Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summary of information for reportable segments
Rental income	$ 290,225	$ 235,938	$ 826,627	$ 615,219
Resident fees and services	174,464	125,125	498,295	319,559
Interest income	8,111	7,858	24,131	32,433
Other income	1,339	1,809	4,505	9,974
Revenues	474,139	370,730	1,353,558	977,185
Property operating expenses	144,479	103,127	409,606	266,081
Net Operating Income from Continuing Operations	329,660	267,603	943,952	711,104
Interest expense	94,580	84,429	280,058	220,527
Loss (gain) on derivatives, net	409	0	(1,712)	0
Depreciation and amortization	132,150	111,582	387,053	286,623
General and administrative	23,679	19,735	77,302	57,009
Transaction costs	8,264	6,739	42,535	56,542
Loss (gain) on extinguishment of debt, net	(215)	0	(791)	0
Provision for loan losses	27,008	132	27,008	547
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	43,355	44,986	130,917	89,856
Total assets	18,282,275		18,282,275		14,924,606
Senior housing - triple net [Member]
Summary of information for reportable segments
Rental income	185,384	158,356	529,553	404,097
Resident fees and services	0	0	0	0
Interest income	6,116	6,810	17,977	27,224
Other income	662	454	2,268	4,878
Revenues	192,162	165,620	549,798	436,199
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	192,162	165,620	549,798	436,199
Interest expense	(1,547)	(1,690)	(4,587)	(1,531)
Loss (gain) on derivatives, net	0		(96)
Depreciation and amortization	(54,189)	(45,726)	(152,702)	(116,227)
General and administrative	0	0	0	0
Transaction costs	(5,590)	(6,080)	(30,796)	(22,872)
Loss (gain) on extinguishment of debt, net	(126)	0	(2,363)	0
Provision for loan losses	(27,008)	(90)	(27,008)	(90)
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	103,702	112,034	332,246	295,479
Total assets	8,744,455		8,744,455
Senior housing - operating [Member]
Summary of information for reportable segments
Rental income	0	0	0	0
Resident fees and services	174,464	125,125	498,295	319,559
Interest income	0	0	0	0
Other income	0	0	0	0
Revenues	174,464	125,125	498,295	319,559
Property operating expenses	(118,369)	(86,218)	(336,952)	(219,824)
Net Operating Income from Continuing Operations	56,095	38,907	161,343	99,735
Interest expense	(17,474)	(13,945)	(49,537)	(33,446)
Loss (gain) on derivatives, net	(409)		1,808
Depreciation and amortization	(39,591)	(39,019)	(123,820)	(97,326)
General and administrative	0	0	0	0
Transaction costs	(1,966)	305	(6,365)	(32,159)
Loss (gain) on extinguishment of debt, net	(89)	0	1,089	0
Provision for loan losses	0	0	0	0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	(3,434)	(13,752)	(15,482)	(63,196)
Total assets	3,705,861		3,705,861
Medical facilities [Member]
Summary of information for reportable segments
Rental income	104,841	77,582	297,074	211,122
Resident fees and services	0	0	0	0
Interest income	1,995	1,048	6,154	5,209
Other income	400	1,048	1,482	3,879
Revenues	107,236	79,678	304,710	220,210
Property operating expenses	(26,110)	(16,909)	(72,654)	(46,257)
Net Operating Income from Continuing Operations	81,126	62,769	232,056	173,953
Interest expense	(9,405)	(7,394)	(27,188)	(20,215)
Loss (gain) on derivatives, net	0		0
Depreciation and amortization	(38,370)	(26,837)	(110,531)	(73,070)
General and administrative	0	0	0	0
Transaction costs	(708)	(964)	(5,374)	(1,511)
Loss (gain) on extinguishment of debt, net	0	0	483	0
Provision for loan losses	0	(42)	0	(457)
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	32,643	27,532	89,446	78,700
Total assets	4,347,505		4,347,505
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	277	307	755	1,217
Revenues	277	307	755	1,217
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	277	307	755	1,217
Interest expense	(66,154)	(61,400)	(198,746)	(165,335)
Loss (gain) on derivatives, net	0		0
Depreciation and amortization	0	0	0	0
General and administrative	(23,679)	(19,735)	(77,302)	(57,009)
Transaction costs	0	0	0	0
Loss (gain) on extinguishment of debt, net	0	0	0	0
Provision for loan losses	0	0	0	0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	(89,556)	(80,828)	(275,293)	(221,127)
Total assets	1,484,454		1,484,454
International [Member]
Summary of information for reportable segments
Revenues	7,091		9,146
Total assets	$ 544,833		$ 544,833
Percent Of Assets	0.030		0.030
Percent Of Revenues	0.015		0.007