Loans and the Allowance for Credit Losses - Summary of Changes in Accretable Yield for Loans Acquired with Deteriorated Credit Quality (Detail) - USD ($) $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period [Abstract] | ||
| Balance at beginning of period | $ 1,724 | $ 1,717 |
| Acquisitions | 0 | 0 |
| Reduction due to change in projected cash flows | (86) | (200) |
| Reclass from non-accretable difference | 2,841 | 174 |
| Transfers out | 0 | 0 |
| Accretion | (268) | (151) |
| Balance at end of period | $ 4,211 | $ 1,540 |