012, is as follows (in thousands):
		As of December 31,
		2014			2013
	Square feet (in thousands):
	CBD properties	21,892			21,889
	Suburban properties	21,027			21,026
	Total properties(1)	42,919			42,915
	(1) The change in total square feet from December 31, 2013 to 2014 is a result of remeasuring certain spaces.
		As of December 31,
		2014				2013
	Investment in real estate properties, net of accumulated depreciation
	CBD properties	$	2,966,926			$	3,001,397
	Suburban properties	1,731,072				1,640,709
	Total properties	$	4,697,998			$	4,642,106
		Year Ended December 31,
		2014				2013			2012
	Rental income:
	CBD properties	$	436,426			$	439,716		$	423,453
	Suburban properties	255,273				323,546			351,147
	Total properties	$	691,699			$	763,262		$	774,600
	Tenant reimbursements and other income:
	CBD properties	$	112,481			$	120,352		$	116,326
	Suburban properties	57,677				69,415			70,161
	Total properties	$	170,158			$	189,767		$	186,487
	NOI:
	CBD properties	$	289,141			$	294,306		$	290,810
	Suburban properties	184,734				248,678			272,604
	Total properties	$	473,875			$	542,984		$	563,414
	As of December 31, 2014, 2013 and 2012, we had assets in Australia of $252.0 million, $285.1 million and $362.0 million, respectively. For the years ended December 31, 2014, 2013 and 2012, we recognized revenues in Australia of $30.1 million, $33.1 million and $34.7 million, respectively. We do not believe either of our segments is dependent on the Australian assets.
	The following table includes the reconciliation of NOI to net income (loss), the most directly comparable financial measure under GAAP reported in our consolidated financial statements. We consider NOI to be an appropriate supplemental measure to net income(loss) because it may help both investors and management to understand the operations of our properties. We use NOI internally to evaluate individual, regional and combined property level performance, and we believe that NOI provides useful information to investors regarding our results of operations because it reflects only those income and expense items that are incurred at the property level and may facilitate comparisons of our operating performance between periods and with other REITs. The calculation of NOI excludes certain components of net income (loss) in order to provide results that are more closely related to our properties' results of operations. NOI does not represent cash generated by operating activities in accordance with GAAP and should not be considered as an alternative to net income (loss), net income (loss) attributable to Equity Commonwealth, net loss attributable to Equity Commonwealth common shareholders, operating (loss) income or cash flow from operating activities, determined in accordance with GAAP, or as an indicator of our financial performance or liquidity, nor is this measure necessarily indicative of sufficient cash flow to fund all of our needs. This measure should be considered in conjunction with net income (loss), net income (loss) attributable to Equity Commonwealth, net (loss) attributable to Equity Commonwealth common shareholders, operating (loss) income and cash flow from operating activities as presented in our consolidated statements of operations, consolidated statements of comprehensive income (loss) and consolidated statements of cash flows. Other REITs and real estate companies may calculate NOI differently than we do.
	A reconciliation of NOI to net income (loss) for the years ended December 31, 2014, 2013 and 2012 is as follows:
		Year Ended December 31,
		2014				2013			2012
	Rental income	$	691,699			$	763,262		$	774,600
	Tenant reimbursements and other income	170,158				189,767			186,487
	Operating expenses	(387,982		)		(410,045		)	(397,673		)
	NOI	$	473,875			$	542,984		$	563,414
	NOI	$	473,875			$	542,984		$	563,414
	Depreciation and amortization	(227,532		)		(234,402		)	(230,284		)
	General and administrative	(113,155		)		(80,504		)	(49,312		)
	Loss on asset impairment	(185,067		)		(124,253		)	—
	Acquisition related costs	(5		)		(318		)	(5,648		)
	Operating (loss) income	(51,884		)		103,507			278,170
	Interest and other income	1,561				1,229			1,410
	Interest expense	(143,230		)		(173,011		)	(202,055		)
	Gain (loss) on early extinguishment of debt	4,909				(60,052		)	(287		)
	Gain on sale of equity investment	171,561				66,293			—
	Gain on issuance of shares by an equity investee	17,020				—			7,246
	Income (loss) from continuing operations before income tax expense and equity in earnings of investees	(63		)		(62,034		)	84,484
	Income tax expense	(3,191		)		(2,634		)	(3,207		)
	Equity in earnings of investees	24,460				25,754			11,420
	Income (loss) from continuing operations	21,206				(38,914		)	92,697
	Income (loss) from discontinued operations	8,389				6,393			(4,341		)
	Loss on asset impairment from discontinued operations	(2,238		)		(102,869		)	(168,632		)
	Loss on early extinguishment of debt from discontinued operations	(3,345		)		(1,011		)	(1,608		)
	Net (loss) gain on sale of properties from discontinued operations	—				(22,162		)	2,039
	Income (loss) before gain on sale of properties	24,012				(158,563		)	(79,845		)
	Gain on sale of properties	—				1,596			—
	Net income (loss)	$	24,012			$	(156,967	)	$	(79,845	)

Related_Person_Transactions

Related Person Transactions	12 Months Ended
	Dec. 31, 2014
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, 2014, 2013 and 2012. 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 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 is $0.2 million for the 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. The license expires on May 31, 2015, unless terminated earlier in accordance with the terms of the license. Mr. Zell, our Chairman, is the Chairman and Chief Executive Officer of Equity Group Investments, and Mr. Helfand, our President and Chief Executive Officer, is the Co-President of Equity Group Investments. This license agreement was approved by the Audit Committee of the Board of Trustees.
	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 initial term of the lease expires on May 31, 2015. The lease payment is $0.2 million for the initial term. 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 is approximately seven months commencing on or about October 22, 2014, expiring on May 31, 2015, with one 3-month renewal option. The sublease payment is approximately $0.2 million for the initial term. This sublease was approved by the Audit Committee of the Board of Trustees.
	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 since February 2013 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 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 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.
	According to Related/Corvex’s Schedule 13D, as amended, Related/Corvex each owned approximately 2.8%, or approximately 5.7% in the aggregate, of our common shares as of August 5, 2014.  Seven of our current Trustees were nominated by Related/Corvex for election at our Special Meeting to fill the vacancies on our Board of Trustees created by the removal of our former Trustees as a result of Related/Corvex’s consent solicitation. In addition, Sam Zell and David Helfand, our Chairman and Chief Executive Officer, respectively, are associated with EGI-CW Holdings, L.L.C., which entered into certain arrangements with Related/Corvex in connection with the agreement of Messrs. Zell and Helfand to become nominees of Related/Corvex. Also, James Lozier, one of our new Trustees, is party to an agreement with Related pursuant to which certain amounts have been paid or are payable to him for consulting and other services provided to Related. In addition, James Corl, one of our new Trustees, is entitled to receive payments based on the performance of funds managed by Siguler Guff, which funds invest in an entity associated with Related.
	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 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 (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.
	Our former Trustees had given our Compensation Committee, which was comprised exclusively of our former independent Trustees, authority to act on our behalf with respect to our management agreements with RMR. The charter of our former Compensation Committee required the committee to annually review the terms of these agreements, evaluate RMR's performance under the agreements and determine whether to renew, amend or terminate the management agreements.
	In 2013, our former Compensation Committee retained FTI Consulting, Inc., a nationally recognized compensation consultant experienced in REIT compensation programs, to assist the committee in developing the terms of the incentive fee payable to RMR under our business management agreement with RMR beginning in 2014. In connection with retaining this consultant, our former Compensation Committee determined that the consultant did not have any conflicts of interest which would prevent the consultant from advising the committee.
	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 amended and restated business management agreement with RMR as described above, we recognized business management fees 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 10.0% of the base business management fee we recognized for such period.
	For 2013 and 2012, 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 and 2012, our business management agreement provided for RMR to be paid an incentive fee equal to 15% 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 2012 results and 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 and $43.6 million for 2013 and 2012, respectively. These amounts are 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 or 2012.
	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 and $33.7 million for 2013 and 2012, respectively. 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 (formerly the MacarthurCook Industrial Property Fund), a subsidiary of ours (CWHAT). The terms of the Australia Management Agreement are substantially similar to the terms of the management agreement we had with MacarthurCook. 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 and the year 2012, 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 and $1.8 million in January 2013 and the year 2012, respectively, 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 and $0.4 million and for 2013 and 2012, respectively, 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 and $0.6 million in rental income from RMR in 2013 and 2012, respectively, 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 and 71,617 restricted shares with an aggregate value of $1.1 million to such persons in 2013 and 2012, respectively, 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 15).
	Termination and Cooperation Agreement: On September 30, 2014, we entered into a termination and cooperation agreement (Termination 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. Our existing Australia Management Agreement with RMR Australia will remain in effect until December 31, 2015, unless earlier terminated.
	Pursuant to the Termination Agreement, until February 28, 2015, Manager has agreed to use best efforts to assist us in the transition of our management and operations. We have agreed to pay Manager $1.2 million per month for transition services from October 1, 2014 to February 28, 2015. The payment of the transition fee also covers continued management and other services for the Australian assets through February 28, 2015. If we require such services beyond February 28, 2015, we have agreed to pay Manager $0.1 million per month until the Australia Management Agreement is terminated.
	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 12, 2012, SIR completed the SIR IPO. Until July 9, 2014, we were SIR's largest shareholder and, until July 2, 2013, SIR was one of our consolidated subsidiaries. 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 is 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. Our annual premiums for this property insurance in 2012 were $6.6 million, before adjustments made for acquisitions or dispositions we made during that period.
	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, including our 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_D

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2014
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 2014 and 2013. Reclassifications have been made to the prior quarterly results to reflect properties reclassified from discontinued operations to continuing operations during 2014.
		2014
		First		Second			Third			Fourth
		Quarter(1)		Quarter(1)			Quarter(1)			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 and 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.
		2013
		First		Second			Third			Fourth
		Quarter(1)		Quarter(1)			Quarter(1)			Quarter
	Total revenues	$	262,612	$	262,188		$	214,201		$	214,028
	Net income (loss) attributable to Equity Commonwealth common shareholders	14,516		7,738			(227,466		)	(16,452		)
	Net income (loss) attributable to Equity Commonwealth common shareholders per share—basic and diluted	0.15		0.07			(1.92		)	(0.14		)
	Common distributions declared	0.25		0.25			0.25			0.25
	-1	Amounts previously reported have been adjusted as follows:
		2013
		First		Second			Third			Fourth
		Quarter		Quarter			Quarter			Quarter
	Total revenues as previously reported	$	242,653	$	246,181		$	198,283		$	198,419
	Total revenues from properties reclassified to discontinued operations during 2014	19,959		16,007			15,918			15,609
	Total revenues restated	$	262,612	$	262,188		$	214,201		$	214,028
	The decrease in revenues and net loss attributable to Equity Commonwealth common shareholders for the third quarter and fourth quarter 2013 were largely the result of the deconsolidation of SIR, which occurred in July 2013. Also, negatively impacting the net loss attributable to Equity Commonwealth common shareholders in the third quarter was the loss on asset impairment of $124.3 million.

Subsequent_Event

Subsequent Event	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event
	On January 29, 2015, we entered into a new unsecured revolving credit facility and unsecured term loan. See Note 9 for additional information regarding this agreement.

SCHEDULE_II_VALUATION_AND_QUAL

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2014
Valuation and Qualifying Accounts [Abstract]
Schedule II Valuation and Qualifying Accounts
	Description	Balance at		Charged to		Deductions			Balance at
		Beginning of		Costs and					End of
		Period		Expenses					Period
	Year Ended December 31, 2012:
	Allowance for doubtful accounts	$	12,575	$	504	$	(3,117	)	$	9,962
	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

