CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Real estate properties:
Land	$ 740,613	$ 1,531,416
Buildings and improvements	4,890,457	6,297,993
Total real estate properties, at cost, gross	5,631,070	7,829,409
Accumulated depreciation	(874,032)	(1,007,606)
Total real estate properties, at cost, net	4,757,038	6,821,803
Properties held for sale	678,250	171,832
Acquired real estate leases, net	272,381	427,756
Equity investments	517,254	184,711
Cash and cash equivalents	165,990	102,219
Restricted cash	17,443	16,626
Rents receivable, net of allowance for doubtful accounts of $7,750 and $9,962, respectively	218,301	253,394
Other assets, net	195,330	211,293
Total assets	6,821,987	8,189,634
LIABILITIES AND SHAREHOLDERS' EQUITY
Revolving credit facility	235,000	297,000
SIR revolving credit facility		95,000
Senior unsecured debt, net	1,954,701	2,972,994
Mortgage notes payable, net	925,120	984,827
Liabilities related to properties held for sale	30,322	2,339
Accounts payable and accrued expenses	169,498	194,184
Assumed real estate lease obligations, net	38,087	69,304
Rent collected in advance	29,220	35,700
Security deposits	12,442	23,860
Due to related persons	6,564	12,958
Total liabilities	3,400,954	4,688,166
Common shares of beneficial interest, $0.01 par value:
Common shares of beneficial interest, $0.01 par value: 350,000,000 shares authorized; 118,387,518 and 83,804,068 shares issued and outstanding, respectively	1,184	838
Additional paid in capital	4,213,472	3,585,400
Cumulative net income	2,215,141	2,386,900
Cumulative other comprehensive (loss) income	(26,930)	565
Cumulative common distributions	(3,052,675)	(2,972,569)
Cumulative preferred distributions	(562,820)	(529,367)
Total shareholders' equity attributable to CommonWealth REIT	3,421,033	3,105,428
Noncontrolling interest in consolidated subsidiary		396,040
Total shareholders' equity	3,421,033	3,501,468
Total liabilities and shareholders' equity	6,821,987	8,189,634
Series D
50,000,000 shares authorized;
Preferred shares of beneficial interest, $0.01 par value	368,270	368,270
Series E
50,000,000 shares authorized;
Preferred shares of beneficial interest, $0.01 par value	$ 265,391	$ 265,391