Segment Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 segment	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
Leverage rate assumption (as a percent)	100.00%
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