Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Rental income																	$ 1,194,060	$ 803,455	$ 523,339
Resident fees and services																	1,229,479	868,095	446,301
Medical office building and other services revenue																	20,741	36,471	14,098
Income from loans and investments																	39,913	34,415	16,412
Interest and other income																	1,106	1,217	484
Total revenues	660,711	[1]	641,520	[1]	614,502	[1]	568,566	[1]	563,145	[2]	554,691	[2]	359,421	[2]	266,396	[2]	2,485,299	1,743,653	1,000,634
Less:
Interest and other income																	1,106	1,217	484
Property-level operating expenses																	969,342	647,193	315,953
Medical office building services costs																	9,883	27,082	9,518
Segment NOI																	1,504,968	1,068,161	674,679
Income from unconsolidated entities																	18,154	(52)	(664)
Segment profit																	1,523,122	1,068,109	674,015
Interest and other income																	1,106	1,217	484
Interest expense																	(293,401)	(229,346)	(172,474)
Depreciation and amortization																	(725,981)	(447,664)	(200,682)
General, administrative and professional fees																	(98,801)	(74,537)	(49,830)
Loss on extinguishment of debt																	(37,640)	(27,604)	(9,791)
Litigation proceeds, net																	0	202,259	0
Merger-related expenses and deal costs																	(63,183)	(153,923)	(19,243)
Other																	(6,956)	(7,270)	(272)
Income tax benefit (expense)																	6,282	30,660	(5,201)
Discontinued operations	(11,725)	[1]	(4,093)	[1]	30,529	[1]	42,516	[1]	(605)	[2]	(306)	[2]	1,226	[2]	1,045	[2]	57,227	1,360	32,723
Net income																	361,775	363,261	249,729
Triple-Net Leased Properties
Revenues:
Rental income																	831,221	637,294	453,592
Resident fees and services																	0	0	0
Medical office building and other services revenue																	4,438	2,217	0
Income from loans and investments																	0	0	0
Interest and other income																	0	0	0
Total revenues																	835,659	639,511	453,592
Less:
Interest and other income																	0	0	0
Property-level operating expenses																	0	0	0
Medical office building services costs																	0	0	0
Segment NOI																	835,659	639,511	453,592
Income from unconsolidated entities																	1,313	295	0
Segment profit																	836,972	639,806	453,592
Interest and other income																	0	0	0
Senior Living Operations
Revenues:
Rental income																	0	0	0
Resident fees and services																	1,229,479	868,095	446,301
Medical office building and other services revenue																	0	0	0
Income from loans and investments																	0	0	0
Interest and other income																	0	0	0
Total revenues																	1,229,479	868,095	446,301
Less:
Interest and other income																	0	0	0
Property-level operating expenses																	843,190	590,151	291,831
Medical office building services costs																	0	0	0
Segment NOI																	386,289	277,944	154,470
Income from unconsolidated entities																	(48)	0	0
Segment profit																	386,241	277,944	154,470
Interest and other income																	0	0	0
MOB Operations
Revenues:
Rental income																	362,839	166,161	69,747
Resident fees and services																	0	0	0
Medical office building and other services revenue																	16,303	34,254	14,098
Income from loans and investments																	0	0	0
Interest and other income																	0	0	0
Total revenues																	379,142	200,415	83,845
Less:
Interest and other income																	0	0	0
Property-level operating expenses																	126,152	57,042	24,122
Medical office building services costs																	9,883	27,082	9,518
Segment NOI																	243,107	116,291	50,205
Income from unconsolidated entities																	16,889	(347)	(664)
Segment profit																	259,996	115,944	49,541
Interest and other income																	0	0	0
All Other
Revenues:
Rental income																	0	0	0
Resident fees and services																	0	0	0
Medical office building and other services revenue																	0	0	0
Income from loans and investments																	39,913	34,415	16,412
Interest and other income																	1,106	1,217	484
Total revenues																	41,019	35,632	16,896
Less:
Interest and other income																	1,106	1,217	484
Property-level operating expenses																	0	0	0
Medical office building services costs																	0	0	0
Segment NOI																	39,913	34,415	16,412
Income from unconsolidated entities																	0	0	0
Segment profit																	39,913	34,415	16,412
Interest and other income																	$ 1,106	$ 1,217	$ 484

[1] The amounts presented for the three months ended March 31, 2012, June 30, 2012 and September 30, 2012 differ from the amounts previously reported in our Quarterly Reports on Form 10-Q as a result of discontinued operations consisting of properties sold in 2012 or classified as held for sale as of December 31, 2012.

[2] The amounts presented for the three months ended March 31, 2011, June 30, 2011, September 30, 2011 and December 31, 2011 differ from the amounts previously reported in our Annual Report on Form 10-K for the year ended December 31, 2011 as a result of discontinued operations consisting of properties sold in 2012 or classified as held for sale as of December 31, 2012.