Segment Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 item	Jun. 30, 2011
Segment reporting information, revenues
Number of reportable segments			5
Rental Revenues	$ 427,184	$ 426,260	$ 848,704	$ 716,180
Resident Fees and Services	35,569	835	71,748	3,340
Interest Income	1,216	60,526	2,035	98,622
Investment Management Fee Income	470	504	963	1,111
Total revenues	464,439	488,125	923,450	819,253
NOI	392,666	380,480	783,016	626,060
Adjusted NOI	357,913	339,830	712,017	562,940
Senior housing
Segment reporting information, revenues
Rental Revenues	116,445	128,862	232,806	238,372
Resident Fees and Services	35,569	835	71,748	3,340
Interest Income	527	7	810	7
Investment Management Fee Income				70
Total revenues	152,541	129,704	305,364	241,789
NOI	128,570	128,927	259,480	239,957
Adjusted NOI	116,509	113,664	233,527	211,275
Post-acute/skilled nursing
Segment reporting information, revenues
Rental Revenues	134,677	123,545	268,672	132,985
Interest Income	427	60,189	707	97,880
Total revenues	135,104	183,734	269,379	230,865
NOI	134,505	123,491	268,300	132,911
Adjusted NOI	116,833	106,055	230,002	115,153
Life science
Segment reporting information, revenues
Rental Revenues	72,545	71,527	144,375	143,952
Investment Management Fee Income	1	1	2	2
Total revenues	72,546	71,528	144,377	143,954
NOI	58,990	58,937	117,936	118,524
Adjusted NOI	55,735	53,136	114,838	106,759
Medical office
Segment reporting information, revenues
Rental Revenues	80,905	80,037	160,861	159,607
Investment Management Fee Income	469	503	961	1,039
Total revenues	81,374	80,540	161,822	160,646
NOI	48,926	48,058	97,178	95,593
Adjusted NOI	47,682	46,533	94,604	91,955
Hospital
Segment reporting information, revenues
Rental Revenues	22,612	22,289	41,990	41,264
Interest Income	262	330	518	735
Total revenues	22,874	22,619	42,508	41,999
NOI	21,675	21,067	40,122	39,075
Adjusted NOI	$ 21,154	$ 20,442	$ 39,046	$ 37,798

NOI is a non-GAAP supplemental financial measure used to evaluate the operating performance of real estate. The Company defines NOI as rental revenues, including tenant recoveries, resident fees and services, and income from direct financing leases, less property level operating expenses. NOI excludes interest income, investment management fee income, depreciation and amortization, interest expense, general and administrative expenses, impairments, impairment recoveries, other income, net, income taxes, equity income from and impairments of investments in unconsolidated joint ventures, and discontinued operations. The Company believes NOI provides relevant and useful information because it reflects only income and operating expense items that are incurred at the property level and presents them on an unleveraged basis. The Company uses NOI to make decisions about resource allocations and to assess and compare property level performance. The Company believes that net income is the most directly comparable GAAP measure to NOI. NOI should not be viewed as an alternative measure of operating performance to net income as defined by GAAP because it does not reflect the aforementioned excluded items. Further, the Company's definition of NOI may not be comparable to the definition used by other REITs, as those companies may use different methodologies for calculating NOI.

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Revenues recognized during the period from services provided to residents in facilities owned or operated by the health care organization (not including patient service revenue), which may be based on contractual rates set forth in agreements with third-party payers.

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