Debt and Preferred Equity Investments (Details) (USD $)	6 Months Ended																			0 Months Ended	1 Months Ended					1 Months Ended					6 Months Ended		9 Months Ended				6 Months Ended												1 Months Ended		1 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013 Debt investment	Dec. 31, 2012 Debt investment	Jun. 30, 2013 Total fixed rate	Dec. 31, 2012 Total fixed rate	Jun. 30, 2013 Other loan with an initial maturity of March 2015	Jun. 30, 2013 Mezzanine loan with an initial maturity date of February 2016	Dec. 31, 2012 Mezzanine loan with an initial maturity date of February 2016	Jun. 30, 2013 Mortgage/Mezzanine loan with an initial maturity date of May 2016	Dec. 31, 2012 Mortgage/Mezzanine loan with an initial maturity date of May 2016	Jun. 30, 2013 Mezzanine loan with an initial maturity date of May 2016	Dec. 31, 2012 Mezzanine loan with an initial maturity date of May 2016	Jun. 30, 2013 Junior participation with an initial maturity date of June 2016	Dec. 31, 2012 Junior participation with an initial maturity date of June 2016	Jun. 30, 2013 Mezzanine loan with an initial maturity date of November 2016	Dec. 31, 2012 Mezzanine loan with an initial maturity date of November 2016	Jan. 13, 2013 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Jan. 31, 2013 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Jun. 30, 2013 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Dec. 31, 2012 Mortgage/Mezzanine loan with an initial maturity date of March 2017	Jun. 30, 2013 Other loan with an initial maturity of September 2021	Dec. 31, 2012 Other loan with an initial maturity of September 2021	May 31, 2013 Mortgage	Nov. 30, 2012 Mortgage	Dec. 31, 2012 Mortgage	Jun. 30, 2013 Total floating rate	Dec. 31, 2012 Total floating rate	Jun. 30, 2013 Mezzanine loan with an initial maturity date of December 2013 item	Feb. 28, 2013 Mezzanine loan with an initial maturity date of December 2013	Sep. 30, 2012 Mortgage/Mezzanine Loan with an initial maturity date of July 2014	Jun. 30, 2013 Mortgage/Mezzanine Loan with an initial maturity date of July 2014	Dec. 31, 2012 Mortgage/Mezzanine Loan with an initial maturity date of July 2014	Jul. 31, 2012 Mortgage/Mezzanine Loan with an initial maturity date of July 2014	Jun. 30, 2013 Junior participation with an initial maturity date of June 2013 extended to February 2014	Dec. 31, 2012 Junior participation with an initial maturity date of June 2013 extended to February 2014	Jun. 30, 2013 Junior participation with an initial maturity date of February 2014	Jun. 30, 2013 Mezzanine loan with an initial maturity date of July 2014	Dec. 31, 2012 Mezzanine loan with an initial maturity date of July 2014	Nov. 30, 2012 Mezzanine loan with an initial maturity date of July 2014	Jun. 30, 2013 Mezzanine loan with an initial maturity date of August 2014	Dec. 31, 2012 Mezzanine loan with an initial maturity date of August 2014	Jun. 30, 2013 Mortgage with initial maturity date of September 2014	Dec. 31, 2012 Mortgage with initial maturity date of September 2014	Jun. 30, 2013 Mortgage/Mezzanine loan with an initial maturity date of February 2015	Dec. 31, 2012 Mortgage/Mezzanine loan with an initial maturity date of February 2015	Jun. 30, 2013 Mezzanine loan with an initial maturity date of December 2015	Dec. 31, 2012 Mezzanine loan with an initial maturity date of December 2015	Mar. 31, 2013 Mortgage with initial maturity date of March 2016	Jun. 30, 2013 Mortgage with initial maturity date of March 2016	Jun. 30, 2013 Mezzanine loan with an initial maturity date of June 2016	Dec. 31, 2012 Mezzanine loan with an initial maturity date of June 2016	Nov. 30, 2011 Mezzanine loan with an initial maturity date of June 2016	Jun. 30, 2013 Mezzanine loan with an initial maturity date of July 2016	Dec. 31, 2012 Mezzanine loan with an initial maturity date of July 2016	Jun. 30, 2013 Mezzanine Loan with initial maturity date of October 2016	Dec. 31, 2012 Mezzanine Loan with initial maturity date of October 2016
Debt and Preferred Equity Investments
Increase in debt and preferred equity investments (net of discounts and deferred origination fees), including investments classified as held-for-sale	$ 298,800,000	$ 159,100,000
Decrease in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	419,800,000	159,800,000
Loan loss reserves recorded	0	3,000,000
Debt investment
Aggregate weighted average current yield (as a percent)	11.20%
Senior Financing	4,277,860,000						2,370,466,000		398,500,000	205,000,000		167,966,000		177,000,000		133,000,000		165,000,000				1,109,000,000		15,000,000					1,907,394,000					330,000,000			57,750,000		78,200,000	62,500,000			180,000,000						92,711,000			775,000,000	160,000,000			87,300,000		83,933,000
Carrying Value, Net of Discounts and Deferred Origination Fees, at fixed rate							340,959,000	583,565,000	14,820,000	67,170,000	66,307,000	44,358,000	44,013,000	15,436,000	15,906,000	49,000,000	49,000,000	71,073,000	70,967,000			75,602,000	115,804,000	3,500,000	3,500,000			218,068,000								49,900,000
Repayments of debt																																																					15,000,000
Mortgage Loans on Real Estate, Commercial and Consumer, Net	1,227,421,000		1,348,434,000
Carrying Value, Net of Discounts and Deferred Origination Fees, at floating rate																													542,161,000	433,290,000	29,826,000			131,470,000	131,231,000	182,000,000	10,863,000	10,869,000	23,057,000	37,359,000	37,288,000		59,812,000	59,739,000	14,817,000	14,745,000	51,227,000	47,253,000	27,734,000	55,336,000		72,358,000	22,503,000	7,624,000		25,572,000	34,761,000	35,563,000	34,444,000
Loan Participation Amount included in Other assets and/or Other liabilities																																										5,000,000											7,400,000		7,400,000
Carrying value, net of discounts					883,120,000	1,016,855,000
Loan loss reserve	(7,000,000)		(7,000,000)	(50,175,000)	(7,000,000)	(7,000,000)
Total, net of reserve					876,120,000	1,009,855,000
Amount funded in origination																																																	56,300,000
Percentage of loan sold																				50.00%																													50.00%		50.00%
Amount recovered from sale of loan																					57,800,000
Additional income recognized on sale																					12,900,000					6,400,000
Loans acquired																											219,000,000
Value of mortgage																																100,000,000				462,000,000						37,500,000							85,000,000		150,000,000		30,000,000		15,000,000
Number of extension options																															2
Extension term																															1 year						4 months
Additional commitments to fund in connection with loan																																							1,700,000								7,100,000		13,600,000									14,100,000
Sale of interest on the senior mortgage loan																																	$ 50,000,000