Derivatives and Hedging Activities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021 USD ($) Derivative	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) Derivative
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net gain (loss) on change in fair value	$ 6,263,000	$ (5,553,000)
Collateral posted with market value on liability positions with credit risk-related contingent features	$ 54,200,000
Interest Rate Swaps [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate swaps | Derivative	122		112
Aggregate notional amount	$ 711,000,000.0		$ 649,900,000
Net gain (loss) on change in fair value	2,800,000	(2,800,000)
Income (loss) on derivative instrument not designated hedges	$ 1,900,000	2,600,000
Risk Participation in Agreements [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate swaps | Derivative	13		12
Aggregate notional amount	$ 119,200,000		$ 101,100,000
Risk Participation out Agreement [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of interest rate swaps | Derivative	1		1
Aggregate notional amount	$ 10,000,000.0		$ 10,000,000.0
Other Contract [Member] | Forward TBA Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	197,000,000.0		$ 183,500,000
Net gain (loss) on change in fair value	$ 4,500,000	$ (2,700,000)