Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans receivable	$ 2,710,159,000	$ 2,047,223,000
Securitized debt obligations	39,394,000	40,181,000
Income accrual, description	Income accrual is generally suspended for loans at the earlier of the date at which payments become 90 days past due or when, in the opinion of our Manager, recovery of income and principal becomes doubtful
Cash and cash equivalents, Description	Cash and cash equivalents represent cash on hand, cash held in banks, and liquid investments with original maturities of three months or less
Consolidation Variable Interest Entities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Loans receivable	47,000,000	47,000,000
Accrued interest receivable and other assets	2,000,000	2,800,000
Securitized debt obligations	$ 39,400,000	$ 40,200,000
Risk Level, Low [Member] | Commercial Real Estate Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of default or principal loss - high	15.00%
Risk Level, Medium [Member] | Commercial Real Estate Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of default or principal loss - high	33.00%
Risk Level, High [Member] | Commercial Real Estate Portfolio Segment [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Probability of default or principal loss - high	67.00%