Segment Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 item	Mar. 31, 2012	Dec. 31, 2012
Segment Information
Number of reportable segments	2
Segment Information
Total revenues	$ 369,971,000	$ 339,133,000
(Loss) income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	29,256,000	21,431,000
Total assets	14,543,965,000		14,387,754,000
Marketing, general and administrative expenses and transaction related costs	22,400,000	21,300,000
Transactions between reportable segments	0
Real Estate Segment
Segment Information
Total revenues	317,263,000	312,795,000
(Loss) income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	(14,559,000)	516,000
Total assets	13,085,589,000		13,021,095,000
Debt and Preferred Equity Segment
Segment Information
Total revenues	52,708,000	26,338,000
(Loss) income from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	43,815,000	20,915,000
Total assets	$ 1,458,376,000		$ 1,366,659,000
Leverage rate assumption (as a percent)	100.00%