Segment Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Information.
Number of segments | item									2
Rental income	$ 61,685	$ 62,092	$ 62,113	$ 62,659	$ 64,625	$ 64,158	$ 62,428	$ 59,820	$ 248,549	$ 251,031	$ 226,910
Expenses:
Real estate taxes									29,906	28,389	25,710
Utility expenses									17,916	19,369	17,116
Other operating expenses									50,425	45,982	41,134
Depreciation and amortization									68,696	66,593	55,699
Loss on impairment of real estate										2,016
Acquisition related costs									811	1,344	2,439
General and administrative									14,826	15,809	12,710
Total expenses									182,580	179,502	154,808
Operating income (loss)									65,969	71,529	72,102
Dividend income									811
Interest and other income									14	69	37
Interest expense									(37,008)	(28,048)	(16,831)
(Loss) gains on early extinguishment of debt									34	(1,307)
Loss on distribution to common shareholders of The RMR Group Inc. common stock									(12,368)
Loss on issuance of shares by Select Income REIT									(42,145)	(53)
Loss on impairment of Select Income REIT investment									(203,297)
Income (loss) from continuing operations before income taxes and equity in earnings of investees									(227,990)	42,190	55,308
Income tax expense									(86)	(117)	(133)
Equity in earnings of an investee									18,640	10,963	334
Income (loss) from continuing operations									(209,436)	53,036	55,509
Income (loss) from discontinued operations									(525)	3,498	(889)
Net income (loss)	(2,339)	$ 16,911	$ (191,163)	$ (33,370)	14,114	$ 12,622	$ 14,608	$ 15,190	(209,961)	56,534	$ 54,620
Total assets	2,174,536				2,427,615				2,174,536	2,427,615
Operating Segments | Investment in Real Estate
Segment Information.
Rental income									248,549	251,031
Expenses:
Real estate taxes									29,906	28,389
Utility expenses									17,916	19,369
Other operating expenses									50,425	45,982
Depreciation and amortization									68,696	66,593
Loss on impairment of real estate										2,016
Acquisition related costs									561	1,344
Total expenses									167,504	163,693
Operating income (loss)									81,045	87,338
Interest and other income									10
Interest expense									(7,908)	(7,820)
(Loss) gains on early extinguishment of debt									34
Income (loss) from continuing operations before income taxes and equity in earnings of investees									73,181	79,518
Income (loss) from continuing operations									73,181	79,518
Income (loss) from discontinued operations									(525)	3,498
Net income (loss)									72,656	83,016
Total assets	1,639,806				1,714,130				1,639,806	1,714,130
Operating Segments | Investment in SIR
Expenses:
Loss on issuance of shares by Select Income REIT									(42,145)	(53)
Loss on impairment of Select Income REIT investment									(203,297)
Income (loss) from continuing operations before income taxes and equity in earnings of investees									(245,442)	(53)
Equity in earnings of an investee									18,620	10,876
Income (loss) from continuing operations									(226,822)	10,823
Net income (loss)									(226,822)	10,823
Total assets	491,369				680,137				491,369	680,137
Corporate, Non-Segment
Expenses:
Acquisition related costs									250
General and administrative									14,826	15,809
Total expenses									15,076	15,809
Operating income (loss)									(15,076)	(15,809)
Dividend income									811
Interest and other income									4	69
Interest expense									(29,100)	(20,228)
(Loss) gains on early extinguishment of debt										(1,307)
Loss on distribution to common shareholders of The RMR Group Inc. common stock									(12,368)
Income (loss) from continuing operations before income taxes and equity in earnings of investees									(55,729)	(37,275)
Income tax expense									(86)	(117)
Equity in earnings of an investee									20	87
Income (loss) from continuing operations									(55,795)	(37,305)
Net income (loss)									(55,795)	(37,305)
Total assets	$ 43,361				$ 33,348				$ 43,361	$ 33,348