Fair Value Measurement - Additional Information (Detail) - non-recoverable rate [Member] - Level 3 - Appraisal Value |
Sep. 30, 2018 |
Dec. 31, 2017 |
---|---|---|
Minimum | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Loans held for investment, measurement input | 0 | 0 |
Maximum | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Loans held for investment, measurement input | 0.51 | 0.77 |
Weighted Average | ||
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Loans held for investment, measurement input | 0.27 | 0.21 |