Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 segment	Sep. 30, 2011	Dec. 31, 2011
Segment Information
Number of reportable segments			2
Segment information
Total revenues:	$ 361,441,000	$ 306,623,000	$ 1,049,638,000	$ 934,551,000
Income from continuing operations before equity in net gain on sale of unconsolidated joint venture and purchase price fair value adjustments	33,214,000	11,341,000	163,484,000	115,896,000
Total assets:	14,284,939,000		14,284,939,000		13,483,852,000
Leverage rate assumption (as a percent)	100.00%
Marketing, general and administrative expenses and transaction related costs	21,900,000	19,100,000	66,000,000	65,200,000
Real Estate Segment
Segment information
Total revenues:	333,572,000	288,190,000	961,983,000	836,295,000
Income from continuing operations before equity in net gain on sale of unconsolidated joint venture and purchase price fair value adjustments	10,942,000	(4,555,000)	93,284,000	23,672,000
Total assets:	13,201,946,000		13,201,946,000		12,490,502,000
Debt and Preferred Equity Segment
Segment information
Total revenues:	27,869,000	18,433,000	87,655,000	98,256,000
Income from continuing operations before equity in net gain on sale of unconsolidated joint venture and purchase price fair value adjustments	22,272,000	15,896,000	70,200,000	92,224,000
Total assets:	$ 1,082,993,000		$ 1,082,993,000		$ 993,350,000