Segment Disclosures - Summary Information for the Reportable Segments (Details) $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2019 USD ($) facility	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($) facility	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($) facility	Jun. 30, 2018 USD ($) facility
Segment reporting information, revenues
Rental revenues	$ 489,153			$ 468,104		$ 923,594	$ 940,936
Operating expenses	(213,993)			(173,866)		(382,920)	(346,418)
Segment NOI	275,160			294,238		540,674	594,518
Adjustments to NOI	(2,950)			(3,662)		(5,288)	(13,349)
Adjusted NOI	272,210			290,576		535,386	581,169
Addback adjustments	2,950			3,662		5,288	13,349
Interest income	2,414			1,447		4,127	7,812
Interest expense	(56,942)			(73,038)		(106,269)	(148,140)
Depreciation and amortization	(165,296)			(143,292)		(297,247)	(286,542)
General and administrative	(27,120)			(22,514)		(48,475)	(51,689)
Transaction costs	(1,337)			(2,404)		(5,855)	(4,599)
Recoveries (impairments), net	(68,538)			(13,912)		(77,396)	(13,912)
Gain (loss) on sales of real estate, net	11,448	$ 8,000	$ 95,000	46,064		19,492	66,879
Other income (expense), net	21,008			1,786		24,141	(38,621)
Income tax benefit (expense)	1,864			4,654		5,322	9,990
Equity income (loss) from unconsolidated joint ventures	(1,506)			(101)		(2,369)	469
Net income (loss)	(9,980)			92,928		55,010	136,165
Corporate and other assets
Segment reporting information, revenues
Rental revenues	0			0		0	0
Operating expenses	0			0		0	0
Segment NOI	0			0		0	0
Adjustments to NOI	0			0		0	0
Adjusted NOI	0			0		0	0
Addback adjustments	0			0		0	0
Interest income	0			0		0	0
Interest expense	(55,231)			(70,500)		(103,121)	(143,084)
Depreciation and amortization	0			0		0	0
General and administrative	(27,120)			(22,514)		(48,475)	(51,689)
Transaction costs	(1,337)			(2,404)		(5,855)	(4,599)
Recoveries (impairments), net	0			0		0	0
Gain (loss) on sales of real estate, net	0			0		0	0
Other income (expense), net	8,191			1,786		11,324	1,946
Income tax benefit (expense)	1,864			4,654		5,322	9,990
Equity income (loss) from unconsolidated joint ventures	0			0		0	0
Net income (loss)	$ (74,768)			$ (88,978)		$ (141,940)	$ (187,436)
Senior housing triple-net
Segment Disclosure
Number of facilities transitioned | facility	21			10		39	10
Segment reporting information, revenues
Gain (loss) on sales of real estate, net				$ 25,000
Senior housing triple-net | Operating segment
Segment reporting information, revenues
Rental revenues	$ 49,866			70,713		$ 108,758	$ 145,003
Operating expenses	(866)			(791)		(1,859)	(1,837)
Segment NOI	49,000			69,922		106,899	143,166
Adjustments to NOI	4,807			1,006		5,371	(858)
Adjusted NOI	53,807			70,928		112,270	142,308
Addback adjustments	(4,807)			(1,006)		(5,371)	858
Interest income	0			0		0	0
Interest expense	(206)			(607)		(795)	(1,207)
Depreciation and amortization	(15,693)			(21,251)		(32,376)	(43,157)
General and administrative	0			0		0	0
Transaction costs	0			0		0	0
Recoveries (impairments), net	(15,485)			(6,273)		(15,485)	(6,273)
Gain (loss) on sales of real estate, net	0			(23,039)		3,557	(23,039)
Other income (expense), net	0			0		0	0
Income tax benefit (expense)	0			0		0	0
Equity income (loss) from unconsolidated joint ventures	0			0		0	0
Net income (loss)	17,616			18,752		61,800	69,490
SHOP
Segment reporting information, revenues
Gain (loss) on sales of real estate, net					$ 21,000
SHOP | Operating segment
Segment reporting information, revenues
Rental revenues	177,001			138,352		303,182	283,022
