Segment Disclosures - Summary Information for the Reportable Segments (Details) - USD ($)	1 Months Ended	3 Months Ended								12 Months Ended
	Jan. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment reporting information, revenues
Rental Revenues										$ 1,792,141,000	$ 2,040,486,000	$ 1,828,305,000
Operating expenses										(666,251,000)	(738,399,000)	(610,679,000)
Segment NOI										1,125,890,000	1,302,087,000	1,217,626,000
Non-cash adjustments to NOI										38,410,000	(19,764,000)	(18,988,000)
Segment adjusted (cash) NOI										1,164,300,000	1,282,323,000	1,198,638,000
Addback adjustments										(38,410,000)	19,764,000	18,988,000
Interest income										56,237,000	88,808,000	112,184,000
Interest expense										(307,716,000)	(464,403,000)	(479,596,000)
Depreciation and amortization										(534,726,000)	(568,108,000)	(504,905,000)
General and administrative										(88,772,000)	(103,611,000)	(95,965,000)
Transaction costs										(7,963,000)	(9,821,000)	(27,309,000)
Recoveries (impairments), net										(166,384,000)	0	(108,349,000)
Gain (loss) on sales of real estate, net										356,641,000	164,698,000	6,377,000
Loss on debt extinguishment						$ (46,000,000)				(54,227,000)	(46,020,000)	0
Other income (expense), net										31,420,000	3,654,000	16,208,000
Income tax benefit (expense)										1,333,000	(4,473,000)	9,807,000
Equity income (loss) from unconsolidated JVs										10,901,000	11,360,000	6,590,000
Total discontinued operations						(18,246,000)	$ 108,215,000	$ 107,378,000	$ 68,408,000	0	265,755,000	(699,086,000)
Net income (loss)		$ (57,924,000)	$ (5,720,000)	$ 22,101,000	$ 464,177,000	$ 61,300,000	$ 154,039,000	$ 304,842,000	$ 119,745,000	422,634,000	639,926,000	(546,418,000)
Corporate and other assets
Segment reporting information, revenues
Rental Revenues										0	0	0
Operating expenses										0	0	0
Segment NOI										0	0	0
Non-cash adjustments to NOI										0	0	0
Segment adjusted (cash) NOI										0	0	0
Addback adjustments										0	0	0
Interest income										0	0	0
Interest expense										(292,169,000)	(407,754,000)	(408,602,000)
Depreciation and amortization										0	0	0
General and administrative										(88,772,000)	(103,611,000)	(95,965,000)
Transaction costs										(7,963,000)	(9,821,000)	(27,309,000)
Recoveries (impairments), net										0		0
Gain (loss) on sales of real estate, net										0	0	0
Loss on debt extinguishment										(54,227,000)	(46,020,000)
Other income (expense), net										(19,475,000)	3,654,000	16,208,000
Income tax benefit (expense)										1,333,000	(4,473,000)	9,807,000
Equity income (loss) from unconsolidated JVs										0	0	0
Total discontinued operations											265,755,000	(699,086,000)
Net income (loss)										(461,273,000)	(302,270,000)	(1,204,947,000)
Senior housing triple-net
Segment reporting information, revenues
Recoveries (impairments), net			$ (23,000,000)
Senior housing triple-net | Operating segment
Segment reporting information, revenues
Rental Revenues										313,547,000	423,118,000	428,269,000
Operating expenses										(3,819,000)	(6,710,000)	(3,427,000)
Segment NOI										309,728,000	416,408,000	424,842,000
Non-cash adjustments to NOI										17,098,000	(7,566,000)	(9,716,000)
Segment adjusted (cash) NOI										326,826,000	408,842,000	415,126,000
Addback adjustments										(17,098,000)	7,566,000	9,716,000
Interest income										0	0	0
Interest expense										(2,518,000)	(9,499,000)	(16,899,000)
Depreciation and amortization										(103,820,000)	(136,146,000)	(125,538,000)
General and administrative										0	0	0
Transaction costs										0	0	0
Recoveries (impairments), net										(22,590,000)		0
Gain (loss) on sales of real estate, net										280,349,000	48,744,000	6,325,000
Loss on debt extinguishment										0
Other income (expense), net										0	0	0
Income tax benefit (expense)										0	0	0
Equity income (loss) from unconsolidated JVs										0	0	0
Total discontinued operations											0	0
Net income (loss)										461,149,000	319,507,000	288,730,000
SHOP | Operating segment
Segment reporting information, revenues
Rental Revenues										525,473,000	686,822,000	518,264,000
Operating expenses										(396,491,000)	(480,870,000)	(371,016,000)
Segment NOI										128,982,000	205,952,000	147,248,000
Non-cash adjustments to NOI										33,227,000	(2,686,000)	8,145,000
