Derivatives and Hedging Activities - Summary of Fair Values of Derivative Instruments on Balance Sheets (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 399,900,000	$ 229,800,000
Asset Derivatives	14,629,000	4,775,000
Liability Derivatives	16,205,000	5,315,000
Interest Rate Swaps [Member] | Loan Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	399,860,000	229,778,000
Asset Derivatives	14,585,000	4,650,000
Liability Derivatives	16,117,000	5,081,000
Interest Rate Loan Commitments [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	34,236,000	16,113,000
Asset Derivatives	44,000	125,000
Forward TBA Contracts [Member] | Other Contract [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	50,000,000	20,000,000
Liability Derivatives	$ 88,000	$ 234,000