Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment information
Number of reportable segments (segment) | segment			2
Total revenues	$ 416,681	$ 432,066	$ 1,489,739	$ 1,237,439
(Loss) Income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate, gain on sale of real estate, depreciable real estate reserves net of recoveries, and loss on sale of investment in marketable securities	42,721	20,994	(18,927)	33,272
Total assets	15,790,942		15,790,942		$ 19,727,646
Marketing, general and administrative	25,458	23,475	73,974	72,139
Operating Segments | Real Estate Segment
Segment information
Total revenues	335,652	375,623	1,300,082	1,085,870
(Loss) Income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate, gain on sale of real estate, depreciable real estate reserves net of recoveries, and loss on sale of investment in marketable securities	(33,613)	(29,577)	(190,633)	(96,333)
Total assets	13,992,319		13,992,319		17,814,787
Operating Segments | Debt and Preferred Equity Segment
Segment information
Total revenues	81,029	56,443	189,657	151,569
(Loss) Income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate, gain on sale of real estate, depreciable real estate reserves net of recoveries, and loss on sale of investment in marketable securities	76,334	$ 50,571	171,706	$ 129,605
Total assets	$ 1,798,623		$ 1,798,623		$ 1,912,859