Subordinate Loan Portfolio (Detail) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Jun. 30, 2012
Mortgage Loans on Real Estate [Line Items]
Original Face Amount	$ 195,525	$ 149,000
Current Face Amount	196,401	149,086
Carrying Value	196,177
Coupon	12.75%	13.00%
Senior Mezz - Retail - Various
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2009-12	2009-12
Maturity Date	2019-12	2019-12
Original Face Amount	30,000	30,000
Current Face Amount	30,000	30,000
Carrying Value	30,000
Coupon	12.24%	12.24%
Appraised LTV (1)	68.00%	68.00%
Junior Mezz - Retail - Various
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2009-12	2009-12
Maturity Date	2019-12	2019-12
Original Face Amount	20,000	20,000
Current Face Amount	20,000	20,000
Carrying Value	20,000
Coupon	14.00%	14.00%
Appraised LTV (1)	72.00%	73.00%
Office - Michigan
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2010-05	2010-05
Maturity Date	2020-06	2020-06
Original Face Amount	9,000	9,000
Current Face Amount	8,923	8,950
Carrying Value	8,923
Coupon	13.00%	13.00%
Amortization Schedule	25 years	25 years
Appraised LTV (1)	68.00%	69.00%
Ski Resort - California
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2011-04	2011-04
Maturity Date	2017-05	2017-05
Original Face Amount	40,000	40,000
Current Face Amount	40,000	40,000	40,000
Carrying Value	39,808
Coupon	14.00%	13.25%
Appraised LTV (1)	56.00%	64.00%
Hotel Portfolio - New York
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2011-08	2011-08
Maturity Date	2013-07	2013-07
Original Face Amount	25,000	25,000
Current Face Amount	25,000	25,000
Carrying Value	25,000
Coupon	11.49%	11.49%
Appraised LTV (1)	60.00%	60.00%
Retail Center - Virginia
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2011-10	2011-10
Maturity Date	2014-10	2014-10
Original Face Amount	25,000	25,000
Current Face Amount	25,953	25,136
Carrying Value	25,953
Coupon	14.00%	14.00%
Appraised LTV (1)	74.00%	74.00%
Hotel New York
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2012-01	2010-01
Maturity Date	2014-02	2015-01
Original Face Amount	15,000
Current Face Amount	15,000
Carrying Value	14,968
Coupon	12.00%
Appraised LTV (1)	63.00%	40.00%
Hotel - New York
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2012-03	2010-08
Maturity Date	2014-03	2012-08
Original Face Amount	15,000
Current Face Amount	15,000
Carrying Value	15,000
Coupon	11.50%
Appraised LTV (1)	65.00%	40.00%
Mixed Use - North Carolina
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2012-07
Maturity Date	2022-07
Original Face Amount	6,525
Current Face Amount	6,525
Carrying Value	6,525
Coupon	11.10%
Appraised LTV (1)	77.00%
Office Complex - Missouri
Mortgage Loans on Real Estate [Line Items]
Date of Investment	2012-09
Maturity Date	2022-10
Original Face Amount	10,000
Current Face Amount	10,000
Carrying Value	$ 10,000
Coupon	11.75%
Amortization Schedule	30 years
Appraised LTV (1)	72.00%