Real Property Acquisitions and Development (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Unsecured debt	$ 7,766,251,000		$ 7,379,308,000
Seniors Housing Operating [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	57,534,000	[1]	445,152,000		146,332,000
Buildings and improvements	297,314,000	[1]	4,275,046,000		1,341,560,000
Acquired lease intangibles	12,983,000	[1]	396,444,000		118,077,000
Construction in progress	27,957,000	[1]	0		0
Restricted cash	804,000	[1]	44,427,000		1,296,000
Receivables and other assets	9,327,000	[1]	79,564,000		10,125,000
Total assets acquired	405,919,000	[1],[2]	5,240,633,000	[2]	1,617,390,000	[2]
Secured debt	(19,834,000)	[1]	(1,275,245,000)		(124,190,000)
Accrued expenses and other liabilities	(17,802,000)	[1]	(96,709,000)		(17,347,000)
Total liabilities assumed	(37,636,000)	[1]	(1,371,954,000)		(141,537,000)
Noncontrolling interests	(482,000)	[1]	(232,575,000)		(56,884,000)
Non-cash acquisition related activity	0	[1],[3]	(555,563,000)	[3]	0	[3]
Cash disbursed for acquisitions	367,801,000	[1]	3,080,541,000		1,418,969,000
Construction in progress additions	12,291,000	[1]	3,894,000		0
Less: Capitalized interest	714,000	[1]	57,000		0
Foreign currency translation	(2,012,000)		0		0
Cash disbursed for construction in progress	9,565,000	[1]	3,837,000		0
Capital improvements to existing properties	86,803,000	[1]	72,258,000		21,751,000
Total cash invested in real property, net of cash acquired	464,169,000	[1]	3,156,636,000		1,440,720,000
Cash acquired from acquisition	9,060,000		92,148,000		20,691,000
Seniors Housing Operating [Member] | Preliminary [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Total cash invested in real property, net of cash acquired	368,313,000
Senior Housing Facilities Triple Net [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	141,387,000	[4]	54,596,000		87,372,000
Buildings and improvements	1,365,638,000	[4]	360,594,000		1,000,278,000
Acquired lease intangibles	19,196,000	[4]	0		0
Restricted cash	0	[4]	189,000		0
Receivables and other assets	4,895,000	[4]	1,020,000		119,000
Total assets acquired	1,531,116,000	[4],[5]	416,399,000	[5]	1,087,769,000	[5]
Secured debt	(130,638,000)	[4]	(9,810,000)		(89,881,000)
Accrued expenses and other liabilities	(9,067,000)	[4]	(540,000)		(3,542,000)
Total liabilities assumed	(188,272,000)	[4]	(10,350,000)		(93,423,000)
Capital in excess of par	0	[4]	0		921,000
Noncontrolling interests	0	[4]	0		(17,215,000)
Non-cash acquisition related activity	(3,453,000)	[4],[6]	(12,207,000)	[6]	(616,000)	[6]
Cash disbursed for acquisitions	1,339,391,000	[4]	393,842,000		977,436,000
Construction in progress additions	135,349,000	[4]	145,624,000		180,009,000
Less: Capitalized interest	4,582,000	[4]	4,828,000		6,042,000
Foreign currency translation	421,000	[4]	0		0
Non-cash related activity	14,459,000	[4]	0		0
Cash disbursed for construction in progress	116,729,000	[4]	140,796,000		173,967,000
Capital improvements to existing properties	18,901,000	[4]	35,912,000		67,026,000
Total cash invested in real property, net of cash acquired	1,475,021,000	[4]	570,550,000		1,218,429,000
Cash acquired from acquisition	51,020,000		0		2,031,000
Senior Housing Facilities Triple Net [Member] | Senior Notes [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Unsecured debt	48,567,000	[4]	0		0
Senior Housing Facilities Triple Net [Member] | Preliminary [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Total cash invested in real property, net of cash acquired			1,081,607,000
Medical Facilities [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements	63,129,000		14,515,000		68,489,000
Buildings and improvements	567,847,000		156,087,000		632,208,000
Acquired lease intangibles	46,661,000		9,432,000		115,233,000
Goodwill	0		0		0
Restricted cash	0	[7]	505,000		975,000
Receivables and other assets	0	[7]	344,000		4,469,000
Total assets acquired	677,637,000	[7]	180,883,000		821,374,000
Secured debt	(66,113,000)	[7]	(55,884,000)		(267,527,000)
Accrued expenses and other liabilities	(22,293,000)	[7]	(1,041,000)		(25,928,000)
Total liabilities assumed	(88,406,000)	[7]	(56,925,000)		(293,455,000)
Capital in excess of par	0	[7]	0		0
Noncontrolling interests	(39,987,000)	[7]	(386,000)		(193,000)
Non-cash acquisition related activity	(45,836,000)	[7],[8]	0	[8]	(880,000)	[8]
Cash disbursed for acquisitions	503,408,000	[7]	123,572,000		526,846,000
Construction in progress additions	99,878,000	[7]	123,494,000		134,505,000
Less: Capitalized interest	1,854,000	[7]	1,815,000		3,735,000
Accruals	26,437,000	[7],[9]	18,752,000	[9]	18,327,000	[9]
Cash disbursed for construction in progress	71,587,000	[7]	102,927,000		112,443,000
Capital improvements to existing properties	27,076,000	[7]	27,662,000		46,673,000
Total cash invested in real property, net of cash acquired	602,071,000	[7]	254,161,000		685,962,000
Contingent Consideration in Stock	12,500,000
Contingent Consideration Total	0		26,187,000		34,692,000
Medical Facilities [Member] | Preliminary [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Total cash invested in real property, net of cash acquired			$ 489,042,000

[1] (1) Includes an aggregate purchase price of $368,313,000 relating to acquisitions for which the allocation of the purchase price consideration is preliminary and subject to change.

[2] (2) Excludes $9,060,000, $92,148,000 and $20,691,000 of cash acquired during the years ended December 31, 2014, 2013 and 2012, respectively.

[3] (3) Represents Sunrise loan and noncontrolling interest acquisitions during the first quarter of 2013.

[4] (1) Includes acquisitions with an aggregate purchase price of $1,081,607,000 for which the allocation of the purchase price consideration is preliminary and subject to change.

[5] (2) Excludes $1,382,000, $0, and $2,031,000 of cash acquired during the year ended December 31, 2014, 2013 and 2012, respectively.

[6] (3) For the year ended December 31, 2013, relates to an asset swap transaction. Please refer to Note 5 for additional information.

[7] (1) Includes acquisitions with an aggregate purchase price of $489,042,000 for which the allocation of the purchase price consideration is preliminary and subject to change.

[8] (2) For the year ended December 31, 2014, relates to an acquisition of assets previously financed as real estate loans. Please refer to Note 6 for additional information.

[9] (3) Represents non-cash consideration accruals for amounts to be paid in future periods relating to properties that converted in the periods noted above.