Segment Reporting (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			4
Number of reportable segments | segment			3
Revenues:
Rental income	$ 166,647	$ 163,997	$ 333,090	$ 325,419
Residents fees and services	98,366	97,370	196,484	194,323
Total revenues	265,013	261,367	529,574	519,742
Expenses:
Property operating expenses	102,795	97,474	203,851	195,422
Depreciation and amortization	69,669	71,372	142,844	142,594
General and administrative	22,922	11,965	38,005	22,828
Acquisition and certain other transaction related costs	0	180	292	619
Impairment of assets	5,082	4,961	5,082	12,351
Total expenses	200,468	185,952	390,074	373,814
Operating income	64,545	75,415	139,500	145,928
Dividend income	659	789	1,319	789
Interest and other income	76	177	195	242
Interest expense	(40,800)	(41,118)	(84,289)	(80,399)
Loss on early extinguishment of debt	(7,353)	0	(7,353)	(6)
Income from continuing operations before income tax expense and equity in earnings of an investee	17,127	35,263	49,372	66,554
Income tax expense	(99)	(108)	(191)	(202)
Equity in earnings of an investee	374	17	502	94
Net income	17,402	39,233	49,683	70,507
Income before gain on sale of properties	17,402	35,172	49,683	66,446
Gain on sale of properties	0	4,061	0	4,061
Net income attributable to noncontrolling interest	(1,360)	0	(1,486)	0
Net income attributable to common shareholders	16,042	39,233	48,197	70,507
Total assets	7,183,620		7,183,620		$ 7,227,754
Triple Net Leased Senior Living Communities
Revenues:
Rental income	67,426	66,441	134,678	131,749
Residents fees and services	0	0	0	0
Total revenues	67,426	66,441	134,678	131,749
Expenses:
Property operating expenses	0	423	0	786
Depreciation and amortization	20,470	19,273	40,804	38,674
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs		0	0	0
Impairment of assets	0	0	0	4,391
Total expenses	20,470	19,696	40,804	43,851
Operating income	46,956	46,745	93,874	87,898
Dividend income	0	0	0	0
Interest and other income	0	0	0	0
Interest expense	(2,211)	(6,282)	(7,550)	(12,665)
Loss on early extinguishment of debt	(7,294)		(7,294)	0
Income from continuing operations before income tax expense and equity in earnings of an investee	37,451	40,463	79,030	75,233
Income tax expense	0	0	0	0
Equity in earnings of an investee	0	0	0	0
Net income	37,451		79,030
Income before gain on sale of properties		40,463		75,233
Gain on sale of properties		4,061		4,061
Net income attributable to noncontrolling interest	0		0
Net income attributable to common shareholders	37,451	44,524	79,030	79,294
Total assets	2,276,979		2,276,979		2,289,045
Managed Senior Living Communities
Revenues:
Rental income	0	0	0	0
Residents fees and services	98,366	97,370	196,484	194,323
Total revenues	98,366	97,370	196,484	194,323
Expenses:
Property operating expenses	75,149	71,642	149,028	143,820
Depreciation and amortization	16,390	20,140	36,605	40,158
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs		0	0	0
Impairment of assets	0	0	0	0
Total expenses	91,539	91,782	185,633	183,978
Operating income	6,827	5,588	10,851	10,345
Dividend income	0	0	0	0
Interest and other income	0	0	0	0
Interest expense	(1,176)	(2,663)	(2,352)	(5,227)
Loss on early extinguishment of debt	0		0	(6)
Income from continuing operations before income tax expense and equity in earnings of an investee	5,651	2,925	8,499	5,112
Income tax expense	0	0	0	0
Equity in earnings of an investee	0	0	0	0
Net income	5,651		8,499
Income before gain on sale of properties		2,925		5,112
Gain on sale of properties		0		0
Net income attributable to noncontrolling interest	0		0
Net income attributable to common shareholders	5,651	2,925	8,499	5,112
Total assets	1,238,723		1,238,723		1,260,032
MOBs
Revenues:
Rental income	94,651	92,978	189,297	184,559
Residents fees and services	0	0	0	0
Total revenues	94,651	92,978	189,297	184,559
Expenses:
Property operating expenses	27,646	25,409	54,823	50,816
Depreciation and amortization	31,861	31,011	63,539	61,866
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs		0	0	0
Impairment of assets	0	4,961	0	7,960
Total expenses	59,507	61,381	118,362	120,642
Operating income	35,144	31,597	70,935	63,917
Dividend income	0	0	0	0
Interest and other income	0	0	0	0
Interest expense	(6,250)	(844)	(12,570)	(1,798)
Loss on early extinguishment of debt	(59)		(59)	0
Income from continuing operations before income tax expense and equity in earnings of an investee	28,835	30,753	58,306	62,119
Income tax expense	0	0	0	0
Equity in earnings of an investee	0	0	0	0
Net income	28,835		58,306
Income before gain on sale of properties		30,753		62,119
Gain on sale of properties		0		0
Net income attributable to noncontrolling interest	(1,360)		(1,486)
Net income attributable to common shareholders	27,475	30,753	56,820	62,119
Total assets	3,309,089		3,309,089		3,333,141
All Other Operations
Revenues:
Rental income	4,570	4,578	9,115	9,111
Residents fees and services	0	0	0	0
Total revenues	4,570	4,578	9,115	9,111
Expenses:
Property operating expenses	0	0	0	0
Depreciation and amortization	948	948	1,896	1,896
General and administrative	22,922	11,965	38,005	22,828
Acquisition and certain other transaction related costs		180	292	619
Impairment of assets	5,082	0	5,082	0
Total expenses	28,952	13,093	45,275	25,343
Operating income	(24,382)	(8,515)	(36,160)	(16,232)
Dividend income	659	789	1,319	789
Interest and other income	76	177	195	242
Interest expense	(31,163)	(31,329)	(61,817)	(60,709)
Loss on early extinguishment of debt	0		0	0
Income from continuing operations before income tax expense and equity in earnings of an investee	(54,810)	(38,878)	(96,463)	(75,910)
Income tax expense	(99)	(108)	(191)	(202)
Equity in earnings of an investee	374	17	502	94
Net income	(54,535)		(96,152)
Income before gain on sale of properties		(38,969)		(76,018)
Gain on sale of properties		0		0
Net income attributable to noncontrolling interest	0		0
Net income attributable to common shareholders	(54,535)	$ (38,969)	(96,152)	$ (76,018)
Total assets	$ 358,829		$ 358,829		$ 345,536