Subordinate Loan Portfolio (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 1,938,589
Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	49,309	$ 29,400
Current Face Amount	26,328	29,751
Carrying Value	26,095	29,762
Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member] \| Condo Conversion [Member] \| Condo Conversion - NY, NY September 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	29,400	29,400
Current Face Amount	6,386	29,751
Carrying Value	6,415	29,762
Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use, New York, NY, March 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	12,347
Current Face Amount	12,347
Carrying Value	12,222
Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel, New York, NY, September 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	2,562
Current Face Amount	2,595
Carrying Value	2,458
Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily - Williston, ND [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	5,000
Current Face Amount	5,000
Carrying Value	5,000
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	915,646	533,034
Current Face Amount	912,678	533,848
Carrying Value	905,256	531,420
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Condo Conversion [Member] \| Condo Conversion, New York, NY, August 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,000
Current Face Amount	52,418
Carrying Value	51,941
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - North Carolina [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	6,525	6,525
Current Face Amount	6,525	6,525
Carrying Value	6,525	6,525
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	17,000	17,000
Current Face Amount	19,500	19,464
Carrying Value	19,377	19,294
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - London, England [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,009	50,009
Current Face Amount	50,676	52,355
Carrying Value	50,676	52,355
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - Pittsburgh, PA [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		22,500
Current Face Amount		22,500
Carrying Value		22,473
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	81,715	50,000
Current Face Amount	88,368	50,000
Carrying Value	87,818	48,973
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use - Various, May 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	45,000
Current Face Amount	45,000
Carrying Value	44,854
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Mixed Use [Member] \| Mixed Use, New York, NY, October 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	30,000
Current Face Amount	30,000
Carrying Value	29,785
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		50,000
Current Face Amount		34,042
Carrying Value		33,995
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel Portfolio - Rochester, MN [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	25,000	25,000
Current Face Amount	24,182	24,486
Carrying Value	24,182	24,486
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel, New York, NY - December 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,000
Current Face Amount	50,000
Carrying Value	49,522
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel - NY, NY, July 2016 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		20,000
Current Face Amount		20,000
Carrying Value		19,870
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel - Burbank, CA [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	20,000
Current Face Amount	20,000
Carrying Value	20,000
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel - Phoenix, AZ [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	25,000
Current Face Amount	25,000
Carrying Value	25,000
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Hotel [Member] \| Hotel - Washington D.C. [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	20,000
Current Face Amount	20,000
Carrying Value	19,934
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily Portfolio - Florida [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	22,000
Current Face Amount	22,000
Carrying Value	21,895
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily Portfolio - Florida (2) [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	15,500
Current Face Amount	15,500
Carrying Value	15,426
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily, New York, New York [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	55,000
Current Face Amount	55,000
Carrying Value	54,558
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Office [Member] \| Office - Michigan [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	9,000	9,000
Current Face Amount	8,753	8,813
Carrying Value	8,753	8,813
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Office [Member] \| Office Complex - Missouri [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	10,000	10,000
Current Face Amount	9,566	9,711
Carrying Value	9,566	9,711
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Office [Member] \| Office Condo New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	14,000	14,000
Current Face Amount	14,000	14,000
Carrying Value	13,631	13,596
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Warehouse [Member] \| Warehouse Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	32,000	32,000
Current Face Amount	32,000	32,000
Carrying Value	32,000	32,000
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Healthcare [Member] \| Healthcare Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,000	50,000
Current Face Amount	39,223	50,000
Carrying Value	39,223	50,000
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Ski Resort [Member] \| Ski Resort - California [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		40,000
Current Face Amount		40,000
Carrying Value		39,771
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Ski Resort [Member] \| Ski Resort Montana [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	15,000	15,000
Current Face Amount	15,000	15,000
Carrying Value	14,878	14,861
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Senior Housing Facility [Member] \| Senior Housing - United Kingdom [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	82,063
Current Face Amount	79,735
Carrying Value	79,735
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Condo Development [Member] \| Condo Development - New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	33,840
Current Face Amount	34,184
Carrying Value	33,567
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Condo Development [Member] \| Condo Pre-development, United Kingdom [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	81,994
Current Face Amount	81,048
Carrying Value	81,048
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Destination Resort [Member] \| Destination Resort, Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	75,000
