Derivatives and Hedging Activities - Summary of Fair Values of Derivative Instruments on Balance Sheets (Detail) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Asset Derivatives	$ 47,120,000	$ 14,629,000
Liability Derivatives	51,078,000	16,205,000
Interest Rate Swaps [Member] | Loan Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	649,857,000	399,860,000
Asset Derivatives	46,418,000	14,585,000
Liability Derivatives	49,917,000	16,117,000
Interest Rate Loan Commitments [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	112,119,000	34,236,000
Asset Derivatives	702,000	44,000
Forward TBA Contracts [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	183,500,000	50,000,000.0
Liability Derivatives	$ 1,161,000	$ 88,000