Segment Reporting (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)		Mar. 31, 2017 USD ($)		Dec. 31, 2017 USD ($)
Summary of information for reportable segments
Rental income	$ 343,369		$ 367,141
Resident fees and services	735,934		670,337
Interest income	14,648		20,748
Other income	3,014		4,072
Total revenues	1,096,965		1,062,298
Property operating expenses	556,465		510,169
Net Operating Income from Continuing Operations	540,500	[1]	552,129
Interest expense	122,775		118,597
Loss (gain) on derivatives and financial instruments, net	(7,173)		1,224
Depreciation and amortization	228,201		228,276
General and administrative	33,705		31,101
Loss (gain) on extinguishment of debt, net	11,707		31,356
Impairment of Asset	28,185		11,031
Other expenses	3,712		11,675
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	119,388		118,869
Income tax expense	(1,588)		(2,245)
(Loss) income from unconsolidated entities	(2,429)		(23,106)
Income (loss) from continuing operations	115,371		93,518
Gain (loss) on real estate dispositions, net	338,184		244,092
Net income	453,555		$ 337,610
Total assets	$ 27,746,659				$ 27,944,445
Percent Of Assets	1				1
Percent Of Revenues	1		1
United States
Summary of information for reportable segments
Total revenues	$ 863,789		$ 858,668
Total assets	$ 21,847,420				$ 22,274,443
Percent Of Assets	0.787				0.797
Percent Of Revenues	0.788		0.809
United Kingdom
Summary of information for reportable segments
Total revenues	$ 116,525		$ 93,843
Total assets	$ 3,397,904				$ 3,239,039
Percent Of Assets	0.123				0.116
Percent Of Revenues	0.106		0.088
Canada
Summary of information for reportable segments
Total revenues	$ 116,651		$ 109,787
Total assets	$ 2,501,335				$ 2,430,963
Percent Of Assets	0.09				0.087
Percent Of Revenues	0.106		0.103
Triple Net [Member]
Summary of information for reportable segments
Rental income	$ 206,831		$ 227,290
Resident fees and services	0		0
Interest income	14,551		20,679
Other income	1,377		1,766
Total revenues	222,759		249,735
Property operating expenses	21		0
Net Operating Income from Continuing Operations	222,738		249,735
Interest expense	3,442		5,511
Loss (gain) on derivatives and financial instruments, net	(7,173)		1,224
Depreciation and amortization	56,032		59,608
General and administrative	0		0
Loss (gain) on extinguishment of debt, net	(32)		29,084
Impairment of Asset	25,884		0
Other expenses	1,120		5,010
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	143,465		149,298
Income tax expense	(1,136)		(800)
(Loss) income from unconsolidated entities	5,821		5,638
Income (loss) from continuing operations	148,150		154,136
Gain (loss) on real estate dispositions, net	123,397		231,081
Net income	271,547		385,217
Total assets	8,937,964
Senior housing - operating [Member]
Summary of information for reportable segments
Rental income	0		0
Resident fees and services	735,934		670,337
Interest income	85		69
Other income	1,148		1,461
Total revenues	737,167		671,867
Property operating expenses	511,941		462,425
Net Operating Income from Continuing Operations	225,226		209,442
Interest expense	16,935		15,816
Loss (gain) on derivatives and financial instruments, net	0		0
Depreciation and amortization	125,769		119,737
General and administrative	0		0
Loss (gain) on extinguishment of debt, net	(189)		890
Impairment of Asset	2,301		5,406
Other expenses	(188)		1,778
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	80,598		65,815
Income tax expense	162		(1,087)
(Loss) income from unconsolidated entities	(9,480)		(29,191)	[2]
Income (loss) from continuing operations	71,280		35,537
Gain (loss) on real estate dispositions, net	5		13,011
Net income	71,285		48,548
Total assets	13,769,265
Outpatient Medical [Member]
Summary of information for reportable segments
Rental income	136,538		139,851
Resident fees and services	0		0
Interest income	12		0
Other income	121		612
Total revenues	136,671		140,463
Property operating expenses	44,503		47,744
Net Operating Income from Continuing Operations	92,168		92,719
Interest expense	1,676		2,291
Loss (gain) on derivatives and financial instruments, net	0		0
Depreciation and amortization	46,400		48,931
General and administrative	0		0
Loss (gain) on extinguishment of debt, net	11,928		1,382
Impairment of Asset	0		5,625
Other expenses	598		360
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	31,566		34,130
Income tax expense	(428)		(335)
(Loss) income from unconsolidated entities	1,230		447
Income (loss) from continuing operations	32,368		34,242
Gain (loss) on real estate dispositions, net	214,782		0
Net income	247,150		34,242
Total assets	4,911,566
Corporate, Non-Segment [Member]
Summary of information for reportable segments
Rental income	0		0
Resident fees and services	0		0
Interest income	0		0
Other income	368		233
Total revenues	368		233
Property operating expenses	0		0
Net Operating Income from Continuing Operations	368		233
Interest expense	100,722		94,979
Loss (gain) on derivatives and financial instruments, net	0		0
Depreciation and amortization	0		0
General and administrative	33,705		31,101
Loss (gain) on extinguishment of debt, net	0		0
Impairment of Asset	0		0
Other expenses	2,182		4,527
Income (loss) from continuing operations before income taxes and income from unconsolidated entities	(136,241)		(130,374)
Income tax expense	(186)		(23)
(Loss) income from unconsolidated entities	0		0
Income (loss) from continuing operations	(136,427)		(130,397)
Gain (loss) on real estate dispositions, net	0		0
Net income	(136,427)		$ (130,397)
Total assets	$ 127,864

[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] Primarily due to the recognition of goodwill and intangible asset impairments on unconsolidated joint ventures, as well as non-recurring income tax expense.