Current Face Amount	75,000
Carrying Value	71,362
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Condo Construction [Member] \| Condo Construction - NY, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		60,000
Current Face Amount		76,344
Carrying Value		76,005
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Multifamily Conversion [Member] \| Multifamily Conversion - New York, NY, December 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		18,000
Current Face Amount		14,608
Carrying Value		14,703
Subordinate Mortgage Loans to Third Party Commercial Mortgage Loans [Member] \| Multifamily Conversion [Member] \| Multifamily Conversion - New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		44,000
Current Face Amount		44,000
Carrying Value		43,989
Subordinate Loans [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	964,955	562,434
Current Face Amount	939,006	563,599
Carrying Value	$ 931,351	$ 561,182
Coupon rate of loan	11.34%	11.34%
Subordinate Loans [Member] \| Condo Conversion [Member] \| Condo Conversion - NY, NY September 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 6,386
Carrying Value	$ 6,415
Coupon rate of loan	7.00%
Subordinate Loans [Member] \| Condo Conversion [Member] \| Condo Conversion, New York, NY, August 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 52,418
Carrying Value	$ 51,941
Coupon rate of loan	12.75%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use - North Carolina [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 6,525
Carrying Value	$ 6,525
Coupon rate of loan	11.10%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 19,500
Carrying Value	$ 19,377
Coupon rate of loan	14.00%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use - London, England [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 50,676
Carrying Value	$ 50,676
Coupon rate of loan	10.25%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use - New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 88,368
Carrying Value	$ 87,818
Coupon rate of loan	10.69%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use - Various, May 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 45,000
Carrying Value	$ 44,854
Coupon rate of loan	9.30%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use, New York, NY, March 2017 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 12,347
Carrying Value	$ 12,222
Coupon rate of loan	10.25%
Subordinate Loans [Member] \| Mixed Use [Member] \| Mixed Use, New York, NY, October 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 30,000
Carrying Value	$ 29,785
Coupon rate of loan	10.50%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel Portfolio - Rochester, MN [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 24,182
Carrying Value	$ 24,182
Coupon rate of loan	11.00%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel, New York, NY - December 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 50,000
Carrying Value	$ 49,522
Coupon rate of loan	12.36%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel - Burbank, CA [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 20,000
Carrying Value	$ 20,000
Coupon rate of loan	10.40%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel - Phoenix, AZ [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 25,000
Carrying Value	$ 25,000
Coupon rate of loan	11.50%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel - Washington D.C. [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 20,000
Carrying Value	$ 19,934
Coupon rate of loan	9.80%
Subordinate Loans [Member] \| Hotel [Member] \| Hotel, New York, NY, September 2018 [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 2,595
Carrying Value	$ 2,458
Coupon rate of loan	5.50%
Subordinate Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily Portfolio - Florida [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 22,000
Carrying Value	$ 21,895
Coupon rate of loan	11.70%
Subordinate Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily Portfolio - Florida (2) [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 15,500
Carrying Value	$ 15,426
Coupon rate of loan	11.70%
Subordinate Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily, New York, New York [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 55,000
Carrying Value	$ 54,558
Coupon rate of loan	10.75%
Subordinate Loans [Member] \| Multifamily Portfolio [Member] \| Multifamily - Williston, ND [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 5,000
Carrying Value	$ 5,000
Coupon rate of loan	6.15%
Subordinate Loans [Member] \| Office [Member] \| Office - Michigan [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 8,753
Carrying Value	$ 8,753
Coupon rate of loan	13.00%
Subordinate Loans [Member] \| Office [Member] \| Office Complex - Missouri [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 9,566
Carrying Value	$ 9,566
Coupon rate of loan	11.75%
Subordinate Loans [Member] \| Office [Member] \| Office Condo New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 14,000
Carrying Value	$ 13,631
Coupon rate of loan	11.25%
Subordinate Loans [Member] \| Warehouse [Member] \| Warehouse Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 32,000
Carrying Value	$ 32,000
Coupon rate of loan	11.50%
Subordinate Loans [Member] \| Healthcare [Member] \| Healthcare Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 39,223
Carrying Value	$ 39,223
Coupon rate of loan	9.47%
Subordinate Loans [Member] \| Ski Resort [Member] \| Ski Resort Montana [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 15,000
Carrying Value	$ 14,878
Coupon rate of loan	14.00%
Subordinate Loans [Member] \| Senior Housing Facility [Member] \| Senior Housing - United Kingdom [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 79,735
Carrying Value	$ 79,735
Coupon rate of loan	8.83%
Subordinate Loans [Member] \| Condo Development [Member] \| Condo Development - New York, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 34,184
Carrying Value	$ 33,567
Coupon rate of loan	13.00%
Subordinate Loans [Member] \| Condo Development [Member] \| Condo Pre-development, United Kingdom [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 81,048
Carrying Value	$ 81,048
Coupon rate of loan	11.14%
Subordinate Loans [Member] \| Destination Resort [Member] \| Destination Resort, Various [Member]
Mortgage Loans on Real Estate [Line Items]
Current Face Amount	$ 75,000
Carrying Value	$ 71,362
Coupon rate of loan	9.10%

Subordinate Loan Portfolio (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2015

Dec. 31, 2014

Mortgage Loans on Real Estate [Line Items]

Current Face Amount

$ 1,938,589

Subordinate Mortgage Loans to Company Commercial Mortgage Loans [Member]

Mortgage Loans on Real Estate [Line Items]

Original Face Amount

49,309

$ 29,400