SCHEDULE_III_REAL_ESTATE_AND_A

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION	12 Months Ended
	Dec. 31, 2014
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		Property		Encumbrances(1)			Land			Buildings and			Costs				Impairment/Write Downs			Land		Buildings and				Total(2)		Accumulated		Date	Original
							Location								Improvements			Capitalized									Improvements						Depreciation(3)		Acquired	Construction
																		Subsequent to																		Date
																		Acquisition, Net
	2501 20th Place South		Birmingham		AL		CBD		$	10,267		$	4,000		$	19,604		$	511			$	—		$	4,002	$	20,113			$	24,115	$	4,153	12/27/06	2001
	420 20th Street North		Birmingham		AL		CBD		—			1,740			49,565			4,397				—			1,740		53,962				55,702		4,724		7/29/11	1986
	Inverness Center		Birmingham		AL		Suburban		—			8,525			38,367			4,807				—			8,525		43,174				51,699		5,214		12/9/10	1980;1981;1982
	785 Schilinger Road South		Mobile		AL		Suburban		—			1,540			9,732			(3		)		—			1,540		9,729				11,269		1,747		10/22/07	1998
	Arizona Center		Phoenix		AZ		CBD		—			22,614			64,105			11,157				—			22,614		75,262				97,876		6,970		3/4/11	1990;1998
	4 South 84th Avenue		Tolleson		AZ		Suburban		—			1,257			9,210			915				—			1,257		10,125				11,382		2,639		12/19/03	1989
	One South Church Avenue		Tucson		AZ		CBD		—			3,261			26,357			3,762				—			3,262		30,118				33,380		9,129		2/27/02	1986
	Parkshore Plaza		Folsom		CA		Suburban		41,275			4,370			41,749			510				—			4,370		42,259				46,629		3,782		6/16/11	1999
	Leased Land		Gonzalez		CA		Suburban		—			18,941			9,060			3,824				—			18,940		12,885				31,825		2,276		8/31/10	-
	Sky Park Centre		San Diego		CA		Suburban		—			936			8,094			756				—			935		8,851				9,786		3,029		6/24/02	1986
	Sorrento Valley Business Park		San Diego		CA		Suburban		—			1,425			12,842			3,308				—			1,425		16,150				17,575		6,951		12/31/96	1984
	1921 E. Alton Avenue		Santa Ana		CA		Suburban		—			1,363			10,158			1				—			1,362		10,160				11,522		2,908		11/10/03	2000
	9110 East Nichols Avenue		Centennial		CO		Suburban		—			1,708			14,616			3,962				—			1,708		18,578				20,286		5,739		11/2/01	1984
	7450 Campus Drive		Colorado Springs		CO		Suburban		—			1,250			7,982			249				—			1,250		8,231				9,481		962		4/30/10	1996
	1225 Seventeenth Street		Denver		CO		CBD		—			22,400			110,090			12,616				—			22,400		122,706				145,106		17,456		6/24/09	1982
	5073, 5075, & 5085 S. Syracuse Street		Denver		CO		Suburban		—			4,720			58,890			—				—			4,720		58,890				63,610		6,871		4/16/10	2007
	1601 Dry Creek Drive		Longmont		CO		Suburban		—			3,714			24,397			4,244				—			3,715		28,640				32,355		8,166		10/26/04	1982
	129 Worthington Ridge Road		Berlin		CT		Suburban		—			2,770			8,409			1,161				(7,088		)	1,114		4,138				5,252		714		10/24/06	1968
	97 Newberry Road		East Windsor		CT		Suburban		6,819			2,960			12,360			30				—			2,943		12,407				15,350		2,555		10/24/06	1989
	185 Asylum Street		Hartford		CT		CBD		—			15,930			60,312			1,856				—			15,930		62,168				78,098		4,247		3/30/12	1983
	599 Research Parkway		Meriden		CT		Suburban		—			768			6,164			1,160				—			768		7,324				8,092		1,938		7/24/03	1982
	33 Stiles Lane		North Haven		CT		Suburban		3,132			2,090			9,141			216				(1,654		)	1,799		7,994				9,793		1,949		10/24/06	1970
	181 Marsh Hill Road		Orange		CT		Suburban		—			2,270			7,943			581				—			2,271		8,523				10,794		1,659		10/24/06	1993
	101 Barnes Road		Wallingford		CT		Suburban		—			367			3,301			1,153				(3,398		)	154		1,269				1,423		39		12/22/98	1988
	15 Sterling Drive		Wallingford		CT		Suburban		—			2,010			7,352			235				(4,792		)	1,139		3,666				4,805		116		10/24/06	1978
	35 Thorpe Avenue		Wallingford		CT		Suburban		—			640			10,017			1,276				(5,431		)	518		5,984				6,502		185		6/1/98	1986
	50 Barnes Industrial Road North		Wallingford		CT		Suburban		—			2,300			8,621			2,955				(2,472		)	1,865		9,539				11,404		2,457		10/24/06	1976
	5-9 Barnes Industrial Road		Wallingford		CT		Suburban		—			740			2,552			218				—			741		2,769				3,510		547		10/24/06	1980
	860 North Main Street		Wallingford		CT		Suburban		—			680			3,144			941				(915		)	537		3,313				3,850		919		10/24/06	1982
	One Barnes Industrial Road South		Wallingford		CT		Suburban		—			800			2,251			6				(691		)	631		1,735				2,366		466		10/24/06	1977
	Village Lane		Wallingford		CT		Suburban		—			1,090			4,448			1,078				(2,600		)	750		3,266				4,016		109		10/24/06	1974;1979
											Initial Cost to Company										Cost Amount Carried at Close of Period
																Costs
																Capitalized
																Subsequent to
	Property		City		State		Property		Encumbrances(1)		Land			Buildings and		Acquisition, Net		Impairment/Write Downs			Land			Buildings and		Total(2)	Accumulated			Date		Original
							Location							Improvements										Improvements			Depreciation(3)			Acquired		Construction
																																Date
	100 Northfield Drive		Windsor		CT		Suburban		—		1,376			11,212		2,791		(2,093	)		1,183			12,103		13,286	4,234			8/29/03		1988
	1250 H Street, NW		Washington		DC		CBD		—		5,975			53,778		5,272		—			5,975			59,050		65,025	24,069			6/23/98		1992
	Georgetown-Green and Harris Buildings		Washington		DC		CBD		—		24,000			35,979		44		—			24,000			36,023		60,023	4,797			9/3/09		1960;1975
	802 Delaware Avenue		Wilmington		DE		CBD		—		4,409			39,681		10,530		(11,156	)		3,390			40,074		43,464	21,964			7/23/98		1986
	6600 North Military Trail		Boca Raton		FL		Suburban		—		15,900			129,790		—		—			15,900			129,790		145,690	12,979			1/11/11		2008
	225 Water Street		Jacksonville		FL		CBD		40,059		1,480			43,770		4,482		(29,720	)		871			19,141		20,012	338			11/24/08		1985
	The Exchange		Atlanta		GA		Suburban		—		1,576			13,134		3,170		—			1,578			16,302		17,880	4,376			9/9/2004; 9/2/2005		1974;1983
	9040 Roswell Road		Atlanta		GA		Suburban		—		2,459			18,549		2,213		—			2,463			20,758		23,221	5,425			8/24/04		1985
	Executive Park		Atlanta		GA		Suburban		—		13,729			78,032		5,980		(54,310	)		10,954			32,477		43,431	13,947			7/16/2004; 7/26/2007		1972
	3920 Arkwright Road		Macon		GA		Suburban		—		2,674			19,311		2,892		(4,383	)		2,243			18,251		20,494	4,825			4/28/06		1988
	1775 West Oak Commons Court		Marietta		GA		Suburban		—		2,190			6,586		1,217		(1,689	)		1,814			6,490		8,304	1,458			9/5/07		1998
	633 Ahua Street		Honolulu		HI		Suburban		—		1,256			3		18,050		(2,912	)		1,100			15,297		16,397	3,397			12/5/03		2006
	625 Crane Street		Aurora		IL		Suburban		—		1,180			3,411		(2	)	(2,978	)		533			1,078		1,611	56			4/2/07		1977
	905 Meridian Lake Drive		Aurora		IL		Suburban		—		1,740			13,586		52		(3,069	)		1,431			10,878		12,309	2,609			5/1/07		1999
	1200 Lakeside Drive		Bannockburn		IL		Suburban		—		5,846			48,568		10,623		—			5,858			59,179		65,037	12,964			12/29/05		1999
	Illinois Center		Chicago		IL		CBD		142,666		66,757			239,143		27,735		—			66,757			266,878		333,635	23,133			5/11/2011; 1/9/2012		1970;1972
	600 West Chicago Avenue		Chicago		IL		CBD		—		34,980			315,643		4,314		—			34,980			319,957		354,937	27,356			8/10/11		1908
	8750 Bryn Mawr Avenue		Chicago		IL		Suburban		—		6,600			77,764		6,460		—			6,600			84,224		90,824	9,137			10/28/10		1985
	1717 Deerfield Road		Deerfield		IL		Suburban		—		2,515			20,186		2,540		(16,742	)		985			7,514		8,499	213			12/14/05		1986
	1955 West Field Court		Lake Forest		IL		Suburban		—		1,258			9,630		2,991		(1,954	)		1,065			10,860		11,925	3,025			12/14/05		2001
11350 North Meridian Street		Carmel		IN		Suburban		—		667			5,815		1,654		(5,415	)		270			2,451		2,721	125			6/15/06		1982
101-115 W. Washington Street		Indianapolis		IN		CBD		—		7,495			60,465		21,160		—			7,496			81,624		89,120	20,875			5/10/05		1977
111 Monument Circle		Indianapolis		IN		CBD		116,000		9,670			158,085		5,014		—			9,670			163,099		172,769	8,737			10/22/12		1959;1990
5015 S. Water Circle		Wichita		KS		Suburban		—		2,720			2,029		1,125		—			2,719			3,155		5,874	731			4/2/07		1995
701 Poydras Street		New Orleans		LA		CBD		—		9,100			78,540		9,971		—			9,100			88,511		97,611	7,252			8/29/11		1972
109 Brookline Avenue		Boston		MA		CBD		—		3,168			30,397		11,492		—			3,168			41,889		45,057	17,245			9/28/95		1915
Adams Place		Braintree/Quincy		MA		Suburban		—		4,145			27,742		8,420		(20,532	)		2,956			16,819		19,775	853			4/3/98		1998
Cabot Business Park		Mansfield		MA		Suburban		—		2,733			23,657		5,376		(17,038	)		1,654			13,074		14,728	556			8/1/03		1978;1981
Cabot Business Park Land		Mansfield		MA		Suburban		—		1,033			—		—		—			1,033			—		1,033	—			8/1/03		0
										Initial Cost to Company					Costs					Cost Amount Carried at Close of Period
															Capitalized
															Subsequent to
Property		City		State		Property		Encumbrances(1)		Land			Buildings and		Acquisition, Net		Impairment/Write Downs			Land			Buildings and		Total(2)	Accumulated			Date		Original
						Location							Improvements										Improvements			Depreciation(3)			Acquired		Construction
																															Date
2300 Crown Colony Drive		Quincy		MA		Suburban		—		774			5,815		1,591		(1,036	)		678			6,466		7,144	2,419			2/24/04		1999
Myles Standish Industrial Park		Taunton		MA		Suburban		—		1,013			8,728		2,214		(4,077	)		686			7,192		7,878	135			8/29/07		1986;1989
340 Thompson Road		Webster		MA		Suburban		—		315			2,834		39		—			315			2,873		3,188	1,270			5/15/97		1995
100 South Charles Street		Baltimore		MD		CBD		—		—			12,430		3,931		—			—			16,361		16,361	6,870			11/18/97		1988
111 Market Place		Baltimore		MD		CBD		—		6,328			54,645		15,070		—			6,328			69,715		76,043	21,931			1/28/03		1990
25 S. Charles Street		Baltimore		MD		CBD		—		2,830			22,996		12,677		—			2,830			35,673		38,503	11,158			7/16/04		1972
820 W. Diamond		Gaithersburg		MD		Suburban		—		4,381			18,798		10,193		—			4,461			28,911		33,372	10,230			3/31/97		1995
6710 Oxon Hill		Oxon Hill		MD		Suburban		—		3,181			13,653		2,998		(2,300	)		2,725			14,807		17,532	7,032			3/31/97		1992
Danac Stiles Business Park		Rockville		MD		Suburban		—		7,638			62,572		5,846		(10,480	)		6,595			58,981		65,576	17,078			7/20/04		2002
East Eisenhower Parkway		Ann Arbor		MI		Suburban		—		6,760			46,988		1,297		—			6,760			48,285		55,045	5,528			6/15/10		1975;2006
8800 Queen Avenue South		Bloomington		MN		Suburban		—		1,898			17,081		2,038		(7,378	)		1,788			11,851		13,639	331			3/19/98		1957
2250 Pilot Knob Road		Mendota Heights		MN		Suburban		—		533			4,795		1,201		—			533			5,996		6,529	2,394			3/19/98		1995
9800 Shelard Parkway		Plymouth		MN		Suburban		—		563			5,064		1,090		(1,433	)		433			4,851		5,284	2,378			8/3/99		1987
Rosedale Corporate Plaza		Roseville		MN		Suburban		—		1,860			16,750		8,938		—			1,859			25,689		27,548	8,775			12/1/99		1987
411 Farwell Avenue		South St. Paul		MN		Suburban		—		1,303			10,451		4,595		—			1,304			15,045		16,349	3,035			6/2/04		1970
6200 Glenn Carlson Drive		St. Cloud		MN		Suburban		—		1,950			13,803		—		—			1,950			13,803		15,753	1,811			10/15/09		1999
1000 Shelard Parkway		St. Louis Park		MN		Suburban		—		695			6,254		1,778		(835	)		622			7,270		7,892	3,017			8/3/99		1986
525 Park Street		St. Paul		MN		CBD		—		696			6,263		1,513		—			695			7,777		8,472	3,104			8/3/99		1987
1900 Meyer Drury Drive		Arnold		MO		Suburban		—		834			7,302		474		—			838			7,772		8,610	2,039			2/11/04		1999
4700 Belleview Avenue		Kansas City		MO		Suburban		—		1,165			3,097		2,375		—			1,165			5,472		6,637	793			7/17/08		1986
131-165 West Ninth Street		N. Kansas City		MO		Suburban		—		494			959		300		—			494			1,259		1,753	200			7/17/08		1970
12655 Olive Boulevard		St. Louis		MO		Suburban		—		4,800			8,020		1,760		—			4,801			9,779		14,580	2,016			10/5/06		1988
1285 Fern Ridge Parkway		St. Louis		MO		Suburban		—		903			7,602		1,495		(3,503	)		556			5,941		6,497	2,497			11/7/03		1998
300 North Greene Street		Greensboro		NC		CBD		—		2,070			37,073		1,616		—			2,070			38,689		40,759	4,322			9/14/10		1989
7-9 Vreeland Road		Florham Park		NJ		Suburban		—		1,412			12,709		2,191		(9,087	)		916			6,309		7,225	442			7/31/98		1979
111 River Street		Hoboken		NJ		CBD		—		—			134,199		602		—			—			134,801		134,801	18,206			8/11/09		2002
5 Paragon Drive		Montvale		NJ		Suburban		—		3,650			13,725		351		(3,298	)		3,075			11,353		14,428	1,363			2/11/11		1984
										Initial Cost to Company					Costs					Cost Amount Carried at Close of Period
															Capitalized
															Subsequent to
Property		City		State		Property		Encumbrances(1)		Land			Buildings and		Acquisition, Net		Impairment/Write Downs			Land			Buildings and		Total(2)	Accumulated			Date		Original
						Location							Improvements										Improvements			Depreciation(3)			Acquired		Construction
																															Date
1000 Voorhees Drive and 333 and 400 Laurel Oak Drive		Voorhees		NJ		Suburban		—		2,171			13,655		2,361		(9,829	)		1,688			6,670		8,358	358			5/26/98		1989
One Park Square		Albuquerque		NM		CBD		—		2,582			21,532		5,756		—			2,583			27,287		29,870	8,448			2/12/02		1985;1987
Widewaters Parkway		Dewitt		NY		Suburban		—		4,574			39,419		8,218		(33,428	)		2,058			16,725		18,783	883			12/28/199;3/14/2006		1977;1982;1986;1988;1989;1991
5062 Brittonfield Parkway		East Syracuse		NY		Suburban		—		718			4,756		(10	)	(1,700	)		590			3,174		3,764	74			3/14/06		1995
Woodcliff Drive		Fairport		NY		Suburban		—		6,538			55,938		11,385		(25,814	)		4,622			43,425		48,047	3,651			3/14/06		1987;1989;1991;1996;1999;2004
1601 Veterans Highway		Islandia		NY		Suburban		—		813			7,319		2,684		(7,281	)		368			3,167		3,535	120			6/11/99		1987
Two Corporate Center Drive		Melville		NY		Suburban		—		3,155			28,395		6,625		(26,344	)		1,868			9,963		11,831	841			7/22/99		1985
Interstate Place		North Syracuse		NY		Suburban		—		563			4,874		1,243		(3,750	)		296			2,634		2,930	79			3/14/06		1972;1973
1000 Pittsford-Victor Road		Pittsford		NY		Suburban		—		583			4,700		967		(3,295	)		314			2,641		2,955	91			3/14/06		1986
1200 Pittsford - Victor Road		Pittsford		NY		Suburban		—		307			2,083		4		(540	)		295			1,559		1,854	38			11/30/04		2004
Corporate Crossing		Pittsford		NY		Suburban		—		3,012			22,546		1,088		(12,224	)		2,047			12,375		14,422	337			11/30/04		1998;1999;2000;2002
Canal View Boulevard		Rochester		NY		Suburban		—		1,575			12,686		1,791		(4,428	)		1,290			10,334		11,624	1,796			1/6/06		1999;2000;2003
14 Classic Street		Sherburne		NY		Suburban		—		140			1,250		15		(16	)		140			1,249		1,389	274			3/14/06		1979
110 W Fayette Street		Syracuse		NY		CBD		—		1,788			16,096		14,881		(17,214	)		1,075			14,476		15,551	651			6/29/99		1972
251 Salina Meadows Parkway		Syracuse		NY		Suburban		—		466			4,196		1,134		(2,748	)		335			2,713		3,048	124			9/24/99		1990
11311 Cornell Park Drive		Blue Ash		OH		Suburban		—		883			7,175		1,120		(2,561	)		773			5,844		6,617	213			6/15/06		1982
North Point Office Complex		Cleveland		OH		CBD		—		12,000			94,448		15,496		—			12,000			109,944		121,944	18,849			2/12/08		1985;1989;1990
5300 Kings Island Drive		Mason		OH		Suburban		—		1,528			13,748		4,620		(8,546	)		1,320			10,030		11,350	725			6/10/98		1994
3 Crown Point Court		Sharonville		OH		Suburban		—		956			8,290		1,362		(181	)		1,125			9,302		10,427	1,915			12/30/05		1999
Raintree Industrial Park		Solon		OH		Suburban		—		1,808			16,620		2,064		(8,359	)		1,339			10,794		12,133	394			7/16/04		1975
401 Vine Street		Delmont		PA		Suburban		—		1,575			5,542		—		—			1,575			5,542		7,117	991			10/22/07		1999
515 Pennsylvania Avenue		Fort Washington		PA		Suburban		—		1,872			8,816		4,091		(4,225	)		1,259			9,295		10,554	4,404			9/22/97		1958
443 Gulph Road		King of Prussia		PA		Suburban		—		634			3,251		773		—			634			4,024		4,658	1,528			9/22/97		1966
4350 Northern Pike		Monroeville		PA		Suburban		—		6,558			51,775		16,926		(34,439	)		3,667			37,153		40,820	15,106			9/16/04		1971
											Initial Cost to Company													Cost Amount Carried at Close of Period
Property		City		State		Property		Encumbrances(1)			Land			Buildings and			Costs				Impairment/Write Downs			Land		Buildings and				Total(2)		Accumulated		Date	Original
						Location								Improvements			Capitalized									Improvements						Depreciation(3)		Acquired	Construction
																	Subsequent to																		Date
																	Acquisition, Net
Cherrington Corporate Center		Moon Township		PA		Suburban		—			11,369			39,892			18,276				(5,440		)	11,164		52,933				64,097		19,102		9/14/1998; 8/23/1999	1987;1988; 1989;1990;
																																			1991;1992;
																																			1994
1500 Market Street		Philadelphia		PA		CBD		—			18,758			167,487			96,002				—			18,758		263,489				282,247		68,976		10/10/02	1974
1525 Locust Street		Philadelphia		PA		CBD		—			931			8,377			1,853				—			930		10,231				11,161		3,719		6/11/99	1987
1600 Market Street		Philadelphia		PA		CBD		—			3,462			111,946			16,320				—			3,462		128,266				131,728		51,508		3/30/98	1983
16th and Race Street		Philadelphia		PA		CBD		—			7,884			71,002			5,749				(48,329		)	5,939		30,367				36,306		1,306		3/30/98	1983
1735 Market Street		Philadelphia		PA		CBD		171,498			24,753			222,775			50,376				—			24,747		273,157				297,904		110,910		6/30/98	1990
Foster Plaza		Pittsburgh		PA		Suburban		—			6,168			51,588			15,524				—			6,171		67,109				73,280		16,665		9/16/05	1987;1990; 1994;
																																			1995; 1996
128 Crews Drive		Columbia		SC		Suburban		—			2,420			4,017			1,322				(4,012		)	1,024		2,723				3,747		385		4/2/07	1968
1320 Main Street		Columbia		SC		CBD		38,979			1,660			53,058			399				—			1,660		53,457				55,117		3,008		9/18/12	2004
111 Southchase Boulevard		Fountain Inn		SC		Suburban		—			520			6,822			1,725				(2,912		)	390		5,765				6,155		1,393		5/23/07	1987
1043 Global Avenue		Graniteville		SC		Suburban		—			720			15,552			598				—			720		16,150				16,870		3,042		4/2/07	1998
633 Frazier Drive		Franklin		TN		Suburban		—			5,800			13,190			(10		)		—			5,800		13,180				18,980		2,381		10/22/07	1999
775 Ridge Lake Boulevard		Memphis		TN		CBD		—			2,113			18,201			515				—			2,114		18,715				20,829		5,044		4/28/04	2000
1601 Rio Grande Street		Austin		TX		CBD		—			688			6,192			1,272				—			697		7,455				8,152		2,874		6/3/99	1985
206 East 9th Street		Austin		TX		CBD		27,965			7,900			38,533			1,822				—			7,900		40,355				48,255		2,568		5/31/12	1984
4515 Seton Center Parkway		Austin		TX		Suburban		—			2,038			18,338			2,487				—			2,037		20,826				22,863		8,310		10/8/99	1997
4516 Seton Center Parkway		Austin		TX		Suburban		—			2,028			18,251			3,046				—			2,027		21,298				23,325		8,717		10/8/99	1985
7800 Shoal Creek Boulevard		Austin		TX		Suburban		—			1,731			14,921			4,407				—			1,731		19,328				21,059		6,842		6/30/99	1974
812 San Antonio Street		Austin		TX		CBD		—			626			5,636			2,286				—			621		7,927				8,548		2,807		8/18/99	1987
8701 N Mopac		Austin		TX		Suburban		—			1,574			14,168			2,511				—			1,573		16,680				18,253		6,201		8/3/99	1982
Bridgepoint Parkway		Austin		TX		Suburban		—			7,784			70,526			9,757				—			7,785		80,282				88,067		34,829		12/5/97	1986;1996; 1997
Lakewood on the Park		Austin		TX		Suburban		—			3,548			31,936			1,629				—			3,548		33,565				37,113		13,597		10/20/98	1998
Research Park		Austin		TX		Suburban		—			15,859			60,175			14,551				—			18,411		72,174				90,585		26,848		10/7/98	1968;1998; 2001
9840 Gateway Boulevard North		El Paso		TX		Suburban		—			1,700			9,736			(4		)		—			1,700		9,732				11,432		1,752		10/22/07	1999
											Initial Cost to Company						Costs							Cost Amount Carried at Close of Period
																	Capitalized
																	Subsequent to
Property		City		State		Property		Encumbrances(1)			Land			Buildings and			Acquisition, Net				Impairment/Write Downs			Land		Buildings and				Total(2)		Accumulated		Date	Original
						Location								Improvements												Improvements						Depreciation(3)		Acquired	Construction
																																			Date
3003 South Expressway 281		Hidalgo		TX		Suburban		—			1,480			15,533			(9		)		—			1,480		15,524				17,004		2,805		10/22/07	1999
3330 N Washington Boulevard		Arlington		VA		Suburban		—			810			7,289			744				—			811		8,032				8,843		3,100		8/26/98	1987
6160 Kempsville Circle		Norfolk		VA		Suburban		—			1,273			11,083			2,931				—			1,273		14,014				15,287		4,087		10/25/02	1987
Thunderbolt Place		Chantilly		VA		Suburban		—			1,374			12,369			819				—			1,375		13,187				14,562		4,998		9/29/99	1988
448 Viking Drive		Virginia Beach		VA		Suburban		—			682			5,431			1,443				—			686		6,870				7,556		1,664		6/4/04	1991
333 108th Avenue NE		Bellevue		WA		CBD		—			14,400			136,412			1,731				—			14,400		138,143				152,543		18,429		11/12/09	2008
600 108th Avenue NE		Bellevue		WA		CBD		—			3,555			30,244			11,912				—			3,555		42,156				45,711		10,119		7/16/04	1980
1331 North Center Parkway		Kennewick		WA		Suburban		—			1,850			7,339			(2		)		—			1,850		7,337				9,187		1,323		10/22/07	1999
100 East Wisconsin Avenue		Milwaukee		WI		CBD		—			3,150			72,113			6,615				—			3,150		78,728				81,878		9,063		8/11/10	1989
111 East Kilbourn Avenue		Milwaukee		WI		CBD		—			2,400			47,562			5,107				—			2,400		52,669				55,069		8,919		6/12/08	1988
Australia:
7 Modal Crescent		Canning Vale		Australia		Suburban		—			9,806			3,925			(505		)		—			8,171		5,055				13,226		454		10/7/10	2001
71-93 Whiteside Road		Clayton		Australia		Suburban		—			9,757			8,495			(3,043		)		—			8,130		7,079				15,209		749		10/7/10	1965
9-13 Titanium Court		Crestmead		Australia		Suburban		—			3,400			3,185			(1,098		)		(409		)	2,621		2,457				5,078		281		10/7/10	2005
16 Rodborough Road		Frenchs Forest		Australia		Suburban		—			7,355			9,498			(2,386		)		—			6,128		8,339				14,467		859		10/7/10	1987
22 Rodborough Road		Frenchs Forest		Australia		Suburban		—			2,452			3,923			453				—			2,043		4,785				6,828		459		10/7/10	1997
127-161 Cherry Lane		Laverton North		Australia		Suburban		—			4,266			5,220			(1,237		)		—			3,554		4,695				8,249		462		10/7/10	1965
310-314 Invermay Road		Mowbray		Australia		Suburban		—			431			535			(919		)		—			56		(9		)		47		47		10/7/10	1963
253-293 George Town Road		Rocherlea		Australia		Suburban		—			2,108			1,331			(574		)		(2,748		)	526		(409		)		117		117		10/7/10	1963
310-320 Pitt Street		Sydney		Australia		CBD		—			63,271			104,588			(30,272		)		—			51,886		85,701				137,587		9,109		12/21/10	1989
44-46 Mandarin Street		Villawood		Australia		Suburban		—			6,374			8,179			(1,096		)		—			5,311		8,146				13,457		814		10/7/10	1980
19 Leadership Way		Wangara		Australia		Suburban		—			4,217			2,685			(961		)		—			3,514		2,427				5,941		247		10/7/10	2000
								$	598,660		$	769,100		$	4,798,293		$	678,281			$	(517,231	)	$	714,238	$	5,014,205			$	5,728,443	$	1,030,445
Analysis of the carrying amount of real estate properties and accumulated depreciation:
	Real Estate				Accumulated
	Properties				Depreciation
Balance at January 1, 2012	$	7,244,232			$	934,170
Additions(4)	1,041,655				188,220
Loss on asset impairment	(242,497		)		(73,865		)
Properties reclassified to discontinued operations	(174,562		)		(10,521		)
Disposals	(39,419		)		(30,398		)
Balance at December 31, 2012	7,829,409				1,007,606
Additions(4)	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(4)	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
-1	Includes net unamortized premiums and discounts.
-2	Excludes value of real estate intangibles. Aggregate cost for federal income tax purposes is approximately $6,672,730.
-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	Includes adjustments to real estate properties additions of $(20,445), $(40,020) and $4,986, and adjustments to accumulated depreciation additions of $(1,279), $(1,528) and $97, related to changes in foreign currency exchange rates during 2014, 2013 and 2012, respectively.

SCHEDULE_IV_MORTGAGE_LOANS_ON_

SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE	12 Months Ended
	Dec. 31, 2014
Mortgage Loans on Real Estate [Abstract]
Schedule IV Mortgage Loans on Real Estate
	Location		Interest	Final	Periodic Payment Terms	Face			Carrying		Principal Amount of Loans Subject to Delinquent Principal or Interest
			Rate	Maturity Date		Amount of			Amount
						Mortgage(1)			of Mortgage
	Salina, NY		6.00%	4/30/19	Interest payable monthly in arrears.	$	419		419		$	—
					$419 due at maturity.
	Dearborn, MI		6.00%	1/24/23	Interest payable monthly in arrears.	7,688			7,688		—
					$7,688 due at maturity.
						$	8,107		$	8,107	$	—
	Reconciliation of the carrying amount of mortgage loans at the beginning of the period:
	Balance at January 1, 2012					$	—
	New mortgage loans					1,419
	Balance at December 31, 2012					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
	-1	Also represents cost for federal income tax purposes.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
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, 2014, 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 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 amount 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 year ended December 31, 2014, we recorded a loss on asset impairment in continuing operations totaling $185.1 million 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, 2014 and 2013, accrued environmental remediation costs by us totaling $0.5 million and $0.4 million, respectively, were included in accounts payable and accrued expenses in our consolidated balance sheets.
Cash and Cash Equivalents	Cash and Cash Equivalents.    We carry cash and short term investments with original maturities of three months or less at the date of purchase at cost plus accrued interest.
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 were converted into our common shares or our restricted share units (RSUs), which could result in a lower EPS amount. The effect of our series D convertible preferred shares and RSUs 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, local and Australian 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.    The U.S. dollar is the functional currency for our consolidated subsidiaries operating in the United States. The functional currency for our consolidated subsidiaries in countries other than the United States is the principal currency in which the entity's assets, liabilities, income and expenses are denominated. The functional currency of our consolidated subsidiary that operates in Australia is the Australian dollar. We translate our Australian subsidiary's financial statements into U.S. dollars when we consolidate that subsidiary's financial statements on a quarterly basis. Generally, we translate assets and liabilities at the exchange rate in effect as of the balance sheet date. The resulting translation adjustments are included in cumulative other comprehensive loss in our consolidated balance sheets. We translate 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 are subject to foreign currency risk due to potential fluctuations in exchange rates between Australian and U.S. currencies. A significant change in the value of Australian currency compared to U.S. currency would have an effect on future reported results of operations and financial position. We do not currently borrow in Australian dollars or enter currency derivative contracts to mitigate foreign currency risk.
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 are required to adopt ASU 2014-08 prospectively for all disposals of components of our business classified as held for sale during fiscal periods beginning after December 15, 2014 and are currently evaluating what impact, if any, its adoption will have to the presentation of our consolidated financial statements.
	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, 2016.  We are currently in the process of evaluating the impact, if any, the adoption of this ASU will have on our consolidated financial statements.

