Debt and Preferred Equity Investments (Details) (USD $)	6 Months Ended				6 Months Ended																	1 Months Ended		1 Months Ended																		1 Months Ended				1 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2012 Debt investment	Dec. 31, 2011 Debt investment	Jun. 30, 2012 Total fixed rate	Jun. 30, 2012 Other loan with an initial maturity of September 2021	Dec. 31, 2011 Other loan with an initial maturity of September 2021	Jun. 30, 2012 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Dec. 31, 2011 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Jun. 30, 2012 Mezzanine loan with an initial maturity date of November 2016	Dec. 31, 2011 Mezzanine loan with an initial maturity date of November 2016	Jun. 30, 2012 Junior participation with an initial maturity date of June 2016	Dec. 31, 2011 Junior participation with an initial maturity date of June 2016	Jun. 30, 2012 Mortgage/Mezzanine loan with an initial maturity date of May 2016	Dec. 31, 2011 Mortgage/Mezzanine loan with an initial maturity date of May 2016	Jun. 30, 2012 Mezzanine loan with an initial maturity date of May 2016	Dec. 31, 2011 Mezzanine loan with an initial maturity date of May 2016	Jun. 30, 2012 Mezzanine loan with an initial maturity date of February 2016	Dec. 31, 2011 Mezzanine loan with an initial maturity date of February 2016	Feb. 29, 2012 Junior Participation	Dec. 31, 2011 Junior Participation	Mar. 30, 2012 Junior Participation	Dec. 31, 2011 Junior Participation	Jun. 30, 2012 Mezzanine Loan with initial maturity date of October 2016	Dec. 31, 2011 Mezzanine Loan with initial maturity date of October 2016	Jun. 30, 2012 Mezzanine loan with an initial maturity date of July 2016	Dec. 31, 2011 Mezzanine loan with an initial maturity date of July 2016	Jun. 30, 2012 Mortgage/Mezzanine loan with an initial maturity date of February 2015	Jun. 30, 2012 Mezzanine Loan with initial maturity date of January 2015	Dec. 31, 2011 Mezzanine Loan with initial maturity date of January 2015	Jun. 30, 2012 Mezzanine loan with an initial maturity date of August 2014	Dec. 31, 2011 Mezzanine loan with an initial maturity date of August 2014	Jun. 30, 2012 Mezzanine loan with an initial maturity date of July 2014	Jun. 30, 2012 Mezzanine loan with an initial maturity date of July 2013	Dec. 31, 2011 Mezzanine loan with an initial maturity date of July 2013	Nov. 30, 2011 Mezzanine loan with an initial maturity date of July 2013	Jun. 30, 2012 Junior participation with an initial maturity date of June 2013	Dec. 31, 2011 Junior participation with an initial maturity date of June 2013	Jun. 30, 2012 Total floating rate	Jun. 30, 2011 Mortgage with an initial maturity date of February 2013	Jun. 30, 2012 Mortgage with an initial maturity date of February 2013	Dec. 31, 2011 Mortgage with an initial maturity date of February 2013	Sep. 30, 2011 Mortgage with an initial maturity date of February 2013	Jun. 30, 2012 Mezzanine loan with an initial maturity date of August 2012	Dec. 31, 2011 Mezzanine loan with an initial maturity date of August 2012	Jun. 30, 2012 Mezzanine Loan with initial maturity date of July 2012	Dec. 31, 2011 Mezzanine Loan with initial maturity date of July 2012	Nov. 30, 2011 Mezzanine Loan with initial maturity date of July 2012	Jun. 30, 2012 Mortgage with an initial maturity date of June 2012	Dec. 31, 2011 Mortgage with an initial maturity date of June 2012	Dec. 31, 2011 Other Loan
Debt and Preferred Equity Investments
Increase in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	$ 159,100,000	$ 162,900,000
Decrease in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	162,800,000	544,300,000
Debt investment
Aggregate weighted average current yield (as a percent)					9.53%
Senior Financing	3,815,340,000						1,974,397,000	15,000,000		1,109,000,000		165,000,000		133,000,000		170,397,000		177,000,000		205,000,000						81,000,000		55,000,000			45,000,000		170,000,000		62,500,000	75,000,000			60,250,000		1,840,943,000		28,500,000			796,693,000		467,000,000
Carrying Value, Net of Discounts, at fixed rate					359,960,000	349,918,000		3,500,000	3,500,000	108,549,000	108,817,000	70,864,000	40,375,000	49,000,000	49,000,000	46,452,000	46,416,000	16,500,000	17,112,000	65,095,000	64,973,000		8,725,000		11,000,000
Carrying Value, Net of Discounts, at floating rate	982,209,000		985,942,000		293,957,000	290,139,000																				34,940,000	34,940,000	35,000,000	35,000,000	36,700,000	10,000,000	10,000,000	60,000,000	60,000,000	37,500,000	7,650,000	7,650,000		10,875,000	10,875,000			3,000,000	3,000,000		8,392,000	8,392,000	49,900,000	30,747,000			86,339,000	3,196,000
Loan Participation Amount included in Other assets & Other liabilities																																						7,400,000							28,500,000
Carrying value, net of discounts					653,917,000	640,057,000
Loan loss reserve	(41,050,000)		(50,175,000)	(61,361,000)	(7,000,000)	(19,125,000)
Total, net of reserve					646,917,000	620,932,000
Amount recovered from sale of loan																						400,000		2,000,000
Ownership interest in consolidated joint venture holding the debt investment (as a percent)																																																			88.00%
Interest in property (as a percent)																																																		50.00%
Additional funding provided																																										5,500,000
Value of mortgage																																						15,000,000							31,500,000
Additional participation interest acquired (as a percent)																																														38.60%
Additional commitments to fund in connection with loan																										$ 15,000,000