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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

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-Name Accounting Standards Codification

-Glossary Contingent Stock Agreement

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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No definition available.

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The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

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-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

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-Subparagraph (SX 210.5-03.13)

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items, and noncontrolling interest.

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-Publisher FASB

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The amount of net income (loss) from continuing operations per each basic and diluted share of common stock or unit when the per share amount is the same for both basic and diluted shares.

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No definition available.

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Amount of income (loss) from a disposal group, net of income tax, reported as a separate component of income before extraordinary items after deduction or consideration of the amount allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Per basic and diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation, when the per share amount is the same.

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No definition available.

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Amount of Net Income (Loss) attributable to noncontrolling interest.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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The amount of preferred stock dividends that is an adjustment to net income apportioned to common stockholders.

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The excess of (1) fair value of the consideration transferred to the holders of the preferred stock over (2) the carrying amount of the preferred stock in the registrant's balance sheet, during the accounting period.

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Average number of shares or units issued and outstanding that are used in calculating basic and diluted earnings per share (EPS).

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Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	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									0us-gaap_GainLossOnSaleOfProperties	1,596us-gaap_GainLossOnSaleOfProperties	0us-gaap_GainLossOnSaleOfProperties
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)us-gaap_PreferredStockRedemptionPremium	0us-gaap_PreferredStockRedemptionPremium	(4,985)us-gaap_PreferredStockRedemptionPremium
(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)us-gaap_EarningsPerShareBasicAndDiluted	$ 1.16us-gaap_EarningsPerShareBasicAndDiluted	$ (0.14)us-gaap_EarningsPerShareBasicAndDiluted	$ 0.08us-gaap_EarningsPerShareBasicAndDiluted	$ (0.14)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.92)us-gaap_EarningsPerShareBasicAndDiluted	$ 0.07us-gaap_EarningsPerShareBasicAndDiluted	$ 0.15us-gaap_EarningsPerShareBasicAndDiluted	$ (0.19)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.97)us-gaap_EarningsPerShareBasicAndDiluted	$ (1.81)us-gaap_EarningsPerShareBasicAndDiluted
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