Segment Disclosures - Revenues and Assets by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Disclosure
Total revenues	$ 454,023	$ 530,557	$ 1,405,119	$ 1,589,349
Operating segment
Segment Disclosure
Total revenues	454,023	530,557	1,405,119	1,589,349
Operating segment | Senior housing triple-net
Segment Disclosure
Total revenues	77,220	104,262	255,332	319,989
Operating segment | SHOP
Segment Disclosure
Total revenues	126,040	170,739	391,684	500,704
Operating segment | Life science
Segment Disclosure
Total revenues	90,174	90,847	262,224	269,994
Operating segment | Medical office
Segment Disclosure
Total revenues	119,847	113,653	357,381	331,881
Operating segment | Other non-reportable segments
Segment Disclosure
Total revenues	$ 40,742	$ 51,056	$ 138,498	$ 166,781