Derivatives and Hedging Activities - Summary of Fair Values of Derivative Instruments on Balance Sheets (Detail) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 33,247,000	$ 47,120,000
Liability Derivatives	32,784,000	51,078,000
Interest Rate Swaps [Member] | Loan Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	710,986,000	649,857,000
Asset Derivatives	31,732,000	46,418,000
Liability Derivatives	32,470,000	49,917,000
Interest Rate Loan Commitments [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	85,435,000	112,119,000
Asset Derivatives		702,000
Liability Derivatives	314,000
Forward TBA Contracts [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	197,000,000.0	183,500,000
Asset Derivatives	$ 1,515,000
Liability Derivatives		$ 1,161,000