Dispositions, Assets Held for Sale and Discontinued Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Real property dispositions:
Total Disposition		$ 1,852,400	$ 543,577	$ 793,415
Gain (loss) on sales of real property, net		364,046	280,387	153,522
Net other assets/liabilities disposed		133,622	0	(35,872)
Proceeds from sales of real property		2,350,068	823,964	911,065
Senior housing - triple net
Real property dispositions:
Total Disposition		1,773,614	356,300	747,720
Outpatient Medical
Real property dispositions:
Total Disposition	[1]	78,786	181,553	45,695
Land parcels
Real property dispositions:
Total Disposition		0	$ 5,724	$ 0
Genesis HealthCare
Real property dispositions:
Loans received for termination fees		$ 74,445

[1] Dispositions occurring in the year ended December 31, 2015 primarily relate to the disposition of an unconsolidated equity investment with Forest City Enterprises.