CONDENSED CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Rental income	$ 255,374	$ 217,938	$ 506,620	$ 428,611
Expenses:
Operating expenses	108,093	90,623	212,183	181,020
Depreciation and amortization	63,552	50,394	124,903	102,683
General and administrative	13,364	11,624	25,674	22,583
Acquisition related costs	1,434	2,358	3,936	4,917
Total expenses	186,443	154,999	366,696	311,203
Operating income	68,931	62,939	139,924	117,408
Interest and other income	413	367	701	1,075
Interest expense (including net amortization of debt discounts, premiums and deferred financing fees of $1,005, $1,920, $1,751 and $3,952, respectively)	(50,237)	(48,200)	(99,343)	(95,614)
Loss on early extinguishment of debt	(1,608)		(1,675)
Equity in earnings of investees	2,829	2,910	5,787	5,622
Income from continuing operations before income tax expense	20,328	18,016	45,394	28,491
Income tax expense	(92)	(90)	(584)	(436)
Income from continuing operations	20,236	17,926	44,810	28,055
Discontinued operations:
Income from discontinued operations		2,038		3,949
Net gain on sale of properties from discontinued operations				34,572
Income before gain on sale of properties	20,236	19,964	44,810	66,576
Gain on sale of properties	350		350
Net income	20,586	19,964	45,160	66,576
Net income attributable to noncontrolling interest	(4,521)		(5,415)
Net income attributable to CommonWealth REIT	16,065	19,964	39,745	66,576
Preferred distributions	(13,823)	(10,500)	(27,646)	(19,339)
Net income available for CommonWealth REIT common shareholders	2,242	9,464	12,099	47,237
Amounts attributable to CommonWealth REIT common shareholders:
Income from continuing operations	2,242	7,426	12,099	8,716
Income from discontinued operations		2,038		3,949
Net gain on sale of properties from discontinued operations				34,572
Net income available for CommonWealth REIT common shareholders	$ 2,242	$ 9,464	$ 12,099	$ 47,237
Weighted average common shares outstanding -- basic (in shares)	83,727	72,144	83,724	72,142
Weighted average common shares outstanding -- diluted (in shares)	83,727	72,144	83,724	72,142
Basic and diluted earnings per common share attributable to CommonWealth REIT common shareholders:
Income from continuing operations (in dollars per share)	$ 0.03	$ 0.10	$ 0.14	$ 0.12
Income from discontinued operations (in dollars per share)		$ 0.03		$ 0.53
Net income available for common shareholders (in dollars per share)	$ 0.03	$ 0.13	$ 0.14	$ 0.65