Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2013
Risk Level, Low [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Probability of default or principal loss - high	15.00%
Risk Level, Medium [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Probability of default or principal loss - high	33.00%
Risk Level, High [Member] | Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Probability of default or principal loss - high	67.00%
Class A Common Stock [Member]
Financing Receivable, Recorded Investment [Line Items]
Description of reverse stock split	On April 26, 2013, our board of directors approved a one-for-ten reverse stock split of our class A common stock which we effected on May 6, 2013.