Organization_Tables

Organization (Tables)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property Level Information by Geographic Region and Property Type, Property Square Feet	At December 31, 2014, our portfolio included the following (square feet in thousands):
		Number of Properties		Number of Buildings			Square Feet
	CBD locations	40		53			21,892
	Suburban locations	116		209			21,027
	Total portfolio	156		262			42,919
	Property level information by operating segment as of December 31, 2014 and 2013, excluding assets held for sale as of December 31, 2013, and for the years ended December 31, 2014, 2013 and 2012, is as follows (in thousands):
		As of December 31,
		2014		2013
	Square feet (in thousands):
	CBD properties	21,892		21,889
	Suburban properties	21,027		21,026
	Total properties(1)	42,919		42,915
	(1) The change in total square feet from December 31, 2013 to 2014 is a result of remeasuring certain spaces.
		As of December 31,
		2014			2013
	Investment in real estate properties, net of accumulated depreciation
	CBD properties	$	2,966,926		$	3,001,397
	Suburban properties	1,731,072			1,640,709
	Total properties	$	4,697,998		$	4,642,106
		Year Ended December 31,
		2014			2013			2012
	Rental income:
	CBD properties	$	436,426		$	439,716		$	423,453
	Suburban properties	255,273			323,546			351,147
	Total properties	$	691,699		$	763,262		$	774,600
	Tenant reimbursements and other income:
	CBD properties	$	112,481		$	120,352		$	116,326
	Suburban properties	57,677			69,415			70,161
	Total properties	$	170,158		$	189,767		$	186,487
	NOI:
	CBD properties	$	289,141		$	294,306		$	290,810
	Suburban properties	184,734			248,678			272,604
	Total properties	$	473,875		$	542,984		$	563,414

Real_Estate_Properties_Tables

Real Estate Properties (Tables)	12 Months Ended
	Dec. 31, 2014
Real Estate [Abstract]
Schedule of Property Sales	During the years ended December 31, 2014, 2013 and 2012 , we sold the following (dollars in thousands):
	Asset		Date Sold		Number of			Number of		Square		Sales Price		Gain
					Properties			Buildings		Footage				(Loss) on
														Sale
	Sales of properties resulting in gains and losses
	Suburban properties		Dec-13		3			40		1,670,104		$	89,000	$	(25,521	)
	Land parcel		Jun-13		—			—		—		2,551		1,765
	Suburban property		Jun-13		1			1		30,105		1,600		317
	Land parcel adjacent to CBD property		Mar-13		—			—		—		1,806		1,596
	Suburban office and industrial properties(1)		Jan-13		3			18		1,060,026		10,250		1,277
					7			59		2,760,235		$	105,207	$	(20,566	)
	Suburban property		Sep-12		1			—		208,850		$	9,900	$	1,689
	Suburban property(2)		Jun-12		1			—		76,978		1,250		192
	Suburban property (3)		Apr-12		1			—		12,934		575		158
					3			—		298,762		$	11,725	$	2,039
	Sales of properties with previously recorded asset impairment losses:
	CBD and suburban properties(4)		Jun-14		14			43		2,784,098		$	215,900	$	—
	Suburban properties		Dec-13		2			2		77,394		$	2,020	$	—
	CBD and suburban properties		Nov-13		18			21		2,125,278		50,500		—
	Suburban property		Oct-13		1			2		199,418		4,000		—
	Suburban property		Oct-13		1			1		665,545		13,900		—
	Suburban properties		Oct-13		9			41		1,211,536		43,000		—
	Suburban property		Aug-13		1			3		129,452		4,100		—
	Suburban property		Jun-13		1			1		143,802		5,250		—
	Suburban property		Jun-13		1			2		356,045		16,300		—
	Suburban property		May-13		1			1		57,250		4,025		—
	Suburban property		Apr-13		1			1		618,000		830		—
					36			75		5,583,720		$	143,925	$	—
	(1) We provided mortgage financing to the buyer, an unrelated third party, totaling $7.7 million at 6.0% per annum (Note 8).
	(2) We provided mortgage financing to the buyer, an unrelated third party, totaling $1.0 million at 5.0% per annum. In September 2013, this mortgage note was prepaid in full (Note 8).
	(3) We provided mortgage financing to the buyer, an unrelated third party, totaling $0.4 million at 6.0% per annum (Note 8).
	(4) 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 were previously classified as held for sale as of December 31, 2013 and are included in income from discontinued operations for all years presented.
Schedule of Disposal Groups, Including Discontinued Operations, Balance Sheet, Income Statement and Additional Disclosures	Summarized balance sheet information for all properties classified as held for sale and income statement information for properties held for sale or sold is as follows (in thousands):
			December 31,
			2013
	Real estate properties		$	536,552
	Acquired real estate leases		6,937
	Rents receivable		14,180
	Other assets, net		15,862
	Properties held for sale		$	573,531
	Mortgage notes payable, net		$	20,018
	Assumed real estate lease obligations		2,070
	Rent collected in advance		4,043
	Security deposits		2,603
	Liabilities related to properties held for sale		$	28,734
		Year Ended December 31,
		2014				2013			2012
	Rental income	$	14,243			$	55,073		$	69,752
	Tenant reimbursements and other income	1,900				6,842			8,156
	Total revenues	16,143				61,915			77,908
	Operating expenses	7,138				37,027			46,705
	Depreciation and amortization	—				12,550			28,008
	General and administrative	10				4,268			5,420
	Total expenses	7,148				53,845			80,133
	Operating income	8,995				8,070			(2,225		)
	Interest and other income	2				65			73
	Interest expense	(608		)		(1,742		)	(2,189		)
	Income from discontinued operations	$	8,389			$	6,393		$	(4,341	)
Schedule of Future Minimum Lease Payments Receivable	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, 2014 are as follows (in thousands):
	2015	$	640,967
	2016	576,172
	2017	513,445
	2018	459,290
	2019	392,832
	Thereafter	1,404,960
		$	3,987,666
Schedule of Future Minimum Lease Payments	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, 2014, are as follows (in thousands):
	2015	$	1,477
	2016	1,477
	2017	1,477
	2018	1,483
	2019	1,503
	Thereafter	129,994
		$	137,411

Lease_Intangibles_Tables

Lease Intangibles (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 and (in thousands):
		December 31,								31-Dec-13
										Properties Held for
		2014				2013				Sale
	Acquired in-place leases	$	272,077			$	282,754			$	9,351
	Acquired above market leases	121,969				127,944				2,047
	Acquired real estate leases	394,046				410,698				11,398
	Accumulated amortization, acquired in-place leases	(136,089		)		(106,045		)		(4,461		)
	Accumulated amortization, acquired above market leases	(59,670		)		(48,841		)		—
	Acquired real estate leases, net	$	198,287			$	255,812			$	6,937
	Acquired below market leases	56,541				56,815				4,996
	Accumulated amortization	(29,757		)		(22,880		)		(2,926		)
	Assumed real estate lease obligations, net	$	26,784			$	33,935			$	2,070
Schedule of Amortization of Lease Intangibles	Amortization of the lease intangibles for the years ended December 31, 2014, 2013 and 2012 is as follows (in thousands):
				December 31,
		Income Statement Location		2014				2013				2012
	Amortization of acquired in-place leases	Depreciation and amortization		$	40,493			$	48,023			$	46,306
	Amortization of acquired in-place leases	Discontinued operations		—				1,720				3,909
	Amortization of above and below market leases	Rental income		(10,650		)		(10,310		)		(10,621		)
	Amortization of above and below market leases	Discontinued operations		—				775				659
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, 2014 are approximately (in thousands):
	2015	$	39,533
	2016	31,702
	2017	24,151
	2018	20,066
	2019	14,765
	Thereafter	41,286
		$	171,503

Investment_in_Direct_Financing1

Investment in Direct Financing Lease (Tables)	12 Months Ended
	Dec. 31, 2014
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Schedule of Future Minimum Rentals Receivable on Direct Financing Lease	Our direct financing lease has an expiration date in 2045. Future minimum rentals receivable on this direct financing lease as of December 31, 2014 are as follows:
	2015	$	8,098
	2016	226
	2017	226
	2018	226
	2019	226
	Thereafter	5,887
		$	14,889

Equity_Investments_Tables

Equity Investments (Tables)	12 Months Ended
	Dec. 31, 2014
Equity Investments
Schedule of Equity Investments	At December 31, 2014 and 2013, we had the following equity investments (in thousands):
		Ownership Percentage						Equity Investments						Equity in Earnings
		December 31,						December 31,						Year Ended December 31,
		2014			2013			2014				2013		2014			2013		2012
	SIR	—	%		44.2	%		$	—			$	512,078	$	24,516		$	21,153	$	—
	GOV	—	%		—	%		—				—		—			4,111		10,836
	AIC	—	%		12.5	%		—				5,913		(56		)	490		584
								$	—			$	517,991	$	24,460		$	25,754	$	11,420
SIR
Equity Investments
Summary of Balance Sheet Information of Equity Method Investee
		9-Jul-14				31-Dec-13
	Real estate properties, net	$	1,772,684			$	1,579,234
	Acquired real estate leases, net	125,163				129,426
	Cash and cash equivalents	27,531				20,025
	Rents receivable, net	60,474				55,335
	Other assets, net	17,698				17,839
	Total assets	$	2,003,550			$	1,801,859
	Revolving credit facility	$	74,000			$	159,000
	Term loan	350,000				350,000
	Mortgage notes payable	19,069				27,147
	Assumed real estate lease obligations, net	26,945				26,966
	Other liabilities	44,225				40,055
	Shareholders' equity	1,489,311				1,198,691
	Total liabilities and shareholders' equity	$	2,003,550			$	1,801,859
Summary of Income Statement Information of Equity Method Investee
		For the Period from				Year Ended December 31,
		1-Jan-14
		through July 9, 2014				2013				2012
	Rental income	$	98,226			$	159,011			$	105,559
	Tenant reimbursements and other income	16,980				29,312				17,231
	Total revenues	115,206				188,323				122,790
	Operating expenses	20,982				36,382				23,796
	Depreciation and amortization	20,832				31,091				14,860
	Acquisition related costs	374				2,002				2,470
	General and administrative	7,731				12,423				8,203
	Total expenses	49,919				81,898				49,329
	Operating income	65,287				106,425				73,461
	Interest expense	(7,287		)		(13,763		)		(7,565		)
	Gain on early extinguishment of debt	243				—				—
	Income before income tax expense and equity in earnings of an investee	58,243				92,662				65,896
	Income tax (expense) benefit	(90		)		96				(290		)
	Equity in earnings of an investee	32				334				269
	Net income	$	58,185			$	93,092			$	65,875
	Weighted average common shares outstanding	52,394				44,565				27,122
	Net income per common share	$	1.11			$	2.09			$	2.43
GOV
Equity Investments
Summary of Income Statement Information of Equity Method Investee
		Year Ended
		December 31, 2012
	Rental income	$	203,700
	Operating expenses	75,326
	Depreciation and amortization	49,070
	Acquisition related costs	1,614
	General and administrative	11,924
	Total expenses	137,934
	Operating income	65,766
	Interest and other income	29
	Interest expense	(16,892		)
	Income from continuing operations before income tax expense and equity in earnings of an investee	48,903
	Income tax expense	(159		)
	Equity in earnings of an investee	316
	Income from continuing operations	49,060
	Income from discontinued operations	900
	Net income	$	49,960
	Weighted average common shares outstanding	48,617
	Per common share:
	Income from continuing operations	$	1.01
	Income from discontinued operations	$	0.02
	Net income	$	1.03

Other_Assets_Tables

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2014
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, 2014 and 2013 and (in thousands):
		December 31,						31-Dec-13
								Properties Held for
		2014			2013			Sale
	Deferred financing fees	$	41,339		$	45,985		$	272
	Accumulated amortization	(24,478		)	(21,455		)	(132		)
	Deferred financing fees, net	$	16,861		$	24,530		$	140
	Deferred leasing costs	$	184,600		$	146,996		$	13,769
	Accumulated amortization	(58,348		)	(46,228		)	(987		)
	Deferred leasing costs, net	$	126,252		$	100,768		$	12,782
	Capitalized lease incentives	$	22,650		$	20,651		$	590
	Accumulated amortization	(7,459		)	(5,392		)	(40		)
	Capitalized lease incentives, net	$	15,191		$	15,259		$	550
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, 2014 are approximately (in thousands):
		Deferred Leasing Costs			Capitalized Lease Incentives
	2015	$	22,515		$	2,514
	2016	18,867			2,471
	2017	16,745			2,386
	2018	14,380			2,292
	2019	12,287			2,121
	Thereafter	41,458			3,407
		$	126,252		$	15,191

Indebtedness_Tables

Indebtedness (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Outstanding Indebtedness	At December 31, 2014 and 2013, our outstanding indebtedness included the following (in thousands):
								December 31,
		Interest Rate at December 31, 2014			Maturity Date			2014		2013
	Unsecured revolving credit facility, at LIBOR plus a premium	1.669	%		10/19/15			$	—	$	235,000
	Unsecured term loan, at LIBOR plus a premium	2.019	%		12/15/16			400,000		500,000
	Unsecured floating rate debt	2.019	%	-1				$	400,000	$	735,000
	6.40% Senior Unsecured Notes due 2015	—	%		—			$	—	$	33,440
	5.75% Senior Unsecured Notes due 2015	5.75	%		11/1/15			138,773		138,773
	6.25% Senior Unsecured Notes due 2016	6.25	%		8/15/16			139,104		139,104
	6.25% Senior Unsecured Notes due 2017	6.25	%		6/15/17			250,000		250,000
	6.65% Senior Unsecured Notes due 2018	6.65	%		1/15/18			250,000		250,000
	7.50% Senior Unsecured Notes due 2019	—	%		—			—		125,000
	5.875% Senior Unsecured Notes due 2020	5.875	%		9/15/20			250,000		250,000
	5.75% Senior Unsecured Notes due 2042	5.75	%		8/1/42			175,000		175,000
	Unsecured fixed rate debt	6.125	%	-1				$	1,202,877	$	1,361,317
	3920 Arkwright Road	—	%		—			$	—	$	12,040
	6200 Glenn Carlson Drive	—	%		—			—		7,987
	111 Monument Circle	5.235	%		3/1/16			116,000		116,000
	225 Water Street(2)	6.03	%		5/11/16			40,059		40,334
	111 East Wacker Drive	6.29	%		7/11/16			142,666		144,522
	2501 20th Place South	7.36	%		8/1/16			10,267		10,804
	Parkshore Plaza	5.67	%		5/1/17			41,275		41,275
	600 West Chicago Avenue	—	%		—			—		265,000
	1735 Market Street(3)	5.66	%		12/2/19			171,498		173,247
	206 East 9th Street	5.69	%		1/5/21			27,965		28,391
	1320 Main Street	5.3	%		6/1/21			38,979		39,598
	33 Stiles Lane	6.75	%		3/1/22			3,132		3,456
	97 Newberry Road	5.71	%		3/1/26			6,819		7,240
	Secured fixed rate debt	5.767	%	-1				$	598,660	$	889,894
								$	2,201,537	$	2,986,211
	Unamortized net premiums and discounts							6,128		19,199
								$	2,207,665	$	3,005,410
	-1	Represents weighted average interest rate at December 31, 2014.
	-2	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 is secured by a non-recourse mortgage loan, with a current principal balance of $40.1 million. 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 has exercised its option to accelerate the maturity of the unpaid balance of the loan. The lender has filed a suit of foreclosure for this property. Since July 11, 2014, we have accrued interest on this loan at 10.03%, to include the 4.0% of default interest.
	-3	Interest on this loan is payable at a spread over LIBOR 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%.
Summary of Outstanding Senior Notes Purchased for Cash Pursuant to a Tender Offer	In March 2013, we purchased a total of $670.3 million of the outstanding principal amount of the following senior notes for $726.2 million, excluding transaction costs, pursuant to a tender offer:
	Senior Note	Principal				Purchase
						Price
	5.75% Senior Notes due February 15, 2014	$	145,612			$	148,746
	6.40% Senior Notes due February 15, 2015	152,560				164,140
	5.75% Senior Notes due November 1, 2015	111,227				121,047
	6.25% Senior Notes due August 15, 2016	260,896				292,218
		$	670,295			$	726,151
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, 2014 are as follows (in thousands):
	2015	$	145,973
	2016	848,708
	2017	295,592
	2018	254,614
	2019	165,422
	Thereafter	491,228
		$	2,201,537

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Schedule of Distributions Paid Per Common Share	The following characterizes distributions paid per common share for the years ended December 31, 2014, 2013 and 2012:
		Year Ended December 31,
		2014		2013		2012
	Ordinary income	—	%	—	%	61.72	%
	Return of capital	—	%	100	%	38.28	%
	Capital gain	100	%	—	%	—	%
	Unrecaptured Section 1250 gain	—	%	—	%	—	%
		100	%	100	%	100	%

Cumulative_Other_Comprehensive1

Cumulative Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Amounts Recognized in Cumulative Other Comprehensive Loss by Component	The following table presents a roll forward of amounts recognized in cumulative other comprehensive loss by component for the year ended December 31, 2014:
		Year Ended December 31, 2014
		Unrealized			Foreign			Equity in			Total
		Gain (Loss)			Currency			Unrealized
		on Derivative			Translation			Gain (Loss) of
		Instruments and Other Assets			Adjustments			an Investee
	Balances as of December 31, 2013	$	(11,706	)	$	(26,647	)	$	22		$	(38,331	)
	Other comprehensive income (loss) before reclassifications	2,387			(22,270		)	42			(19,841		)
	Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	5,020			—			(64		)	4,956
	Net current period other comprehensive income (loss)	7,407			(22,270		)	(22		)	(14,885		)
	Balances as of December 31, 2014	$	(4,299	)	$	(48,917	)	$	—		$	(53,216	)
Schedule of Reclassifications Out of Cumulative Other Comprehensive Loss	The following table presents reclassifications out of cumulative other comprehensive loss for the year ended December 31, 2014:
		Year Ended December 31, 2014
	Details about Cumulative Other Comprehensive Loss Components	Amounts Reclassified from			Affected Line Items in the
		Cumulative Other Comprehensive			Statement of Operations
		Loss to Net Income (Loss)
	Interest rate swap contracts	$	5,020		Interest expense
	Realized gains and losses on available for sale securities	(64		)	Equity in earnings of investees
		$	4,956

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Components of Provision for Income Taxes	Our provision for income taxes consists of the following (amounts in thousands):
		Year Ended December 31,
		2014			2013				2012
	Current:
	State	$	350		$	519			$	765
	Foreign	2,772			2,572				199
		3,122			3,091				964
	Deferred:
	Foreign	69			(457		)		2,243
		69			(457		)		2,243
	Income tax provision	$	3,191		$	2,634			$	3,207
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,
		2014		2013			2012
	Taxes at statutory U.S. federal income tax rate	35	%	35	%		35	%
	Dividends paid deduction and net operating loss utilization	(35.00	)%	(35.00	)%		(35.00	)%
	State, local, and foreign income taxes, net of federal tax benefit	11.73	%	(1.71	)%		(4.20	)%
	Effective tax rate	11.73	%	(1.71	)%		(4.20	)%

Derivative_Instruments_Tables

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Interest Rate Derivatives Designated as Cash Flow Hedges	As of December 31, 2014, 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			$171,498
Schedule of Derivative Financial Instruments at Fair Value	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, 2014 and 2013 (amounts in thousands):
					Fair Value as of December 31,
	Interest Rate Derivative Designated as Hedging Instrument		Balance Sheet Location		2014				2013
	Pay-fixed swaps		Accounts payable and accrued expenses		$	7,462			$	11,706
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, 2014, 2013 and 2012 (amounts in thousands):
		Year Ended December 31,
		2014				2013				2012
	Balance at beginning of year	$	(11,706	)		$	(16,624	)		$	(15,796	)
	Amount of loss recognized in cumulative other comprehensive loss	(776		)		(103		)		(5,790		)
	Amount of loss reclassified from cumulative other comprehensive loss into interest expense	5,020				5,021				4,962
	Unrealized gain (loss) on derivative instruments	4,244				4,918				(828		)
	Balance at end of year	$	(7,462	)		$	(11,706	)		$	(16,624	)

ShareBased_Compensation_Tables

Share-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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, 2013 and 2012, is as follows:
		Number			Weighted
		of			Average
		Shares			Grant Date
					Fair Value
	Unvested shares at December 31, 2011	103,615			23.32
	Granted	83,617			15.99
	Vested	(71,244	)		15.75
	Forfeited	(1,285	)		18.74
	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			20.7
	Granted	4,000			23.46
	Vested	(134,914	)		25.79
	Unvested shares at December 31, 2014	—			—
Summary of Restricted Share and Restricted Stock Unit Activity	A summary of restricted share and RSU activity under the Plan for the year ended December 31, 2014 is as follows:
		Number			Weighted		Number	Weighted
		of			Average		of	Average
		Restricted Shares			Grant Date		RSUs	Grant Date
					Fair Value			Fair Value
	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	$	—
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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 year ended December 31, 2014 is included in the following table on a per share basis.
		2014
	Fair value of RSUs granted	$	15.99
	Expected term (years)	4
	Expected volatility	—
	Expected dividend yield	1.88		%
	Risk-free rate	0.84		%

Fair_Value_of_Assets_and_Liabi1

Fair Value of Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Measure at Fair Value

The table below presents certain of our assets and liabilities measured at fair value during 2014 and 2013, categorized by the level of inputs used in the valuation of each asset and liability:

Fair Value at December 31, 2014 Using

Description

Total

Quoted Prices in

Significant Other

Significant

Active Markets for

Observable Inputs

Unobservable

Identical Assets

(Level 2)

Inputs

(Level 1)

(Level 3)

Recurring Fair Value Measurements:

Effective portion of interest rate contracts

$

(7,462

)

$

—

$

(7,462

)

$

—

Derivative liability

$

(6,658

)

$

—

$

—

$

(6,658

)

Fair Value at December 31, 2013 Using

Description

Total

Quoted Prices in

Significant Other

Significant

Active Markets for

Observable Inputs

Unobservable

Identical Assets

(Level 2)

Inputs

(Level 1)

(Level 3)

Recurring Fair Value Measurements:

Effective portion of interest rate contracts

$

(11,706

)

$

—

$

(11,706

)

$

—

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 measurements at December 31, 2014 were as follows:

Description

Fair Value at

Primary

Unobservable

Weighted Average(1)

31-Dec-14

Valuation

Inputs

Techniques

Properties held and used on which we recognized impairment losses

$

414,625

Discounted cash flows

Discount rate

10.20%

Exit capitalization rate

9.10%

The valuation techniques and significant unobservable inputs used for our level 3 fair value measurement at December 31, 2014 were as follows:

Description

Fair Value at December 31, 2014

Primary

Unobservable Inputs

Rate

Valuation

Techniques

Derivative liability

$

(6,658

)

Monte Carlo

Risk-free rate

0.50%

simulation

Volatility

20.00%

The valuation techniques and significant unobservable inputs used for our level 3 fair value measurements at December 31, 2013 were as follows:

Description

Fair Value at

Primary

Unobservable

Weighted Average

31-Dec-13

Valuation

Inputs

Techniques

Properties held for sale on which we recognized impairment losses

$

471,457

Discounted cash flows

Discount rate

10.30%

Exit capitalization rate

8.80%

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

Primary

Unobservable

Rate

June 30, 2014

Valuation

Inputs

Techniques

225 Water Street

$

19,589

Discounted cash flows

Discount rate

8%

Exit capitalization rate

8%

Schedule of Fair Value and Carrying Value of Financial Instruments

At December 31, 2014 and 2013, the fair values of these additional financial instruments, excluding mortgage debt related to properties held for sale, were not materially different from their carrying values, except as follows (in thousands):

December 31, 2014

December 31, 2013

Carrying

Fair

Carrying

Fair

Amount

Value

Amount

Value

Revolving credit facility, senior unsecured debt and mortgage notes payable, net

$

2,207,665

$

2,263,535

$

3,005,410

$

3,037,649

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2014
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,
		2014			2013			2012
	Numerator for earnings per common share - basic and diluted:
	Income (loss) from continuing operations	$	21,206		$	(38,914	)	$	92,697
	Gain on sale of properties	—			1,596			—
	Net income attributable to noncontrolling interest in consolidated subsidiary	—			(20,093		)	(15,576		)
	Preferred distributions	(32,095		)	(44,604		)	(51,552		)
	Distribution on conversion of preferred shares	(16,205		)	—			(4,985		)
	(Loss) income from continuing operations attributable to Equity Commonwealth common shareholders	(27,094		)	(102,015		)	20,584
	Discontinued operations	2,806			(119,649		)	(172,542		)
	Numerator for net loss per share - basic and diluted	$	(24,288	)	$	(221,664	)	$	(151,958	)
	Denominator for earnings per common share - basic and diluted:
	Weighted average number of common shares outstanding - basic and diluted	125,163			112,378			83,750
	Earnings per share - basic and diluted:
	(Loss) income from continuing operations attributable to Equity Commonwealth common shareholders	$	(0.21	)	$	(0.91	)	$	0.25
	Discontinued operations	0.02			(1.06		)	(2.06		)
	Net loss per share - basic and diluted	$	(0.19	)	$	(1.97	)	$	(1.81	)
	Anti-dilutive securities:
	Effect of Series D preferred shares; 6 1/2% cumulative convertible(1)	4,175			7,298			7,298
	Effect of RSUs(2)	—			—			—
	(1) The Series D preferred shares are anti-dilutive as the Company reported a net loss for the year ended December 31, 2014.
	(2) As of December 31, 2014, the Company's performance criteria detailed in the Plan would have resulted in zero RSU's being issued.