Segment adjusted (cash) NOI										162,209,000	203,266,000	155,393,000
Addback adjustments										(33,227,000)	2,686,000	(8,145,000)
Interest income										0	0	0
Interest expense										(7,920,000)	(29,745,000)	(31,869,000)
Depreciation and amortization										(103,162,000)	(108,806,000)	(80,981,000)
General and administrative										0	0	0
Transaction costs										0	0	0
Recoveries (impairments), net										0		0
Gain (loss) on sales of real estate, net										17,485,000	675,000	0
Loss on debt extinguishment										0
Other income (expense), net										0	0	0
Income tax benefit (expense)										0	0	0
Equity income (loss) from unconsolidated JVs										0	0	0
Total discontinued operations											0	0
Net income (loss)										35,385,000	68,076,000	34,398,000
Life science
Segment reporting information, revenues
Gain (loss) on sales of real estate, net	$ 45,000,000
Life science | Operating segment
Segment reporting information, revenues
Rental Revenues										358,816,000	358,537,000	342,984,000
Operating expenses										(78,001,000)	(72,478,000)	(70,217,000)
Segment NOI										280,815,000	286,059,000	272,767,000
Non-cash adjustments to NOI										(4,517,000)	(2,954,000)	(10,128,000)
Segment adjusted (cash) NOI										276,298,000	283,105,000	262,639,000
Addback adjustments										4,517,000	2,954,000	10,128,000
Interest income										0	0	0
Interest expense										(373,000)	(2,357,000)	(2,878,000)
Depreciation and amortization										(128,864,000)	(130,829,000)	(126,241,000)
General and administrative										0	0	0
Transaction costs										0	0	0
Recoveries (impairments), net										0		0
Gain (loss) on sales of real estate, net										45,916,000	49,042,000	0
Loss on debt extinguishment										0
Other income (expense), net										0	0	0
Income tax benefit (expense)										0	0	0
Equity income (loss) from unconsolidated JVs										0	0	0
Total discontinued operations											0	0
Net income (loss)										197,494,000	201,915,000	143,648,000
Medical office | Operating segment
Segment reporting information, revenues
Rental Revenues										477,459,000	446,280,000	415,351,000
Operating expenses										(183,197,000)	(173,687,000)	(162,054,000)
Segment NOI										294,262,000	272,593,000	253,297,000
Non-cash adjustments to NOI										(2,952,000)	(3,536,000)	(4,933,000)
Segment adjusted (cash) NOI										291,310,000	269,057,000	248,364,000
Addback adjustments										2,952,000	3,536,000	4,933,000
Interest income										0	0	0
Interest expense										(506,000)	(5,895,000)	(9,603,000)
Depreciation and amortization										(169,795,000)	(161,790,000)	(143,682,000)
General and administrative										0	0	0
Transaction costs										0	0	0
Recoveries (impairments), net										0		0
Gain (loss) on sales of real estate, net										9,095,000	8,333,000	52,000
Loss on debt extinguishment										0
Other income (expense), net										0	0	0
Income tax benefit (expense)										0	0	0
Equity income (loss) from unconsolidated JVs										0	0	0
Total discontinued operations											0	0
Net income (loss)										133,056,000	113,241,000	100,064,000
Other non-reportable segments | Operating segment
Segment reporting information, revenues
Rental Revenues										116,846,000	125,729,000	123,437,000
Operating expenses										(4,743,000)	(4,654,000)	(3,965,000)
Segment NOI										112,103,000	121,075,000	119,472,000
Non-cash adjustments to NOI										(4,446,000)	(3,022,000)	(2,356,000)
Segment adjusted (cash) NOI										107,657,000	118,053,000	117,116,000
Addback adjustments										4,446,000	3,022,000	2,356,000
Interest income										56,237,000	88,808,000	112,184,000
Interest expense										(4,230,000)	(9,153,000)	(9,745,000)
Depreciation and amortization										(29,085,000)	(30,537,000)	(28,463,000)
General and administrative										0	0	0
Transaction costs										0	0	0
Recoveries (impairments), net										(143,794,000)		(108,349,000)
Gain (loss) on sales of real estate, net										3,796,000	57,904,000	0
Loss on debt extinguishment										0
Other income (expense), net										50,895,000	0	0
Income tax benefit (expense)										0	0	0
Equity income (loss) from unconsolidated JVs										10,901,000	11,360,000	6,590,000
Total discontinued operations											0	0
Net income (loss)										$ 56,823,000	$ 239,457,000	$ 91,689,000