Debt and Preferred Equity Investments (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Debt investment
Increase in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	$ 464,900	$ 476,600
Decrease in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	$ 372,100	348,500
Aggregate weighted average current yield (as a percent)	10.32%
Debt Investments Held [Abstract]
Carrying Value, Net of Discounts and Deferred Origination Fees	$ 1,501,619		$ 1,408,804
Debt investment
Debt Investments Held [Abstract]
Future Funding Obligations	110,176
Senior Financing	5,653,399
Carrying Value, Net of Discounts and Deferred Origination Fees	1,459,470		1,275,809
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	155
Senior Financing	2,853,100
Carrying Value, Net of Discounts and Deferred Origination Fees	556,559		582,174
Total fixed rate | Junior Mortgage Participation/Mezzanine Loan, February 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	205,000
Carrying Value, Net of Discounts and Deferred Origination Fees	72,541		70,688
Total fixed rate | Junior Mortgage Participation/Mezzanine Loan, May 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	23,371		45,611
Total fixed rate | Junior Mortgage Participation, June 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	133,000
Carrying Value, Net of Discounts and Deferred Origination Fees	49,000		49,000
Total fixed rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	165,000
Carrying Value, Net of Discounts and Deferred Origination Fees	72,031		71,656
Total fixed rate | Junior Mortgage Participation/Mezzanine Loan, March 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	1,109,000
Carrying Value, Net of Discounts and Deferred Origination Fees	102,709		98,934
Total fixed rate | Mezzanine Loan, March 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	66,075		65,770
Total fixed rate | Mezzanine Loan, June 2017
Debt Investments Held [Abstract]
Future Funding Obligations	155
Senior Financing	502,100
Carrying Value, Net of Discounts and Deferred Origination Fees	40,938		24,608
Amount participated out	41,300
Total fixed rate | Mezzanine Loan, July 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	539,000
Carrying Value, Net of Discounts and Deferred Origination Fees	49,666		49,629
Total fixed rate | Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	26,249		26,209
Loan acquired		26,400
Discount amount		200
Total fixed rate | Mortgage Loan, August 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	545		637
Total fixed rate | Mezzanine Loan, September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000
Carrying Value, Net of Discounts and Deferred Origination Fees	3,500		3,500
Total fixed rate | Mezzanine Loan, November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	90,000
Carrying Value, Net of Discounts and Deferred Origination Fees	19,934		19,930
Amount participated out	5,000
Total fixed rate | Mezzanine Loan, January 2025
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	95,000
Carrying Value, Net of Discounts and Deferred Origination Fees	30,000		30,000
Total fixed rate | Mezzanine Loan Repaid in February 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	0		14,068
Total fixed rate | Junior Mortgage Participation Repaid in March 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	0		11,934
Total fixed rate | Junior Mortgage Participation, Sold July 2015
Debt Investments Held [Abstract]
Carrying amount of Notes	22,900
Total fixed rate | Junior Mortgage Participation, Related To Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Loan acquired		5,700
Discount amount		$ 5,700
Total floating rate
Debt Investments Held [Abstract]
Future Funding Obligations	110,021
Senior Financing	2,800,299
Carrying Value, Net of Discounts and Deferred Origination Fees	902,911		693,635
Total floating rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	9,726
Senior Financing	304,610
Carrying Value, Net of Discounts and Deferred Origination Fees	64,430		0
Total floating rate | Mezzanine Loan, March 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	775,000
Carrying Value, Net of Discounts and Deferred Origination Fees	74,349		73,402
Total floating rate | Mortgage/Mezzanine Loan, April 2016
Debt Investments Held [Abstract]
Future Funding Obligations	14,981
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	81,730		0
Total floating rate | Mezzanine Loan, June 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	160,000
Carrying Value, Net of Discounts and Deferred Origination Fees	22,612		22,573
Amount participated out	7,400
Total floating rate | Jr Mortgage Participation, July 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	30,000
Carrying Value, Net of Discounts and Deferred Origination Fees	15,000		0
Total floating rate | Mezzanine Loan, July 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	115,000
Carrying Value, Net of Discounts and Deferred Origination Fees	24,914		24,910
Total floating rate | Mezzanine Loan, September 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	110,000
Carrying Value, Net of Discounts and Deferred Origination Fees	50,000		49,614
Total floating rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	360,000
Carrying Value, Net of Discounts and Deferred Origination Fees	99,398		99,023
Total floating rate | Mezzanine Loan, December 2016
Debt Investments Held [Abstract]
Future Funding Obligations	12,885
Senior Financing	127,824
Carrying Value, Net of Discounts and Deferred Origination Fees	48,226		42,750
Total floating rate | Mezzanine Loan, December 2016
Debt Investments Held [Abstract]
Future Funding Obligations	461
Senior Financing	38,687
Carrying Value, Net of Discounts and Deferred Origination Fees	13,539		11,835
Total floating rate | Mortgage/Mezzanine Loan, January 2017
Debt Investments Held [Abstract]
Future Funding Obligations	66,314
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	124,789		0
Amount participated out	25,000
Total floating rate | Mezzanine Loan, January 2017
Debt Investments Held [Abstract]
Future Funding Obligations	1,851
Senior Financing	118,718
Carrying Value, Net of Discounts and Deferred Origination Fees	27,956		20,651
Total floating rate | Jr. Mortgage Participation/Mezzanine Loan, July 2017
Debt Investments Held [Abstract]
Future Funding Obligations	1,508
Senior Financing	117,460
Carrying Value, Net of Discounts and Deferred Origination Fees	40,034		38,524
Total floating rate | Mortgage/Mezzanine Loan, July 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	22,858		22,803
Total floating rate | Mortgage/Mezzanine Loan, September 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	16,887		16,848
Total floating rate | Mezzanine Loan, November 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	60,000
Carrying Value, Net of Discounts and Deferred Origination Fees	14,892		14,859
Total floating rate | Mortgage Mezzanine Loan, December 2017
Debt Investments Held [Abstract]
Future Funding Obligations	795
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	14,917		14,845
Amount participated out	5,100
Total floating rate | Junior Mortgage Participation Loan, April 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	40,000
Carrying Value, Net of Discounts and Deferred Origination Fees	19,830		0
Total floating rate | Mezzanine Loan, April 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	350,000
Carrying Value, Net of Discounts and Deferred Origination Fees	34,698		0
Total floating rate | Junior Mortgage Participation/Mezzanine Loan, July 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	55,000
Carrying Value, Net of Discounts and Deferred Origination Fees	20,516		20,533
Total floating rate | Mortgage/Mezzanine Loan, August 2018
Debt Investments Held [Abstract]
Future Funding Obligations	1,500
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	31,185		0
Total floating rate | Mortgage/Mezzanine Loan, February 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	18,316		18,083
Total floating rate | Mezzanine Loan, March 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	38,000
Carrying Value, Net of Discounts and Deferred Origination Fees	21,835		21,807
Total floating rate | Mezzanine Loan, Repaid April 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	0		33,726
Total floating rate | Mezzanine Loan, Repaid April 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	0		37,322
Total floating rate | Mortgage/Mezzanine Loan Repaid in August 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value, Net of Discounts and Deferred Origination Fees	$ 0		$ 109,527