CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 156,740	$ (216,207)	$ 182,573	$ (151,666)
Other comprehensive income (loss), net of tax:
Unrealized gain on derivative instruments	1,805	178	3,432	4,011
Foreign currency translation adjustments	(20,392)	5,455	(4,844)	(31,393)
Equity in unrealized income (loss) of an investee	27	13	(22)	(149)
Total comprehensive income (loss)	138,180	(210,561)	181,139	(179,197)
Less: comprehensive income attributable to noncontrolling interest in consolidated subsidiary	0	(108)	0	(20,057)
Comprehensive income (loss) attributable to Equity Commonwealth	$ 138,180	$ (210,669)	$ 181,139	$ (199,254)