Debt, Preferred Equity and Other Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Sep. 30, 2014
Debt investment
Increase in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	$ 781,400	$ 680,100
Decrease in debt and preferred equity investments (net of discounts), including investments classified as held-for-sale	$ 520,200	576,100
Aggregate weighted average current yield (as a percent)	10.23%
Debt Investments Held [Abstract]
Future Funding Obligations	$ 5,580
Senior Financing	131,669
Carrying Value	42,176	132,995
Debt investment
Debt Investments Held [Abstract]
Future Funding Obligations	131,430
Senior Financing	5,693,825
Carrying Value	1,627,844	1,275,809
Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Carrying Value	0	0
Total fixed rate
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	2,762,980
Carrying Value	511,389	607,084
Total fixed rate | Junior Mortgage Participation/Mezzanine Loan, May 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	23,510	45,611
Total fixed rate | Junior Mortgage Participation, June 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	133,000
Carrying Value	49,000	49,000
Total fixed rate | Mezzanine Loan, July 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	115,000
Carrying Value	24,916	24,910
Total fixed rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	165,000
Carrying Value	72,102	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	104,661	98,934
Total fixed rate | Mezzanine Loan, March 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	66,183	65,770
Total fixed rate | Mezzanine Loan, June 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	502,100
Carrying Value	41,115	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	49,691	49,629
Total fixed rate | Mortgage Loan, February 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	26,262	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	513	637
Total fixed rate | Mezzanine Loan, September 2021
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	15,000
Carrying Value	3,500	3,500
Total fixed rate | Mezzanine Loan, November 2023
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	89,880
Carrying Value	19,936	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	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	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	0	11,934
Total fixed rate | Junior Mortgage Participation/Mezzanine Loan Repaid in December 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	70,688
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	131,430
Senior Financing	2,930,845
Carrying Value	1,116,455	668,725
Total floating rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	7,942
Senior Financing	312,939
Carrying Value	66,398	0
Total floating rate | Mezzanine Loan, March 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	775,000
Carrying Value	74,700	73,402
Total floating rate | Mortgage/Mezzanine Loan, April 2016
Debt Investments Held [Abstract]
Future Funding Obligations	10,156
Senior Financing	0
Carrying Value	94,901	0
Total floating rate | Mezzanine Loan, June 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	160,000
Carrying Value	22,625	22,573
Amount participated out	7,400
Total floating rate | Mezzanine Loan, November 2016
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	360,000
Carrying Value	99,530	99,023
Total floating rate | Mezzanine Loan, December 2016
Debt Investments Held [Abstract]
Future Funding Obligations	11,414
Senior Financing	131,939
Carrying Value	49,751	42,750
Total floating rate | Mezzanine Loan, December 2016
Debt Investments Held [Abstract]
Future Funding Obligations	281
Senior Financing	39,201
Carrying Value	13,731	11,835
Total floating rate | Mortgage/Mezzanine Loan, January 2017
Debt Investments Held [Abstract]
Future Funding Obligations	57,108
Senior Financing	0
Carrying Value	134,264	0
Amount participated out	25,000
Total floating rate | Mezzanine Loan, January 2017
Debt Investments Held [Abstract]
Future Funding Obligations	1,293
Senior Financing	118,949
Carrying Value	28,551	20,651
Total floating rate | Mortgage/Mezzanine Loan, June 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	68,977	0
Total floating rate | Junior Mortgage Participation/Mezzanine Loan, July 2017
Debt Investments Held [Abstract]
Future Funding Obligations	1,257
Senior Financing	118,717
Carrying Value	40,346	38,524
Total floating rate | Mortgage/Mezzanine Loan, July 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	22,877	22,803
Total floating rate | Mortgage/Mezzanine Loan, September 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	16,901	16,848
Total floating rate | Mortgage/Mezzanine Loan, October 2017
Debt Investments Held [Abstract]
Future Funding Obligations	4,500
Senior Financing	0
Carrying Value	19,282	0
Total floating rate | Mezzanine Loan, November 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	60,000
Carrying Value	14,904	14,859
Total floating rate | Mezzanine Loan, December 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	85,000
Carrying Value	29,505	0
Total floating rate | Mezzanine Loan, December 2017
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	65,000
Carrying Value	28,563	0
Total floating rate | Mortgage/Mezzanine Loan, December 2017
Debt Investments Held [Abstract]
Future Funding Obligations	795
Senior Financing	0
Carrying Value	14,942	14,845
Amount participated out	5,100
Total floating rate | Junior Mortgage Participation, April 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	40,000
Carrying Value	19,846	0
Total floating rate | Mezzanine Loan, April 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	175,000
Carrying Value	34,725	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	20,510	20,533
Total floating rate | Mortgage/Mezzanine Loan, August 2018
Debt Investments Held [Abstract]
Future Funding Obligations	1,500
Senior Financing	0
Carrying Value	31,210	0
Total floating rate | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	33,000
Carrying Value	26,777	0
Total floating rate | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations	6,383
Senior Financing	156,383
Carrying Value	52,774	0
Total floating rate | Mezzanine Loan, December 2018
Debt Investments Held [Abstract]
Future Funding Obligations	28,801
Senior Financing	206,717
Carrying Value	49,625	0
Total floating rate | Mortgage/Mezzanine Loan, February 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	18,395	18,083
Total floating rate | Mezzanine Loan, March 2019
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	38,000
Carrying Value	21,845	21,807
Total floating rate | Mezzanine Loan Repaid April 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	0	33,726
Total floating rate | Mezzanine Loan Repaid April 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	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	0	109,527
Total floating rate | Mezzanine Loan Repaid in November 2015
Debt Investments Held [Abstract]
Future Funding Obligations	0
Senior Financing	0
Carrying Value	$ 0	$ 49,614