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2014
Segment Reporting [Abstract]
Schedule of Property Level Information by Geographic Region and Property Type, Property Square Feet	At December 31, 2014, our portfolio included the following (square feet in thousands):
		Number of Properties			Number of Buildings			Square Feet
	CBD locations	40			53			21,892
	Suburban locations	116			209			21,027
	Total portfolio	156			262			42,919
	Property level information by operating segment as of December 31, 2014 and 2013, excluding assets held for sale as of December 31, 2013, and for the years ended December 31, 2014, 2013 and 2012, is as follows (in thousands):
		As of December 31,
		2014			2013
	Square feet (in thousands):
	CBD properties	21,892			21,889
	Suburban properties	21,027			21,026
	Total properties(1)	42,919			42,915
	(1) The change in total square feet from December 31, 2013 to 2014 is a result of remeasuring certain spaces.
		As of December 31,
		2014				2013
	Investment in real estate properties, net of accumulated depreciation
	CBD properties	$	2,966,926			$	3,001,397
	Suburban properties	1,731,072				1,640,709
	Total properties	$	4,697,998			$	4,642,106
		Year Ended December 31,
		2014				2013			2012
	Rental income:
	CBD properties	$	436,426			$	439,716		$	423,453
	Suburban properties	255,273				323,546			351,147
	Total properties	$	691,699			$	763,262		$	774,600
	Tenant reimbursements and other income:
	CBD properties	$	112,481			$	120,352		$	116,326
	Suburban properties	57,677				69,415			70,161
	Total properties	$	170,158			$	189,767		$	186,487
	NOI:
	CBD properties	$	289,141			$	294,306		$	290,810
	Suburban properties	184,734				248,678			272,604
	Total properties	$	473,875			$	542,984		$	563,414
Schedule of Reconciliation of NOI to Net Income	A reconciliation of NOI to net income (loss) for the years ended December 31, 2014, 2013 and 2012 is as follows:
		Year Ended December 31,
		2014				2013			2012
	Rental income	$	691,699			$	763,262		$	774,600
	Tenant reimbursements and other income	170,158				189,767			186,487
	Operating expenses	(387,982		)		(410,045		)	(397,673		)
	NOI	$	473,875			$	542,984		$	563,414
	NOI	$	473,875			$	542,984		$	563,414
	Depreciation and amortization	(227,532		)		(234,402		)	(230,284		)
	General and administrative	(113,155		)		(80,504		)	(49,312		)
	Loss on asset impairment	(185,067		)		(124,253		)	—
	Acquisition related costs	(5		)		(318		)	(5,648		)
	Operating (loss) income	(51,884		)		103,507			278,170
	Interest and other income	1,561				1,229			1,410
	Interest expense	(143,230		)		(173,011		)	(202,055		)
	Gain (loss) on early extinguishment of debt	4,909				(60,052		)	(287		)
	Gain on sale of equity investment	171,561				66,293			—
	Gain on issuance of shares by an equity investee	17,020				—			7,246
	Income (loss) from continuing operations before income tax expense and equity in earnings of investees	(63		)		(62,034		)	84,484
	Income tax expense	(3,191		)		(2,634		)	(3,207		)
	Equity in earnings of investees	24,460				25,754			11,420
	Income (loss) from continuing operations	21,206				(38,914		)	92,697
	Income (loss) from discontinued operations	8,389				6,393			(4,341		)
	Loss on asset impairment from discontinued operations	(2,238		)		(102,869		)	(168,632		)
	Loss on early extinguishment of debt from discontinued operations	(3,345		)		(1,011		)	(1,608		)
	Net (loss) gain on sale of properties from discontinued operations	—				(22,162		)	2,039
	Income (loss) before gain on sale of properties	24,012				(158,563		)	(79,845		)
	Gain on sale of properties	—				1,596			—
	Net income (loss)	$	24,012			$	(156,967	)	$	(79,845	)

Selected_Quarterly_Financial_D1

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Summary of Unaudited Quarterly Results of Operations
		2013
		First		Second			Third			Fourth
		Quarter(1)		Quarter(1)			Quarter(1)			Quarter
	Total revenues	$	262,612	$	262,188		$	214,201		$	214,028
	Net income (loss) attributable to Equity Commonwealth common shareholders	14,516		7,738			(227,466		)	(16,452		)
	Net income (loss) attributable to Equity Commonwealth common shareholders per share—basic and diluted	0.15		0.07			(1.92		)	(0.14		)
	Common distributions declared	0.25		0.25			0.25			0.25
	-1	Amounts previously reported have been adjusted as follows:
		2013
		First		Second			Third			Fourth
		Quarter		Quarter			Quarter			Quarter
	Total revenues as previously reported	$	242,653	$	246,181		$	198,283		$	198,419
	Total revenues from properties reclassified to discontinued operations during 2014	19,959		16,007			15,918			15,609
	Total revenues restated	$	262,612	$	262,188		$	214,201		$	214,028
	The following is a summary of our unaudited quarterly results of operations for 2014 and 2013. Reclassifications have been made to the prior quarterly results to reflect properties reclassified from discontinued operations to continuing operations during 2014.
		2014
		First		Second			Third			Fourth
		Quarter(1)		Quarter(1)			Quarter(1)			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 and diluted	0.08		(0.14		)	1.16			(1.28		)
	Common distributions declared	0.25		—			—			—
Schedule of Amounts Previously Reported and Adjustments	Amounts previously reported have been adjusted as follows:
		2013
		First		Second			Third			Fourth
		Quarter		Quarter			Quarter			Quarter
	Total revenues as previously reported	$	242,653	$	246,181		$	198,283		$	198,419
	Total revenues from properties reclassified to discontinued operations during 2014	19,959		16,007			15,918			15,609
	Total revenues restated	$	262,612	$	262,188		$	214,201		$	214,028

Organization_Narrative_Details

Organization - Narrative (Details)	0 Months Ended		3 Months Ended	0 Months Ended	12 Months Ended
	Jul. 09, 2014	Jul. 02, 2013	Jun. 30, 2014	Mar. 12, 2012	Dec. 31, 2014	Dec. 31, 2013	Jul. 03, 2013	Mar. 15, 2013	Jul. 01, 2013	Mar. 31, 2013	Dec. 31, 2012	Feb. 16, 2012
						sqft						sqft
Organization
Property square feet					42,919,000	42,915,000
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%		0.00%	44.20%
Equity investments, common shares owned (in shares)		22,000,000				22,000,000	22,000,000
GOV
Organization
Ownership Percentage					0.00%	0.00%		18.20%
Equity investments, common shares owned (in shares)								9,950,000
Australia | Wholly owned portfolio
Organization
Number of buildings					11
Property square feet					1,759,000
SIR
Organization
Property square feet												21,400,000
Wholly owned subsidiary, common shares owned (in shares)	22,000,000		22,000,000			22,000,000			22,000,000	22,000,000	22,000,000
Ownership percentage prior to initial public offering				100.00%	100.00%
Equity investments, number of shares sold (in shares)	22,000,000
Issuance of shares, net (in shares)		10,500,000		9,200,000
Ownership percentage											56.00%
Ownership Percentage	0.00%		36.70%			44.20%	44.20%
SIR | Previously reported
Organization
Ownership percentage									56.00%

Organization_Schedule_of_Prope

Organization - Schedule of Property Level Information by Geographic Region and Property Type, Property Square Feet (Details)	Dec. 31, 2014	Dec. 31, 2013
	sqft	sqft
Segment Reporting Information [Line Items]
Square Feet	42,919,000	42,915,000
Consolidated portfolio
Segment Reporting Information [Line Items]
Number of Properties	156
Number of Buildings	262
Square Feet	42,919,000
Suburban property
Segment Reporting Information [Line Items]
Number of Properties	29
Suburban property | Wholly owned portfolio
Segment Reporting Information [Line Items]
Number of Properties	116
Number of Buildings	209
Square Feet	21,027,000
CBD | Wholly owned portfolio
Segment Reporting Information [Line Items]
Number of Properties	40
Number of Buildings	53
Square Feet	21,892,000

Summary_of_Significant_Account2

Summary of Significant Accounting Policies - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		property
Property, Plant and Equipment [Line Items]
Percentage of investments in subsidiaries	100.00%
Loss on asset impairment	$185,067,000	$124,253,000	$0
Loss on asset impairment in discontinuing operations		79,800,000
Number of properties impaired		39
Number of buildings impaired		93
Losses on asset impairment for properties sold		23,100,000
Accrued environmental remediation costs	500,000	400,000
Minimum percentage of likelihood of realization of tax benefits	50.00%
Foreign currency translation adjustments	($48,900,000)	($26,600,000)
Maximum
Property, Plant and Equipment [Line Items]
Maximum percentage of investment accounted for under equity method of accounting	50.00%
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Maximum estimated useful life	40 years
Personal property | Maximum
Property, Plant and Equipment [Line Items]
Maximum estimated useful life	12 years

Board_of_Trustees_Narrative_De

Board of Trustees - Narrative (Details)	23-May-14
	trustee
Board of Trustees
Number of individuals elected to serve on Board of Trustees	7

Real_Estate_Properties_Narrati

Real Estate Properties - Narrative (Details) (USD $)	1 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		sqft	sqft
		property
Real Estate Properties [Line Items]
Real estate property improvements		$91.60	$122.90	$134.60
Committed expenditures on leases executed during period		88.6
Square feet of leases committed for expenditures during the period		4,792,000
Committed but unspent tenant related obligations based on existing leases		99.9
Square feet of property held for sale			8,425,548
Property square feet		42,919,000	42,915,000
Reversal of previously recorded impairment losses	4.8
Number of real estate properties subject to ground lease		1
Ground lease expenses		$1.80	$1.90	$1.80
CBD
Real Estate Properties [Line Items]
Number of real estate properties held for sale			3
Number of buildings held for sale			4
Number of real estate properties held for use	2
Number of buildings held for use	2
Suburban property
Real Estate Properties [Line Items]
Number of real estate properties held for sale			42
Number of buildings held for sale			106
Number of real estate properties held for use	29
Number of buildings held for use	65
CBD and suburban properties
Real Estate Properties [Line Items]
Property square feet	5,641,450	5,641,450

Real_Estate_Properties_Schedul

Real Estate Properties - Schedule of Property Sales (Details) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended
In Thousands, unless otherwise specified	Jan. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jun. 30, 2013	Sep. 30, 2012	Jun. 30, 2012	Apr. 30, 2012	Mar. 31, 2013	Oct. 31, 2013	Aug. 31, 2013	31-May-13	Apr. 30, 2013	Jun. 30, 2014	Nov. 30, 2013	Mar. 31, 2014
	building	sqft	sqft		property	property	building	property	property	building	building	property	property	building	property	property	sqft
	property				building	building	property	building	building	property	property	building	building	property	sqft	building
					sqft	sqft	sqft	sqft	sqft	sqft	sqft	sqft	sqft	sqft		sqft
Real Estate Properties [Line Items]
Number of Properties	3
Number of Buildings	18
Square Feet		42,919,000	42,915,000		42,915,000
Gain (Loss) on Sale		$0	$1,596	$0
CBD and suburban properties
Real Estate Properties [Line Items]
Square Feet		5,641,450															5,641,450
Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Number of Properties			7	3
Number of Buildings			59	0
Square Feet			2,760,235	298,762	2,760,235
Sales Price			105,207	11,725
Gain (Loss) on Sale			-20,566	2,039
Sales of properties resulting in gains and losses | Suburban property
Real Estate Properties [Line Items]
Number of Properties					3	1	1	1	1
Number of Buildings					40	1	0	0	0
Square Feet			1,670,104		1,670,104	30,105	208,850	76,978	12,934
Sales Price					89,000	1,600	9,900	1,250	575
Gain (Loss) on Sale					-25,521	317	1,689	192	158
Sales of properties resulting in gains and losses | Land parcel
Real Estate Properties [Line Items]
Number of Properties						0				0
Number of Buildings						0				0
Square Feet						0				0
Sales Price						2,551				1,806
Gain (Loss) on Sale						1,765				1,596
Sales of properties resulting in gains and losses | Suburban office and industrial properties
Real Estate Properties [Line Items]
Number of Properties	3
Number of Buildings	18
Square Feet	1,060,026
Sales Price	10,250
Gain (Loss) on Sale	1,277
Sales of properties with previously recorded asset impairment losses
Real Estate Properties [Line Items]
Number of Properties			36
Number of Buildings			75
Square Feet			5,583,720		5,583,720
Sales Price			143,925
Gain (Loss) on Sale			0
Sales of properties with previously recorded asset impairment losses | Suburban property
Real Estate Properties [Line Items]
Number of Properties					2	1					9	1	1	1
Number of Buildings					2	2					41	3	1	1
Square Feet			77,394		77,394	356,045					1,211,536	129,452	57,250	618,000
Sales Price					2,020	16,300					43,000	4,100	4,025	830
Gain (Loss) on Sale					0	0					0	0	0	0
Sales of properties with previously recorded asset impairment losses | Suburban property
Real Estate Properties [Line Items]
Number of Properties						1					1
Number of Buildings						1					1
Square Feet						143,802					665,545
Sales Price						5,250					13,900
Gain (Loss) on Sale						0					0
Sales of properties with previously recorded asset impairment losses | Suburban property
Real Estate Properties [Line Items]
Number of Properties											1
Number of Buildings											2
Square Feet											199,418
Sales Price											4,000
Gain (Loss) on Sale											0
Sales of properties with previously recorded asset impairment losses | CBD and suburban properties
Real Estate Properties [Line Items]
Number of Properties															14	18
Number of Buildings															43	21
Square Feet															2,784,098	2,125,278
Sales Price															215,900	50,500
Gain (Loss) on Sale															$0	$0

Real_Estate_Properties_Schedul1

Real Estate Properties - Schedule of Property Sales (Footnote) (Details) (USD $)	12 Months Ended			1 Months Ended			9 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2013	Jun. 30, 2012	Apr. 30, 2012	Sep. 30, 2013
Real Estate Properties [Line Items]
Mortgage financing related to property sold		$7,688	$1,419
Loss on asset impairment from discontinued operations	-2,238	-102,869	-168,632
Loss on early extinguishment of debt from discontinued operations	-3,345	-1,011	-1,608
Suburban office and industrial properties | 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%
Suburban property | Sales of properties resulting in gains and losses
Real Estate Properties [Line Items]
Mortgage financing related to property sold						400	1,000
Interest rate on real estate mortgage receivable					5.00%	6.00%
CBD and suburban properties | 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_Schedul2

Real Estate Properties - Schedule of Disposal Groups, Including Discontinued Operations, Balance Sheet and Additional Disclosures (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheets:
Real estate properties	$5,728,443	$5,537,165
Acquired real estate leases	171,503
Rents receivable, net	248,101	223,769
Other assets, net	220,480	188,675
Properties held for sale	0	573,531
Mortgage notes payable, net	609,249	914,510
Assumed real estate lease obligations	26,784	33,935
Rent collected in advance	31,359	27,553
Security deposits	14,044	11,976
Liabilities related to properties held for sale	0	28,734
Real estate properties held for sale
Balance Sheets:
Real estate properties		536,552
Acquired real estate leases		6,937
Rents receivable, net		14,180
Other assets, net		15,862
Properties held for sale		573,531
Mortgage notes payable, net		20,018
Assumed real estate lease obligations		2,070
Rent collected in advance		4,043
Security deposits		2,603
Liabilities related to properties held for sale		$28,734

Real_Estate_Properties_Schedul3

Real Estate Properties - Schedule of Disposal Groups, Including Discontinued Operations, Income Statement and Additional Disclosures (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statements of Operations:
Rental income									$691,699	$763,262	$774,600
Tenant reimbursements and other income									170,158	189,767	186,487
Total revenues	212,808	216,595	215,194	217,260	214,028	214,201	262,188	262,612	861,857	953,029	961,087
Operating expenses									387,982	410,045	397,673
Depreciation and amortization									227,532	234,402	230,284
General and administrative									113,155	80,504	49,312
Total expenses									913,741	849,522	682,917
Operating (loss) income									-51,884	103,507	278,170
Interest and other income									1,561	1,229	1,410
Interest expense									-143,230	-173,011	-202,055
(Loss) income from discontinued operations									8,389	6,393	-4,341
Discontinued operations, properties sold or held for sale
Statements of Operations:
Rental income									14,243	55,073	69,752
Tenant reimbursements and other income									1,900	6,842	8,156
Total revenues									16,143	61,915	77,908
Operating expenses									7,138	37,027	46,705
Depreciation and amortization									0	12,550	28,008
General and administrative									10	4,268	5,420
Total expenses									7,148	53,845	80,133
Operating (loss) income									8,995	8,070	-2,225
Interest and other income									2	65	73
Interest expense									-608	-1,742	-2,189
(Loss) income from discontinued operations									$8,389	$6,393	($4,341)

Real_Estate_Properties_Schedul4

Real Estate Properties - Schedule of Future Minimum Lease Payment Receivables and Payments (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Future minimum lease payments receivable:
2015	$640,967
2016	576,172
2017	513,445
2018	459,290
2019	392,832
Thereafter	1,404,960
Total	3,987,666
Future minimum lease payments:
2015	1,477
2016	1,477
2017	1,477
2018	1,483
2019	1,503
Thereafter	129,994
Total	$137,411

Lease_Intangibles_Summary_of_t

Lease Intangibles - Summary of the Carrying Amounts for Acquired Real Estate Leases and Assumed Real Estate Lease Obligations (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	$394,046	$410,698
Acquired real estate leases, properties held for sale		11,398
Acquired real estate leases, net	198,287	255,812
Acquired real estate leases, properties held for sale, net		6,937
Assumed real estate lease obligations, net	26,784	33,935
Assumed real estate lease obligations, properties held for sale, net		2,070
Leases, Acquired-in-Place
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	272,077	282,754
Acquired real estate leases, properties held for sale		9,351
Accumulated amortization	-136,089	-106,045
Accumulated amortization, properties held for sale		-4,461
Leases Acquired-in-Place, Above Market Lease
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	121,969	127,944
Acquired real estate leases, properties held for sale		2,047
Accumulated amortization	-59,670	-48,841
Accumulated amortization, properties held for sale		0
Leases Acquired-in-Place, Below Market Lease
Finite-Lived Intangible Assets [Line Items]
Acquired real estate leases	56,541	56,815
Acquired real estate leases, properties held for sale		4,996
Accumulated amortization	-29,757	-22,880
Accumulated amortization, properties held for sale		($2,926)

Lease_Intangibles_Schedule_of_

Lease Intangibles - Schedule of Amortization of Lease Intangibles (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Leases [Abstract]
Amortization of acquired in-place leases, Depreciation and amortization	$40,493	$48,023	$46,306
Amortization of acquired in-place leases, Discontinued operations	0	1,720	3,909
Amortization of above and below market leases, Rental income	-10,650	-10,310	-10,621
Amortization of above and below market leases, Discontinued operations	$0	$775	$659

Lease_Intangibles_Schedule_of_1

Lease Intangibles - Schedule of Future Amortization of Net Intangible Lease Assets and Liabilities (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Leases [Abstract]
2015	$39,533
2016	31,702
2017	24,151
2018	20,066
2019	14,765
Thereafter	41,286
Total	$171,503

Investment_in_Direct_Financing2

Investment in Direct Financing Lease - Narrative (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Leases [Abstract]
Percentage of term exceeding useful life of one office tower	75.00%
Carrying amount of net investment	$12,500,000	$19,800,000
Allowance for losses related to our direct financing lease	$0	$0

Investment_in_Direct_Financing3

Investment in Direct Financing Lease - Schedule of Future Minimum Rentals Receivable on Direct Financing Lease (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Leases [Abstract]
2015	$8,098
2016	226
2017	226
2018	226
2019	226
Thereafter	5,887
Total	$14,889

Equity_Investments_Schedule_of

Equity Investments - Schedule of Equity Investments (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 09, 2014	Jun. 30, 2014	Jul. 02, 2013	Mar. 15, 2013
Equity Investments
Equity investments	$0	$517,991
Equity in earnings of investees	24,460	25,754	11,420
SIR
Equity Investments
Ownership Percentage	0.00%	44.20%		0.00%	36.70%	56.00%
Equity investments	0	512,078
Equity in earnings of investees	24,516	21,153	0
GOV
Equity Investments
Ownership Percentage	0.00%	0.00%					18.20%
Equity investments	0	0
Equity in earnings of investees	0	4,111	10,836
AIC
Equity Investments
Ownership Percentage	0.00%	12.50%
Equity investments	0	5,913
Equity in earnings of investees	($56)	$490	$584

Equity_Investments_Narrative_D

Equity Investments - Narrative (Details) (USD $)	12 Months Ended			0 Months Ended		3 Months Ended		6 Months Ended		0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 09, 2014	Jul. 02, 2013	Sep. 30, 2014	Jun. 30, 2014	Jul. 09, 2014	Dec. 31, 2013	Mar. 15, 2013	9-May-14	Jul. 03, 2013
Equity Investments
Equity investments	$0	$517,991,000							$517,991,000
Gain on sale of equity investment	171,561,000	66,293,000	0
Proceeds from issuance of common shares, net	0	626,809,000	363,657,000
Gain on issuance of shares by an equity investee	17,020,000	0	7,246,000
SIR
Equity Investments
Equity investments, common shares owned (in shares)		22,000,000			22,000,000				22,000,000			22,000,000
Ownership Percentage	0.00%	44.20%		0.00%	56.00%		36.70%	0.00%	44.20%
Equity investments	0	512,078,000							512,078,000
Equity investments, market value based on quoted market prices		588,300,000							588,300,000
Equity investments, quoted market price of common share (in dollars per share)		$26.74							$26.74
Equity investments, number of shares sold (in shares)				22,000,000
Equity investments, sales proceeds				704,800,000
Share price (in dollars per share)				$32.04				$32.04
Gain on sale of equity investment				171,600,000		171,800,000
Issuance of shares, net (in shares)					10,500,000		10,000,000
Common stock price per share (in dollars per share)					$28.25		$29
Proceeds from issuance of common shares, net							277,400,000
Gain on issuance of shares by an equity investee							16,900,000
Less than wholly owned subsidiary, parent ownership interest percentage												44.20%
Market value of common shares exceeding carrying value					17,600,000
Amortization of the difference between carrying value and share of underlying equity					34 years
Cash distributions								20,700,000	19,800,000
GOV
Equity Investments
Equity investments, common shares owned (in shares)										9,950,000
Ownership Percentage	0.00%	0.00%							0.00%	18.20%
Equity investments	0	0							0
Common stock price per share (in dollars per share)										$25.20
Gain on issuance of shares by an equity investee										66,300,000
Cash distributions		4,300,000	16,800,000
Sale of Stock Consideration Gross Received on Transaction										250,700,000
Net proceeds received on issuance or sale of common shares										239,600,000
AIC
Equity Investments
Ownership Percentage											0.00%
Equity investments, number of shares sold (in shares)											20,000
Amount invested in equity investee											$5,800,000
Number of other companies which are shareholders of related party											4

Equity_Investments_Summary_of_

Equity Investments - Summary of Balance Sheet Information of Equity Method Investee (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 09, 2014
In Thousands, unless otherwise specified
Equity Investments
Real estate properties, net	$4,697,998	$4,642,106
Acquired real estate leases, net	171,503
Cash and cash equivalents	379,058	222,449	102,219	192,763
Rents receivable, net	248,101	223,769
Other assets, net	220,480	188,675
Total assets	5,761,639	6,646,434
Revolving credit facility	0	235,000
Term loan	1,598,416	1,855,900
Mortgage notes payable	609,249	914,510
Assumed real estate lease obligations, net	26,784	33,935
Other liabilities	162,204	165,855
Total liabilities and shareholders' equity	5,761,639	6,646,434
SIR
Equity Investments
Real estate properties, net		1,579,234			1,772,684
Acquired real estate leases, net		129,426			125,163
Cash and cash equivalents		20,025			27,531
Rents receivable, net		55,335			60,474
Other assets, net		17,839			17,698
Total assets		1,801,859			2,003,550
Revolving credit facility		159,000			74,000
Term loan		350,000			350,000
Mortgage notes payable		27,147			19,069
Assumed real estate lease obligations, net		26,966			26,945
Other liabilities		40,055			44,225
Shareholders' equity		1,198,691			1,489,311
Total liabilities and shareholders' equity		$1,801,859			$2,003,550

