Segment Disclosures - Revenues and Assets by Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Disclosure
Total revenues	$ 531,691	$ 537,971	$ 491,567	$ 436,154	$ 441,919	$ 456,022	$ 469,551	$ 479,197	$ 1,997,383	$ 1,846,689	$ 1,848,378
Total assets	14,032,891				12,718,553				14,032,891	12,718,553
Assets held for sale and discontinued operations, net	504,394				108,086				504,394	108,086
Operating segment
Segment Disclosure
Gross assets	14,432,330				14,046,739				14,432,330	14,046,739
Accumulated depreciation and amortization	(2,966,987)				(2,997,012)				(2,966,987)	(2,997,012)
Total assets	11,465,343				11,049,727				11,465,343	11,049,727
Operating segment | Senior housing triple-net
Segment Disclosure
Total revenues									199,441	276,091	313,547
Gross assets	1,012,443				2,965,679				1,012,443	2,965,679
Operating segment | SHOP
Segment Disclosure
Total revenues									725,171	547,976	525,473
Gross assets	2,969,871				2,173,795				2,969,871	2,173,795
Operating segment | Life science
Segment Disclosure
Total revenues									440,784	395,064	358,816
Gross assets	5,688,659				4,303,471				5,688,659	4,303,471
Operating segment | Medical office
Segment Disclosure
Total revenues									571,530	547,375	512,385
Gross assets	4,761,357				4,603,794				4,761,357	4,603,794
Operating segment | Other non-reportable segments
Segment Disclosure
Total revenues									60,457	80,183	$ 138,157
Total assets	1,233,752				847,921				1,233,752	847,921
Other non-segment
Segment Disclosure
Total assets	$ 829,402				$ 712,819				$ 829,402	$ 712,819