Segment Reporting (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary of information for reportable segments
Rental income	$ 1,405,767,000	$ 1,227,589,000	$ 1,063,214,000
Resident fees and services	1,892,237,000	1,616,290,000	697,494,000
Interest income	37,667,000	32,663,000	39,065,000
Other income	7,875,000	4,066,000	5,271,000
Total revenues	3,343,546,000	2,880,608,000	1,805,044,000
Property operating expenses	1,403,358,000	1,206,813,000	567,989,000
Net Operating Income, Total	1,940,188,000	1,673,795,000	1,237,055,000
Interest expense	481,039,000	458,360,000	361,565,000
Loss (gain) on derivatives, net	(1,495,000)	4,470,000	(1,825,000)
Depreciation and amortization expenses	844,130,000	865,800,000	506,220,000
General and administrative	142,943,000	108,318,000	97,341,000
Transaction costs	69,538,000	133,401,000	61,609,000
Loss (gain) on extinguishment of debt, net	(9,558,000)	909,000	775,000
Other expenses	10,262,000	0	0
Provision for loan losses	0	(2,110,000)	(27,008,000)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total	384,213,000	102,245,000	185,912,000
Income tax (expense) benefit	(1,267,000)	7,491,000	7,612,000
(Loss) income from unconsolidated entities	(27,426,000)	(8,187,000)	2,482,000
Income (loss) from continuing operations	358,054,000	86,567,000	180,782,000
Discontinued operations, net	7,135,000	51,713,000	114,058,000
Gain (loss) on real estate dispositions, net	147,111,000	0	0
Net income (loss)	512,300,000	138,280,000	294,840,000
Total assets	25,014,296,000	23,083,957,000
Segment Reporting (Textuals)
Percent of Assets	1	1
Percent of Revenues	1	1	1
Senior Housing Facilities Triple Net [Member]
Summary of information for reportable segments
Rental income	992,638,000	866,138,000	762,968,000
Resident fees and services	0	0	0
Interest income	32,255,000	28,214,000	30,654,000
Other income	2,973,000	1,504,000	2,471,000
Total revenues	1,027,866,000	895,856,000	796,093,000
Property operating expenses	732,000	1,235,000	1,082,000
Net Operating Income, Total	1,027,134,000	894,621,000	795,011,000
Interest expense	38,460,000	23,322,000	1,745,000
Loss (gain) on derivatives, net	(1,770,000)	4,877,000	96,000
Depreciation and amortization expenses	273,296,000	249,913,000	223,921,000
General and administrative	0	0	0
Transaction costs	45,146,000	24,426,000	35,705,000
Loss (gain) on extinguishment of debt, net	(98,000)	(40,000)	2,405,000
Other expenses	8,825,000
Provision for loan losses	0	(2,110,000)	(27,008,000)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total	663,079,000	589,933,000	504,131,000
Income tax (expense) benefit	(6,141,000)	1,817,000	2,852,000
(Loss) income from unconsolidated entities	5,423,000	5,035,000	(33,000)
Income (loss) from continuing operations	674,643,000	593,151,000	501,246,000
Discontinued operations, net	7,135,000	57,742,000	130,053,000
Gain (loss) on real estate dispositions, net	146,205,000
Net income (loss)	827,983,000	650,893,000	631,299,000
Total assets	10,958,269,000	10,121,813,000
Senior Housing Facilities Operating [Member]
Summary of information for reportable segments
Rental income	0	0	0
Resident fees and services	1,892,237,000	1,616,290,000	697,494,000
Interest income	2,119,000	757,000	6,208,000
Other income	3,215,000	355,000	0
Total revenues	1,897,571,000	1,617,402,000	703,702,000
Property operating expenses	1,266,308,000	1,089,239,000	471,678,000
Net Operating Income, Total	631,263,000	528,163,000	232,024,000
Interest expense	113,099,000	92,148,000	67,524,000
Loss (gain) on derivatives, net	275,000	(407,000)	(1,921,000)
Depreciation and amortization expenses	418,199,000	478,007,000	165,798,000
General and administrative	0	0	0
