SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014 segment	Mar. 31, 2013	Dec. 31, 2013
Segment Reporting [Abstract]
Number of reportable business segments	3
Revenues:
Rental income	$ 353,069	$ 322,950
Resident fees and services	371,061	339,170
Medical office building and other services revenue	6,300	3,648
Income from loans and investments	10,767	16,103
Interest and other income	273	1,038
Total revenues	741,470	682,909
Less:
Interest and other income	273	1,038
Property-level operating expenses	287,640	267,201
Medical office building services costs	3,371	1,639
Segment NOI	450,186	413,031
Income from unconsolidated entities	248	929
Segment profit	450,434	413,960
Interest and other income	273	1,038
Interest expense	(87,841)	(78,634)
Depreciation and amortization	(193,594)	(175,468)
General, administrative and professional fees	(32,866)	(28,774)
Gain (loss) on extinguishment of debt	259	0
Merger-related expenses and deal costs	(10,760)	(4,262)
Other	(5,229)	(4,587)
Income tax expense	(3,433)	(1,744)
Discontinued operations	3,031	(8,431)
Gain on real estate dispositions, net	1,000	0
Net income	121,274	113,098	454,889
Triple-Net Leased Properties
Revenues:
Rental income	237,846	212,534
Medical office building and other services revenue	1,148	1,111
Total revenues	238,994	213,645
Less:
Segment NOI	238,994	213,645
Income from unconsolidated entities	569	187
Segment profit	239,563	213,832
Senior Living Operations
Revenues:
Resident fees and services	371,061	339,170
Total revenues	371,061	339,170
Less:
Property-level operating expenses	248,295	230,908
Segment NOI	122,766	108,262
Income from unconsolidated entities	(144)	(600)
Segment profit	122,622	107,662
MOB Operations
Revenues:
Rental income	115,223	110,416
Medical office building and other services revenue	4,652	2,537
Total revenues	119,875	112,953
Less:
Property-level operating expenses	39,345	36,293
Medical office building services costs	3,371	1,639
Segment NOI	77,159	75,021
Income from unconsolidated entities	(47)	1,342
Segment profit	77,112	76,363
All Other
Revenues:
Medical office building and other services revenue	500	0
Income from loans and investments	10,767	16,103
Interest and other income	273	1,038
Total revenues	11,540	17,141
Less:
Interest and other income	273	1,038
Segment NOI	11,267	16,103
Income from unconsolidated entities	(130)
Segment profit	11,137	16,103
Interest and other income	$ 273	$ 1,038