CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Rental revenue	$ 62,134,000	$ 116,869,000	$ 184,368,000
Other revenue	4,144,000	10,981,000	12,654,000
Revenues, Total	66,278,000	127,850,000	197,022,000
Expenses:
Operating expenses	28,858,000	46,418,000	79,916,000
Depreciation and amortization	19,329,000	28,122,000	49,041,000
General and administrative	33,233,000	38,442,000	44,439,000
Loss on asset impairment	0	0	12,087,000
Total expenses	81,420,000	112,982,000	185,483,000
Interest and other income, net	21,228,000	72,392,000	46,815,000
Interest expense (including net amortization of debt discounts, premiums and deferred financing fees of $(119), $204 and $2,553, respectively)	(620,000)	(8,908,000)	(26,585,000)
Gain (loss) on early extinguishment of debt	131,000	(6,374,000)	(7,122,000)
Gain on sale of properties, net	446,744,000	422,172,000	251,417,000
Income before income taxes	452,341,000	494,150,000	276,064,000
Income tax expense	(248,000)	(1,284,000)	(3,156,000)
Net income	452,093,000	492,866,000	272,908,000
Net income attributable to noncontrolling interest	(799,000)	(186,000)	(95,000)
Net income attributable to Equity Commonwealth	451,294,000	492,680,000	272,813,000
Preferred distributions	(7,988,000)	(7,988,000)	(7,988,000)
Net income attributable to Equity Commonwealth common shareholders	$ 443,306,000	$ 484,692,000	$ 264,825,000
Weighted average common shares outstanding — basic (in shares)	121,786	122,091	122,314
Weighted average common shares outstanding — diluted (in shares)	126,606	126,260	123,385
Earnings per common share attributable to Equity Commonwealth common shareholders:
Basic (in dollars per share)	$ 3.64	$ 3.97	$ 2.17
Diluted (in dollars per share)	$ 3.56	$ 3.90	$ 2.15