Dispositions, Assets Held for Sale and Discontinued Operations (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Real property dispositions:
Total dispositions	$ 927,512	$ 374,151
Gain (loss) on sale of properties	287,869	163,881
Net other assets/liabilities disposed	22,470	0
Proceeds from sales of real property	1,237,851	538,032
Triple Net [Member]
Real property dispositions:
Total dispositions	899,104	295,365
Senior housing - operating [Member]
Real property dispositions:
Total dispositions	16,206	0
Outpatient Medical [Member]
Real property dispositions:
Total dispositions	$ 12,202	$ 78,786