Segment Disclosures - Summary Information for the Reportable Segments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($) facility	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($) facility
Segment reporting information, revenues
Rental revenues	$ 434,441			$ 472,832
Operating expenses	(168,927)			(172,552)
Segment NOI	265,514			300,280
Adjustments to NOI	(2,338)			(9,686)
Adjusted NOI	263,176			290,594
Addback adjustments	2,338			9,686
Interest income	1,713			6,365
Interest expense	(49,327)			(75,102)
Depreciation and amortization	(131,951)			(143,250)
General and administrative	(21,355)			(29,175)
Transaction costs	(4,518)			(2,195)
Recoveries (impairments), net	(8,858)			0
Gain (loss) on sales of real estate, net	8,044	$ 95,000	$ 25,000	20,815
Other income (expense), net	3,133			(40,407)
Income tax benefit (expense)	3,458			5,336
Equity income (loss) from unconsolidated joint ventures	(863)			570
Net income (loss)	64,990			43,237
Corporate and other assets
Segment reporting information, revenues
Rental revenues	0			0
Operating expenses	0			0
Segment NOI	0			0
Adjustments to NOI	0			0
Adjusted NOI	0			0
Addback adjustments	0			0
Interest income	0			0
Interest expense	(47,891)			(72,583)
Depreciation and amortization	0			0
General and administrative	(21,355)			(29,175)
Transaction costs	(4,518)			(2,195)
Recoveries (impairments), net	0
Gain (loss) on sales of real estate, net	0			0
Other income (expense), net	3,133			160
Income tax benefit (expense)	3,458			5,336
Equity income (loss) from unconsolidated joint ventures	0			0
Net income (loss)	$ (67,173)			$ (98,457)
Senior housing triple-net
Segment Disclosure
Number of facilities transitioned | facility	18			0
Senior housing triple-net | Operating segment
Segment reporting information, revenues
Rental revenues	$ 58,892			$ 74,289
Operating expenses	(993)			(1,045)
Segment NOI	57,899			73,244
Adjustments to NOI	564			(1,865)
Adjusted NOI	58,463			71,379
Addback adjustments	(564)			1,865
Interest income	0			0
Interest expense	(589)			(600)
Depreciation and amortization	(16,683)			(21,906)
General and administrative	0			0
Transaction costs	0			0
Recoveries (impairments), net	0
Gain (loss) on sales of real estate, net	3,557			0
Other income (expense), net	0			0
Income tax benefit (expense)	0			0
Equity income (loss) from unconsolidated joint ventures	0			0
Net income (loss)	44,184			50,738
SHOP
Segment reporting information, revenues
Gain (loss) on sales of real estate, net				21,000
SHOP | Operating segment
Segment reporting information, revenues
Rental revenues	126,181			144,670
Operating expenses	(96,948)			(101,746)
Segment NOI	29,233			42,924
Adjustments to NOI	1,152			(1,607)
Adjusted NOI	30,385			41,317
Addback adjustments	(1,152)			1,607
Interest income	0			0
Interest expense	(663)			(988)
Depreciation and amortization	(24,086)			(27,628)
General and administrative	0			0
Transaction costs	0			0
Recoveries (impairments), net	0
Gain (loss) on sales of real estate, net	4,487			20,815
Other income (expense), net	0			0
Income tax benefit (expense)	0			0
Equity income (loss) from unconsolidated joint ventures	0			0
Net income (loss)	8,971			35,123
Life science | Operating segment
Segment reporting information, revenues
Rental revenues	94,473			99,622
Operating expenses	(21,992)			(21,809)
Segment NOI	72,481			77,813
Adjustments to NOI	(2,478)			(3,751)
Adjusted NOI	70,003			74,062
Addback adjustments	2,478			3,751
Interest income	0			0
Interest expense	(73)			(83)
Depreciation and amortization	(36,246)			(36,080)
General and administrative	0			0
Transaction costs	0			0
Recoveries (impairments), net	0
Gain (loss) on sales of real estate, net	0			0
Other income (expense), net	0			0
Income tax benefit (expense)	0			0
Equity income (loss) from unconsolidated joint ventures	0			0
Net income (loss)	$ 36,162			41,650
Medical office
Segment Disclosure
Number of facilities transitioned | facility	2
Medical office | Operating segment
Segment reporting information, revenues
Rental revenues	$ 142,195			133,220
Operating expenses	(48,987)			(47,878)
Segment NOI	93,208			85,342
Adjustments to NOI	(1,771)			(1,932)
Adjusted NOI	91,437			83,410
Addback adjustments	1,771			1,932
Interest income	0			0
Interest expense	(111)			(120)
Depreciation and amortization	(53,101)			(47,198)
General and administrative	0			0
Transaction costs	0			0
Recoveries (impairments), net	(8,858)
Gain (loss) on sales of real estate, net	0			0
Other income (expense), net	0			0
Income tax benefit (expense)	0			0
Equity income (loss) from unconsolidated joint ventures	0			0
Net income (loss)	31,138			38,024
Other non-reportable segments | Operating segment
Segment reporting information, revenues
Rental revenues	12,700			21,031
Operating expenses	(7)			(74)
Segment NOI	12,693			20,957
Adjustments to NOI	195			(531)
Adjusted NOI	12,888			20,426
Addback adjustments	(195)			531
Interest income	1,713			6,365
Interest expense	0			(728)
Depreciation and amortization	(1,835)			(10,438)
General and administrative	0			0
Transaction costs	0			0
Recoveries (impairments), net	0
Gain (loss) on sales of real estate, net	0			0
Other income (expense), net	0			(40,567)
Income tax benefit (expense)	0			0
Equity income (loss) from unconsolidated joint ventures	(863)			570
Net income (loss)	$ 11,708			$ (23,841)