Equity_Investments_Summary_of_1

Equity Investments - Summary of Income Statement Information of Equity Method Investee (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended			6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 09, 2014
Equity Investments
Rental income										$691,699	$763,262	$774,600
Tenant reimbursements and other income										170,158	189,767	186,487
Total revenues		212,808	216,595	215,194	217,260	214,028	214,201	262,188	262,612	861,857	953,029	961,087
Operating expenses										387,982	410,045	397,673
General and administrative										113,155	80,504	49,312
Total expenses										913,741	849,522	682,917
Operating (loss) income										-51,884	103,507	278,170
Interest and other income										1,561	1,229	1,410
Interest expense										-143,230	-173,011	-202,055
Gain (loss) on early extinguishment of debt	-60,000									4,909	-60,052	-287
(Loss) income from continuing operations before income tax expense and equity in earnings of investees										-63	-62,034	84,484
Income tax (expense) benefit										-3,191	-2,634	-3,207
Equity in earnings of an investee										24,460	25,754	11,420
Income (loss) from continuing operations										21,206	-38,914	92,697
Net income (loss)										24,012	-156,967	-79,845
GOV
Equity Investments
Rental income												203,700
Operating expenses												75,326
Depreciation and amortization												49,070
Acquisition related costs												1,614
General and administrative												11,924
Total expenses												137,934
Operating (loss) income												65,766
Interest and other income												29
Interest expense												-16,892
(Loss) income from continuing operations before income tax expense and equity in earnings of investees												48,903
Income tax (expense) benefit												-159
Equity in earnings of an investee												316
Income (loss) from continuing operations												49,060
Income from discontinued operations												900
Net income (loss)												49,960
Weighted average common shares outstanding (in shares)												48,617
Income from continuing operations (in dollars per share)												$1.01
Income from discontinued operations (in dollars per share)												$0.02
Net income per common share (in dollars per share)												$1.03
SIR
Equity Investments
Rental income											159,011	105,559	98,226
Tenant reimbursements and other income											29,312	17,231	16,980
Total revenues											188,323	122,790	115,206
Operating expenses											36,382	23,796	20,982
Depreciation and amortization											31,091	14,860	20,832
Acquisition related costs											2,002	2,470	374
General and administrative											12,423	8,203	7,731
Total expenses											81,898	49,329	49,919
Operating (loss) income											106,425	73,461	65,287
Interest expense											-13,763	-7,565	-7,287
Gain (loss) on early extinguishment of debt											0	0	243
(Loss) income from continuing operations before income tax expense and equity in earnings of investees											92,662	65,896	58,243
Income tax (expense) benefit											96	-290	-90
Equity in earnings of an investee											334	269	32
Net income (loss)											$93,092	$65,875	$58,185
Weighted average common shares outstanding (in shares)											44,565	27,122	52,394
Net income per common share (in dollars per share)											$2.09	$2.43	$1.11

Other_Assets_Narrative_Details

Other Assets - Narrative (Details) (USD $)	1 Months Ended	12 Months Ended		1 Months Ended					9 Months Ended
	Jan. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jun. 30, 2013	Sep. 30, 2012	Jun. 30, 2012	Apr. 30, 2012	Sep. 30, 2013	Dec. 31, 2014
	building			property	building	building	property	property
	property			building	property	property	building	building
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total real estate mortgage receivable included in other assets, carrying value		$8,100,000		8,100,000						$8,107,000
Mortgage financing related to property sold		7,688,000	1,419,000
Number of properties sold or agreed to be sold	3
Number of buildings	18
Real estate mortgages receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for losses related to real estate mortgages receivable		0		0						0
Sales of properties resulting in gains and losses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of properties sold or agreed to be sold		7	3
Number of buildings		59	0
Sales of properties resulting in gains and losses | Suburban office and industrial properties
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	3
Number of buildings	18
Sales of properties resulting in gains and losses | Suburban property
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage financing related to property sold								$400,000	$1,000,000
Interest rate on real estate mortgage receivable							5.00%	6.00%
Number of properties sold or agreed to be sold				3	1	1	1	1
Number of buildings				40	1	0	0	0

Other_Assets_Summary_of_Deferr

Other Assets - Summary of Deferred Financing Fees, Deferred Leasing Costs and Capitalized Lease Incentives (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Finance Costs [Abstract]
Deferred Finance Costs, Gross	$41,339	$45,985
Deferred Finance Costs, Gross, Properties Held-for-sale		272
Accumulated Amortization, Deferred Finance Costs	-24,478	-21,455
Accumulated Amortization of Deferred Finance Costs, Properties Held-for-sale		-132
Deferred Finance Costs, Net	16,861	24,530
Deferred Finance Costs, Net, Properties Held-for-sale		140
Deferred Costs, Leasing, Net [Abstract]
Deferred Costs Leasing, Gross, Properties Held and Used in Operations	184,600	146,996
Deferred Costs Leasing, Gross, Properties Held-for-sale		13,769
Deferred Costs Leasing Accumulated Amortization, Properties Held and Used in Operations	-58,348	-46,228
Deferred Costs Leasing Accumulated Amortization, Properties Held-for-sale		-987
Deferred Costs Leasing, Net, Properties Held and Used in Operations	126,252	100,768
Deferred Costs Leasing, Net, Properties Held-for-sale		12,782
Capital Lease Incentives, Net [Abstract]
Capital Lease Incentives, Gross, Properties Held and Used in Operations	22,650	20,651
Capital Lease Incentives, Gross, Properties Held-for-sale		590
Accumulated Amortization of Capital Lease Incentives, Properties Held and Used in Operations	-7,459	-5,392
Accumulated Amortization of Capital Lease Incentives, Properties Held-for-sale		-40
Capital Lease Incentives, Net, Properties Held and Used in Operations	15,191	15,259
Capital Lease Incentives, Net, Properties Held-for-sale		$550

Other_Assets_Summary_of_Future

Other Assets - Summary of Future Amortization of Deferred Leasing Costs and Capitalized Lease Incentives (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs, Leasing, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	$22,515
2016	18,867
2017	16,745
2018	14,380
2019	12,287
Thereafter	41,458
Deferred Costs Leasing, Net, Properties Held and Used in Operations	126,252	100,768
Capitalized Lease Incentives, Amortization Expense, Fiscal Year Maturity [Abstract]
2015	2,514
2016	2,471
2017	2,386
2018	2,292
2019	2,121
Thereafter	3,407
Capital Lease Incentives, Net, Properties Held and Used in Operations	$15,191	$15,259

Indebtedness_Schedule_of_Outst

Indebtedness - Schedule of Outstanding Indebtedness (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Outstanding indebtedness	$2,201,537	$2,986,211
Unamortized net premiums and discounts	6,128	19,199
Total	2,207,665	3,005,410
Unsecured Revolving Credit Facility, due October 2015
Debt Instrument [Line Items]
Interest rate stated percentage	1.67%
Outstanding indebtedness	0	235,000
Unsecured Term Loan, due December 2016
Debt Instrument [Line Items]
Interest rate stated percentage	2.02%
Outstanding indebtedness	400,000	500,000
Unsecured Floating Rate Debt
Debt Instrument [Line Items]
Interest rate stated percentage	2.02%
Outstanding indebtedness	400,000	735,000
Senior Notes, due 2015 at 6.40%
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	0	33,440
Senior Notes, due 2015 at 5.75%
Debt Instrument [Line Items]
Interest rate stated percentage	5.75%
Outstanding indebtedness	138,773	138,773
Senior Notes, due 2016 at 6.25%
Debt Instrument [Line Items]
Interest rate stated percentage	6.25%
Outstanding indebtedness	139,104	139,104
Senior Notes, due 2017 at 6.25%
Debt Instrument [Line Items]
Interest rate stated percentage	6.25%
Outstanding indebtedness	250,000	250,000
Senior Notes, due 2018 at 6.65%
Debt Instrument [Line Items]
Interest rate stated percentage	6.65%
Outstanding indebtedness	250,000	250,000
Senior Notes, due 2019 at 7.50%
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	0	125,000
Senior Notes, due 2020 at 5.875%
Debt Instrument [Line Items]
Interest rate stated percentage	5.88%
Outstanding indebtedness	250,000	250,000
Senior Notes, due 2042 at 5.75%
Debt Instrument [Line Items]
Interest rate stated percentage	5.75%
Outstanding indebtedness	175,000	175,000
Unsecured Fixed Rate Debt
Debt Instrument [Line Items]
Interest rate stated percentage	6.13%
Outstanding indebtedness	1,202,877	1,361,317
Mortgage Notes Payable Encumbering 3920 Arkwright Road
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	0	12,040
Mortgage Notes Payable Encumbering 6200 Glenn Carlson Drive
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	0	7,987
Mortgage Notes Payable Encumbering 111 Monument Circle
Debt Instrument [Line Items]
Interest rate stated percentage	5.24%
Outstanding indebtedness	116,000	116,000
Mortgage Notes Payable Encumbering 225 Water Street
Debt Instrument [Line Items]
Interest rate stated percentage	6.03%
Outstanding indebtedness	40,059	40,334
Mortgage Notes Payable Encumbering 111 East Wacker Drive
Debt Instrument [Line Items]
Interest rate stated percentage	6.29%
Outstanding indebtedness	142,666	144,522
Mortgage Notes Payable Encumbering 2501 20th Place South
Debt Instrument [Line Items]
Interest rate stated percentage	7.36%
Outstanding indebtedness	10,267	10,804
Mortgage Notes Payable Encumbering Parkshore Plaza
Debt Instrument [Line Items]
Interest rate stated percentage	5.67%
Outstanding indebtedness	41,275	41,275
Mortgage Notes Payable Encumbering 600 West Chicago Avenue
Debt Instrument [Line Items]
Interest rate stated percentage	0.00%
Outstanding indebtedness	0	265,000
Mortgage Notes Payable Encumbering 1735 Market Street
Debt Instrument [Line Items]
Interest rate stated percentage	5.66%
Outstanding indebtedness	171,498	173,247
Mortgage Notes Payable Encumbering 206 East 9th Street
Debt Instrument [Line Items]
Interest rate stated percentage	5.69%
Outstanding indebtedness	27,965	28,391
Mortgage Notes Payable Encumbering 1320 Main Street
Debt Instrument [Line Items]
Interest rate stated percentage	5.30%
Outstanding indebtedness	38,979	39,598
Mortgage Notes Payable Encumbering 33 Stiles Lane
Debt Instrument [Line Items]
Interest rate stated percentage	6.75%
Outstanding indebtedness	3,132	3,456
Mortgage Notes Payable Encumbering 97 Newberry Road
Debt Instrument [Line Items]
Interest rate stated percentage	5.71%
Outstanding indebtedness	6,819	7,240
Secured Fixed Rate Debt
Debt Instrument [Line Items]
Interest rate stated percentage	5.77%
Outstanding indebtedness	$598,660	$889,894

Indebtedness_Schedule_of_Outst1

Indebtedness - Schedule of Outstanding Indebtedness (Footnote) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Jul. 11, 2014
Debt Instrument [Line Items]
Outstanding indebtedness	$2,201,537	$2,986,211
Mortgage Notes Payable Encumbering 1735 Market Street
Debt Instrument [Line Items]
Outstanding indebtedness	171,498	173,247
Interest rate stated percentage	5.66%
Variable rate basis	LIBOR
Period for which interest on loan payable is fixed by a cash flow hedge	7 years
Interest rate	5.66%
225 Water Street, Jacksonville, FL | Mortgages
Debt Instrument [Line Items]
Outstanding indebtedness	$40,100
Interest rate stated percentage			10.03%
Default interest			4.00%

Indebtedness_Narrative_Details

Indebtedness - Narrative (Details) (USD $)

1 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Jan. 29, 2015

Dec. 05, 2014

Oct. 31, 2014

Dec. 31, 2013

Jun. 27, 2014

Nov. 17, 2014

Sep. 15, 2014

Oct. 31, 2013

Aug. 01, 2014

Mar. 11, 2014

Jun. 06, 2014

Jun. 05, 2014

Jul. 11, 2014

option

Debt Instrument [Line Items]

Gain (loss) on early extinguishment of debt

($60,000,000)

$4,909,000

($60,052,000)

($287,000)

Outstanding principal

670,295,000

Purchase price

726,151,000

Real estate properties, net

4,697,998,000

4,642,106,000

4,642,106,000

Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Number of extensions

2

Extension period

6 months

Extension fee, percent

0.08%

Unsecured Revolving Credit Facility, due October 2015

Debt Instrument [Line Items]

Maximum borrowing capacity

750,000,000

Maturity date extension period available

1 year

Basis spread on variable rate

1.50%

1.50%

Commitment fee percentage

0.35%

Interest rate payable percent

1.70%

1.70%

Amount outstanding

0

Available borrowing capacity

750,000,000

Interest rate stated percentage

1.67%

Unsecured Term Loan, due December 2016

Debt Instrument [Line Items]

Basis spread on variable rate

1.85%

1.85%

Interest rate payable percent

2.00%

2.00%

Amount outstanding

400,000,000

Increased maximum borrowing capacity available under specified circumstances

1,000,000,000

Variable rate basis

LIBOR

Repayments of debt

100,000,000

Interest rate stated percentage

2.02%

Unsecured Revolving Credit Facility and Unsecured Term Loan

Debt Instrument [Line Items]

Change of control event of default

35.00%

25.00%

Unsecured Revolving Credit Facility | Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

750,000,000

Loan Facility, 5 Year Term | Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

200,000,000

Term of loan

5 years

Loan Facility, 7 Year Term | Revolving Credit Facility | Subsequent Event

Debt Instrument [Line Items]

Maximum borrowing capacity

200,000,000

Term of loan

7 years

Mortgages

Debt Instrument [Line Items]

Number of real estate properties secured by mortgage

10

Number of buildings secured by mortgage

14

Real estate properties, net

705,300,000

Mortgages | 225 Water Street, Jacksonville, FL

Debt Instrument [Line Items]

Interest rate stated percentage

10.03%

Senior Notes, due 2019 at 7.50%

Debt Instrument [Line Items]

Interest rate stated percentage

0.00%

Senior Notes, due 2015 at 6.40%

Debt Instrument [Line Items]

Interest rate stated percentage

0.00%

Senior Notes, due 2014 at 5.75%

Debt Instrument [Line Items]

Outstanding principal

145,612,000

Purchase price

148,746,000

Mortgage Notes Payable Encumbering 6200 Glenn Carlson Drive

Debt Instrument [Line Items]

Repayments of debt

7,800,000

Interest rate stated percentage

0.00%

Mortgage Notes Payable Encumbering 3920 Arkwright Road

Debt Instrument [Line Items]

Interest rate stated percentage

0.00%

Mortgages

Debt Instrument [Line Items]

Prepayments of debt

7,100,000

Interest rate stated percentage

5.76%

5.76%

Gain (loss) on early extinguishment of debt

-1,000,000

Mortgages | Mortgages

Debt Instrument [Line Items]

Gain (loss) on early extinguishment of debt

-3,300,000

Mortgages | Senior Notes, due 2019 at 7.50%

Debt Instrument [Line Items]

Prepayments of debt

125,000,000

Interest rate stated percentage

7.50%

Gain (loss) on early extinguishment of debt

-1,800,000

Mortgages | Senior Notes, due 2015 at 6.40%

Debt Instrument [Line Items]

Prepayments of debt

33,400,000

Interest rate stated percentage

6.40%

Mortgages | Senior Notes, due 2014 at 5.75%

Debt Instrument [Line Items]

Prepayments of debt

99,000,000

Interest rate stated percentage

5.75%

Mortgages | Mortgage Notes Payable, due 2017 at 5.68%

Debt Instrument [Line Items]

Prepayments of debt

265,000,000

Interest rate stated percentage

5.68%

Gain (loss) on early extinguishment of debt

6,700,000

Mortgages | Mortgage Notes Payable, due 2023 at 6.14%

Debt Instrument [Line Items]

Prepayments of debt

11,200,000

Interest rate stated percentage

6.14%

Mortgages | Mortgage Notes Payable, due 2015 at 5.78%

Debt Instrument [Line Items]

Prepayments of debt

8,500,000

Interest rate stated percentage

5.78%

Mortgages | Mortgage Notes Payable Encumbering 3920 Arkwright Road

Debt Instrument [Line Items]

Prepayments of debt

$12,000,000

Interest rate stated percentage

4.95%

Indebtedness_Summary_of_Outsta

Indebtedness - Summary of Outstanding Senior Notes Purchased for Cash Pursuant to a Tender Offer (Details) (USD $)	Mar. 31, 2013
In Thousands, unless otherwise specified
Debt Instrument [Line Items]
Principal	$670,295
Purchase Price	726,151
Senior Notes, due 2014 at 5.75%
Debt Instrument [Line Items]
Principal	145,612
Purchase Price	148,746
Senior Notes, due 2015 at 6.40%
Debt Instrument [Line Items]
Principal	152,560
Purchase Price	164,140
Senior Notes, due 2015 at 5.75%
Debt Instrument [Line Items]
Principal	111,227
Purchase Price	121,047
Senior Notes, due 2016 at 6.25%
Debt Instrument [Line Items]
Principal	260,896
Purchase Price	$292,218

Indebtedness_Schedule_of_Requi

Indebtedness - Schedule of Required Principal Payments on Outstanding Debt (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Long-term Debt, Fiscal Year Maturity [Abstract]
2015	$145,973
2016	848,708
2017	295,592
2018	254,614
2019	165,422
Thereafter	491,228
Total	$2,201,537	$2,986,211

Shareholders_Equity_Narrative_

Shareholders' Equity - Narrative (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended	0 Months Ended	12 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Jan. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Jul. 25, 2014	Dec. 31, 2013	14-May-14
Shareholders' Equity
Distributions on common stock declared (in dollars per share)	$0.25	$0	$0	$0	$0.25	$0.25	$0.25	$0.25	$0.25
Distributions paid or declared on common shares	$29.60
Distribution percentage to shareholders consisting of an alternative minimum tax adjustment										15.41%
Series D
Shareholders' Equity
Conversion of stock, common shares issued (in shares)										10,412,499
Conversion of stock, preferred shares outstanding (in shares)										10,264,503
Preferred shares outstanding (in shares)		4,915,497				15,180,000				4,915,497		15,180,000
Preferred shares dividend (in dollars per share)										1.625
Preferred shares, percent dividend yield										6.50%		6.50%
Initial conversion rate		0.480775								0.480775
Initial conversion price per share (in dollars per share)		$52								52
Additional common shares (in shares)										2,363,248
Liquidation preference (in dollars per share)		$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%
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
Outstanding convertible shares (in shares)		4,915,497								4,915,497
Distributions on preferred stock declared (in dollars per share)											$0.81
Common Stock
Shareholders' Equity
Fundamental change conversion rate, numerator (in shares)										1.0145
Outstanding convertible shares (in shares)		2,363,248								2,363,248
Series E
Shareholders' Equity
Preferred shares outstanding (in shares)		11,000,000				11,000,000				11,000,000		11,000,000
Preferred shares dividend (in dollars per share)										1.8125
Preferred shares, percent dividend yield										7.25%		7.25%
Liquidation preference (in dollars per share)		$25								25
Redemption price (in dollars per share)		$25								25
Distributions on preferred stock declared (in dollars per share)											$0.91
RMR
Shareholders' Equity
Common shares issued (in shares)										90,135
Fundamental Change Conversion Right | Series D
Shareholders' Equity
Conversion of stock, preferred shares outstanding (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													$16.20
Fundamental Change Conversion Right | Common Stock
Shareholders' Equity
Conversion of stock, preferred shares outstanding (in shares)													10,411,779
Period from February 15, 2014 to May 14, 2014 | Series D
Shareholders' Equity
Dividends payable (in dollars per share)											$0.41
Period from February 15, 2014 to May 14, 2014 | Series E
Shareholders' Equity
Dividends payable (in dollars per share)											$0.45
Period from May 15, 2014 to August 14, 2014 | Series D
Shareholders' Equity
Dividends payable (in dollars per share)											$0.41
Period from May 15, 2014 to August 14, 2014 | Series E
Shareholders' Equity
Dividends payable (in dollars per share)											$0.45

Shareholders_Equity_Schedule_o

Shareholders' Equity - Schedule of Distributions Paid Per Common Share (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Ordinary income	0.00%	0.00%	61.72%
Return of capital	0.00%	100.00%	38.28%
Capital gain	100.00%	0.00%	0.00%
Unrecaptured Section 1250 gain	0.00%	0.00%	0.00%
Common Stock, Dividends, Distribution Percentage	100.00%	100.00%	100.00%

Cumulative_Other_Comprehensive2

Cumulative Other Comprehensive Loss - Schedule of Amounts Recognized in Cumulative Other Comprehensive Loss by Component (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014
Roll forward of amounts recognized in cumulative other comprehensive loss by component
Balances at beginning of period	($38,331)
Other comprehensive income (loss) before reclassifications	-19,841
Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	4,956
Net current period other comprehensive income (loss)	-14,885
Balances at end of period	-53,216
Unrealized Gain (Loss) on Derivative Instruments and Other Assets
Roll forward of amounts recognized in cumulative other comprehensive loss by component
Balances at beginning of period	-11,706
Other comprehensive income (loss) before reclassifications	2,387
Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	5,020
Net current period other comprehensive income (loss)	7,407
Balances at end of period	-4,299
Foreign Currency Translation Adjustments
Roll forward of amounts recognized in cumulative other comprehensive loss by component
Balances at beginning of period	-26,647
Other comprehensive income (loss) before reclassifications	-22,270
Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	0
Net current period other comprehensive income (loss)	-22,270
Balances at end of period	-48,917
Equity in Unrealized Gain (Loss) of an Investee
Roll forward of amounts recognized in cumulative other comprehensive loss by component
Balances at beginning of period	22
Other comprehensive income (loss) before reclassifications	42
Amounts reclassified from cumulative other comprehensive income (loss) to net income (loss)	-64
Net current period other comprehensive income (loss)	-22
Balances at end of period	$0

Cumulative_Other_Comprehensive3

Cumulative Other Comprehensive Loss - Schedule of Reclassifications Out of Cumulative Other Comprehensive Loss (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassifications out of cumulative other comprehensive income (loss)
Interest rate swap contracts	$143,230	$173,011	$202,055
Realized gains and losses on available for sale securities	-24,460	-25,754	-11,420
Total reclassifications	-4,956
Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income (Loss)
Reclassifications out of cumulative other comprehensive income (loss)
Total reclassifications	4,956
Equity in Unrealized Gain (Loss) of an Investee
Reclassifications out of cumulative other comprehensive income (loss)
Total reclassifications	64
Equity in Unrealized Gain (Loss) of an Investee | Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income (Loss)
Reclassifications out of cumulative other comprehensive income (loss)
Realized gains and losses on available for sale securities	-64
Interest rate swap contracts | Amounts Reclassified from Cumulative Other Comprehensive Loss to Net Income (Loss)
Reclassifications out of cumulative other comprehensive income (loss)
Interest rate swap contracts	$5,020

Noncontrolling_Interest_in_Con1

Noncontrolling Interest in Consolidated Subsidiary - Narrative (Details) (SIR)	0 Months Ended	12 Months Ended
	Mar. 12, 2012	Dec. 31, 2014	Jul. 09, 2014	Jun. 30, 2014	Dec. 31, 2013	Jul. 03, 2013	Jul. 01, 2013	Mar. 31, 2013	Dec. 31, 2012
SIR
Noncontrolling Interest [Line Items]
Less than wholly owned subsidiary, common shares owned (in shares)			22,000,000	22,000,000	22,000,000		22,000,000	22,000,000	22,000,000
Ownership Percentage			0.00%	36.70%	44.20%	44.20%
Less than wholly owned subsidiary, parent ownership interest percentage									56.00%
Ownership percentage prior to initial public offering	100.00%	100.00%

