CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 24,012us-gaap_ProfitLoss	$ (156,967)us-gaap_ProfitLoss	$ (79,845)us-gaap_ProfitLoss
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	$ 9,127us-gaap_ComprehensiveIncomeNetOfTax	$ (215,956)us-gaap_ComprehensiveIncomeNetOfTax	$ (90,147)us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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