Dispositions, Assets Held for Sale and Discontinued Operations (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Real property dispositions:
Total Disposition		$ 543,577	$ 793,415	$ 448,939
Gain (loss) on sales of real property, net		280,387	153,522	49,138
Sellers financing		0	0	(3,850)
Non-cash disposition activity		0	(35,872)	(12,204)
Proceeds from sales of real property		823,964	911,065	482,023
Triple Net [Member]
Real property dispositions:
Total Disposition		356,300	747,720	189,572
Sellers financing		0	0	(3,850)
Outpatient Medical [Member]
Real property dispositions:
Total Disposition	[1]	181,553	45,695	259,367
Sellers financing		0	0	0
Land parcels [Member]
Real property dispositions:
Total Disposition		$ 5,724	$ 0	$ 0

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