SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015 segment	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting [Abstract]
Number of reportable business segments	3
Revenues:
Rental income	$ 403,196	$ 353,069
Resident fees and services	446,914	371,061
Medical office building and other services revenue	10,543	6,300
Income from loans and investments	22,899	10,767
Interest and other income	472	273
Total revenues	884,024	741,470
Less:
Interest and other income	472	273
Property-level operating expenses	340,711	287,640
Medical office building services costs	6,918	3,371
Segment NOI	535,923	450,186
(Loss) income from unconsolidated entities	(251)	248
Segment profit	535,672	450,434
Interest and other income	472	273
Interest expense	(106,590)	(87,841)
Depreciation and amortization	(247,441)	(193,594)
General, administrative and professional fees	(34,330)	(32,866)
Gain (loss) on extinguishment of debt	(21)	259
Merger-related expenses and deal costs	(35,172)	(10,760)
Other	(5,296)	(5,229)
Income tax benefit (expense)	7,250	(3,433)
Discontinued operations	(423)	3,031
Gain on real estate dispositions	6,686	1,000
Net income	120,807	121,274	477,186
Triple-Net Leased Properties
Revenues:
Rental income	266,206	237,846
Medical office building and other services revenue	1,136	1,148
Total revenues	267,342	238,994
Less:
Segment NOI	267,342	238,994
(Loss) income from unconsolidated entities	425	569
Segment profit	267,767	239,563
Senior Living Operations
Revenues:
Resident fees and services	446,914	371,061
Total revenues	446,914	371,061
Less:
Property-level operating expenses	298,362	248,295
Segment NOI	148,552	122,766
(Loss) income from unconsolidated entities	(422)	(144)
Segment profit	148,130	122,622
MOB Operations
Revenues:
Rental income	136,990	115,223
Medical office building and other services revenue	8,858	4,652
Total revenues	145,848	119,875
Less:
Property-level operating expenses	42,349	39,345
Medical office building services costs	6,918	3,371
Segment NOI	96,581	77,159
(Loss) income from unconsolidated entities	(25)	(47)
Segment profit	96,556	77,112
All Other
Revenues:
Medical office building and other services revenue	549	500
Income from loans and investments	22,899	10,767
Interest and other income	472	273
Total revenues	23,920	11,540
Less:
Interest and other income	472	273
Segment NOI	23,448	11,267
(Loss) income from unconsolidated entities	(229)	(130)
Segment profit	23,219	11,137
Interest and other income	$ 472	$ 273