Derivatives and Hedging Activities - Additional Information (Detail) |
3 Months Ended | ||
|---|---|---|---|
|
Mar. 31, 2018
USD ($)
Derivative
|
Mar. 31, 2017
USD ($)
|
Dec. 31, 2017
USD ($)
Derivative
|
|
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
| Aggregate notional amount | $ 309,200,000 | $ 298,200,000 | |
| Net gain (loss) on change in fair value | 336,000 | $ 195,000 | |
| Collateral posted with market value on liability positions with credit risk-related contingent features | $ 2,900,000 | ||
| Interest Rate Swaps [Member] | |||
| Derivative Instruments and Hedging Activities Disclosures [Line Items] | |||
| Number of interest rate swaps | Derivative | 43 | 39 | |
| Net gain (loss) on change in fair value | $ 200,000 | (200,000) | |
| Income (loss) on derivative instrument not designated hedges | $ 400,000 | $ 1,000,000 | |