Operating expenses	(137,460)			(101,767)		(234,407)	(203,513)
Segment NOI	39,541			36,585		68,775	79,509
Adjustments to NOI	841			(124)		1,993	(1,732)
Adjusted NOI	40,382			36,461		70,768	77,777
Addback adjustments	(841)			124		(1,993)	1,732
Interest income	0			0		0	0
Interest expense	(1,326)			(990)		(1,989)	(1,979)
Depreciation and amortization	(52,242)			(28,002)		(76,328)	(55,630)
General and administrative	0			0		0	0
Transaction costs	0			0		0	0
Recoveries (impairments), net	(52,963)			0		(52,963)	0
Gain (loss) on sales of real estate, net	4,691			48,252		9,314	69,067
Other income (expense), net	0			0		0	0
Income tax benefit (expense)	0			0		0	0
Equity income (loss) from unconsolidated joint ventures	0			0		0	0
Net income (loss)	(62,299)			55,845		(53,191)	90,967
Life science | Operating segment
Segment reporting information, revenues
Rental revenues	107,596			101,031		202,068	200,653
Operating expenses	(25,480)			(22,732)		(47,472)	(44,541)
Segment NOI	82,116			78,299		154,596	156,112
Adjustments to NOI	(7,614)			(2,233)		(10,091)	(5,984)
Adjusted NOI	74,502			76,066		144,505	150,128
Addback adjustments	7,614			2,233		10,091	5,984
Interest income	0			0		0	0
Interest expense	(70)			(80)		(143)	(162)
Depreciation and amortization	(41,431)			(35,269)		(77,677)	(71,350)
General and administrative	0			0		0	0
Transaction costs	0			0		0	0
Recoveries (impairments), net	0			(7,639)		0	(7,639)
Gain (loss) on sales of real estate, net	3,816			0		3,738	0
Other income (expense), net	0			0		0	0
Income tax benefit (expense)	0			0		0	0
Equity income (loss) from unconsolidated joint ventures	0			0		0	0
Net income (loss)	44,431			35,311		$ 80,514	76,961
Medical office
Segment Disclosure
Number of facilities transitioned | facility						2
Medical office | Operating segment
Segment reporting information, revenues
Rental revenues	141,927			134,574		$ 284,122	267,794
Operating expenses	(50,176)			(48,528)		(99,163)	(96,406)
Segment NOI	91,751			86,046		184,959	171,388
Adjustments to NOI	(1,203)			(1,831)		(2,974)	(3,764)
Adjusted NOI	90,548			84,215		181,985	167,624
Addback adjustments	1,203			1,831		2,974	3,764
Interest income	0			0		0	0
Interest expense	(109)			(119)		(221)	(239)
Depreciation and amortization	(54,096)			(48,098)		(107,198)	(95,295)
General and administrative	0			0		0	0
Transaction costs	0			0		0	0
Recoveries (impairments), net	(90)			0		(8,948)	0
Gain (loss) on sales of real estate, net	2,941			0		2,883	0
Other income (expense), net	0			0		0	0
Income tax benefit (expense)	0			0		0	0
Equity income (loss) from unconsolidated joint ventures	0			0		0	0
Net income (loss)	40,397			37,829		71,475	75,854
Other non-reportable segments | Operating segment
Segment reporting information, revenues
Rental revenues	12,763			23,434		25,464	44,464
Operating expenses	(11)			(48)		(19)	(121)
Segment NOI	12,752			23,386		25,445	44,343
Adjustments to NOI	219			(480)		413	(1,011)
Adjusted NOI	12,971			22,906		25,858	43,332
Addback adjustments	(219)			480		(413)	1,011
Interest income	2,414			1,447		4,127	7,812
Interest expense	0			(742)		0	(1,469)
Depreciation and amortization	(1,834)			(10,672)		(3,668)	(21,110)
General and administrative	0			0		0	0
Transaction costs	0			0		0	0
Recoveries (impairments), net	0			0		0	0
Gain (loss) on sales of real estate, net	0			20,851		0	20,851
Other income (expense), net	12,817			0		12,817	(40,567)
Income tax benefit (expense)	0			0		0	0
Equity income (loss) from unconsolidated joint ventures	(1,506)			(101)		(2,369)	469
Net income (loss)	$ 24,643			$ 34,169		$ 36,352	$ 10,329