SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 segment	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting [Abstract]
Number of reportable business segments			3
Revenues:
Rental income	$ 325,185	$ 293,671	$ 649,852	$ 560,873
Resident fees and services	341,594	303,437	680,764	588,630
Medical office building and other services revenue	3,537	6,639	7,185	12,247
Income from loans and investments	14,733	8,152	30,836	16,188
Interest and other income	797	65	1,835	112
Total revenues	685,846	611,964	1,370,472	1,178,050
Less:
Interest and other income	797	65	1,835	112
Property-level operating expenses	269,738	236,652	537,187	452,489
Medical office building services costs	1,667	3,839	3,306	6,827
Segment NOI	413,644	371,408	828,144	718,622
(Loss) income from unconsolidated entities	(506)	514	423	831
Segment profit	413,138	371,922	828,567	719,453
Interest and other income	797	65	1,835	112
Interest expense	(83,046)	(72,767)	(162,452)	(140,678)
Depreciation and amortization	(172,706)	(187,367)	(351,495)	(347,563)
General, administrative and professional fees	(27,327)	(26,423)	(56,101)	(48,621)
Gain (loss) on extinguishment of debt	720	(9,989)	720	(39,533)
Merger-related expenses and deal costs	(6,667)	(36,668)	(10,929)	(44,649)
Other	(4,385)	(1,510)	(8,972)	(3,086)
Income tax benefit (expense)	12,064	5,179	10,320	(6,159)
Discontinued operations	(18,055)	31,294	(23,862)	74,552
Net income	114,533	73,736	227,631	163,828	361,775
Triple-Net Leased Properties
Revenues:
Rental income	214,239	204,561	427,760	407,798
Resident fees and services			0	0
Medical office building and other services revenue	1,115	1,110	2,226	2,219
Income from loans and investments			0	0
Interest and other income			0	0
Total revenues	215,354	205,671	429,986	410,017
Less:
Interest and other income			0	0
Property-level operating expenses			0	0
Medical office building services costs			0	0
Segment NOI	215,354	205,671	429,986	410,017
(Loss) income from unconsolidated entities	183	454	370	720
Segment profit	215,537	206,125	430,356	410,737
Interest and other income			0	0
Senior Living Operations
Revenues:
Rental income			0	0
Medical office building and other services revenue			0	0
Income from loans and investments			0	0
Interest and other income			0	0
Total revenues	341,594	303,437	680,764	588,630
Less:
Interest and other income			0	0
Property-level operating expenses	231,337	207,031	462,245	402,165
Medical office building services costs			0	0
Segment NOI	110,257	96,406	218,519	186,465
(Loss) income from unconsolidated entities	(541)		(1,141)	0
Segment profit	109,716	96,406	217,378	186,465
Interest and other income			0	0
MOB Operations
Revenues:
Rental income	110,946	89,110	222,092	153,075
Resident fees and services			0	0
Medical office building and other services revenue	2,159	5,529	4,696	10,028
Income from loans and investments			0	0
Interest and other income			0	0
Total revenues	113,105	94,639	226,788	163,103
Less:
Interest and other income			0	0
Property-level operating expenses	38,401	29,621	74,942	50,324
Medical office building services costs		3,839	3,306
Segment NOI	73,037	61,179	148,540	105,952
(Loss) income from unconsolidated entities	43	60	1,385	111
Segment profit	73,080	61,239	149,925	106,063
Interest and other income			0	0
All Other
Revenues:
Rental income			0	0
Resident fees and services			0	0
Medical office building and other services revenue	263		263	0
Income from loans and investments	14,733	8,152	30,836	16,188
Interest and other income	797	65	1,835	112
Total revenues	15,793	8,217	32,934	16,300
Less:
Interest and other income	797	65	1,835	112
Property-level operating expenses			0	0
Medical office building services costs			0	0
Segment NOI	14,996	8,152	31,099	16,188
(Loss) income from unconsolidated entities	(191)		(191)	0
Segment profit	14,805	8,152	30,908	16,188
Interest and other income	$ 797	$ 65	$ 1,835	$ 112