Segment Reporting (Details) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)		Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Summary of information for reportable segments
Rental income	$ 362,880		$ 421,152	$ 1,085,621		$ 1,259,442
Resident fees and services	702,380		630,017	2,049,757		1,847,386
Interest income	20,187		25,080	61,836		74,275
Other income	6,036		2,884	15,169		21,735
Total revenues	1,091,483		1,079,133	3,212,383		3,202,838
Property operating expenses	523,997		473,680	1,536,021		1,382,148
Net Operating Income from Continuing Operations	567,486		605,453	1,676,362	[1]	1,820,690
Interest expense	122,578		129,699	357,405		394,985
Loss (gain) on derivatives, net	324		(2,516)	2,284		(2,516)
Depreciation and amortization	230,138		218,061	683,262		673,326
General and administrative	29,913		36,828	93,643		122,434
Transaction costs	0		19,842	0		33,207
Loss (gain) on extinguishment of debt, net	0		0	36,870		9
Impairment of Asset	0		9,705	24,662		24,019
Other expenses	99,595		0	117,608		3,161
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	84,938		193,834	360,628		572,065
Income tax expense	(669)		305	5,535		2,543
(Loss) income from unconsolidated entities	3,408		(1,749)	(23,676)		(7,528)
Income (loss) from continuing operations	87,677		192,390	342,487		567,080
Gain (loss) on real estate dispositions, net	1,622		162,351	287,869		163,881
Net income	89,299		$ 354,741	630,356		$ 730,961
Total assets	$ 28,180,379			$ 28,180,379			$ 28,865,184
Percent Of Assets	1			1			1
Percent Of Revenues	1		1	1		1
United States
Summary of information for reportable segments
Total revenues	$ 871,431		$ 874,050	$ 2,582,042		$ 2,581,533
Total assets	$ 22,535,209			$ 22,535,209			$ 23,572,459
Percent Of Assets	0.8			0.8			0.817
Percent Of Revenues	0.799		0.81	0.804		0.806
United Kingdom
Summary of information for reportable segments
Total revenues	$ 105,028		$ 95,068	$ 298,618		$ 295,203
Total assets	$ 3,202,180			$ 3,202,180			$ 2,782,489
Percent Of Assets	0.113			0.113			0.096
Percent Of Revenues	0.096		0.088	0.093		0.092
Canada
Summary of information for reportable segments
Total revenues	$ 115,024		$ 110,015	$ 331,723		$ 326,102
Total assets	$ 2,442,990			$ 2,442,990			$ 2,510,236
Percent Of Assets	0.087			0.087			0.087
Percent Of Revenues	0.105		0.102	0.103		0.102
Triple Net [Member]
Summary of information for reportable segments
Rental income	$ 221,555		$ 286,226	$ 666,735		$ 857,184
Resident fees and services	0		0	0		0
Interest income	20,187		23,017	61,767		67,842
Other income	3,174		1,621	7,496		4,317
Total revenues	244,916		310,864	735,998		929,343
Property operating expenses	0		0	0		0
Net Operating Income from Continuing Operations	244,916		310,864	735,998		929,343
Interest expense	3,622		4,714	11,647		16,832
Loss (gain) on derivatives, net	324		0	2,284		0
Depreciation and amortization	62,891		74,296	182,672		229,906
General and administrative	0		0	0		0
Transaction costs			1,613			5,760
Loss (gain) on extinguishment of debt, net			0	29,083		97
Impairment of Asset			5,070	4,846		19,384
Other expenses	89,236	[2]		96,425		0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	88,843		225,171	409,041		657,364
Income tax expense	(816)		(896)	(2,070)		(1,425)
(Loss) income from unconsolidated entities	5,478		1,998	14,983		8,097
Income (loss) from continuing operations	93,505		226,273	421,954		664,036
Gain (loss) on real estate dispositions, net	(185)		163,579	273,051		165,109
Net income	93,320		389,852	695,005		829,145
Total assets	9,463,910			9,463,910
Senior housing - operating [Member]
Summary of information for reportable segments
Rental income	0		0	0		0
Resident fees and services	702,380		630,017	2,049,757		1,847,386
Interest income	0		1,054	69		3,126
Other income	1,497		716	4,005		11,889
Total revenues	703,877		631,787	2,053,831		1,862,401
