Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment reporting
Number of operating segments | segment			4
Number of reportable segments | segment			3
Revenues:
Rental income	$ 165,503	$ 158,863	$ 490,922	$ 460,193
Residents fees and services	98,480	96,412	292,803	271,061
Total revenues	263,983	255,275	783,725	731,254
Expenses:
Property operating expenses	103,347	96,927	298,776	276,313
Depreciation and amortization	72,344	70,016	214,938	186,234
General and administrative	12,107	10,316	34,931	32,563
Acquisition and certain other transaction related costs	824	742	1,443	6,517
Impairment of assets	4,578	(98)	16,930	(98)
Total expenses	193,200	177,903	567,018	501,529
Operating income	70,783	77,372	216,707	229,725
Dividend income	659		1,449
Interest and other income	89	57	330	274
Interest expense	(43,438)	(38,989)	(123,837)	(112,838)
Loss on early extinguishment of debt	(84)	(21)	(90)	(1,469)
Income from continuing operations before income tax expense and equity in earnings (losses) of an investee	28,009	38,419	94,559	115,692
Income tax expense	(119)	(146)	(318)	(385)
Equity in earnings (losses) of an investee	13	(24)	107	70
Income from continuing operations	27,903	38,249	94,348	115,377
Discontinued operations:
Loss from discontinued operations	0	0	0	(350)
Impairment of assets from discontinued operations	0	0	0	(602)
Income before gain on sale of properties	27,903	38,249	94,348	114,425
Gain on sale of properties	0	0	4,061	0
Net income	27,903	38,249	98,409	114,425
Total assets	7,230,098		7,230,098		$ 7,160,090
Triple Net Leased Senior Living Communities
Revenues:
Rental income	66,520	64,222	198,269	180,820
Residents fees and services	0	0	0	0
Total revenues	66,520	64,222	198,269	180,820
Expenses:
Property operating expenses	47	0	833	0
Depreciation and amortization	19,727	19,140	58,401	51,322
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs	0	0		0
Impairment of assets	2,191	(98)	6,583	(98)
Total expenses	21,965	19,042	65,817	51,224
Operating income	44,555	45,180	132,452	129,596
Dividend income	0		0
Interest and other income	0	0	0	0
Interest expense	(6,228)	(6,342)	(18,892)	(18,598)
Loss on early extinguishment of debt	0	0	0	(6)
Income from continuing operations before income tax expense and equity in earnings (losses) of an investee	38,327	38,838	113,560	110,992
Income tax expense	0	0	0	0
Equity in earnings (losses) of an investee	0	0	0	0
Income from continuing operations				110,992
Discontinued operations:
Loss from discontinued operations				0
Impairment of assets from discontinued operations				0
Income before gain on sale of properties		38,838	113,560
Gain on sale of properties			4,061
Net income	38,327		117,621	110,992
Total assets	2,281,420		2,281,420		2,251,212
Managed senior living communities
Revenues:
Rental income	0	0	0	0
Residents fees and services	98,480	96,412	292,803	271,061
Total revenues	98,480	96,412	292,803	271,061
Expenses:
Property operating expenses	74,763	71,983	218,582	204,178
Depreciation and amortization	20,747	19,248	60,905	41,357
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs	0	0		0
Impairment of assets	2,394	0	2,394	0
Total expenses	97,904	91,231	281,881	245,535
Operating income	576	5,181	10,922	25,526
Dividend income	0		0
Interest and other income	0	0	0	0
Interest expense	(2,104)	(2,705)	(7,332)	(7,285)
Loss on early extinguishment of debt	(84)	0	(90)	(33)
Income from continuing operations before income tax expense and equity in earnings (losses) of an investee	(1,612)	2,476	3,500	18,208
Income tax expense	0	0	0	0
Equity in earnings (losses) of an investee	0	0	0	0
Income from continuing operations				18,208
Discontinued operations:
Loss from discontinued operations				0
Impairment of assets from discontinued operations				0
Income before gain on sale of properties		2,476	3,500
Gain on sale of properties			0
Net income	(1,612)		3,500	18,208
Total assets	1,272,441		1,272,441		1,260,425
MOBs
Revenues:
Rental income	94,404	90,072	278,964	265,664
Residents fees and services	0	0	0	0
Total revenues	94,404	90,072	278,964	265,664
Expenses:
Property operating expenses	28,537	24,944	79,361	72,135
Depreciation and amortization	30,922	30,680	92,788	90,711
General and administrative	0	0	0	0
Acquisition and certain other transaction related costs	0	0		0
Impairment of assets	(7)	0	7,953	0
Total expenses	59,452	55,624	180,102	162,846
Operating income	34,952	34,448	98,862	102,818
Dividend income	0		0
Interest and other income	0	0	0	0
Interest expense	(5,599)	(1,707)	(7,398)	(5,232)
Loss on early extinguishment of debt	0	0	0	0
Income from continuing operations before income tax expense and equity in earnings (losses) of an investee	29,353	32,741	91,464	97,586
Income tax expense	0	0	0	0
Equity in earnings (losses) of an investee	0	0	0	0
Income from continuing operations				97,586
Discontinued operations:
Loss from discontinued operations				(350)
Impairment of assets from discontinued operations				(602)
Income before gain on sale of properties		32,741	91,464
Gain on sale of properties			0
Net income	29,353		91,464	96,634
Total assets	3,343,492		3,343,492		3,362,214
All Other Operations
Revenues:
Rental income	4,579	4,569	13,689	13,709
Residents fees and services	0	0	0	0
Total revenues	4,579	4,569	13,689	13,709
Expenses:
Property operating expenses	0	0	0	0
Depreciation and amortization	948	948	2,844	2,844
General and administrative	12,107	10,316	34,931	32,563
Acquisition and certain other transaction related costs	824	742	1,443	6,517
Impairment of assets	0	0	0	0
Total expenses	13,879	12,006	39,218	41,924
Operating income	(9,300)	(7,437)	(25,529)	(28,215)
Dividend income	659		1,449
Interest and other income	89	57	330	274
Interest expense	(29,507)	(28,235)	(90,215)	(81,723)
Loss on early extinguishment of debt	0	(21)	0	(1,430)
Income from continuing operations before income tax expense and equity in earnings (losses) of an investee	(38,059)	(35,636)	(113,965)	(111,094)
Income tax expense	(119)	(146)	(318)	(385)
Equity in earnings (losses) of an investee	13	(24)	107	70
Income from continuing operations				(111,409)
Discontinued operations:
Loss from discontinued operations				0
Impairment of assets from discontinued operations				0
Income before gain on sale of properties		$ (35,806)	(114,176)
Gain on sale of properties			0
Net income	(38,165)		(114,176)	$ (111,409)
Total assets	$ 332,745		$ 332,745		$ 286,239