SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 segment	Jun. 30, 2013	Dec. 31, 2013
Segment Reporting [Abstract]
Number of reportable business segments			3
Revenues:
Rental income	$ 357,616	$ 323,448	$ 710,685	$ 646,398
Resident fees and services	374,473	341,594	745,534	680,764
Medical office building and other services revenue	4,367	3,537	10,667	7,185
Income from loans and investments	14,625	14,733	25,392	30,836
Interest and other income	173	797	446	1,835
Total revenues	751,254	684,109	1,492,724	1,367,018
Less:
Interest and other income	173	797	446	1,835
Property-level operating expenses	288,759	269,488	576,399	536,689
Medical office building services costs	1,626	1,667	4,997	3,306
Segment NOI	460,696	412,157	910,882	825,188
Income (loss) from unconsolidated entities	348	(506)	596	423
Segment profit	461,044	411,651	911,478	825,611
Interest and other income	173	797	446	1,835
Interest expense	(91,501)	(82,237)	(179,342)	(160,871)
Depreciation and amortization	(190,818)	(171,527)	(384,412)	(346,995)
General, administrative and professional fees	(31,306)	(27,324)	(64,172)	(56,098)
Gain (loss) on extinguishment of debt	(2,924)	720	(2,665)	720
Merger-related expenses and deal costs	(9,599)	(6,667)	(20,359)	(10,929)
Other	(4,863)	(4,385)	(10,092)	(8,972)
Income tax (expense) benefit	(3,274)	12,064	(6,707)	10,320
Discontinued operations	(255)	(18,559)	2,776	(26,990)
Gain on real estate dispositions	11,889	0	12,889	0
Net income	138,566	114,533	259,840	227,631	454,889
Triple-Net Leased Properties
Revenues:
Rental income	242,726	213,171	480,572	425,705
Medical office building and other services revenue	1,145	1,115	2,293	2,226
Total revenues	243,871	214,286	482,865	427,931
Less:
Segment NOI	243,871	214,286	482,865	427,931
Income (loss) from unconsolidated entities	17	183	586	370
Segment profit	243,888	214,469	483,451	428,301
Senior Living Operations
Revenues:
Resident fees and services	374,473	341,594	745,534	680,764
Total revenues	374,473	341,594	745,534	680,764
Less:
Property-level operating expenses	249,424	231,337	497,719	462,245
Segment NOI	125,049	110,257	247,815	218,519
Income (loss) from unconsolidated entities	160	(541)	16	(1,141)
Segment profit	125,209	109,716	247,831	217,378
MOB Operations
Revenues:
Rental income	114,890	110,277	230,113	220,693
Medical office building and other services revenue	2,722	2,159	7,374	4,696
Total revenues	117,612	112,436	237,487	225,389
Less:
Property-level operating expenses	39,335	38,151	78,680	74,444
Medical office building services costs	1,626	1,667	4,997	3,306
Segment NOI	76,651	72,618	153,810	147,639
Income (loss) from unconsolidated entities	307	43	260	1,385
Segment profit	76,958	72,661	154,070	149,024
All Other
Revenues:
Medical office building and other services revenue	500	263	1,000	263
Income from loans and investments	14,625	14,733	25,392	30,836
Interest and other income	173	797	446	1,835
Total revenues	15,298	15,793	26,838	32,934
Less:
Interest and other income	173	797	446	1,835
Segment NOI	15,125	14,996	26,392	31,099
Income (loss) from unconsolidated entities	(136)	(191)	(266)	(191)
Segment profit	14,989	14,805	26,126	30,908
Interest and other income	$ 173	$ 797	$ 446	$ 1,835