Real Property Acquisitions and Development (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Unsecured debt		$ (8,548,055)		$ (7,729,405)
Seniors Housing Operating [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements		218,581	[1]	57,534	$ 445,152
Buildings and improvements		2,367,486	[1]	297,314	4,275,046
Acquired lease intangibles		187,512	[1]	12,983	396,444
Construction in progress		0	[1]	27,957	0
Restricted cash		11,798	[1]	804	44,427
Receivables and other assets		29,501	[1]	9,327	79,564
Total assets acquired	[2]	2,814,878	[1]	405,919	5,240,633
Secured debt		(871,471)	[1]	(19,834)	(1,275,245)
Unsecured debt		(24,621)	[1]	0	0
Accrued expenses and other liabilities		(81,778)	[1]	(17,802)	(96,709)
Total liabilities assumed		(977,870)	[1]	(37,636)	(1,371,954)
Noncontrolling interests		(183,854)	[1]	(482)	(232,575)
Non-cash acquisition related activity	[3]	0	[1]	0	(555,563)
Cash disbursed for acquisitions		1,653,154	[1]	367,801	3,080,541
Construction in progress additions		44,173	[1]	12,291	3,894
Less: Capitalized interest		(1,740)	[1]	(714)	(57)
Foreign currency translation		(2,499)	[1]	(2,012)	0
Cash disbursed for construction in progress		39,934	[1]	9,565	3,837
Capital improvements to existing properties		104,308	[1]	86,803	72,258
Total cash invested in real property, net of cash acquired		1,797,396	[1]	464,169	3,156,636
Cash acquired from acquisition		30,930		9,060	92,148
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		2,002,698
Triple Net [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements		142,854	[4]	141,387	54,596
Buildings and improvements		1,358,717	[4]	1,365,638	360,594
Acquired lease intangibles		4,408	[4]	19,196	0
Restricted cash		6	[4]	0	189
Receivables and other assets		194	[4]	4,895	1,020
Total assets acquired	[5]	1,506,179	[4]	1,531,116	416,399
Secured debt		(47,741)	[4]	(130,638)	(9,810)
Unsecured debt		0	[4]	(48,567)	0
Accrued expenses and other liabilities		(2,905)	[4]	(9,067)	(540)
Total liabilities assumed		(50,646)	[4]	(188,272)	(10,350)
Capital in excess of par		0	[4]	0	0
Noncontrolling interests		(13,465)	[4]	0	0
Non-cash acquisition related activity	[6]	(38,355)	[4]	(3,453)	(12,207)
Cash disbursed for acquisitions		1,403,713	[4]	1,339,391	393,842
Construction in progress additions		143,140	[4]	135,349	145,624
Less: Capitalized interest		(5,699)	[4]	(4,582)	(4,828)
Foreign currency translation		(167)	[4]	421	0
Non-cash related activity		0	[4]	14,459	0
Cash disbursed for construction in progress		137,274	[4]	116,729	140,796
Capital improvements to existing properties		45,293	[4]	18,901	35,912
Total cash invested in real property, net of cash acquired		1,586,280	[4]	1,475,021	570,550
Cash acquired from acquisition		16,572		1,382	0
Non Cash Acquisition Financed As Real Estate Loan Receivable		23,288
Non Cash Acquisition Related To Swap Transaction					12,204
Non cash acquisition financed as equity investments		6,743
Triple Net [Member] | Senior Notes [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Unsecured debt		0		(48,567)	0
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		910,443
Outpatient Medical [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Land and land improvements		176,689	[7]	63,129	14,515
Buildings and improvements		317,484	[7]	567,847	156,087
Acquired lease intangibles		45,226	[7]	46,661	9,432
Restricted cash		0	[7]	0	505
Receivables and other assets		939	[7]	0	344
Total assets acquired	[8]	540,338	[7]	677,637	180,883
Secured debt		(120,977)	[7]	(66,113)	(55,884)
Accrued expenses and other liabilities		(7,777)	[7]	(22,293)	(1,041)
Total liabilities assumed		(128,754)	[7]	(88,406)	(56,925)
Noncontrolling interests		(76,535)	[7]	(39,987)	(386)
Non-cash acquisition related activity	[9]	(27,025)	[7]	(45,836)	0
Cash disbursed for acquisitions		308,024	[7]	503,408	123,572
Construction in progress additions		70,560	[7]	99,878	123,494
Less: Capitalized interest		(1,286)	[7]	(1,854)	(1,815)
Accruals	[10]	1,921	[7]	26,437	18,752
Cash disbursed for construction in progress		67,353	[7]	71,587	102,927
Capital improvements to existing properties		38,151	[7]	27,076	27,662
Total cash invested in real property, net of cash acquired		413,528	[7]	602,071	254,161
Cash acquired from acquisition		5,522		0	0
Contingent Consideration Total		0		$ 27,374	$ 26,187
Outpatient Medical [Member] | Preliminary [Member]
Estimated Fair Value of Allocated Purchase Price of Asset and Liabilities
Total cash invested in real property, net of cash acquired		$ 91,829

[1] Includes an aggregate purchase price of $2,002,698,000 relating to acquisitions for which the allocation of the purchase price consideration is preliminary and subject to change.

[2] Excludes $30,930,000, $9,060,000 and $92,148,000 of cash acquired during the years ended December 31, 2015, 2014 and 2013, respectively.

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

[4] Includes acquisitions with an aggregate purchase price of $910,433,000 for which the allocation of the purchase price consideration is preliminary and subject to change.

[5] Excludes $16,572,000, $1,382,000, and $0 of cash acquired during the year ended December 31, 2015, 2014 and 2013, respectively.

[6] For the year ended December 31, 2015, $23,288,000 relates to the acquisition of assets previously financed as real estate loans receivable and $6,743,000 previously financed as equity investments. For the year ended December 31, 2013, $12,204,000 relates to an asset swap transaction. Please refer to Notes 5 and 6.

[7] Includes acquisitions with an aggregate purchase price of $91,829,000 for which the allocation of the purchase price consideration is preliminary and subject to change.

[8] Excludes $5,522,000, $0 and $0 of cash acquired during the years ended December 31, 2015, 2014 and 2013, respectively.

[9] Non-cash activity relates to the acquisition of a controlling interest in a portfolio of properties that was historically reported as an unconsolidated property investment for the year ended December 31, 2015. For the year ended December 31, 2014, the non-cash activity relates to an acquisition of assets previously financed as real estate loans. Please refer to Note 6 for additional information.

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