Segment Disclosures - Revenues and Assets by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Disclosure
Total revenues	$ 479,197	$ 492,168
Operating segment
Segment Disclosure
Total revenues	479,197	492,168
Operating segment | Senior housing triple-net
Segment Disclosure
Total revenues	74,289	100,034
Operating segment | SHOP
Segment Disclosure
Total revenues	144,670	140,228
Operating segment | Life science
Segment Disclosure
Total revenues	99,622	85,321
Operating segment | Medical office
Segment Disclosure
Total revenues	123,935	118,371
Operating segment | Other non-reportable segments
Segment Disclosure
Total revenues	$ 36,681	$ 48,214