Segment Disclosures - Revenues and Assets by Segment (Details) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Disclosure
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
Loss on debt extinguishments	(1,135)			0		(1,135)	0
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
Total revenues	491,567			469,551		927,721	948,748
Senior housing triple-net
Segment Disclosure
Gain (loss) on sales of real estate, net				25,000
SHOP
Segment Disclosure
Gain (loss) on sales of real estate, net					$ 21,000
Operating segment
Segment Disclosure
Total revenues	491,567			469,551		927,721	948,748
Operating segment | Senior housing triple-net
Segment Disclosure
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)
Loss on debt extinguishments	0					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)	17,616			18,752		61,800	69,490
Total revenues	49,866			70,713		108,758	145,003
Operating segment | SHOP
Segment Disclosure
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
Loss on debt extinguishments	0					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)	(62,299)			55,845		(53,191)	90,967
Total revenues	177,001			138,352		303,182	283,022
Operating segment | Life science
Segment Disclosure
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
Loss on debt extinguishments	0					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
Total revenues	107,596			101,031		202,068	200,653
Operating segment | Medical office
Segment Disclosure
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
Loss on debt extinguishments	0					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
Total revenues	141,927			134,574		284,122	267,794
Operating segment | Other non-reportable segments
Segment Disclosure
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
Loss on debt extinguishments	0					0
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
Total revenues	15,177			24,881		29,591	52,276
Corporate and other assets
Segment Disclosure
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
Loss on debt extinguishments	(1,135)					(1,135)
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)