Income_Taxes_Schedule_of_Compo

Income Taxes - Schedule of Components of Provision for Income Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
State	$350	$519	$765
Foreign	2,772	2,572	199
Current tax	3,122	3,091	964
Deferred:
Foreign	69	-457	2,243
Deferred tax	69	-457	2,243
Income tax provision	$3,191	$2,634	$3,207

Income_Taxes_Schedule_of_Recon

Income Taxes - Schedule of Reconciliation of Effective Tax Rate and the U.S. Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
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%
State, local, and foreign income taxes, net of federal tax benefit	11.73%	-1.71%	-4.20%
Effective tax rate	11.73%	-1.71%	-4.20%

Income_Taxes_Narrative_Details

Income Taxes - Narrative (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Income Tax Disclosure [Abstract]
Deferred tax assets	$2.40	$2.60
Deferred tax liabilities	3.1	3.3
Valuation allowance	$0.60	$0.50

Derivative_Instruments_Narrati

Derivative Instruments - Narrative (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014
Derivative [Line Items]
Aggregate termination value	$8.10
Interest rate swap
Derivative [Line Items]
Amount of hedged item	171.5
Description of variable rate basis	LIBOR
Fair value of derivatives in a net liability position	8.1
Cash flow hedging
Derivative [Line Items]
Estimated gain (loss) reclassification from OCI to income	$4.70

Derivative_Instruments_Schedul

Derivative Instruments - Schedule of Interest Rate Derivatives Designated as Cash Flow Hedges (Details) (Interest rate swap, USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified	financial_instrument
Interest rate swap
Derivative [Line Items]
Number of Instruments	2
Notional Amount	$171,498

Derivative_Instruments_Schedul1

Derivative Instruments - Schedule of Derivative Financial Instruments at Fair Value (Details) (Designated as Hedging Instrument [Member], Interest rate swap, Accounts payable and accrued expenses, USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Designated as Hedging Instrument [Member] | Interest rate swap | Accounts payable and accrued expenses
Derivatives, Fair Value [Line Items]
Pay-fixed swaps	$7,462	$11,706

Derivative_Instruments_Schedul2

Derivative Instruments - Schedule of Gain or Loss Recognized on Interest Rate Derivatives Designated as Cash Flow Hedges (Details) (Cash flow hedging, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flow hedging
Interest Rate Cash Flow Hedges [Roll Forward]
Balance at beginning of period	($11,706)	($16,624)	($15,796)
Amount of loss recognized in cumulative other comprehensive loss	-776	-103	-5,790
Amount of loss reclassified from cumulative other comprehensive loss into interest expense	5,020	5,021	4,962
Unrealized gain (loss) on derivative instruments	4,244	4,918	-828
Balance at end of period	($7,462)	($11,706)	($16,624)

ShareBased_Compensation_Narrat

Share-Based Compensation - Narrative (Details) (USD $)	12 Months Ended			0 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 28, 2014	Jan. 28, 2014	Mar. 25, 2014	Dec. 31, 2011	Jul. 09, 2014
				trustee	trustee
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Par value (in dollars per share)	$0.01	$0.01
Number of shares granted under the Award Plan (in shares)	4,000	83,450	83,617
Granted shares value (in dollars per share)	$23.46	$23.29	$15.99
Unvested restricted shares (in shares)	0	130,914	114,703				103,615
Shares vested (in shares)	134,914	66,639	71,244
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of independent trustees receiving pro-rata grant of fully vested common shares				5
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)	713,727
Vesting period	4 years
Granted shares value (in dollars per share)	$26.66			26.66
Unvested restricted shares (in shares)	710,182	0
Shares vested (in shares)	3,545
Estimated future compensation expense for unvested shares	$17.40
Weighted average period over which compensation expense will be recorded	3 years 6 months
Restricted shares | Vesting in 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	86,517
Restricted shares | Vesting in 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	155,916
Restricted shares | Vesting in 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	155,916
Restricted shares | Vesting in 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vested (in shares)	311,833
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)	1,266,237
Granted shares value (in dollars per share)	$15.99
Unvested restricted shares (in shares)	1,266,237	0
Shares vested (in shares)	0
Estimated future compensation expense for unvested shares	19.2
Weighted average period over which compensation expense will be recorded	3 years 3 months 18 days
Number of tranches	2
Restricted stock units | Vesting on October 28, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent	50.00%
Restricted stock units | Vesting on October 28, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percent	50.00%
Share award plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	3.4	1.8	1.2
Common shares available for issuance (in shares)	849,569
Trustees | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares granted in period (in shares)					2,000
Par value (in dollars per share)					$0.01
Share price (in dollars per share)					$23.46
Number of trustees					2
Trustees | Share award plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)		2,000	2,000
Aggregate market value of shares awarded		0.2	0.2
RMR | Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted under the Award Plan (in shares)		73,450	71,617
Vesting period	4 years
Employee Stock | RMR | Officers and Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	3.4
Employee Stock | RMR | Officers and Employees | Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares issued (in shares)						130,914
SIR
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (in dollars per share)								$32.04
Compensation expense		0.4	0.5
Minimum | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU grants grant recipients may earn				0.00%
Maximum | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of RSU grants grant recipients may earn				100.00%
General and Administrative Expense | Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	$2.60

ShareBased_Compensation_Schedu

Share-Based Compensation - Schedule of Shares Granted and Vested (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Number of Shares
Unvested Number of Shares, Beginning (in shares)	130,914	114,703	103,615
Granted (in shares)	4,000	83,450	83,617
Vested (in shares)	-134,914	-66,639	-71,244
Forfeited (in shares)		-600	-1,285
Unvested Number of Shares, Ending (in shares)	0	130,914	114,703
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)	$20.70	$19.39	$23.32
Granted (in dollars per share)	$23.46	$23.29	$15.99
Vested (in dollars per share)	$25.79	$23.06	$15.75
Forfeited (in dollars per share)		$22.49	$18.74
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$0	$20.70	$19.39

ShareBased_Compensation_Summar

Share-Based Compensation - Summary of Restricted Share and Restricted Stock Unit Activity (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 28, 2014
Number of Shares
Unvested Number of Shares, Beginning (in shares)	130,914	114,703	103,615
Granted (in shares)	4,000	83,450	83,617
Vested (in shares)	-134,914	-66,639	-71,244
Unvested Number of Shares, Ending (in shares)	0	130,914	114,703
Weighted Average Grant Date Fair Value
Unvested Shares, Weighted Average Grant Date Fair Value, Beginning (in dollars per share)	$20.70	$19.39	$23.32
Granted (in dollars per share)	$23.46	$23.29	$15.99
Vested (in dollars per share)	$25.79	$23.06	$15.75
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$0	$20.70	$19.39
Restricted shares
Number of Shares
Unvested Number of Shares, Beginning (in shares)	0
Granted (in shares)	713,727
Vested (in shares)	-3,545
Unvested Number of Shares, Ending (in shares)	710,182
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)	$26.66			$26.66
Vested (in dollars per share)	$26.66
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)	0
Granted (in shares)	1,266,237
Vested (in shares)	0
Unvested Number of Shares, Ending (in shares)	1,266,237
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)	$15.99
Vested (in dollars per share)	$0
Unvested Shares, Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$0

ShareBased_Compensation_Summar1

Share-Based Compensation - Summary of Assumptions and Fair Values for Restricted Stock Units Granted in the Period (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Granted (in dollars per share)	$23.46	$23.29	$15.99
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Granted (in dollars per share)	$15.99
Expected term (years)	4 years
Expected volatility	0.00%
Expected dividend yield	1.88%
Risk-free rate	0.84%

Fair_Value_of_Assets_and_Liabi2

Fair Value of Assets and Liabilities - Schedule of Assets and Liabilities Measure at Fair Value (Details) (Recurring, USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Level 1
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	$0	$0
Derivative liability	0
Level 2
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	-7,462	-11,706
Derivative liability	0
Level 3
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	0	0
Derivative liability	-6,658
Fair Value
Recurring Fair Value Measurements:
Effective portion of interest rate swap contracts	-7,462	-11,706
Derivative liability	($6,658)

Fair_Value_of_Assets_and_Liabi3

Fair Value of Assets and Liabilities - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Jul. 31, 2014	Mar. 31, 2014
	sqft	Tenant		sqft
Fair value of assets and liabilities
Property square feet	42,915,000	42,919,000
Loss on asset impairment	$204,000,000
Real estate properties, net	4,642,106,000	4,697,998,000
Losses on asset impairment for properties sold	23,100,000
Total rents | Credit concentration
Fair value of assets and liabilities
Number of tenants responsible for more than 3% of total annualized rents		0
Concentration risk		3.00%
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			8,400,000
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
Minimum
Fair value of assets and liabilities
Price per common share during one year period after date (in dollars per share)			$26
Price per common share during first and second year after date (in dollars per share)			$26
Level 3 | Nonrecurring
Fair value of assets and liabilities
Number of available for sale real estate properties	39
Carrying Amount | Nonrecurring
Fair value of assets and liabilities
Real estate properties, net	668,300,000
Fair Value | Nonrecurring
Fair value of assets and liabilities
Real estate properties, net	464,300,000
Cost to sell	7,200,000
CBD
Fair value of assets and liabilities
Number of properties		2
Suburban property
Fair value of assets and liabilities
Number of properties		29
CBD and suburban properties
Fair value of assets and liabilities
Property square feet		5,641,450		5,641,450
Previously reported
Fair value of assets and liabilities
Loss on asset impairment		4,800,000
Disposition Plan
Fair value of assets and liabilities
Number of properties		34
Loss on asset impairment		167,100,000
Disposition Plan | Carrying Amount | Nonrecurring
Fair value of assets and liabilities
Real estate properties, net		581,700,000
Discounted cash flows | Real estate properties held for sale | Level 3
Fair value of assets and liabilities
Fair value of assets	471,457,000	414,625,000
225 Water Street, Jacksonville, FL
Fair value of assets and liabilities
Loss on asset impairment		22,700,000
225 Water Street, Jacksonville, FL | Carrying Amount | Nonrecurring
Fair value of assets and liabilities
Real estate properties, net		42,300,000
225 Water Street, Jacksonville, FL | Fair Value | Nonrecurring
Fair value of assets and liabilities
Fair value of assets		19,600,000

Fair_Value_of_Assets_and_Liabi4

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 $)	12 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2014
Real estate properties held for sale | Discounted cash flows
Fair Value of Assets and Liabilities
Fair value of assets	$414,625	$471,457
Discount rate	10.20%	10.30%
Exit capitalization rate	9.10%	8.80%
225 Water Street | 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	($6,658)
Risk free rate	0.50%
Volatility rate	20.00%

Fair_Value_of_Assets_and_Liabi5

Fair Value of Assets and Liabilities - Schedule of Fair Value and Carrying Value of Financial Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Carrying Amount
Fair value of financial instruments
Revolving credit facility, senior unsecured debt and mortgage notes payable, net	$2,207,665	$3,005,410
Fair Value
Fair value of financial instruments
Revolving credit facility, senior unsecured debt and mortgage notes payable, net	$2,263,535	$3,037,649

Earnings_Per_Common_Share_Sche

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator for earnings per common share - basic and diluted:
Income (loss) from continuing operations									$21,206	($38,914)	$92,697
Gain on sale of properties									0	1,596	0
Net income attributable to noncontrolling interest in consolidated subsidiary									0	-20,093	-15,576
Preferred distributions									-32,095	-44,604	-51,552
Distribution on conversion of preferred shares									-16,205	0	-4,985
(Loss) income from continuing operations attributable to Equity Commonwealth common shareholders									-27,094	-102,015	20,584
Discontinued operations									2,806	-119,649	-172,542
Numerator for net loss per share - basic and diluted	($165,542)	$149,759	($17,802)	$9,297	($16,452)	($227,466)	$7,738	$14,516	($24,288)	($221,664)	($151,958)
Denominator for earnings per common share - basic and diluted:
Weighted average number of common shares outstanding - basic and diluted									125,163	112,378	83,750
Earnings per share - basic and diluted:
(Loss) income from continuing operations available for Equity Commonwealth common shareholders (in dollars per share)									($0.21)	($0.91)	$0.25
Discontinued operations (in dollars per share)									$0.02	($1.06)	($2.06)
Net loss per share - basic and diluted (in dollars per share)	($1.28)	$1.16	($0.14)	$0.08	($0.14)	($1.92)	$0.07	$0.15	($0.19)	($1.97)	($1.81)
Series D
Anti-dilutive securities:
Anti-dilutive securities (in shares)									4,175	7,298	7,298
Restricted stock units
Anti-dilutive securities:
Anti-dilutive securities (in shares)									0	0	0

Earnings_Per_Common_Share_Sche1

Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Footnote) (Details) (Share award plan, Restricted stock units)	12 Months Ended
	Dec. 31, 2014
Share award plan | Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of RSUs that would have been issued based on the Company's performance criteria detailed in the Plan (in shares)	0

Segment_Information_Narrative_

Segment Information - Narrative (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	segment
Segment Reporting Information [Line Items]
Number of reportable segments	2
Real estate properties, net	$4,697,998	$4,642,106
Rental income	691,699	763,262	774,600
CBD properties
Segment Reporting Information [Line Items]
Number of properties	40
Number of buildings	53
Real estate properties, net	2,966,926	3,001,397
Rental income	436,426	439,716	423,453
Suburban properties
Segment Reporting Information [Line Items]
Number of properties	116
Number of buildings	209
Real estate properties, net	1,731,072	1,640,709
Rental income	255,273	323,546	351,147
Minimum
Segment Reporting Information [Line Items]
Percentage of CBD and suburban properties that are office properties	90.00%
Australia
Segment Reporting Information [Line Items]
Real estate properties, net	252,000	285,100	362,000
Rental income	$30,100	$33,100	$34,700

Segment_Information_Schedule_o

Segment Information - Schedule of Property Level Information by Geographic Region and Property Type, Property Square Feet (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	sqft	sqft
Segment Reporting Information [Line Items]
Property square feet	42,919,000	42,915,000
Real estate properties, net	$4,697,998	$4,642,106
Rental income	691,699	763,262	774,600
Tenant reimbursements and other income	170,158	189,767	186,487
NOI	473,875	542,984	563,414
CBD properties
Segment Reporting Information [Line Items]
Property square feet	21,892,000	21,889,000
Real estate properties, net	2,966,926	3,001,397
Rental income	436,426	439,716	423,453
Tenant reimbursements and other income	112,481	120,352	116,326
NOI	289,141	294,306	290,810
Suburban properties
Segment Reporting Information [Line Items]
Property square feet	21,027,000	21,026,000
Real estate properties, net	1,731,072	1,640,709
Rental income	255,273	323,546	351,147
Tenant reimbursements and other income	57,677	69,415	70,161
NOI	$184,734	$248,678	$272,604

Segment_Information_Schedule_o1

Segment Information - Schedule of Reconciliation of NOI to Net Income (Details) (USD $)	1 Months Ended	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting [Abstract]
Rental income		$691,699	$763,262	$774,600
Tenant reimbursements and other income		170,158	189,767	186,487
Operating expenses		-387,982	-410,045	-397,673
NOI		473,875	542,984	563,414
Depreciation and amortization		-227,532	-234,402	-230,284
General and administrative		-113,155	-80,504	-49,312
Loss on asset impairment		-185,067	-124,253	0
Acquisition related costs		-5	-318	-5,648
Operating (loss) income		-51,884	103,507	278,170
Interest and other income		1,561	1,229	1,410
Interest expense		-143,230	-173,011	-202,055
Gain (loss) on early extinguishment of debt	-60,000	4,909	-60,052	-287
Gain on sale of equity investment		171,561	66,293	0
Gain on issuance of shares by an equity investee		17,020	0	7,246
(Loss) income from continuing operations before income tax expense and equity in earnings of investees		-63	-62,034	84,484
Income tax expense		-3,191	-2,634	-3,207
Equity in earnings of investees		24,460	25,754	11,420
Income (loss) from continuing operations		21,206	-38,914	92,697
Income (loss) from discontinued operations		8,389	6,393	-4,341
Loss on asset impairment from discontinued operations		-2,238	-102,869	-168,632
Loss on early extinguishment of debt from discontinued operations		-3,345	-1,011	-1,608
Net (loss) gain on sale of properties from discontinued operations		0	-22,162	2,039
Income (loss) before gain on sale of properties		24,012	-158,563	-79,845
Gain on sale of properties		0	1,596	0
Net income (loss)		$24,012	($156,967)	($79,845)

Related_Person_Transactions_Na

Related Person Transactions - Narrative (Details) (USD $)	0 Months Ended		12 Months Ended			0 Months Ended	1 Months Ended	6 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended		3 Months Ended		0 Months Ended
	Jul. 31, 2014	Jun. 01, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 05, 2014	Jan. 31, 2013	Jun. 30, 2014	Dec. 31, 2014	Sep. 30, 2014	Mar. 15, 2013	9-May-14	Sep. 30, 2014	Jun. 30, 2014	Dec. 19, 2013	Jul. 09, 2014	Jul. 02, 2013	Mar. 12, 2012	Feb. 16, 2012	Mar. 01, 2014	Feb. 28, 2015	23-May-14	8-May-14	Jul. 03, 2013	Jul. 01, 2013	Mar. 31, 2013
	option	option	sqft	sqft											installment				building	property		trustee
																			property
																			sqft
Related person transactions
Lease term	7 months	1 year
Number of renewal options	1	1
Renewal option term	3 months	3 months
Lease payment for initial term	$200,000	$200,000
Amount of reimbursements payable to related party			0	9,385,000					0
Number of individuals elected to serve on Board of Trustees																						7
Property square feet			42,919,000	42,915,000					42,919,000
Number of shares granted under the Award Plan (in shares)			4,000	83,450	83,617
Equity Group Investments
Related person transactions
License agreement term		1 year
License fee		200,000
Number of parking spaces		1
Related/Corvex
Related person transactions
Amount of reimbursements payable to related party	33,500,000
Reimbursement amount paid			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
Ownership percentage						5.70%
Number of individuals elected to serve on Board of Trustees																						7
Related Fund Management LLC
Related person transactions
Ownership percentage						2.80%
RMR
Related person transactions
Lease term			3 years
Number of agreements			3						3
Number of former managing trustees			1
Number of former independent trustees			2
Annual business management fee as a percentage of aggregate cost of properties acquired in excess of $250,000				0.50%	0.50%
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%	1.00%
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%	15.00%
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%	0.70%
Business management fees								31,700,000
Shares issued (in shares)								68,206
Incentive fees paid				0	0
Property management fees as a percentage of gross collected rents			3.00%						3.00%
Construction supervision fees as a percentage of construction costs			5.00%						5.00%
Payments to MacArthur Cook Fund Management Limited					1,800,000		200,000
Number of regional offices leased			11
Rental income earned				800,000	600,000			400,000
Property square feet			36,500						36,500
Legal fees and costs				30,400,000				5,400,000
Number of properties																				2
Total rent due			1,100,000						1,100,000
RMR Australia
Related person transactions
Property management fees as a percentage of gross collected rents			3.00%						3.00%
Compensation for construction supervision services as a percentage of difference between 5.0% of constructions costs and any amounts paid to third parties for construction management and/or supervision			50.00%						50.00%
Construction supervision fees as a percentage of construction costs			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%
Compensation for property management services as a percentage of 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			50.00%						50.00%
Business and property management fees				1,600,000				900,000
RMR and RMR Australia
Related person transactions
Monthly management fees									1,200,000
Pro-rata portion of the current yearbs incentive fee under the existing business management agreement										15,300,000
GOV
Related person transactions
Amount of reimbursements payable to related party				300,000
Prior ownership percentage			100.00%
Shares sold (in 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 person transactions
Ownership Percentage																0.00%							12.50%
Equity investments, number of shares sold (in shares)												20,000
Equity investments, sales proceeds												5,800,000
Amount invested in equity investee												5,200,000
Number of other companies which are shareholders of related party												4
Coverage amount for property insurance								500,000,000						500,000,000
Premium for property insurance					6,600,000			6,000,000
Equity Commonwealth and REIT Management and Research LLC
Related person transactions
Settlement receivable			12,000,000						12,000,000
Number of settlement receivable installments			3
Settlement receivable installment amount									3,000,000				3,000,000	6,000,000
Equity Commonwealth
Related person transactions
Total rent due			9,200,000						9,200,000
Minimum
Related person transactions
Price per common share during one year period after date (in dollars per share)	$26
Price per common share during first and second year after date (in dollars per share)	$26
Maximum
Related person transactions
Ownership Percentage			50.00%						50.00%
Maximum | RMR
Related person transactions
Threshold amount of real estate investments for payment of base management fee				250,000,000	250,000,000
Amended Agreement | RMR
Related person transactions
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 market capitalization exceeding specified amount															0.50%
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 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%							10.00%
Incentive management fee payable (as a percent)															12.00%
Measurement period of incentive management fee															3 years
Percentage of common shares issued in payment of an incentive management fee vested on the date of issuance															33.00%
Percentage of common shares issued in payment of an incentive management fee vesting after date of issuance															67.00%
Number of equal annual installments for vesting of common shares															2
Amended Agreement | Maximum | RMR
Related person transactions
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
SIR
Related person transactions
Amount of reimbursements payable to related party																										600,000
Number of former independent trustees			1
Property square feet																			21,400,000
Prior ownership percentage			100.00%															100.00%
Shares sold (in shares)																	10,500,000	9,200,000
Less than wholly owned subsidiary, common shares owned (in shares)				22,000,000	22,000,000			22,000,000						22,000,000		22,000,000									22,000,000	22,000,000
Ownership Percentage				44.20%				36.70%						36.70%		0.00%								44.20%
Proceeds from IPO																		180,800,000
Repayment of promissory note																			400,000,000
Common shares consideration received on transfer of properties (in shares)																			22,000,000
Number of properties sold or transferred or agreed to be sold or transferred																			79
Number of separate buildings or land parcels sold or transferred or agreed to be sold or transferred																			251
Equity investments, number of shares sold (in shares)																22,000,000
Share price (in dollars per share)																$32.04
Equity investments, sales proceeds																704,800,000
SIR | RMR
Related person transactions
Business management fees				43,300,000	43,600,000
Property management and construction supervision fees				32,500,000	33,700,000			13,800,000
Pro rata share of related party's costs of providing internal audit function				300,000	400,000
Parent Company
Related person transactions
Number of properties																				1
Parent Company | RMR
Related person transactions
Number of properties acquired or agreed to be acquired																				1
Restricted shares
Related person transactions
Number of shares granted under the Award Plan (in shares)			713,727
Number of anniversaries of the grant date for vesting of restricted shares			4 years
Restricted shares | RMR
Related person transactions
Number of shares granted under the Award Plan (in shares)				73,450	71,617
Aggregate value of restricted shares granted				1,700,000	1,100,000
Number of anniversaries of the grant date for vesting of restricted shares			4 years
Vesting Rights Percentage			20.00%
Vesting Rights Percentage on Each of Next Four Anniversaries			20.00%
Scenario, Forecast | RMR and RMR Australia
Related person transactions
Monthly management fees																					$100,000
2014 | Amended Agreement | RMR
Related person transactions
Measurement period of incentive management fee															1 year
2015 | Amended Agreement | RMR
Related person transactions
Measurement period of incentive management fee															2 years

