Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment reporting
Number of operating segments | segment									4
Number of reportable segments | segment									3
Revenues:
Rental income									$ 666,200	$ 630,899	$ 526,703
Residents fees and services									391,822	367,874	318,184
Total revenues	$ 274,296	$ 263,983	$ 261,367	$ 258,375	$ 267,519	$ 255,275	$ 247,402	$ 228,577	1,058,022	998,773	844,887
Expenses:
Property operating expenses									399,790	377,579	324,564
Depreciation and amortization									287,831	257,783	185,391
General and administrative									46,559	42,830	38,946
Acquisition and certain other transaction related costs									2,085	6,853	4,607
Impairment of assets	2,795								18,674	194	(10)
Total expenses									754,939	685,239	553,498
Operating income									303,083	313,534	291,389
Dividend income									2,108	2,773	63
Interest and other income									430	379	362
Interest expense									(167,574)	(150,881)	(135,114)
Loss on distribution to common shareholders of RMR common stock					(38,437)				0	(38,437)	0
Loss on early extinguishment of debt								(1,409)	(526)	(1,894)	(12)
Income from continuing operations before income tax expense and equity in earnings of an investee									137,521	125,474	156,688
Income tax expense									(424)	(574)	(576)
Equity in earnings of an investee									137	20	87
Income before gain on sale of properties	42,885	$ 27,903	$ 39,233	$ 31,272	9,544	$ 38,249	$ 36,387	$ 39,789	137,234	123,968	153,184
Income from continuing operations									137,234	124,920	156,199
Discontinued Operations:
(Loss) income from discontinued operations									0	(350)	1,362
Loss on impairment of assets from discontinued operations									0	(602)	(4,377)
Income (loss) before gain on sale of properties											153,184
Gain on sale of properties									4,061	0	5,453
Total assets	7,227,754				7,160,090				7,227,754	7,160,090	5,941,930
Net Income (Loss) Attributable to Parent									141,295	123,968	158,637
Triple Net Leased Senior Living Communities
Revenues:
Rental income									275,697	256,035	230,718
Residents fees and services									0
Total revenues									275,697	256,035	230,718
Expenses:
Property operating expenses									833
Depreciation and amortization									78,361	70,417	61,825
General and administrative									0
Acquisition and certain other transaction related costs									0
Impairment of assets									6,583	194	(10)
Total expenses									85,777	70,611	61,815
Operating income									189,920	185,424	168,903
Dividend income									0
Interest and other income									0
Interest expense									(24,795)	(25,015)	(25,473)
Loss on early extinguishment of debt									(467)	(6)	128
Income from continuing operations before income tax expense and equity in earnings of an investee									164,658	160,403	143,558
Income tax expense									0
Equity in earnings of an investee									0
Income before gain on sale of properties									164,658
Income from continuing operations										160,403	143,558
Discontinued Operations:
Income (loss) before gain on sale of properties											143,558
Gain on sale of properties									4,061		5,453
Total assets	2,289,045				2,251,212				2,289,045	2,251,212	1,777,684
Net Income (Loss) Attributable to Parent									168,719	160,403	149,011
Managed Senior Living Communities
Revenues:
Rental income									0
Residents fees and services									391,822	367,874	318,184
Total revenues									391,822	367,874	318,184
Expenses:
Property operating expenses									293,195	278,242	245,093
Depreciation and amortization									81,482	60,600	32,462
General and administrative									0
Acquisition and certain other transaction related costs									0
Impairment of assets									2,174
Total expenses									376,851	338,842	277,555
Operating income									14,971	29,032	40,629
Dividend income									0
Interest and other income									0
Interest expense									(8,540)	(9,973)	(10,599)
Loss on early extinguishment of debt									(59)	(34)	(140)
Income from continuing operations before income tax expense and equity in earnings of an investee									6,372	19,025	29,890
Income tax expense									0
Equity in earnings of an investee									0
Income before gain on sale of properties									6,372
Income from continuing operations										19,025	29,890
Discontinued Operations:
Income (loss) before gain on sale of properties											29,890
Gain on sale of properties									0
Total assets	1,260,032				1,260,425				1,260,032	1,260,425	961,618
Net Income (Loss) Attributable to Parent									6,372	19,025	29,890
MOBs
Revenues:
Rental income									372,233	356,586	278,041
Residents fees and services									0
Total revenues									372,233	356,586	278,041
Expenses:
Property operating expenses									105,762	99,337	79,471
Depreciation and amortization									124,196	122,974	87,312
General and administrative									0
Acquisition and certain other transaction related costs									0
Impairment of assets									7,122
Total expenses									237,080	222,311	166,783
Operating income									135,153	134,275	111,258
Dividend income									0
Interest and other income									0
Interest expense									(13,852)	(6,214)	(5,844)
Loss on early extinguishment of debt									0	(250)
Income from continuing operations before income tax expense and equity in earnings of an investee									121,301	127,811	105,414
Income tax expense									0
Equity in earnings of an investee									0
Income before gain on sale of properties									121,301
Income from continuing operations										127,811	105,414
Discontinued Operations:
(Loss) income from discontinued operations										(350)	1,362
Loss on impairment of assets from discontinued operations										(602)	(4,377)
Income (loss) before gain on sale of properties											102,399
Gain on sale of properties									0
Total assets	3,333,141				3,362,214				3,333,141	3,362,214	2,922,623
Net Income (Loss) Attributable to Parent									121,301	126,859	102,399
All Other Operations
Revenues:
Rental income									18,270	18,278	17,944
Residents fees and services									0
Total revenues									18,270	18,278	17,944
Expenses:
Property operating expenses									0
Depreciation and amortization									3,792	3,792	3,792
General and administrative									46,559	42,830	38,946
Acquisition and certain other transaction related costs									2,085	6,853	4,607
Impairment of assets									2,795
Total expenses									55,231	53,475	47,345
Operating income									(36,961)	(35,197)	(29,401)
Dividend income									2,108	2,773	63
Interest and other income									430	379	362
Interest expense									(120,387)	(109,679)	(93,198)
Loss on distribution to common shareholders of RMR common stock										(38,437)
Loss on early extinguishment of debt									0	(1,604)
Income from continuing operations before income tax expense and equity in earnings of an investee									(154,810)	(181,765)	(122,174)
Income tax expense									(424)	(574)	(576)
Equity in earnings of an investee									137	20	87
Income before gain on sale of properties									(155,097)
Income from continuing operations										(182,319)	(122,663)
Discontinued Operations:
Income (loss) before gain on sale of properties											(122,663)
Gain on sale of properties									0
Total assets	$ 345,536				$ 286,239				345,536	286,239	280,005
Net Income (Loss) Attributable to Parent									$ (155,097)	$ (182,319)	$ (122,663)