Loans and the Allowance for Credit Losses - Summary of Other Real Estate Owned and Repossessed Assets (Detail) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Receivables [Abstract] | ||
| Other real estate owned | $ 3,991 | $ 5,195 |
| Repossessed assets | 76 | 102 |
| Total other real estate owned and repossessed assets | $ 4,067 | $ 5,297 |