Fair Value Measurement - Carrying Amount and Fair Value of Financial Instruments Not Measured at Fair Value on a Recurring or Nonrecurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financial Assets:
Cash and due from financial institutions	$ 431,778	$ 128,222
Other securities	20,537	20,537
Loans, net of allowance	2,034,106	2,032,474
Bank owned life insurance	46,219	45,976
Accrued interest receivable	8,571	9,421
Financial Liabilities:
Long-term FHLB advances	125,000	125,000
Securities sold under agreement to repurchase	29,513	28,914
Carrying Amount [Member]
Financial Assets:
Cash and due from financial institutions	437,238	139,522
Other securities	20,537	20,537
Loans, held for sale	10,769	7,001
Loans, net of allowance	2,034,106	2,032,474
Bank owned life insurance	46,219	45,976
Accrued interest receivable	8,571	9,421
Financial Liabilities:
Nonmaturing deposits	2,200,075	1,902,560
Time deposits	275,832	286,838
Long-term FHLB advances	125,000	125,000
Securities sold under agreement to repurchase	29,513	28,914
Subordinated debentures	29,427	29,427
Accrued interest payable	178	204
Total Fair Value [Member]
Financial Assets:
Cash and due from financial institutions	437,238	139,522
Other securities	20,537	20,537
Loans, held for sale	10,985	7,141
Loans, net of allowance	2,061,428	2,063,249
Bank owned life insurance	46,219	45,976
Accrued interest receivable	8,571	9,421
Financial Liabilities:
Nonmaturing deposits	2,200,075	1,902,560
Time deposits	276,832	288,298
Long-term FHLB advances	136,056	130,942
Securities sold under agreement to repurchase	29,513	28,914
Subordinated debentures	29,358	31,479
Accrued interest payable	178	204
(Level 1) [Member]
Financial Assets:
Cash and due from financial institutions	437,238	139,522
Other securities	20,537	20,537
Loans, held for sale	10,985	7,141
Bank owned life insurance	46,219	45,976
Accrued interest receivable	8,571	9,421
Financial Liabilities:
Nonmaturing deposits	2,200,075	1,902,560
Securities sold under agreement to repurchase	29,513	28,914
Accrued interest payable	178	204
(Level 3) [Member]
Financial Assets:
Loans, net of allowance	2,061,428	2,063,249
Financial Liabilities:
Time deposits	276,832	288,298
Long-term FHLB advances	136,056	130,942
Subordinated debentures	$ 29,358	$ 31,479