Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Summary of information for reportable segments
Rental income	$ 278,067	$ 228,246	$ 541,208	$ 384,009
Resident fees and services	165,654	123,149	323,828	194,435
Interest income	7,879	12,866	16,020	24,575
Other income	1,482	5,341	3,166	8,165
Revenues	453,082	369,602	884,222	611,184
Property operating expenses	136,303	99,808	265,572	163,371
Net Operating Income from Continuing Operations	316,779	269,794	618,650	447,813
Interest expense	94,968	81,484	186,941	137,613
Loss (gain) on derivatives	2,676	0	2,121	0
Depreciation and amortization	131,917	107,255	256,821	176,939
General and administrative	25,870	19,562	53,621	37,276
Transaction costs	28,691	13,738	34,270	49,803
Loss (gain) on extinguishment of debt	(576)	0	(576)	0
Provision for loan losses	0	168	0	416
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	37,433	47,587	88,542	45,766
Total assets	16,347,426		16,347,426		14,924,606
Senior housing - triple net [Member]
Summary of information for reportable segments
Rental income	176,777	155,413	345,456	247,021
Resident fees and services	0	0	0	0
Interest income	5,984	11,036	11,861	20,415
Other income	761	4,497	1,606	5,004
Revenues	183,522	170,946	358,923	272,440
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	183,522	170,946	358,923	272,440
Interest expense	(1,599)	(829)	(3,380)	(199)
Loss (gain) on derivatives	(96)		(96)
General and administrative	0	0	0	0
Transaction costs	(23,683)	(12,692)	(25,205)	(16,699)
Loss (gain) on extinguishment of debt	(2,238)	0	(2,238)	0
Provision for loan losses	0	0	0	0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	101,328	113,023	222,252	184,523
Total assets	8,159,852		8,159,852
Senior housing - operating [Member]
Summary of information for reportable segments
Rental income	0	0	0	0
Resident fees and services	165,654	123,149	323,828	194,435
Interest income	0	0	0	0
Other income	0	0	0	0
Revenues	165,654	123,149	323,828	194,435
Property operating expenses	(111,340)	(84,334)	(218,583)	(133,606)
Net Operating Income from Continuing Operations	54,314	38,815	105,245	60,829
Interest expense	(16,227)	(12,974)	(32,062)	(19,501)
Loss (gain) on derivatives	2,772		2,217
General and administrative	0	0	0	0
Transaction costs	(2,821)	(488)	(4,399)	(32,557)
Loss (gain) on extinguishment of debt	1,179	0	1,179	0
Provision for loan losses	0	0	0	0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	1,472	(12,823)	(5,338)	(49,536)
Total assets	3,485,380		3,485,380
Medical facilities [Member]
Summary of information for reportable segments
Rental income	101,290	72,833	195,752	136,988
Resident fees and services	0	0	0	0
Interest income	1,895	1,830	4,159	4,160
Other income	478	466	1,082	2,251
Revenues	103,663	75,129	200,993	143,399
Property operating expenses	(24,963)	(15,474)	(46,989)	(29,765)
Net Operating Income from Continuing Operations	78,700	59,655	154,004	113,634
Interest expense	(8,666)	(7,200)	(18,904)	(13,981)
Loss (gain) on derivatives	0		0
General and administrative	0	0	0	0
Transaction costs	(2,187)	(558)	(4,666)	(547)
Loss (gain) on extinguishment of debt	483	0	483	0
Provision for loan losses	0	(168)	0	(416)
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	28,736	27,052	57,366	51,077
Total assets	4,397,011		4,397,011
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	243	378	478	910
Revenues	243	378	478	910
Property operating expenses	0	0	0	0
Net Operating Income from Continuing Operations	243	378	478	910
Interest expense	(68,476)	(60,481)	(132,595)	(103,932)
Loss (gain) on derivatives	0		0
General and administrative	(25,870)	(19,562)	(53,621)	(37,276)
Transaction costs	0	0	0	0
Loss (gain) on extinguishment of debt	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	(94,103)	(79,665)	(185,738)	(140,298)
Total assets	305,183		305,183
Canada [Member]
Summary of information for reportable segments
Revenues	2,055
Total assets	$ 296,573		$ 296,573
Percent Of Assets	0.018		0.018
Percent Of Revenues	0.005