Transaction costs	16,880,000	107,066,000	12,756,000
Loss (gain) on extinguishment of debt, net	(383,000)	3,372,000	(2,697,000)
Other expenses	1,437,000
Provision for loan losses	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total	80,990,000	(145,279,000)	(9,436,000)
Income tax (expense) benefit	3,047,000	5,337,000	1,086,000
(Loss) income from unconsolidated entities	(38,204,000)	(22,695,000)	(6,364,000)
Income (loss) from continuing operations	39,739,000	(173,311,000)	(16,886,000)
Discontinued operations, net	0	0	0
Gain (loss) on real estate dispositions, net	0
Net income (loss)	39,739,000	(173,311,000)	(16,886,000)
Total assets	9,531,608,000	8,984,316,000
Medical Facilities [Member]
Summary of information for reportable segments
Rental income	413,129,000	361,451,000	300,246,000
Resident fees and services	0	0	0
Interest income	3,293,000	3,692,000	2,203,000
Other income	1,010,000	1,911,000	1,888,000
Total revenues	417,432,000	367,054,000	304,337,000
Property operating expenses	136,318,000	116,339,000	95,229,000
Net Operating Income, Total	281,114,000	250,715,000	209,108,000
Interest expense	32,904,000	36,823,000	28,878,000
Loss (gain) on derivatives, net	0	0	0
Depreciation and amortization expenses	152,635,000	137,880,000	116,501,000
General and administrative	0	0	0
Transaction costs	7,512,000	1,909,000	13,148,000
Loss (gain) on extinguishment of debt, net	(405,000)	0	(483,000)
Other expenses	0
Provision for loan losses	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total	87,658,000	74,103,000	51,064,000
Income tax (expense) benefit	1,827,000	270,000	2,381,000
(Loss) income from unconsolidated entities	5,355,000	9,473,000	8,879,000
Income (loss) from continuing operations	91,186,000	83,306,000	57,562,000
Discontinued operations, net	0	(6,029,000)	(15,995,000)
Gain (loss) on real estate dispositions, net	906,000
Net income (loss)	92,092,000	77,277,000	41,567,000
Total assets	4,465,130,000	3,829,547,000
Non Segment Corporate [Member]
Summary of information for reportable segments
Rental income	0	0	0
Resident fees and services	0	0	0
Interest income	0	0	0
Other income	677,000	296,000	912,000
Total revenues	677,000	296,000	912,000
Property operating expenses	0	0	0
Net Operating Income, Total	677,000	296,000	912,000
Interest expense	296,576,000	306,067,000	263,418,000
Loss (gain) on derivatives, net	0	0	0
Depreciation and amortization expenses	0	0	0
General and administrative	142,943,000	108,318,000	97,341,000
Transaction costs	0	0	0
Loss (gain) on extinguishment of debt, net	(8,672,000)	(2,423,000)	0
Other expenses	0
Provision for loan losses	0	0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Cumulative Effects of Changes in Accounting Principles, Noncontrolling Interest, Total	(447,514,000)	(416,512,000)	(359,847,000)
Income tax (expense) benefit	0	67,000	1,293,000
(Loss) income from unconsolidated entities	0	0	0
Income (loss) from continuing operations	(447,514,000)	(416,579,000)	(361,140,000)
Discontinued operations, net	0	0	0
Gain (loss) on real estate dispositions, net	0
Net income (loss)	(447,514,000)	(416,579,000)	(361,140,000)
Total assets	59,287,000	148,281,000
International [Member]
Summary of information for reportable segments
Total revenues	542,072,000	391,412,000	26,537,000
Total assets	4,285,819,000	3,324,012,000
Segment Reporting (Textuals)
Percent of Assets	0.171	0.144
Percent of Revenues	0.162	0.136	0.015
United States [Member]
Summary of information for reportable segments
Total revenues	2,801,474,000	2,489,196,000	1,778,507,000
Total assets	$ 20,728,477,000	$ 19,759,945,000
Segment Reporting (Textuals)
Percent of Assets	0.829	0.856
Percent of Revenues	0.838	0.864	0.985