Fair Value Measurement - Additional Information (Detail) - Level 3 - Loans Held for Investment - Appraisal Value	Dec. 31, 2016	Dec. 31, 2015
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-recoverable rate	0.00%	9.00%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-recoverable rate	73.00%	73.00%
Weighted Average
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-recoverable rate	16.00%	20.00%