Selected_Quarterly_Financial_D2

Selected Quarterly Financial Data (Unaudited) - Summary of Unaudited Quarterly Results of Operations (Details) (USD $)	1 Months Ended	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jan. 31, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total revenues		$212,808	$216,595	$215,194	$217,260	$214,028	$214,201	$262,188	$262,612	$861,857	$953,029	$961,087
Net income (loss) attributable to Equity Commonwealth common shareholders		($165,542)	$149,759	($17,802)	$9,297	($16,452)	($227,466)	$7,738	$14,516	($24,288)	($221,664)	($151,958)
Net income (loss) attributable to Equity Commonwealth common shareholders per sharebbasic and diluted (in dollars per share)		($1.28)	$1.16	($0.14)	$0.08	($0.14)	($1.92)	$0.07	$0.15	($0.19)	($1.97)	($1.81)
Common distributions declared (in dollars per share)	$0.25	$0	$0	$0	$0.25	$0.25	$0.25	$0.25	$0.25

Selected_Quarterly_Financial_D3

Selected Quarterly Financial Data (Unaudited) - Narrative (Details) (USD $)	3 Months Ended			12 Months Ended			0 Months Ended	3 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Jun. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 09, 2014	Sep. 30, 2014
Equity Investments
Gain on sale of equity investment				$171,561	$66,293	$0
Loss on asset impairment	167,100	22,700	124,300	191,490	384,141	242,497
SIR
Equity Investments
Gain on sale of equity investment							$171,600	$171,800

Selected_Quarterly_Financial_D4

Selected Quarterly Financial Data (Unaudited) - Schedule of Amounts Previously Reported and Adjustments (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total revenues	$212,808	$216,595	$215,194	$217,260	$214,028	$214,201	$262,188	$262,612	$861,857	$953,029	$961,087
Previously reported
Total revenues					198,419	198,283	246,181	242,653
Revenues from properties reclassified (to) from discontinued operations					$15,609	$15,918	$16,007	$19,959

SCHEDULE_II_VALUATION_AND_QUAL1

SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) (Allowance for doubtful accounts, USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for doubtful accounts
Movement in valuation and qualifying accounts
Balance at Beginning of Period	$7,885	$9,962	$12,575
Charged to Costs and Expenses	2,196	818	504
Deductions	-3,516	-2,895	-3,117
Balance at End of Period	$6,565	$7,885	$9,962

