Segment Reporting (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Summary of information for reportable segments
Rental income	$ 354,148,000	$ 308,512,000	$ 1,038,451,000	$ 900,028,000
Resident fees and services	482,412,000	466,127,000	1,406,316,000	1,164,446,000
Interest income	9,344,000	7,629,000	26,871,000	24,325,000
Other income	1,619,000	1,443,000	4,139,000	3,168,000
Total revenues	847,523,000	783,711,000	2,475,777,000	2,091,967,000
Property operating expenses	355,157,000	341,921,000	1,040,342,000	872,701,000
Net Operating Income from Continuing Operations	492,366,000	441,790,000	1,435,435,000	1,219,266,000
Interest expense	118,435,000	116,020,000	360,334,000	334,321,000
Loss (gain) on derivatives, net	49,000	4,872,000	400,000	4,465,000
Depreciation and amortization	200,970,000	241,027,000	648,737,000	623,777,000
General and administrative	30,803,000	28,718,000	115,327,000	79,799,000
Transaction costs	13,554,000	23,591,000	21,546,000	117,707,000
Loss (gain) on extinguishment of debt, net	2,692,000	(4,068,000)	(3,075,000)	4,376,000
Other expenses	10,262,000		10,262,000
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	115,601,000	31,630,000	275,754,000	63,573,000
Total assets	24,541,722,000		24,541,722,000		23,083,957,000
Percent Of Assets	1	1	1	1	1
Percent Of Revenues	1	1	1	1
Senior housing - triple net [Member]
Summary of information for reportable segments
Rental income	231,512,000	197,950,000	671,813,000	568,764,000
Resident fees and services	0	0	0	0
Interest income	5,852,000	5,035,000	16,958,000	16,311,000
Other income	836,000	778,000	1,281,000	1,183,000
Total revenues	238,200,000	203,763,000	690,052,000	586,258,000
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	238,200,000	203,763,000	690,052,000	586,258,000
Interest expense	10,294,000	5,869,000	28,064,000	14,921,000
Loss (gain) on derivatives, net	52,000	4,872,000	125,000	4,872,000
Depreciation and amortization	63,223,000	57,214,000	186,240,000	166,801,000
General and administrative	0	0	0	0
Transaction costs	1,619,000	4,026,000	5,900,000	15,730,000
Loss (gain) on extinguishment of debt, net	(36,000)		(36,000)	0
Other expenses	8,825,000		8,825,000
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	154,223,000	131,782,000	460,934,000	383,934,000
Total assets	10,354,397,000		10,354,397,000
Senior housing - operating [Member]
Summary of information for reportable segments
Rental income	0	0	0	0
Resident fees and services	482,412,000	466,127,000	1,406,316,000	1,164,446,000
Interest income	1,054,000	0	1,065,000	757,000
Other income	325,000	167,000	1,643,000	169,000
Total revenues	483,791,000	466,294,000	1,409,024,000	1,165,372,000
Property operating expenses	320,895,000	311,575,000	939,108,000	785,050,000
Net Operating Income from Continuing Operations	162,896,000	154,719,000	469,916,000	380,322,000
Interest expense	26,612,000	24,693,000	82,924,000	63,175,000
Loss (gain) on derivatives, net	(3,000)	0	275,000	(407,000)
Depreciation and amortization	95,819,000	144,578,000	334,625,000	338,099,000
General and administrative	0	0	0	0
Transaction costs	10,572,000	18,882,000	12,863,000	101,006,000
Loss (gain) on extinguishment of debt, net	0	(5,252,000)	383,000	(5,560,000)
Other expenses	1,437,000		1,437,000
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	28,459,000	(28,182,000)	37,409,000	(115,991,000)
Total assets	9,248,040,000		9,248,040,000
Medical facilities [Member]
Summary of information for reportable segments
Rental income	122,636,000	110,562,000	366,638,000	331,264,000
Resident fees and services	0	0	0	0
Interest income	2,438,000	2,594,000	8,848,000	7,257,000
Other income	352,000	466,000	1,017,000	1,539,000
Total revenues	125,426,000	113,622,000	376,503,000	340,060,000
Property operating expenses	34,262,000	30,346,000	101,234,000	87,651,000
Net Operating Income from Continuing Operations	91,164,000	83,276,000	275,269,000	252,409,000
Interest expense	7,692,000	8,732,000	25,422,000	27,097,000
Loss (gain) on derivatives, net	0	0	0	0
Depreciation and amortization	41,928,000	39,235,000	127,872,000	118,877,000
General and administrative	0	0	0	0
Transaction costs	1,363,000	683,000	2,783,000	971,000
Loss (gain) on extinguishment of debt, net	0		0	0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	40,181,000	34,626,000	119,192,000	105,464,000
Total assets	4,886,894,000		4,886,894,000
Non Segment Corporate [Member]
Summary of information for reportable segments
Rental income	0	0	0	0
Resident fees and services	0	0	0	0
Interest income	0	0	0	0
Other income	106,000	32,000	198,000	277,000
Total revenues	106,000	32,000	198,000	277,000
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	106,000	32,000	198,000	277,000
Interest expense	73,837,000	76,726,000	223,924,000	229,128,000
Loss (gain) on derivatives, net	0	0	0	0
Depreciation and amortization	0	0	0	0
General and administrative	30,803,000	28,718,000	115,327,000	79,799,000
Transaction costs	0	0	0	0
Loss (gain) on extinguishment of debt, net	2,728,000	1,184,000	2,728,000	1,184,000
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	(107,262,000)	(106,596,000)	(341,781,000)	(309,834,000)
Total assets	52,391,000		52,391,000
International [Member]
Summary of information for reportable segments
Total revenues	139,681,000	120,789,000	396,914,000	264,497,000
Total assets	3,341,994,000		3,341,994,000		3,324,012,000
Percent Of Assets	0.136		0.136		0.144
Percent Of Revenues	0.165	0.154	0.16	0.126
United States [Member]
Summary of information for reportable segments
Total revenues	707,842,000	662,922,000	2,078,863,000	1,827,470,000
Total assets	$ 21,199,728,000		$ 21,199,728,000		$ 19,759,945,000
Percent Of Assets	0.864		0.864		0.856
Percent Of Revenues	0.835	0.846	0.84	0.874