CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 492,866	$ 272,908	$ 29,666
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on derivative instruments and other assets	0
Unrealized gain (loss) on derivative instruments		456	(248)
Unrealized gain, net on marketable securities	342	1,199	361
Total comprehensive income	493,208	274,563	29,779
Comprehensive income attributable to the noncontrolling interest	(186)	(95)	(10)
Total comprehensive income attributable to Equity Commonwealth	$ 493,022	$ 274,468	$ 29,769