Segment Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 segment	Jun. 30, 2012	Dec. 31, 2012
Segment Information
Number of reportable segments			2
Segment information
Total revenues:	$ 365,145,000	$ 344,535,000	$ 730,613,000	$ 679,120,000
Income (loss) from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	37,814,000	108,024,000	66,040,000	128,262,000
Total assets	14,401,925,000		14,401,925,000		14,378,985,000
Leverage rate assumption (as a percent)			100.00%
Marketing, general and administrative expenses and transaction related costs	23,200,000	22,700,000	45,700,000	43,900,000
Transactions between reportable segments			0
Real Estate Segment
Segment information
Total revenues:	318,414,000	311,087,000	631,174,000	619,334,000
Income (loss) from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	(233,000)	81,011,000	(15,821,000)	80,334,000
Total assets	13,163,696,000		13,163,696,000		13,021,095,000
Debt and Preferred Equity Segment
Segment information
Total revenues:	46,731,000	33,448,000	99,439,000	59,786,000
Income (loss) from continuing operations before equity in net gain on sale of interest in unconsolidated joint venture/real estate	38,047,000	27,013,000	81,861,000	47,928,000
Total assets	$ 1,238,229,000		$ 1,238,229,000		$ 1,357,890,000