Segment Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 item	Sep. 30, 2011
Segment reporting information, revenues
Number of reportable segments			5
Rental Revenues	$ 428,668	$ 428,184	$ 1,271,646	$ 1,138,639
Resident Fees and Services	36,076	11,974	107,824	15,314
Interest Income	10,278	577	12,313	99,199
Investment Management Fee Income	460	494	1,423	1,605
Total revenues	475,482	441,229	1,393,206	1,254,757
NOI	392,077	382,496	1,169,387	1,002,850
Adjusted NOI	356,450	344,000	1,063,715	902,303
Senior housing
Segment reporting information, revenues
Rental Revenues	114,856	122,849	341,936	355,496
Resident Fees and Services	36,076	11,974	107,824	15,314
Interest Income	876	42	1,686	49
Investment Management Fee Income				70
Total revenues	151,808	134,865	451,446	370,929
NOI	126,060	125,209	379,834	359,460
Adjusted NOI	113,592	112,755	342,368	319,393
Post-acute/skilled nursing
Segment reporting information, revenues
Rental Revenues	135,508	132,392	404,180	265,377
Interest Income	9,135	287	9,842	98,167
Total revenues	144,643	132,679	414,022	363,544
NOI	135,354	132,148	403,654	265,059
Adjusted NOI	116,898	112,881	346,900	228,034
Life science
Segment reporting information, revenues
Rental Revenues	71,194	71,093	215,569	215,045
Investment Management Fee Income	1	1	3	3
Total revenues	71,195	71,094	215,572	215,048
NOI	59,403	57,860	177,339	176,384
Adjusted NOI	56,341	52,785	171,179	159,544
Medical office
Segment reporting information, revenues
Rental Revenues	85,800	80,996	246,661	240,603
Investment Management Fee Income	459	493	1,420	1,532
Total revenues	86,259	81,489	248,081	242,135
NOI	50,852	47,650	148,030	143,243
Adjusted NOI	49,669	46,514	144,272	138,469
Hospital
Segment reporting information, revenues
Rental Revenues	21,310	20,854	63,300	62,118
Interest Income	267	248	785	983
Total revenues	21,577	21,102	64,085	63,101
NOI	20,408	19,629	60,530	58,704
Adjusted NOI	$ 19,950	$ 19,065	$ 58,996	$ 56,863

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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Amount of revenues recognized 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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