Segment Disclosures - Summary Information for the Reportable Segments (Details) $ in Thousands	1 Months Ended			3 Months Ended		6 Months Ended
	Jan. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Jan. 31, 2017 USD ($)	Jun. 30, 2018 USD ($) facility	Jun. 30, 2017 USD ($) facility	Jun. 30, 2018 USD ($) facility	Jun. 30, 2017 USD ($) facility
Segment reporting information, revenues
Rental revenues				$ 468,104	$ 438,059	$ 940,936	$ 911,896
Operating expenses				(173,866)	(153,163)	(346,418)	(312,244)
Segment NOI				294,238	284,896	594,518	599,652
Adjustments to NOI				(3,662)	(2,144)	(13,349)	(6,575)
Adjusted NOI				290,576	282,752	581,169	593,077
Addback adjustments				3,662	2,144	13,349	6,575
Interest income				1,447	20,869	7,812	39,200
Interest expense				(73,038)	(77,788)	(148,140)	(164,506)
Depreciation and amortization				(143,292)	(130,751)	(286,542)	(267,305)
General and administrative				(22,514)	(21,286)	(51,689)	(43,764)
Transaction costs				(2,404)	(867)	(4,599)	(1,924)
Recoveries (impairments), net				(13,912)	(56,682)	(13,912)	(56,682)
Gain (loss) on sales of real estate, net				46,064	412	66,879	317,670
Other income (expense), net				1,786	71	(38,621)	51,279
Income tax benefit (expense)				4,654	2,987	9,990	9,149
Equity income (loss) from unconsolidated JVs				(101)	240	469	3,509
Net income (loss)				92,928	22,101	136,165	486,278
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				(70,500)	(74,587)	(143,084)	(153,852)
Depreciation and amortization				0	0	0	0
General and administrative				(22,514)	(21,286)	(51,689)	(43,764)
Transaction costs				(2,404)	(867)	(4,599)	(1,924)
Recoveries (impairments), net				0	0	0	0
Gain (loss) on sales of real estate, net				0	0	0	0
Other income (expense), net				1,786	71	1,946	384
Income tax benefit (expense)				4,654	2,987	9,990	9,149
Equity income (loss) from unconsolidated JVs				0	0	0	0
Net income (loss)				$ (88,978)	$ (93,682)	$ (187,436)	$ (190,007)
Senior housing triple-net
Segment Disclosure
Number of SH NNN facilities transitioned to RIDEA structure | facility				10,000	1,000	10	1
Segment reporting information, revenues
Gain (loss) on sales of real estate, net		$ 170,000
Senior housing triple-net | Operating segment
Segment reporting information, revenues
Rental revenues				$ 70,713	$ 78,079	$ 145,003	$ 178,112
Operating expenses				(791)	(882)	(1,837)	(1,993)
Segment NOI				69,922	77,197	143,166	176,119
Adjustments to NOI				1,006	(406)	(858)	(2,245)
Adjusted NOI				70,928	76,791	142,308	173,874
Addback adjustments				(1,006)	406	858	2,245
Interest income				0	0	0	0
Interest expense				(607)	(631)	(1,207)	(1,258)
Depreciation and amortization				(21,251)	(25,519)	(43,157)	(51,930)
General and administrative				0	0	0	0
Transaction costs				0	0	0	0
Recoveries (impairments), net				(6,273)	0	(6,273)	0
Gain (loss) on sales of real estate, net				(23,039)	(230)	(23,039)	268,234
Other income (expense), net				0	0	0	0
Income tax benefit (expense)				0	0	0	0
Equity income (loss) from unconsolidated JVs				0	0	0	0
Net income (loss)				18,752	50,817	69,490	391,165
SHOP
Segment reporting information, revenues
Gain (loss) on sales of real estate, net	$ 21,000
SHOP | Operating segment
Segment reporting information, revenues
Rental revenues				138,352	125,416	283,022	265,644
