SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 segment	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting [Abstract]
Number of reportable business segments			3
Revenues:
Rental income	$ 360,804	$ 333,477	$ 1,071,489	$ 979,875
Resident fees and services	396,247	359,112	1,141,781	1,039,876
Medical office building and other services revenue	7,573	4,146	18,240	11,331
Income from loans and investments	14,043	14,448	39,435	45,284
Interest and other income	368	66	814	1,901
Total revenues	779,035	711,249	2,271,759	2,078,267
Less:
Interest and other income	368	66	814	1,901
Property-level operating expenses	306,421	284,882	882,820	821,571
Medical office building services costs	4,568	1,651	9,565	4,957
Segment NOI	467,678	424,650	1,378,560	1,249,838
(Loss) income from unconsolidated entities	(47)	110	549	533
Segment profit	467,631	424,760	1,379,109	1,250,371
Interest and other income	368	66	814	1,901
Interest expense	(98,469)	(83,764)	(277,811)	(244,635)
Depreciation and amortization	(201,224)	(177,038)	(585,636)	(524,033)
General, administrative and professional fees	(29,466)	(28,659)	(93,638)	(84,757)
Gain (loss) on extinguishment of debt	(2,414)	189	(5,079)	909
Merger-related expenses and deal costs	(16,749)	(6,208)	(37,108)	(17,137)
Other	(15,229)	(4,353)	(25,321)	(13,325)
Income tax benefit (expense)	1,887	2,780	(4,820)	13,100
Discontinued operations	(259)	(9,174)	2,517	(36,164)
Gain on real estate dispositions	3,625	0	16,514	0
Net income	109,701	118,599	369,541	346,230	454,889
Triple-Net Leased Properties
Revenues:
Rental income	244,206	218,698	724,778	644,403
Medical office building and other services revenue	1,136	1,116	3,429	3,342
Total revenues	245,342	219,814	728,207	647,745
Less:
Segment NOI	245,342	219,814	728,207	647,745
(Loss) income from unconsolidated entities	252	203	838	573
Segment profit	245,594	220,017	729,045	648,318
Senior Living Operations
Revenues:
Resident fees and services	396,247	359,112	1,141,781	1,039,876
Total revenues	396,247	359,112	1,141,781	1,039,876
Less:
Property-level operating expenses	265,274	244,316	762,993	706,561
Segment NOI	130,973	114,796	378,788	333,315
(Loss) income from unconsolidated entities	(225)	(32)	(209)	(1,173)
Segment profit	130,748	114,764	378,579	332,142
MOB Operations
Revenues:
Rental income	116,598	114,779	346,711	335,472
Medical office building and other services revenue	5,937	2,530	13,311	7,226
Total revenues	122,535	117,309	360,022	342,698
Less:
Property-level operating expenses	41,147	40,566	119,827	115,010
Medical office building services costs	4,568	1,651	9,565	4,957
Segment NOI	76,820	75,092	230,630	222,731
(Loss) income from unconsolidated entities	66	71	326	1,456
Segment profit	76,886	75,163	230,956	224,187
All Other
Revenues:
Medical office building and other services revenue	500	500	1,500	763
Income from loans and investments	14,043	14,448	39,435	45,284
Interest and other income	368	66	814	1,901
Total revenues	14,911	15,014	41,749	47,948
Less:
Interest and other income	368	66	814	1,901
Segment NOI	14,543	14,948	40,935	46,047
(Loss) income from unconsolidated entities	(140)	(132)	(406)	(323)
Segment profit	14,403	14,816	40,529	45,724
Interest and other income	$ 368	$ 66	$ 814	$ 1,901