Dispositions, Assets Held for Sale and Discontinued Operations (Details) - USD ($)		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Real property dispositions:
Total dispositions		$ 276,219,000	$ 127,740,000
Net loss (gain) on sales of properties		(246,956,000)	(13,079,000)
Noncash disposition activity			0
Proceeds from sales of real property		523,175,000	140,819,000
Triple Net [Member]
Real property dispositions:
Total dispositions		105,274,000	41,124,000
Outpatient Medical [Member]
Real property dispositions:
Total dispositions	[1]	165,221,000	$ 86,616,000
Land parcels [Member]
Real property dispositions:
Total dispositions		$ 5,724,000

[1] (1) Primarily related to the disposition of an unconsolidated equity investment with Forest City Enterprises.