CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Cumulative Preferred Distributions	Common shares	Cumulative Common Distributions	Additional Paid-in-Capital	Cumulative Net Income	Cumulative Other Comprehensive Income (Loss)	Series C	Series D	Total
Balance at Dec. 31, 2012	$ (253,426)	$ 1,236	$ (3,301,782)	$ 3,458,144	$ 2,384,876	$ 2,770	$ 161,873	$ 280,107	$ 2,733,798
Balance (in shares) at Dec. 31, 2012		123,637,424					6,700,000	11,600,000
Increase (Decrease) in Shareholders' Equity
Net income					133,178				133,178
Unrealized gain (loss) on investments						13,182			13,182
Issuance of shares, net		$ 259		654,952					655,211
Issuance of shares, net (in shares)		25,875,000
Redemption of shares, net							$ (161,873)		(161,873)
Redemption of shares, net (in shares)							(6,700,000)
Common share grants		$ 1		2,131					2,132
Share grants (in shares)		93,600
Excess of liquidation preference over carrying value of preferred shares redeemed				(5,627)					(5,627)
Distributions	(26,559)		(256,587)						(283,146)
Balance at Dec. 31, 2013	(279,985)	$ 1,496	(3,558,369)	4,109,600	2,518,054	15,952		$ 280,107	3,086,855
Balance (in shares) at Dec. 31, 2013		149,606,024						11,600,000
Increase (Decrease) in Shareholders' Equity
Net income					197,185				197,185
Unrealized gain (loss) on investments						9,852			9,852
Issuance of shares, net		$ 2		6,444					6,446
Issuance of shares, net (in shares)		222,200
Common share grants		$ 1		2,507					2,508
Share grants (in shares)		92,225
Distributions	(20,664)		(292,029)						(312,693)
Balance at Dec. 31, 2014	(300,649)	$ 1,499	(3,850,398)	4,118,551	2,715,239	25,804		$ 280,107	2,990,153
Balance (in shares) at Dec. 31, 2014		149,920,449						11,600,000
Increase (Decrease) in Shareholders' Equity
Net income					166,418				166,418
Unrealized gain (loss) on investments						(41,327)			(41,327)
Issuance of shares, net		$ 15		45,247					45,262
Issuance of shares, net (in shares)		1,553,119
Common share grants		$ 1		2,531					2,532
Share grants (in shares)		90,060
Common share repurchases				(418)					(418)
Common share repurchases (in shares)		(16,340)
Distributions	(20,664)		(299,963)					$ (20,664)	(320,627)
Distribution to common shareholders of the RMR Inc. common stock			(29,911)						(29,911)
Balance at Dec. 31, 2015	$ (321,313)	$ 1,515	$ (4,180,272)	$ 4,165,911	$ 2,881,657	$ (15,523)		$ 280,107	$ 2,812,082
Balance (in shares) at Dec. 31, 2015		151,547,288						11,600,000