Debt and Preferred Equity Investments (Details 2) (USD $) In Thousands, unless otherwise specified				6 Months Ended	12 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2011 Preferred equity investments	Dec. 31, 2010 Preferred equity investments	Jun. 30, 2011 Preferred equity with initial mandatory redemption on February, 2014	Dec. 31, 2010 Preferred equity with initial mandatory redemption on February, 2014	Jun. 30, 2011 Preferred equity with initial mandatory redemption on August, 2012	Dec. 31, 2010 Preferred equity with initial mandatory redemption on August, 2012
Preferred equity investment
Aggregate weighted average current yield (as a percent)				8.35%	8.35%
Senior Financing				$ 1,183,131		$ 203,956		$ 979,175
Amount Outstanding						47,857	45,912	46,372	46,372
Amount Outstanding	41,800	61,361	93,844	(23,400)	(20,900)
Amount Outstanding	$ 582,418	$ 963,772		$ 70,829	$ 71,384