Segment Disclosures - Revenues and Assets by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Disclosure
Total revenues	$ 456,022	$ 454,023	$ 1,404,770	$ 1,405,119
Operating segment
Segment Disclosure
Total revenues	456,022	454,023	1,404,770	1,405,119
Operating segment | Senior housing triple-net
Segment Disclosure
Total revenues	67,487	77,220	212,489	255,332
Operating segment | SHOP
Segment Disclosure
Total revenues	137,044	126,040	420,067	391,684
Operating segment | Life science
Segment Disclosure
Total revenues	98,040	90,174	298,692	262,224
Operating segment | Medical office
Segment Disclosure
Total revenues	129,618	119,847	378,798	357,381
Operating segment | Other non-reportable segments
Segment Disclosure
Total revenues	$ 23,833	$ 40,742	$ 94,724	$ 138,498