SCHEDULE_III_REAL_ESTATE_AND_A1

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$598,660
Initial Cost to Company
Land	769,100
Buildings and Equipment	4,798,293
Costs Capitalized Subsequent to Acquisition	678,281
Impairment/Write Downs	-517,231
Cost Amount Carried at Close of Period
Land	714,238
Buildings and Improvements	5,014,205
Total	5,728,443	5,537,165	7,829,409	7,244,232
Accumulated Depreciation	1,030,445	895,059	1,007,606	934,170
2501 20th Place South, Birmingham, AL | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	10,267
Initial Cost to Company
Land	4,000
Buildings and Equipment	19,604
Costs Capitalized Subsequent to Acquisition	511
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	4,002
Buildings and Improvements	20,113
Total	24,115
Accumulated Depreciation	4,153
420 20th Street North, Birmingham, AL | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,740
Buildings and Equipment	49,565
Costs Capitalized Subsequent to Acquisition	4,397
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,740
Buildings and Improvements	53,962
Total	55,702
Accumulated Depreciation	4,724
Inverness Center, Birmingham, AL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	8,525
Buildings and Equipment	38,367
Costs Capitalized Subsequent to Acquisition	4,807
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	8,525
Buildings and Improvements	43,174
Total	51,699
Accumulated Depreciation	5,214
785 Schilinger Road South, Mobile, AL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,540
Buildings and Equipment	9,732
Costs Capitalized Subsequent to Acquisition	-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	1,747
Arizona Center, Phoenix, AZ | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	22,614
Buildings and Equipment	64,105
Costs Capitalized Subsequent to Acquisition	11,157
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	22,614
Buildings and Improvements	75,262
Total	97,876
Accumulated Depreciation	6,970
4 South 84th Avenue, Tolleson, AZ | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,257
Buildings and Equipment	9,210
Costs Capitalized Subsequent to Acquisition	915
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,257
Buildings and Improvements	10,125
Total	11,382
Accumulated Depreciation	2,639
One South Church Avenue, Tucson, AZ | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,261
Buildings and Equipment	26,357
Costs Capitalized Subsequent to Acquisition	3,762
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,262
Buildings and Improvements	30,118
Total	33,380
Accumulated Depreciation	9,129
Parkshore Plaza, Folsom, CA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	41,275
Initial Cost to Company
Land	4,370
Buildings and Equipment	41,749
Costs Capitalized Subsequent to Acquisition	510
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	4,370
Buildings and Improvements	42,259
Total	46,629
Accumulated Depreciation	3,782
Leased Land, Gonzalez, CA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	18,941
Buildings and Equipment	9,060
Costs Capitalized Subsequent to Acquisition	3,824
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	18,940
Buildings and Improvements	12,885
Total	31,825
Accumulated Depreciation	2,276
Sky Park Centre, San Diego, CA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	936
Buildings and Equipment	8,094
Costs Capitalized Subsequent to Acquisition	756
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	935
Buildings and Improvements	8,851
Total	9,786
Accumulated Depreciation	3,029
Sorrento Valley Business Park, San Diego, CA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,425
Buildings and Equipment	12,842
Costs Capitalized Subsequent to Acquisition	3,308
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,425
Buildings and Improvements	16,150
Total	17,575
Accumulated Depreciation	6,951
1921 E. Alton Avenue, Santa Ana, CA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,363
Buildings and Equipment	10,158
Costs Capitalized Subsequent to Acquisition	1
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,362
Buildings and Improvements	10,160
Total	11,522
Accumulated Depreciation	2,908
9110 East Nichols Avenue, Centennial, CO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,708
Buildings and Equipment	14,616
Costs Capitalized Subsequent to Acquisition	3,962
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,708
Buildings and Improvements	18,578
Total	20,286
Accumulated Depreciation	5,739
7450 Campus Drive, Colorado Springs, CO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,250
Buildings and Equipment	7,982
Costs Capitalized Subsequent to Acquisition	249
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,250
Buildings and Improvements	8,231
Total	9,481
Accumulated Depreciation	962
1225 Seventeenth Street, Denver, CO | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	22,400
Buildings and Equipment	110,090
Costs Capitalized Subsequent to Acquisition	12,616
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	22,400
Buildings and Improvements	122,706
Total	145,106
Accumulated Depreciation	17,456
5073, 5075, & 5085 S. Syracuse Street, Denver, CO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,720
Buildings and Equipment	58,890
Costs Capitalized Subsequent to Acquisition	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	6,871
1601 Dry Creek Drive, Longmont, CO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,714
Buildings and Equipment	24,397
Costs Capitalized Subsequent to Acquisition	4,244
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,715
Buildings and Improvements	28,640
Total	32,355
Accumulated Depreciation	8,166
129 Worthington Ridge Road, Berlin, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,770
Buildings and Equipment	8,409
Costs Capitalized Subsequent to Acquisition	1,161
Impairment/Write Downs	-7,088
Cost Amount Carried at Close of Period
Land	1,114
Buildings and Improvements	4,138
Total	5,252
Accumulated Depreciation	714
97 Newberry Road, East Windsor, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	6,819
Initial Cost to Company
Land	2,960
Buildings and Equipment	12,360
Costs Capitalized Subsequent to Acquisition	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	2,555
185 Asylum Street, Hartford, CT | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	15,930
Buildings and Equipment	60,312
Costs Capitalized Subsequent to Acquisition	1,856
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	15,930
Buildings and Improvements	62,168
Total	78,098
Accumulated Depreciation	4,247
599 Research Parkway, Meriden, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	768
Buildings and Equipment	6,164
Costs Capitalized Subsequent to Acquisition	1,160
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	768
Buildings and Improvements	7,324
Total	8,092
Accumulated Depreciation	1,938
33 Stiles Lane, North Haven, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	3,132
Initial Cost to Company
Land	2,090
Buildings and Equipment	9,141
Costs Capitalized Subsequent to Acquisition	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	1,949
181 Marsh Hill Road, Orange, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,270
Buildings and Equipment	7,943
Costs Capitalized Subsequent to Acquisition	581
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,271
Buildings and Improvements	8,523
Total	10,794
Accumulated Depreciation	1,659
101 Barnes Road, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	367
Buildings and Equipment	3,301
Costs Capitalized Subsequent to Acquisition	1,153
Impairment/Write Downs	-3,398
Cost Amount Carried at Close of Period
Land	154
Buildings and Improvements	1,269
Total	1,423
Accumulated Depreciation	39
15 Sterling Drive, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,010
Buildings and Equipment	7,352
Costs Capitalized Subsequent to Acquisition	235
Impairment/Write Downs	-4,792
Cost Amount Carried at Close of Period
Land	1,139
Buildings and Improvements	3,666
Total	4,805
Accumulated Depreciation	116
35 Thorpe Avenue, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	640
Buildings and Equipment	10,017
Costs Capitalized Subsequent to Acquisition	1,276
Impairment/Write Downs	-5,431
Cost Amount Carried at Close of Period
Land	518
Buildings and Improvements	5,984
Total	6,502
Accumulated Depreciation	185
50 Barnes Industrial Road North, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,300
Buildings and Equipment	8,621
Costs Capitalized Subsequent to Acquisition	2,955
Impairment/Write Downs	-2,472
Cost Amount Carried at Close of Period
Land	1,865
Buildings and Improvements	9,539
Total	11,404
Accumulated Depreciation	2,457
5-9 Barnes Industrial Road, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	740
Buildings and Equipment	2,552
Costs Capitalized Subsequent to Acquisition	218
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	741
Buildings and Improvements	2,769
Total	3,510
Accumulated Depreciation	547
860 North Main Street, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	680
Buildings and Equipment	3,144
Costs Capitalized Subsequent to Acquisition	941
Impairment/Write Downs	-915
Cost Amount Carried at Close of Period
Land	537
Buildings and Improvements	3,313
Total	3,850
Accumulated Depreciation	919
One Barnes Industrial Road South, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	800
Buildings and Equipment	2,251
Costs Capitalized Subsequent to Acquisition	6
Impairment/Write Downs	-691
Cost Amount Carried at Close of Period
Land	631
Buildings and Improvements	1,735
Total	2,366
Accumulated Depreciation	466
Village Lane, Wallingford, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,090
Buildings and Equipment	4,448
Costs Capitalized Subsequent to Acquisition	1,078
Impairment/Write Downs	-2,600
Cost Amount Carried at Close of Period
Land	750
Buildings and Improvements	3,266
Total	4,016
Accumulated Depreciation	109
100 Northfield Drive, Windsor, CT | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,376
Buildings and Equipment	11,212
Costs Capitalized Subsequent to Acquisition	2,791
Impairment/Write Downs	-2,093
Cost Amount Carried at Close of Period
Land	1,183
Buildings and Improvements	12,103
Total	13,286
Accumulated Depreciation	4,234
1250 H Street, NW, Washington, DC | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,975
Buildings and Equipment	53,778
Costs Capitalized Subsequent to Acquisition	5,272
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	5,975
Buildings and Improvements	59,050
Total	65,025
Accumulated Depreciation	24,069
Georgetown-Green and Harris Buildings, Washington, DC | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	24,000
Buildings and Equipment	35,979
Costs Capitalized Subsequent to Acquisition	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	4,797
802 Delaware Avenue, Wilmington, DE | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,409
Buildings and Equipment	39,681
Costs Capitalized Subsequent to Acquisition	10,530
Impairment/Write Downs	-11,156
Cost Amount Carried at Close of Period
Land	3,390
Buildings and Improvements	40,074
Total	43,464
Accumulated Depreciation	21,964
6600 North Military Trail, Boca Raton, FL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	15,900
Buildings and Equipment	129,790
Costs Capitalized Subsequent to Acquisition	0
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	15,900
Buildings and Improvements	129,790
Total	145,690
Accumulated Depreciation	12,979
225 Water Street, Jacksonville, FL | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	40,059
Initial Cost to Company
Land	1,480
Buildings and Equipment	43,770
Costs Capitalized Subsequent to Acquisition	4,482
Impairment/Write Downs	-29,720
Cost Amount Carried at Close of Period
Land	871
Buildings and Improvements	19,141
Total	20,012
Accumulated Depreciation	338
The Exchange, Atlanta, GA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,576
Buildings and Equipment	13,134
Costs Capitalized Subsequent to Acquisition	3,170
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,578
Buildings and Improvements	16,302
Total	17,880
Accumulated Depreciation	4,376
9040 Roswell Road, Atlanta, GA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,459
Buildings and Equipment	18,549
Costs Capitalized Subsequent to Acquisition	2,213
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,463
Buildings and Improvements	20,758
Total	23,221
Accumulated Depreciation	5,425
Executive Park, Atlanta, GA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	13,729
Buildings and Equipment	78,032
Costs Capitalized Subsequent to Acquisition	5,980
Impairment/Write Downs	-54,310
Cost Amount Carried at Close of Period
Land	10,954
Buildings and Improvements	32,477
Total	43,431
Accumulated Depreciation	13,947
3920 Arkwright Road, Macon, GA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,674
Buildings and Equipment	19,311
Costs Capitalized Subsequent to Acquisition	2,892
Impairment/Write Downs	-4,383
Cost Amount Carried at Close of Period
Land	2,243
Buildings and Improvements	18,251
Total	20,494
Accumulated Depreciation	4,825
1775 West Oak Commons Court, Marietta, GA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,190
Buildings and Equipment	6,586
Costs Capitalized Subsequent to Acquisition	1,217
Impairment/Write Downs	-1,689
Cost Amount Carried at Close of Period
Land	1,814
Buildings and Improvements	6,490
Total	8,304
Accumulated Depreciation	1,458
633 Ahua Street, Honolulu, HI | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,256
Buildings and Equipment	3
Costs Capitalized Subsequent to Acquisition	18,050
Impairment/Write Downs	-2,912
Cost Amount Carried at Close of Period
Land	1,100
Buildings and Improvements	15,297
Total	16,397
Accumulated Depreciation	3,397
625 Crane Street, Aurora, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,180
Buildings and Equipment	3,411
Costs Capitalized Subsequent to Acquisition	-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	56
905 Meridian Lake Drive, Aurora, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,740
Buildings and Equipment	13,586
Costs Capitalized Subsequent to Acquisition	52
Impairment/Write Downs	-3,069
Cost Amount Carried at Close of Period
Land	1,431
Buildings and Improvements	10,878
Total	12,309
Accumulated Depreciation	2,609
1200 Lakeside Drive, Bannockburn, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,846
Buildings and Equipment	48,568
Costs Capitalized Subsequent to Acquisition	10,623
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	5,858
Buildings and Improvements	59,179
Total	65,037
Accumulated Depreciation	12,964
Illinois Center, Chicago, IL | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	142,666
Initial Cost to Company
Land	66,757
Buildings and Equipment	239,143
Costs Capitalized Subsequent to Acquisition	27,735
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	66,757
Buildings and Improvements	266,878
Total	333,635
Accumulated Depreciation	23,133
600 West Chicago Avenue, Chicago, IL | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	34,980
Buildings and Equipment	315,643
Costs Capitalized Subsequent to Acquisition	4,314
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	34,980
Buildings and Improvements	319,957
Total	354,937
Accumulated Depreciation	27,356
8750 Bryn Mawr Avenue, Chicago, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,600
Buildings and Equipment	77,764
Costs Capitalized Subsequent to Acquisition	6,460
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,600
Buildings and Improvements	84,224
Total	90,824
Accumulated Depreciation	9,137
1717 Deerfield Road, Deerfield, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,515
Buildings and Equipment	20,186
Costs Capitalized Subsequent to Acquisition	2,540
Impairment/Write Downs	-16,742
Cost Amount Carried at Close of Period
Land	985
Buildings and Improvements	7,514
Total	8,499
Accumulated Depreciation	213
1955 West Field Court, Lake Forest, IL | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,258
Buildings and Equipment	9,630
Costs Capitalized Subsequent to Acquisition	2,991
Impairment/Write Downs	-1,954
Cost Amount Carried at Close of Period
Land	1,065
Buildings and Improvements	10,860
Total	11,925
Accumulated Depreciation	3,025
11350 North Meridian Street, Carmel, IN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	667
Buildings and Equipment	5,815
Costs Capitalized Subsequent to Acquisition	1,654
Impairment/Write Downs	-5,415
Cost Amount Carried at Close of Period
Land	270
Buildings and Improvements	2,451
Total	2,721
Accumulated Depreciation	125
101-115 W. Washington Street, Indianapolis, IN | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,495
Buildings and Equipment	60,465
Costs Capitalized Subsequent to Acquisition	21,160
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	7,496
Buildings and Improvements	81,624
Total	89,120
Accumulated Depreciation	20,875
111 Monument Circle, Indianapolis, IN | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	116,000
Initial Cost to Company
Land	9,670
Buildings and Equipment	158,085
Costs Capitalized Subsequent to Acquisition	5,014
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	9,670
Buildings and Improvements	163,099
Total	172,769
Accumulated Depreciation	8,737
5015 S. Water Circle, Wichita, KS | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,720
Buildings and Equipment	2,029
Costs Capitalized Subsequent to Acquisition	1,125
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,719
Buildings and Improvements	3,155
Total	5,874
Accumulated Depreciation	731
701 Poydras Street, New Orleans, LA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	9,100
Buildings and Equipment	78,540
Costs Capitalized Subsequent to Acquisition	9,971
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	9,100
Buildings and Improvements	88,511
Total	97,611
Accumulated Depreciation	7,252
109 Brookline Avenue, Boston, MA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,168
Buildings and Equipment	30,397
Costs Capitalized Subsequent to Acquisition	11,492
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,168
Buildings and Improvements	41,889
Total	45,057
Accumulated Depreciation	17,245
Adams Place, Braintree/Quincy, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,145
Buildings and Equipment	27,742
Costs Capitalized Subsequent to Acquisition	8,420
Impairment/Write Downs	-20,532
Cost Amount Carried at Close of Period
Land	2,956
Buildings and Improvements	16,819
Total	19,775
Accumulated Depreciation	853
Cabot Business Park, Mansfield, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,733
Buildings and Equipment	23,657
Costs Capitalized Subsequent to Acquisition	5,376
Impairment/Write Downs	-17,038
Cost Amount Carried at Close of Period
Land	1,654
Buildings and Improvements	13,074
Total	14,728
Accumulated Depreciation	556
Cabot Business Park Land, Mansfield, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,033
Buildings and Equipment	0
Costs Capitalized Subsequent to Acquisition	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
2300 Crown Colony Drive, Quincy, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	774
Buildings and Equipment	5,815
Costs Capitalized Subsequent to Acquisition	1,591
Impairment/Write Downs	-1,036
Cost Amount Carried at Close of Period
Land	678
Buildings and Improvements	6,466
Total	7,144
Accumulated Depreciation	2,419
Myles Standish Industrial Park, Taunton, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,013
Buildings and Equipment	8,728
Costs Capitalized Subsequent to Acquisition	2,214
Impairment/Write Downs	-4,077
Cost Amount Carried at Close of Period
Land	686
Buildings and Improvements	7,192
Total	7,878
Accumulated Depreciation	135
340 Thompson Road, Webster, MA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	315
Buildings and Equipment	2,834
Costs Capitalized Subsequent to Acquisition	39
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	315
Buildings and Improvements	2,873
Total	3,188
Accumulated Depreciation	1,270
100 South Charles Street, Baltimore, MD | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	0
Buildings and Equipment	12,430
Costs Capitalized Subsequent to Acquisition	3,931
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	0
Buildings and Improvements	16,361
Total	16,361
Accumulated Depreciation	6,870
111 Market Place, Baltimore, MD | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,328
Buildings and Equipment	54,645
Costs Capitalized Subsequent to Acquisition	15,070
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,328
Buildings and Improvements	69,715
Total	76,043
Accumulated Depreciation	21,931
25 S. Charles Street, Baltimore, MD | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,830
Buildings and Equipment	22,996
Costs Capitalized Subsequent to Acquisition	12,677
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,830
Buildings and Improvements	35,673
Total	38,503
Accumulated Depreciation	11,158
820 W. Diamond, Gaithersburg, MD | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,381
Buildings and Equipment	18,798
Costs Capitalized Subsequent to Acquisition	10,193
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	4,461
Buildings and Improvements	28,911
Total	33,372
Accumulated Depreciation	10,230
6710 Oxon Hill, Oxon Hill, MD | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,181
Buildings and Equipment	13,653
Costs Capitalized Subsequent to Acquisition	2,998
Impairment/Write Downs	-2,300
Cost Amount Carried at Close of Period
Land	2,725
Buildings and Improvements	14,807
Total	17,532
Accumulated Depreciation	7,032
Danac Stiles Business Park, Rockville, MD | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,638
Buildings and Equipment	62,572
Costs Capitalized Subsequent to Acquisition	5,846
Impairment/Write Downs	-10,480
Cost Amount Carried at Close of Period
Land	6,595
Buildings and Improvements	58,981
Total	65,576
Accumulated Depreciation	17,078
East Eisenhower Parkway, Ann Arbor, MI | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,760
Buildings and Equipment	46,988
Costs Capitalized Subsequent to Acquisition	1,297
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,760
Buildings and Improvements	48,285
Total	55,045
Accumulated Depreciation	5,528
8800 Queen Avenue South, Bloomington, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,898
Buildings and Equipment	17,081
Costs Capitalized Subsequent to Acquisition	2,038
Impairment/Write Downs	-7,378
Cost Amount Carried at Close of Period
Land	1,788
Buildings and Improvements	11,851
Total	13,639
Accumulated Depreciation	331
2250 Pilot Knob Road, Mendota Heights, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	533
Buildings and Equipment	4,795
Costs Capitalized Subsequent to Acquisition	1,201
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	533
Buildings and Improvements	5,996
Total	6,529
Accumulated Depreciation	2,394
9800 Shelard Parkway, Plymouth, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	563
Buildings and Equipment	5,064
Costs Capitalized Subsequent to Acquisition	1,090
Impairment/Write Downs	-1,433
Cost Amount Carried at Close of Period
Land	433
Buildings and Improvements	4,851
Total	5,284
Accumulated Depreciation	2,378
Rosedale Corporate Plaza, Roseville, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,860
Buildings and Equipment	16,750
Costs Capitalized Subsequent to Acquisition	8,938
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,859
Buildings and Improvements	25,689
Total	27,548
Accumulated Depreciation	8,775
411 Farwell Avenue, South St. Paul, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,303
Buildings and Equipment	10,451
Costs Capitalized Subsequent to Acquisition	4,595
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,304
Buildings and Improvements	15,045
Total	16,349
Accumulated Depreciation	3,035
6200 Glenn Carlson Drive, St. Cloud, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,950
Buildings and Equipment	13,803
Costs Capitalized Subsequent to Acquisition	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	1,811
1000 Shelard Parkway, St. Louis Park, MN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	695
Buildings and Equipment	6,254
Costs Capitalized Subsequent to Acquisition	1,778
Impairment/Write Downs	-835
Cost Amount Carried at Close of Period
Land	622
Buildings and Improvements	7,270
Total	7,892
Accumulated Depreciation	3,017
525 Park Street, St. Paul, MN | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	696
Buildings and Equipment	6,263
Costs Capitalized Subsequent to Acquisition	1,513
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	695
Buildings and Improvements	7,777
Total	8,472
Accumulated Depreciation	3,104
1900 Meyer Drury Drive, Arnold, MO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	834
Buildings and Equipment	7,302
Costs Capitalized Subsequent to Acquisition	474
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	838
Buildings and Improvements	7,772
Total	8,610
Accumulated Depreciation	2,039
4700 Belleview Avenue, Kansas City, MO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,165
Buildings and Equipment	3,097
Costs Capitalized Subsequent to Acquisition	2,375
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,165
Buildings and Improvements	5,472
Total	6,637
Accumulated Depreciation	793
131-165 West Ninth Street, N. Kansas City, MO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	494
Buildings and Equipment	959
Costs Capitalized Subsequent to Acquisition	300
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	494
Buildings and Improvements	1,259
Total	1,753
Accumulated Depreciation	200
12655 Olive Boulevard, St. Louis, MO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,800
Buildings and Equipment	8,020
Costs Capitalized Subsequent to Acquisition	1,760
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	4,801
Buildings and Improvements	9,779
Total	14,580
Accumulated Depreciation	2,016
1285 Fern Ridge Parkway, St. Louis, MO | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	903
Buildings and Equipment	7,602
Costs Capitalized Subsequent to Acquisition	1,495
Impairment/Write Downs	-3,503
Cost Amount Carried at Close of Period
Land	556
Buildings and Improvements	5,941
Total	6,497
Accumulated Depreciation	2,497
300 North Greene Street, Greensboro, NC | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,070
Buildings and Equipment	37,073
Costs Capitalized Subsequent to Acquisition	1,616
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,070
Buildings and Improvements	38,689
Total	40,759
Accumulated Depreciation	4,322
7-9 Vreeland Road, Florham Park, NJ | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,412
Buildings and Equipment	12,709
Costs Capitalized Subsequent to Acquisition	2,191
Impairment/Write Downs	-9,087
Cost Amount Carried at Close of Period
Land	916
Buildings and Improvements	6,309
Total	7,225
Accumulated Depreciation	442
111 River Street, Hoboken, NJ | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	0
Buildings and Equipment	134,199
Costs Capitalized Subsequent to Acquisition	602
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	0
Buildings and Improvements	134,801
Total	134,801
Accumulated Depreciation	18,206
5 Paragon Drive, Montvale, NJ | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,650
Buildings and Equipment	13,725
Costs Capitalized Subsequent to Acquisition	351
Impairment/Write Downs	-3,298
Cost Amount Carried at Close of Period
Land	3,075
Buildings and Improvements	11,353
Total	14,428
Accumulated Depreciation	1,363
1000 Voorhees Drive and 333 and 400 Laurel Oak Drive, Voorhees, NJ | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,171
Buildings and Equipment	13,655
Costs Capitalized Subsequent to Acquisition	2,361
Impairment/Write Downs	-9,829
Cost Amount Carried at Close of Period
Land	1,688
Buildings and Improvements	6,670
Total	8,358
Accumulated Depreciation	358
One Park Square, Albuquerque, NM | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,582
Buildings and Equipment	21,532
Costs Capitalized Subsequent to Acquisition	5,756
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,583
Buildings and Improvements	27,287
Total	29,870
Accumulated Depreciation	8,448
Widewaters Parkway, Dewitt, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,574
Buildings and Equipment	39,419
Costs Capitalized Subsequent to Acquisition	8,218
Impairment/Write Downs	-33,428
Cost Amount Carried at Close of Period
Land	2,058
Buildings and Improvements	16,725
Total	18,783
Accumulated Depreciation	883
5062 Brittonfield Parkway, East Syracuse, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	718
Buildings and Equipment	4,756
Costs Capitalized Subsequent to Acquisition	-10
Impairment/Write Downs	-1,700
Cost Amount Carried at Close of Period
Land	590
Buildings and Improvements	3,174
Total	3,764
Accumulated Depreciation	74
Woodcliff Drive, Fairport, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,538
Buildings and Equipment	55,938
Costs Capitalized Subsequent to Acquisition	11,385
Impairment/Write Downs	-25,814
Cost Amount Carried at Close of Period
Land	4,622
Buildings and Improvements	43,425
Total	48,047
Accumulated Depreciation	3,651
1601 Veterans Highway, Islandia, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	813
Buildings and Equipment	7,319
Costs Capitalized Subsequent to Acquisition	2,684
Impairment/Write Downs	-7,281
Cost Amount Carried at Close of Period
Land	368
Buildings and Improvements	3,167
Total	3,535
Accumulated Depreciation	120
Two Corporate Drive Center, Melville, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,155
Buildings and Equipment	28,395
Costs Capitalized Subsequent to Acquisition	6,625
Impairment/Write Downs	-26,344
Cost Amount Carried at Close of Period
Land	1,868
Buildings and Improvements	9,963
Total	11,831
Accumulated Depreciation	841
Interstate Place, North Syracuse, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	563
Buildings and Equipment	4,874
Costs Capitalized Subsequent to Acquisition	1,243
Impairment/Write Downs	-3,750
Cost Amount Carried at Close of Period
Land	296
Buildings and Improvements	2,634
Total	2,930
Accumulated Depreciation	79
1000 Pittsford-Victor Road, Pittsford, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	583
Buildings and Equipment	4,700
Costs Capitalized Subsequent to Acquisition	967
Impairment/Write Downs	-3,295
Cost Amount Carried at Close of Period
Land	314
Buildings and Improvements	2,641
Total	2,955
Accumulated Depreciation	91
1200 Pittsford-Victor Road, Pittsford, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	307
Buildings and Equipment	2,083
Costs Capitalized Subsequent to Acquisition	4
Impairment/Write Downs	-540
Cost Amount Carried at Close of Period
Land	295
Buildings and Improvements	1,559
Total	1,854
Accumulated Depreciation	38
Corporate Crossing, Pittsford, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,012
Buildings and Equipment	22,546
Costs Capitalized Subsequent to Acquisition	1,088
Impairment/Write Downs	-12,224
Cost Amount Carried at Close of Period
Land	2,047
Buildings and Improvements	12,375
Total	14,422
Accumulated Depreciation	337
Canal View Boulevard, Rochester, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,575
Buildings and Equipment	12,686
Costs Capitalized Subsequent to Acquisition	1,791
Impairment/Write Downs	-4,428
Cost Amount Carried at Close of Period
Land	1,290
Buildings and Improvements	10,334
Total	11,624
Accumulated Depreciation	1,796
14 Classic Street, Sherburne, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	140
Buildings and Equipment	1,250
Costs Capitalized Subsequent to Acquisition	15
Impairment/Write Downs	-16
Cost Amount Carried at Close of Period
Land	140
Buildings and Improvements	1,249
Total	1,389
Accumulated Depreciation	274
110 W. Fayette Street, Syracuse, NY | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,788
Buildings and Equipment	16,096
Costs Capitalized Subsequent to Acquisition	14,881
Impairment/Write Downs	-17,214
Cost Amount Carried at Close of Period
Land	1,075
Buildings and Improvements	14,476
Total	15,551
Accumulated Depreciation	651
251 Salina Meadows Parkway, Syracuse, NY | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	466
Buildings and Equipment	4,196
Costs Capitalized Subsequent to Acquisition	1,134
Impairment/Write Downs	-2,748
Cost Amount Carried at Close of Period
Land	335
Buildings and Improvements	2,713
Total	3,048
Accumulated Depreciation	124
11311 Cornell Park Drive, Blue Ash, OH | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	883
Buildings and Equipment	7,175
Costs Capitalized Subsequent to Acquisition	1,120
Impairment/Write Downs	-2,561
Cost Amount Carried at Close of Period
Land	773
Buildings and Improvements	5,844
Total	6,617
Accumulated Depreciation	213
North Point Office Complex, Cleveland, OH | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	12,000
Buildings and Equipment	94,448
Costs Capitalized Subsequent to Acquisition	15,496
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	12,000
Buildings and Improvements	109,944
Total	121,944
Accumulated Depreciation	18,849
5300 Kings Island Drive, Mason, OH | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,528
Buildings and Equipment	13,748
Costs Capitalized Subsequent to Acquisition	4,620
Impairment/Write Downs	-8,546
Cost Amount Carried at Close of Period
Land	1,320
Buildings and Improvements	10,030
Total	11,350
Accumulated Depreciation	725
3 Crown Point Court, Sharonville, OH | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	956
Buildings and Equipment	8,290
Costs Capitalized Subsequent to Acquisition	1,362
Impairment/Write Downs	-181
Cost Amount Carried at Close of Period
Land	1,125
Buildings and Improvements	9,302
Total	10,427
Accumulated Depreciation	1,915
Raintree Industrial Park, Solon, OH | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,808
Buildings and Equipment	16,620
Costs Capitalized Subsequent to Acquisition	2,064
Impairment/Write Downs	-8,359
Cost Amount Carried at Close of Period
Land	1,339
Buildings and Improvements	10,794
Total	12,133
Accumulated Depreciation	394
401 Vine Street, Delmont, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,575
Buildings and Equipment	5,542
Costs Capitalized Subsequent to Acquisition	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	991
515 Pennsylvania Avenue, Fort Washington, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,872
Buildings and Equipment	8,816
Costs Capitalized Subsequent to Acquisition	4,091
Impairment/Write Downs	-4,225
Cost Amount Carried at Close of Period
Land	1,259
Buildings and Improvements	9,295
Total	10,554
Accumulated Depreciation	4,404
443 Gulph Road, King of Prussia, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	634
Buildings and Equipment	3,251
Costs Capitalized Subsequent to Acquisition	773
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	634
Buildings and Improvements	4,024
Total	4,658
Accumulated Depreciation	1,528
4350 Northern Pike, Monroeville, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,558
Buildings and Equipment	51,775
Costs Capitalized Subsequent to Acquisition	16,926
Impairment/Write Downs	-34,439
Cost Amount Carried at Close of Period
Land	3,667
Buildings and Improvements	37,153
Total	40,820
Accumulated Depreciation	15,106
Cherrington Corporate Center Moon, Township, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	11,369
Buildings and Equipment	39,892
Costs Capitalized Subsequent to Acquisition	18,276
Impairment/Write Downs	-5,440
Cost Amount Carried at Close of Period
Land	11,164
Buildings and Improvements	52,933
Total	64,097
Accumulated Depreciation	19,102
1500 Market Street, Philadelphia, PA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	18,758
Buildings and Equipment	167,487
Costs Capitalized Subsequent to Acquisition	96,002
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	18,758
Buildings and Improvements	263,489
Total	282,247
Accumulated Depreciation	68,976
1525 Locust Street, Philadelphia, PA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	931
Buildings and Equipment	8,377
Costs Capitalized Subsequent to Acquisition	1,853
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	930
Buildings and Improvements	10,231
Total	11,161
Accumulated Depreciation	3,719
1600 Market Street, Philadelphia, PA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,462
Buildings and Equipment	111,946
Costs Capitalized Subsequent to Acquisition	16,320
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,462
Buildings and Improvements	128,266
Total	131,728
Accumulated Depreciation	51,508
16th and Race Street, Philadelphia, PA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,884
Buildings and Equipment	71,002
Costs Capitalized Subsequent to Acquisition	5,749
Impairment/Write Downs	-48,329
Cost Amount Carried at Close of Period
Land	5,939
Buildings and Improvements	30,367
Total	36,306
Accumulated Depreciation	1,306
1735 Market Street, Philadelphia, PA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	171,498
Initial Cost to Company
Land	24,753
Buildings and Equipment	222,775
Costs Capitalized Subsequent to Acquisition	50,376
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	24,747
Buildings and Improvements	273,157
Total	297,904
Accumulated Depreciation	110,910
Foster Plaza, Pittsburgh, PA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,168
Buildings and Equipment	51,588
Costs Capitalized Subsequent to Acquisition	15,524
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,171
Buildings and Improvements	67,109
Total	73,280
Accumulated Depreciation	16,665
128 Crews Drive, Columbia, SC | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,420
Buildings and Equipment	4,017
Costs Capitalized Subsequent to Acquisition	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	385
1320 Main Street, Columbia, SC | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	38,979
Initial Cost to Company
Land	1,660
Buildings and Equipment	53,058
Costs Capitalized Subsequent to Acquisition	399
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,660
Buildings and Improvements	53,457
Total	55,117
Accumulated Depreciation	3,008
111 Southchase Boulevard, Fountain Inn, SC | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	520
Buildings and Equipment	6,822
Costs Capitalized Subsequent to Acquisition	1,725
Impairment/Write Downs	-2,912
Cost Amount Carried at Close of Period
Land	390
Buildings and Improvements	5,765
Total	6,155
Accumulated Depreciation	1,393
1043 Global Avenue, Graniteville, SC | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	720
Buildings and Equipment	15,552
Costs Capitalized Subsequent to Acquisition	598
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	720
Buildings and Improvements	16,150
Total	16,870
Accumulated Depreciation	3,042
633 Frazier Drive, Franklin, TN | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	5,800
Buildings and Equipment	13,190
Costs Capitalized Subsequent to Acquisition	-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	2,381
775 Ridge Lake Boulevard, Memphis, TN | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,113
Buildings and Equipment	18,201
Costs Capitalized Subsequent to Acquisition	515
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,114
Buildings and Improvements	18,715
Total	20,829
Accumulated Depreciation	5,044
1601 Rio Grande Street, Austin, TX | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	688
Buildings and Equipment	6,192
Costs Capitalized Subsequent to Acquisition	1,272
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	697
Buildings and Improvements	7,455
Total	8,152
Accumulated Depreciation	2,874
206 East 9th Street, Austin, TX | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	27,965
Initial Cost to Company
Land	7,900
Buildings and Equipment	38,533
Costs Capitalized Subsequent to Acquisition	1,822
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	7,900
Buildings and Improvements	40,355
Total	48,255
Accumulated Depreciation	2,568
4515 Seton Center Parkway, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,038
Buildings and Equipment	18,338
Costs Capitalized Subsequent to Acquisition	2,487
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,037
Buildings and Improvements	20,826
Total	22,863
Accumulated Depreciation	8,310
4516 Seton Center Parkway, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,028
Buildings and Equipment	18,251
Costs Capitalized Subsequent to Acquisition	3,046
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,027
Buildings and Improvements	21,298
Total	23,325
Accumulated Depreciation	8,717
7800 Shoal Creek Boulevard, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,731
Buildings and Equipment	14,921
Costs Capitalized Subsequent to Acquisition	4,407
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,731
Buildings and Improvements	19,328
Total	21,059
Accumulated Depreciation	6,842
812 San Antonio Street, Austin, TX | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	626
Buildings and Equipment	5,636
Costs Capitalized Subsequent to Acquisition	2,286
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	621
Buildings and Improvements	7,927
Total	8,548
Accumulated Depreciation	2,807
8701 N. Mopac, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,574
Buildings and Equipment	14,168
Costs Capitalized Subsequent to Acquisition	2,511
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,573
Buildings and Improvements	16,680
Total	18,253
Accumulated Depreciation	6,201
Bridgepoint Parkway, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,784
Buildings and Equipment	70,526
Costs Capitalized Subsequent to Acquisition	9,757
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	7,785
Buildings and Improvements	80,282
Total	88,067
Accumulated Depreciation	34,829
Lakewood on the Park, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,548
Buildings and Equipment	31,936
Costs Capitalized Subsequent to Acquisition	1,629
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,548
Buildings and Improvements	33,565
Total	37,113
Accumulated Depreciation	13,597
Research Park, Austin, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	15,859
Buildings and Equipment	60,175
Costs Capitalized Subsequent to Acquisition	14,551
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	18,411
Buildings and Improvements	72,174
Total	90,585
Accumulated Depreciation	26,848
9840 Gateway Boulevard North, El Paso, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,700
Buildings and Equipment	9,736
Costs Capitalized Subsequent to Acquisition	-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	1,752
3003 South Expressway 281, Hidalgo, TX | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,480
Buildings and Equipment	15,533
Costs Capitalized Subsequent to Acquisition	-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	2,805
3330 N Washington Boulevard, Arlington, VA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	810
Buildings and Equipment	7,289
Costs Capitalized Subsequent to Acquisition	744
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	811
Buildings and Improvements	8,032
Total	8,843
Accumulated Depreciation	3,100
6160 Kempsville Circle, Norfolk, VA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,273
Buildings and Equipment	11,083
Costs Capitalized Subsequent to Acquisition	2,931
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,273
Buildings and Improvements	14,014
Total	15,287
Accumulated Depreciation	4,087
Thunderbolt Place, Chantilly, VA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,374
Buildings and Equipment	12,369
Costs Capitalized Subsequent to Acquisition	819
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	1,375
Buildings and Improvements	13,187
Total	14,562
Accumulated Depreciation	4,998
448 Viking Drive, Virginia Beach, VA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	682
Buildings and Equipment	5,431
Costs Capitalized Subsequent to Acquisition	1,443
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	686
Buildings and Improvements	6,870
Total	7,556
Accumulated Depreciation	1,664
333 108th Avenue NE, Bellevue, WA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	14,400
Buildings and Equipment	136,412
Costs Capitalized Subsequent to Acquisition	1,731
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	14,400
Buildings and Improvements	138,143
Total	152,543
Accumulated Depreciation	18,429
600 108th Avenue NE, Bellevue, WA | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,555
Buildings and Equipment	30,244
Costs Capitalized Subsequent to Acquisition	11,912
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,555
Buildings and Improvements	42,156
Total	45,711
Accumulated Depreciation	10,119
1331 North Center Parkway, Kennewick, WA | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	1,850
Buildings and Equipment	7,339
Costs Capitalized Subsequent to Acquisition	-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	1,323
100 East Wisconsin Avenue, Milwaukee, WI | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,150
Buildings and Equipment	72,113
Costs Capitalized Subsequent to Acquisition	6,615
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,150
Buildings and Improvements	78,728
Total	81,878
Accumulated Depreciation	9,063
111 East Kilbourn Avenue, Milwaukee, WI | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,400
Buildings and Equipment	47,562
Costs Capitalized Subsequent to Acquisition	5,107
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,400
Buildings and Improvements	52,669
Total	55,069
Accumulated Depreciation	8,919
7 Modal Crescent, Canning Vale, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	9,806
Buildings and Equipment	3,925
Costs Capitalized Subsequent to Acquisition	-505
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	8,171
Buildings and Improvements	5,055
Total	13,226
Accumulated Depreciation	454
71-93 Whiteside Road, Clayton, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	9,757
Buildings and Equipment	8,495
Costs Capitalized Subsequent to Acquisition	-3,043
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	8,130
Buildings and Improvements	7,079
Total	15,209
Accumulated Depreciation	749
9-13 Titanium Court, Crestmead, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	3,400
Buildings and Equipment	3,185
Costs Capitalized Subsequent to Acquisition	-1,098
Impairment/Write Downs	-409
Cost Amount Carried at Close of Period
Land	2,621
Buildings and Improvements	2,457
Total	5,078
Accumulated Depreciation	281
16 Rodborough Road, Frenchs Forest, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	7,355
Buildings and Equipment	9,498
Costs Capitalized Subsequent to Acquisition	-2,386
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	6,128
Buildings and Improvements	8,339
Total	14,467
Accumulated Depreciation	859
22 Rodborough Road, Frenchs Forest, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,452
Buildings and Equipment	3,923
Costs Capitalized Subsequent to Acquisition	453
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	2,043
Buildings and Improvements	4,785
Total	6,828
Accumulated Depreciation	459
127-161 Cherry Lane, Laverton North, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,266
Buildings and Equipment	5,220
Costs Capitalized Subsequent to Acquisition	-1,237
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,554
Buildings and Improvements	4,695
Total	8,249
Accumulated Depreciation	462
310-314 Invermay Road, Mowbray, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	431
Buildings and Equipment	535
Costs Capitalized Subsequent to Acquisition	-919
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	56
Buildings and Improvements	-9
Total	47
Accumulated Depreciation	47
253-293 George Town Road, Rocherlea, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	2,108
Buildings and Equipment	1,331
Costs Capitalized Subsequent to Acquisition	-574
Impairment/Write Downs	-2,748
Cost Amount Carried at Close of Period
Land	526
Buildings and Improvements	-409
Total	117
Accumulated Depreciation	117
310-320 Pitt Street, Sydney, Australia | CBD
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	63,271
Buildings and Equipment	104,588
Costs Capitalized Subsequent to Acquisition	-30,272
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	51,886
Buildings and Improvements	85,701
Total	137,587
Accumulated Depreciation	9,109
44-46 Mandarin Street, Villawood, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	6,374
Buildings and Equipment	8,179
Costs Capitalized Subsequent to Acquisition	-1,096
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	5,311
Buildings and Improvements	8,146
Total	13,457
Accumulated Depreciation	814
19 Leadership Way, Wangara, Australia | Suburban property
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to Company
Land	4,217
Buildings and Equipment	2,685
Costs Capitalized Subsequent to Acquisition	-961
Impairment/Write Downs	0
Cost Amount Carried at Close of Period
Land	3,514
Buildings and Improvements	2,427
Total	5,941
Accumulated Depreciation	$247

SCHEDULE_III_REAL_ESTATE_AND_A2

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Analysis of Carrying Amount of Real Estate Properties and Accumulated Depreciation (Details) (USD $)	3 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Jun. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Real Estate Properties
Balance at the beginning of the year				$5,537,165	$7,829,409	$7,244,232
Additions				70,963	231,485	1,041,655
Loss on asset impairment	-167,100	-22,700	-124,300	-191,490	-384,141	-242,497
Deconsolidation of SIR					-1,446,781
Properties reclassified to discontinued operations					-552,024	-174,562
Properties reclassified to continuing operations				341,024
Disposals				-29,219	-140,783	-39,419
Balance at the end of the year	5,728,443			5,728,443	5,537,165	7,829,409
Accumulated Depreciation
Balance at the beginning of the year				895,059	1,007,606	934,170
Additions				164,815	176,777	188,220
Loss on asset impairment				-6,423	-185,795	-73,865
Deconsolidation of SIR					-56,023
Properties reclassified to discontinued operations					-15,471	-10,521
Properties reclassified to continuing operations				5,724
Disposals				-28,730	-32,035	-30,398
Balance at the end of the year	$1,030,445			$1,030,445	$895,059	$1,007,606

SCHEDULE_III_REAL_ESTATE_AND_A3

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Analysis of Carrying Amount of Real Estate Properties and Accumulated Depreciation (Footnote) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
SEC Schedule III, Real Estate and Accumulated Depreciation [Line Items]
Aggregate cost of properties for federal income tax purposes	$6,672,730
Real estate properties additions due to changes in foreign currency exchange	-20,445	-40,020	4,986
Accumulated depreciation additions due to changes in foreign currency exchange	($1,279)	($1,528)	$97
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_ON_1

SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
SCHEDULE IV MORTGAGE LOANS ON REAL ESTATE
Face Amount of Mortgage			$8,107
Carrying Amount of Mortgage	8,100		8,107
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	1,419	0
New mortgage loans	7,688	1,419
Collections of principal	-1,000
Balance at the end of period	8,107	1,419	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			419
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