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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Segment Disclosures (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 item	Dec. 31, 2011	Dec. 31, 2010
Segment reporting information, revenues
Number of reportable segments									5
Rental Revenues									$ 1,730,546	$ 1,559,540	$ 1,042,781
Resident Fees and Services									143,745	50,619	32,596
Interest Income									24,536	99,864	160,163
Investment Management Fee Income									1,895	2,073	4,666
Total revenues	508,487	475,157	461,251	455,827	458,281	440,914	484,941	327,960	1,900,722	1,712,096	1,240,206
NOI									1,590,293	1,390,008	865,219
Adjusted NOI (Cash NOI)									1,447,360	1,248,506	795,601
Senior housing
Segment reporting information, revenues
Rental Revenues									482,336	470,592	337,220
Resident Fees and Services									143,745	50,619	32,596
Interest Income									3,503	178	364
Investment Management Fee Income										70	2,300
Total revenues									629,584	521,459	372,480
NOI									531,419	486,673	341,043
Adjusted NOI (Cash NOI)									480,872	433,728	306,682
Post-acute/skilled nursing
Segment reporting information, revenues
Rental Revenues									539,242	397,554	36,023
Interest Income									19,993	98,450	121,703
Total revenues									559,235	496,004	157,726
NOI									538,856	396,969	35,847
Adjusted NOI (Cash NOI)									462,927	339,946	34,685
Life science
Segment reporting information, revenues
Rental Revenues									289,664	288,151	276,762
Investment Management Fee Income									4	4	4
Total revenues									289,668	288,155	276,766
NOI									236,491	235,355	228,270
Adjusted NOI (Cash NOI)									226,997	212,250	204,938
Medical office
Segment reporting information, revenues
Rental Revenues									334,811	320,115	309,285
Investment Management Fee Income									1,891	1,999	2,362
Total revenues									336,702	322,114	311,647
NOI									202,547	192,213	181,398
Adjusted NOI (Cash NOI)									197,569	186,180	175,654
Hospital
Segment reporting information, revenues
Rental Revenues									84,493	83,128	83,491
Interest Income									1,040	1,236	38,096
Total revenues									85,533	84,364	121,587
NOI									80,980	78,798	78,661
Adjusted NOI (Cash NOI)									$ 78,995	$ 76,402	$ 73,642