Subordinate Loan Portfolio (Detail) (Subordinate loans [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	$ 580,601	$ 495,319
Current Face Amount	587,005	500,037
Carrying Value	585,504	497,484
Coupon rate of loan	11.20%	11.60%
Office [Member] | Office - Michigan [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	9,000	9,000
Current Face Amount	8,828	8,866
Carrying Value	8,828	8,866
Office [Member] | Office Complex - Missouri [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	10,000	10,000
Current Face Amount	9,747	9,849
Carrying Value	9,747	9,849
Office [Member] | Office Condo - NY, 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	13,588	13,565
Ski Resort [Member] | Ski Resort - California [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	40,000	40,000
Current Face Amount	40,000	40,000
Carrying Value	39,714	39,781
Ski Resort [Member] | Ski Resort - Montana [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	15,000
Current Face Amount	15,000
Carrying Value	14,851
Hotel [Member] | Hotel - NY, NY February 2014 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		15,000
Current Face Amount		15,000
Carrying Value		15,207
Hotel [Member] | Hotel Portfolio - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,000	50,000
Current Face Amount	47,172	48,431
Carrying Value	47,260	48,397
Hotel [Member] | Hotel Portfolio - Rochester, MN [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	25,000	25,000
Current Face Amount	24,560	24,771
Carrying Value	24,560	24,771
Hotel [Member] | Hotel - NY, NY, December 2014 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	28,250
Current Face Amount	28,250
Carrying Value	28,250
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	19,834
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
Mixed Use [Member] | Mixed Use - Pittsburgh, PA [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	22,500	22,500
Current Face Amount	22,500	22,500
Carrying Value	22,445	22,342
Mixed Use [Member] | Mixed Use - Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	17,000	17,000
Current Face Amount	18,791	17,000
Carrying Value	18,608	16,805
Mixed Use [Member] | Mixed Use - London, England [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	54,926
Current Face Amount	52,034
Carrying Value	52,034
Mixed Use [Member] | Mixed Use Florida [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		50,000
Current Face Amount		50,000
Carrying Value		49,535
Condo Conversion [Member] | Condo Conversion - NY, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	35,000	35,000
Current Face Amount	35,545	35,000
Carrying Value	35,722	34,734
Condo Conversion [Member] | Condo Conversion - NY, NY September 2015 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	29,400	294
Current Face Amount	29,601	295
Carrying Value	29,491	2
Condo Construction [Member] | Condo Construction - NY, NY [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	60,000	60,000
Current Face Amount	73,844	66,800
Carrying Value	73,457	66,340
Multifamily Conversion [Member] | Multifamily Conversion - NY, NY December 2014 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	18,000	18,000
Current Face Amount	14,608	18,000
Carrying Value	14,683	17,906
Multifamily Conversion [Member] | Multifamily Conversion - NY,NY September 2014 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	44,000
Current Face Amount	44,000
Carrying Value	43,907
Multifamily Conversion [Member] | Multifamily Conversion - NY,NY June 2014 [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount		44,000
Current Face Amount		44,000
Carrying Value		43,859
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
Healthcare [Member] | Healthcare Portfolio Various [Member]
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	50,000	47,000
Current Face Amount	50,000	47,000
Carrying Value	$ 50,000	$ 47,000