SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 segment	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting [Abstract]
Number of reportable business segments			3
Revenues:
Rental income	$ 334,614	$ 308,186	$ 983,255	$ 867,828
Resident fees and services	359,112	316,560	1,039,876	905,190
Medical office building and other services revenue	4,146	4,544	11,331	16,791
Income from loans and investments	14,448	9,035	45,284	25,223
Interest and other income	66	330	1,901	442
Total revenues	712,386	638,655	2,081,647	1,815,474
Less:
Interest and other income	66	330	1,901	442
Property-level operating expenses	285,112	252,450	822,299	704,939
Medical office building services costs	1,651	1,487	4,957	8,314
Segment NOI	425,557	384,388	1,252,490	1,101,779
Income from unconsolidated entities	110	17,074	533	17,905
Segment profit	425,667	401,462	1,253,023	1,119,684
Interest and other income	66	330	1,901	442
Interest expense	(84,089)	(74,037)	(245,622)	(214,028)
Depreciation and amortization	(177,710)	(188,540)	(528,180)	(534,792)
General, administrative and professional fees	(28,659)	(26,867)	(84,760)	(75,488)
Gain (loss) on extinguishment of debt	189	1,194	909	(38,339)
Merger-related expenses and deal costs	(6,208)	(4,917)	(17,137)	(49,566)
Other	(4,353)	(1,966)	(13,325)	(5,052)
Income tax benefit	2,780	8,886	13,100	2,727
Discontinued operations	(9,084)	(3,724)	(33,679)	70,061
Net income	118,599	111,821	346,230	275,649	361,775
Triple-Net Leased Properties
Revenues:
Rental income	219,170	207,372	645,719	613,939
Medical office building and other services revenue	1,116	1,110	3,342	3,329
Total revenues	220,286	208,482	649,061	617,268
Less:
Segment NOI	220,286	208,482	649,061	617,268
Income from unconsolidated entities	203	348	573	1,068
Segment profit	220,489	208,830	649,634	618,336
Senior Living Operations
Revenues:
Total revenues	359,112	316,560	1,039,876	905,190
Less:
Property-level operating expenses	244,316	216,306	706,561	618,471
Segment NOI	114,796	100,254	333,315	286,719
Income from unconsolidated entities	(32)		(1,173)
Segment profit	114,764	100,254	332,142	286,719
MOB Operations
Revenues:
Rental income	115,444	100,814	337,536	253,889
Medical office building and other services revenue	2,530	3,434	7,226	13,462
Total revenues	117,974	104,248	344,762	267,351
Less:
Property-level operating expenses	40,796	36,144	115,738	86,468
Medical office building services costs	1,651	1,487	4,957	8,314
Segment NOI	75,527	66,617	224,067	172,569
Income from unconsolidated entities	71	16,726	1,456	16,837
Segment profit	75,598	83,343	225,523	189,406
All Other
Revenues:
Medical office building and other services revenue	500		763
Income from loans and investments	14,448	9,035	45,284	25,223
Interest and other income	66	330	1,901	442
Total revenues	15,014	9,365	47,948	25,665
Less:
Interest and other income	66	330	1,901	442
Segment NOI	14,948	9,035	46,047	25,223
Income from unconsolidated entities	(132)		(323)
Segment profit	14,816	9,035	45,724	25,223
Interest and other income	$ 66	$ 330	$ 1,901	$ 442