Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 segment	Mar. 31, 2014	Dec. 31, 2014
Segment reporting
Number of operating segments	4
Number of reportable segments	3
Revenues:
Rental income	$ 145,784	$ 112,055
Residents fees and services	82,793	79,442
Total revenues	228,577	191,497
Expenses:
Property operating expenses	85,794	77,802
Depreciation	53,707	38,355
General and administrative	10,574	8,290
Acquisition related costs	1,158	122
Total expenses	151,233	124,569
Operating income	77,344	66,928
Interest and other income	75	105
Interest expense	(35,942)	(28,900)
Loss on extinguishment of debt	(1,409)
Gain on lease terminations	105
Income (loss) before income tax expense and equity in earnings of an investee	40,068	38,133
Income tax expense	(110)	(191)
Equity in earnings of an investee	72	(97)
Income from continuing operations	40,030	37,845
Discontinued Operations:
Income from discontinued operations	(241)	1,300
Impairment of assets from discontinued operations		(721)
Income before gain on sale of properties	39,789	38,424
Gain on sale of properties		156
Net income	39,789	38,580
Total assets	6,537,095	4,778,667	5,968,269
Triple Net Leased Net Senior Living Communities
Revenues:
Rental income	55,251	54,890
Total revenues	55,251	54,890
Expenses:
Depreciation	15,125	15,637
Total expenses	15,125	15,637
Operating income	40,126	39,253
Interest expense	(5,985)	(6,388)
Income (loss) before income tax expense and equity in earnings of an investee	34,141	32,865
Income from continuing operations	34,141	32,865
Discontinued Operations:
Income before gain on sale of properties		32,865
Gain on sale of properties		156
Net income	34,141	33,021
Total assets	1,767,189	1,843,510
Managed Senior Living Communities
Revenues:
Residents fees and services	82,793	79,442
Total revenues	82,793	79,442
Expenses:
Property operating expenses	62,403	60,788
Depreciation	8,460	8,155
Total expenses	70,863	68,943
Operating income	11,930	10,499
Interest expense	(2,019)	(2,988)
Income (loss) before income tax expense and equity in earnings of an investee	9,911	7,511
Income from continuing operations	9,911	7,511
Discontinued Operations:
Income before gain on sale of properties		7,511
Net income	9,911	7,511
Total assets	967,751	949,468
MOBs
Revenues:
Rental income	86,001	52,763
Total revenues	86,001	52,763
Expenses:
Property operating expenses	23,391	17,014
Depreciation	29,174	13,615
Total expenses	52,565	30,629
Operating income	33,436	22,134
Interest expense	(1,768)	(1,337)
Income (loss) before income tax expense and equity in earnings of an investee	31,668	20,797
Income from continuing operations	31,668	20,797
Discontinued Operations:
Income from discontinued operations	(241)	1,300
Impairment of assets from discontinued operations		(721)
Income before gain on sale of properties		21,376
Net income	31,427	21,376
Total assets	3,451,814	1,717,000
All Other Operations
Revenues:
Rental income	4,532	4,402
Total revenues	4,532	4,402
Expenses:
Depreciation	948	948
General and administrative	10,574	8,290
Acquisition related costs	1,158	122
Total expenses	12,680	9,360
Operating income	(8,148)	(4,958)
Interest and other income	75	105
Interest expense	(26,170)	(18,187)
Loss on extinguishment of debt	(1,409)
Income (loss) before income tax expense and equity in earnings of an investee	(35,652)	(23,040)
Income tax expense	(110)	(191)
Equity in earnings of an investee	72	(97)
Income from continuing operations	(35,690)	(23,328)
Discontinued Operations:
Income before gain on sale of properties		(23,328)
Net income	(35,690)	(23,328)
Total assets	$ 350,341	$ 268,689