Property operating expenses	478,777		432,292	1,400,313		1,259,182
Net Operating Income from Continuing Operations	225,100		199,495	653,518		603,219
Interest expense	16,369		20,360	47,587		61,157
Loss (gain) on derivatives, net	0		0	0		0
Depreciation and amortization	119,089		97,210	356,023		301,354
General and administrative	0		0	0		0
Transaction costs			18,083			25,259
Loss (gain) on extinguishment of debt, net			0	3,414		(88)
Impairment of Asset			0	14,191		0
Other expenses	5,157			8,100		0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	84,485		63,842	224,203		215,537
Income tax expense	(1,519)		515	9,133		5,304
(Loss) income from unconsolidated entities	(2,886)		(3,891)	(40,527)		(15,713)
Income (loss) from continuing operations	80,080		60,466	192,809		205,128
Gain (loss) on real estate dispositions, net	(197)		0	12,814		0
Net income	79,883		60,466	205,623		205,128
Total assets	13,538,090			13,538,090
Outpatient Medical [Member]
Summary of information for reportable segments
Rental income	141,325		134,926	418,886		402,258
Resident fees and services	0		0	0		0
Interest income	0		1,009	0		3,307
Other income	667		358	2,497		4,824
Total revenues	141,992		136,293	421,383		410,389
Property operating expenses	45,220		41,388	135,708		122,966
Net Operating Income from Continuing Operations	96,772		94,905	285,675		287,423
Interest expense	2,929		3,986	7,342		15,132
Loss (gain) on derivatives, net	0		0	0		0
Depreciation and amortization	48,158		46,555	144,567		142,066
General and administrative	0		0	0		0
Transaction costs			146			2,188
Loss (gain) on extinguishment of debt, net			0	4,373		0
Impairment of Asset			4,635	5,625		4,635
Other expenses	530			2,201		0
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	45,155		39,583	121,567		123,402
Income tax expense	(366)		417	(655)		(59)
(Loss) income from unconsolidated entities	816		144	1,868		88
Income (loss) from continuing operations	45,605		40,144	122,780		123,431
Gain (loss) on real estate dispositions, net	2,004		(1,228)	2,004		(1,228)
Net income	47,609		38,916	124,784		122,203
Total assets	4,992,534			4,992,534
Corporate, Non-Segment [Member]
Summary of information for reportable segments
Rental income	0		0	0		0
Resident fees and services	0		0	0		0
Interest income	0		0	0		0
Other income	698		189	1,171		705
Total revenues	698		189	1,171		705
Property operating expenses	0		0	0		0
Net Operating Income from Continuing Operations	698		189	1,171		705
Interest expense	99,658		100,639	290,829		301,864
Loss (gain) on derivatives, net	0		(2,516)	0		(2,516)
Depreciation and amortization	0		0	0		0
General and administrative	29,913		36,828	93,643		122,434
Transaction costs			0			0
Loss (gain) on extinguishment of debt, net			0	0		0
Impairment of Asset			0	0		0
Other expenses	4,672			10,882		3,161
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	(133,545)		(134,762)	(394,183)		(424,238)
Income tax expense	2,032		269	(873)		(1,277)
(Loss) income from unconsolidated entities	0		0	0		0
Income (loss) from continuing operations	(131,513)		(134,493)	(395,056)		(425,515)
Gain (loss) on real estate dispositions, net	0		0	0		0
Net income	(131,513)		$ (134,493)	(395,056)		$ (425,515)
Total assets	$ 185,845			$ 185,845

[1] Genesis Healthcare is in our triple-net segment. Sunrise Senior Living and Revera are in our seniors housing operating segment. Benchmark Senior Living and Brookdale Senior Living are in both our triple-net and seniors housing operating segments.

[2] Represents non-capitalizable transaction costs primarily related to a joint venture transaction with an existing seniors housing operator including the conversion of properties from triple-net to seniors housing operating, an exchange of PropCo/OpCo interests, and termination/restructuring of pre-existing relationships.