Derivatives and Hedging Activities - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) Derivative	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) Derivative	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) Derivative
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	$ 320,100,000		$ 320,100,000		$ 229,800,000
Net gain (loss) on change in fair value	(1,366,000)	$ 40,000	(1,982,000)	$ 753,000
Collateral posted with market value on liability positions with credit risk-related contingent features	$ 21,300,000		$ 21,300,000
Interest Rate Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate swaps | Derivative	53		53		43
Net gain (loss) on change in fair value			$ (1,100,000)	200,000
Income (loss) on derivative instrument not designated hedges			$ 1,900,000	$ 500,000