Investment Securities - Schedule of Amortized Cost and Approximate Fair Value of Investment Securities Classified as Held to Maturity (Detail) - USD ($) $ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Schedule of Held-to-maturity Securities [Line Items] | ||
| Amortized Cost | $ 21,454 | $ 26,408 |
| Gross Unrealized Gains | 171 | 23 |
| Gross Unrealized Losses | (160) | |
| Fair Value | 21,625 | 26,271 |
| Residential mortgage-backed securities [Member] | ||
| Schedule of Held-to-maturity Securities [Line Items] | ||
| Amortized Cost | 7,718 | 8,373 |
| Gross Unrealized Gains | 146 | 5 |
| Gross Unrealized Losses | (91) | |
| Fair Value | 7,864 | 8,287 |
| Obligations of state and political subdivisions [Member] | ||
| Schedule of Held-to-maturity Securities [Line Items] | ||
| Amortized Cost | 13,736 | 14,048 |
| Gross Unrealized Gains | 25 | 18 |
| Gross Unrealized Losses | (5) | |
| Fair Value | $ 13,761 | 14,061 |
| Obligations of other U.S. government agencies and corporations [Member] | ||
| Schedule of Held-to-maturity Securities [Line Items] | ||
| Amortized Cost | 3,987 | |
| Gross Unrealized Losses | (64) | |
| Fair Value | $ 3,923 |