Operating expenses				(101,767)	(85,866)	(203,513)	(180,405)
Segment NOI				36,585	39,550	79,509	85,239
Adjustments to NOI				(124)	12	(1,732)	(299)
Adjusted NOI				36,461	39,562	77,777	84,940
Addback adjustments				124	(12)	1,732	299
Interest income				0	0	0	0
Interest expense				(990)	(1,166)	(1,979)	(6,017)
Depreciation and amortization				(28,002)	(24,415)	(55,630)	(50,773)
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				48,252	(232)	69,067	134
Other income (expense), net				0	0	0	0
Income tax benefit (expense)				0	0	0	0
Equity income (loss) from unconsolidated JVs				0	0	0	0
Net income (loss)				55,845	13,737	90,967	28,583
Life science
Segment reporting information, revenues
Gain (loss) on sales of real estate, net			$ 45,000
Life science | Operating segment
Segment reporting information, revenues
Rental revenues				101,031	86,730	200,653	172,050
Operating expenses				(22,732)	(18,744)	(44,541)	(36,064)
Segment NOI				78,299	67,986	156,112	135,986
Adjustments to NOI				(2,233)	(123)	(5,984)	(426)
Adjusted NOI				76,066	67,863	150,128	135,560
Addback adjustments				2,233	123	5,984	426
Interest income				0	0	0	0
Interest expense				(80)	(96)	(162)	(200)
Depreciation and amortization				(35,269)	(31,004)	(71,350)	(64,795)
General and administrative				0	0	0	0
Transaction costs				0	0	0	0
Recoveries (impairments), net				(7,639)	0	(7,639)	0
Gain (loss) on sales of real estate, net				0	1,280	0	45,913
Other income (expense), net				0	0	0	0
Income tax benefit (expense)				0	0	0	0
Equity income (loss) from unconsolidated JVs				0	0	0	0
Net income (loss)				35,311	38,166	76,961	116,904
Medical office | Operating segment
Segment reporting information, revenues
Rental revenues				125,246	119,164	249,180	237,535
Operating expenses				(47,271)	(46,581)	(93,967)	(91,444)
Segment NOI				77,975	72,583	155,213	146,091
Adjustments to NOI				(993)	(763)	(2,064)	(1,726)
Adjusted NOI				76,982	71,820	153,149	144,365
Addback adjustments				993	763	2,064	1,726
Interest income				0	0	0	0
Interest expense				(119)	(127)	(239)	(256)
Depreciation and amortization				(46,419)	(42,488)	(91,937)	(85,217)
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	(406)	0	(406)
Other income (expense), net				0	0	0	0
Income tax benefit (expense)				0	0	0	0
Equity income (loss) from unconsolidated JVs				0	0	0	0
Net income (loss)				31,437	29,562	63,037	60,212
Other non-reportable segments | Operating segment
Segment reporting information, revenues
Rental revenues				32,762	28,670	63,078	58,555
Operating expenses				(1,305)	(1,090)	(2,560)	(2,338)
Segment NOI				31,457	27,580	60,518	56,217
Adjustments to NOI				(1,318)	(864)	(2,711)	(1,879)
Adjusted NOI				30,139	26,716	57,807	54,338
Addback adjustments				1,318	864	2,711	1,879
Interest income				1,447	20,869	7,812	39,200
Interest expense				(742)	(1,181)	(1,469)	(2,923)
Depreciation and amortization				(12,351)	(7,325)	(24,468)	(14,590)
General and administrative				0	0	0	0
Transaction costs				0	0	0	0
Recoveries (impairments), net				0	(56,682)	0	(56,682)
Gain (loss) on sales of real estate, net				20,851	0	20,851	3,795
Other income (expense), net				0	0	(40,567)	50,895
Income tax benefit (expense)				0	0	0	0
Equity income (loss) from unconsolidated JVs				(101)	240	469	3,509
Net income (loss)				$ 40,561	$ (16,499)	$ 23,146	$ 79,421