Debt and Preferred Equity Investments (Details)	3 Months Ended			12 Months Ended				12 Months Ended						1 Months Ended															1 Months Ended		1 Months Ended													1 Months Ended					1 Months Ended		1 Months Ended						1 Months Ended			1 Months Ended			1 Months Ended
	Dec. 31, 2012 USD ($)	Sep. 30, 2011 USD ($)	Jun. 30, 2011 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2012 Debt investment USD ($)	Dec. 31, 2011 Debt investment USD ($)	Dec. 31, 2012 Total fixed rate USD ($)	Dec. 31, 2011 Total fixed rate USD ($)	Dec. 31, 2012 Other loan with an initial maturity date of September 2021 USD ($)	Dec. 31, 2011 Other loan with an initial maturity date of September 2021 USD ($)	Jan. 31, 2013 Mortgage Or Mezzanine Loan With An Initial Maturity Date Of March 2017	Dec. 31, 2012 Mortgage Or Mezzanine Loan With An Initial Maturity Date Of March 2017 USD ($)	Dec. 31, 2011 Mortgage Or Mezzanine Loan With An Initial Maturity Date Of March 2017 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of November 2016 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of November 2016 USD ($)	Dec. 31, 2012 Junior participation with an initial maturity date of June 2016 USD ($)	Dec. 31, 2011 Junior participation with an initial maturity date of June 2016 USD ($)	Dec. 31, 2012 Mortgage/Mezzanine loan with an initial maturity date of May 2016 USD ($)	Dec. 31, 2011 Mortgage/Mezzanine loan with an initial maturity date of May 2016 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of May 2016 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of May 2016 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of February 2016 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of February 2016 USD ($)	Dec. 31, 2012 Mortgage USD ($)	Nov. 30, 2012 Mortgage USD ($)	Feb. 29, 2012 Junior participation sold in February 2012 USD ($)	Dec. 31, 2011 Junior participation sold in February 2012 USD ($)	Mar. 31, 2012 Junior participation sold in March 2012 USD ($)	Dec. 31, 2011 Junior participation sold in March 2012 USD ($)	Dec. 31, 2012 Total floating rate USD ($)	Dec. 31, 2011 Total floating rate USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of October 2016 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of October 2016 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of July 2016 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of July 2016 USD ($)	Dec. 31, 2012 Mezzanine Loan with initial maturity date of December 2015 USD ($)	Dec. 31, 2012 Mortgage/Mezzanine loan with an initial maturity date of February 2015 USD ($)	Dec. 31, 2012 Mortgage with initial maturity date of September 2014 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of August 2014 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of August 2014 USD ($)	Sep. 30, 2012 Mortgage/Mezzanine Loan with initial maturity date of July 2014 USD ($)	Jul. 31, 2012 Mortgage/Mezzanine Loan with initial maturity date of July 2014 USD ($)	Dec. 31, 2012 Mortgage/Mezzanine Loan with initial maturity date of July 2014 USD ($)	Dec. 31, 2011 Mortgage/Mezzanine Loan with initial maturity date of July 2014 USD ($)	Nov. 30, 2011 Mortgage/Mezzanine Loan with initial maturity date of July 2014	Nov. 30, 2012 Mezzanine loan with an initial maturity date of July 2014 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of July 2014 USD ($)	Nov. 30, 2011 Mezzanine loan with an initial maturity date of July 2013 USD ($)	Dec. 31, 2012 Mezzanine loan with an initial maturity date of July 2013 USD ($)	Dec. 31, 2011 Mezzanine loan with an initial maturity date of July 2013 USD ($)	Dec. 31, 2012 Junior participation with an initial maturity date of June 2013 USD ($)	Dec. 31, 2011 Junior participation with an initial maturity date of June 2013 USD ($)	Dec. 31, 2011 Mezzanine Loan USD ($)	Sep. 30, 2011 Mortgage with an initial maturity date of February 2013 USD ($)	Dec. 31, 2011 Mortgage with an initial maturity date of February 2013 USD ($)	Jun. 30, 2011 Mortgage with an initial maturity date of February 2013 USD ($)	Jun. 30, 2012 Mezzanine loan with an initial maturity date of August 2012	Dec. 31, 2012 Mezzanine loan with an initial maturity date of August 2012	Dec. 31, 2011 Mezzanine loan with an initial maturity date of August 2012 USD ($)	Nov. 30, 2012 Mortgage with an initial maturity date of June 2012 USD ($)	Nov. 30, 2012 Mortgage with an initial maturity date of June 2012 GBP (£)	Dec. 31, 2012 Mortgage with an initial maturity date of June 2012	Dec. 31, 2011 Mortgage with an initial maturity date of June 2012 USD ($)	Dec. 31, 2011 Other Loan USD ($)
Debt and Preferred Equity Investments
Increase in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale				$ 672,900,000	$ 622,500,000
Decrease in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale				298,700,000	589,400,000
Loan loss reserves recorded				3,000,000	10,900,000
Debt investment
Aggregate weighted average current yield (as a percent)								9.79%
Senior Financing	2,899,673,000			2,899,673,000				2,899,673,000		1,973,212,000		15,000,000			1,109,000,000		165,000,000		133,000,000		169,212,000		177,000,000		205,000,000								926,461,000		81,000,000		55,000,000		92,711,000			170,000,000				330,000,000				62,500,000		75,000,000		60,250,000
Carrying Value, Net of Discounts								1,023,318,000	640,057,000	586,385,000	349,918,000	3,500,000	3,500,000		115,804,000	108,817,000	71,067,000	40,375,000	49,000,000	49,000,000	46,496,000	46,416,000	15,906,000	17,112,000	66,544,000	64,973,000	218,068,000			8,725,000		11,000,000	436,933,000	290,139,000	34,940,000	34,940,000	35,000,000	35,000,000	56,289,000	47,679,000	15,000,000	60,000,000	60,000,000			132,000,000	30,747,000			37,500,000		7,650,000	7,650,000	10,875,000	10,875,000	10,000,000		3,000,000				8,392,000				86,339,000	3,196,000
Acquisition of non-performing loan																												219,000,000
Loan loss reserve	(7,000,000)			(7,000,000)	(50,175,000)	(61,361,000)	(93,844,000)	(7,000,000)	(19,125,000)
Carrying value after deduction of loan loss reserves	1,357,203,000			1,357,203,000	985,942,000			1,016,318,000	620,932,000
Percentage of loan sold														50.00%
Sales price of loan as a percentage of accrued balance														97.00%
Amount recovered from sale of loan																													400,000		2,000,000														49,900,000
Additional commitments to fund in connection with loan																																			15,100,000				28,700,000	11,000,000																			5,500,000
Loan participation amount included in other assets and other liabilities																																													182,000,000				5,000,000		7,400,000						28,500,000
Value of mortgage																																													462,000,000						15,000,000						31,500,000
Interest in senior mortgage sold																																												50,000,000
Interest in property (as a percent)																																																50.00%													27.63%
Ownership interest in the consolidated joint venture holding the debt investment (as a percent)																																																																	88.00%
Ownership interest in the unconsolidated joint venture held by Blackstone (as a percent)																																																													56.30%
Additional participation interest acquired (as a percent)																																																												38.60%
Consideration from sale of loan																																																															100,000,000	62,500,000
Additional income recognized on repayment of debt	$ (6,978,000)	$ (67,000)	$ 971,000	$ (6,978,000)	$ 904,000	$ (1,900,000)																																																									$ 8,900,000