Segment Reporting (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) segment	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment reporting
Number of operating segments | segment	4
Number of reportable segments | segment	3
Revenues:
Rental income	$ 166,443	$ 161,421
Residents fees and services	98,118	96,954
Total revenues	264,561	258,375
Expenses:
Property operating expenses	101,057	97,949
Depreciation and amortization	73,175	71,223
General and administrative	15,083	10,863
Acquisition and certain other transaction related costs	292	439
Impairment of assets	0	7,390
Total expenses	189,607	187,864
Operating income	74,954	70,511
Dividend income	659
Interest and other income	120	64
Interest expense	(43,488)	(39,280)
Loss on early extinguishment of debt	0	(6)
Income from continuing operations before income tax expense and equity in earnings of an investee	32,245	31,289
Income tax expense	(92)	(94)
Equity in earnings of an investee	128	77
Net income	32,281	31,272
Net income attributable to noncontrolling interest	(126)	0
Net income attributable to common shareholders	32,155	31,272
Total assets	7,220,204		$ 7,227,754
Triple Net Leased Senior Living Communities
Revenues:
Rental income	67,252	65,308
Residents fees and services	0	0
Total revenues	67,252	65,308
Expenses:
Property operating expenses	0	363
Depreciation and amortization	20,334	19,401
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets		4,391
Total expenses	20,334	24,155
Operating income	46,918	41,153
Dividend income	0
Interest and other income	0	0
Interest expense	(5,339)	(6,382)
Loss on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	41,579	34,771
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income	41,579
Net income attributable to noncontrolling interest	0
Net income attributable to common shareholders	41,579	34,771
Total assets	2,279,923		2,289,045
Managed senior living communities
Revenues:
Rental income	0	0
Residents fees and services	98,118	96,954
Total revenues	98,118	96,954
Expenses:
Property operating expenses	73,880	72,178
Depreciation and amortization	20,215	20,018
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets		0
Total expenses	94,095	92,196
Operating income	4,023	4,758
Dividend income	0
Interest and other income	0	0
Interest expense	(1,176)	(2,564)
Loss on early extinguishment of debt		(6)
Income from continuing operations before income tax expense and equity in earnings of an investee	2,847	2,188
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income	2,847
Net income attributable to noncontrolling interest	0
Net income attributable to common shareholders	2,847	2,188
Total assets	1,245,955		1,260,032
MOBs
Revenues:
Rental income	94,646	91,582
Residents fees and services	0	0
Total revenues	94,646	91,582
Expenses:
Property operating expenses	27,177	25,408
Depreciation and amortization	31,678	30,856
General and administrative	0	0
Acquisition and certain other transaction related costs	0	0
Impairment of assets		2,999
Total expenses	58,855	59,263
Operating income	35,791	32,319
Dividend income	0
Interest and other income	0	0
Interest expense	(6,321)	(953)
Loss on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	29,470	31,366
Income tax expense	0	0
Equity in earnings of an investee	0	0
Net income	29,470
Net income attributable to noncontrolling interest	(126)
Net income attributable to common shareholders	29,344	31,366
Total assets	3,323,735		3,333,141
All Other Operations
Revenues:
Rental income	4,545	4,531
Residents fees and services	0	0
Total revenues	4,545	4,531
Expenses:
Property operating expenses	0	0
Depreciation and amortization	948	948
General and administrative	15,083	10,863
Acquisition and certain other transaction related costs	292	439
Impairment of assets		0
Total expenses	16,323	12,250
Operating income	(11,778)	(7,719)
Dividend income	659
Interest and other income	120	64
Interest expense	(30,652)	(29,381)
Loss on early extinguishment of debt		0
Income from continuing operations before income tax expense and equity in earnings of an investee	(41,651)	(37,036)
Income tax expense	(92)	(94)
Equity in earnings of an investee	128	77
Net income	(41,615)
Net income attributable to noncontrolling interest	0
Net income attributable to common shareholders	(41,615)	$ (37,053)
Total assets	$ 370,591		$ 345,536