CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 23,896	$ 32,777	$ 476,870	$ 257,486
Other comprehensive income, net of tax:
Unrealized gain on derivative instruments	0		0
Unrealized gain on derivative instruments		0		456
Unrealized gain on marketable securities	0	463	342	535
Total comprehensive income	23,896	33,240	477,212	258,477
Comprehensive income attributable to the noncontrolling interest	(10)	(13)	(180)	(90)
Total comprehensive income attributable to Equity Commonwealth	$ 23,886	$ 33,227	$ 477,032	$ 258,387