Loans and the Allowance for Credit Losses - Allowance for Credit Losses and Recorded Investments in Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans individually evaluated for impairment	$ 5,591	$ 5,745
Allowance for loans collectively evaluated for impairment	123,599	124,930
Allowance for loan commitments	8,175	8,604	$ 9,127	$ 8,368
Total allowance for credit losses - loans and commitments	137,365	139,279	127,825	126,158
Individually evaluated for credit loss	36,746	37,045
Collectively-evaluated for credit losses	11,836,421	11,601,416
Total loans	11,873,167	11,638,461
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	38,041	36,644
Allowance for loan commitments	553	429	797
Total allowance for credit losses - loans and commitments	38,594	37,073	29,368	31,540
Individually evaluated for credit loss	45	116
Collectively-evaluated for credit losses	1,683,127	1,670,543
Total loans	1,683,172	1,670,659
Deposit Overdraft [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	1,235	1,366
Total allowance for credit losses - loans and commitments	1,235	1,366	921	1,285
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,754,933	6,565,448
Commercial Real Estate [Member] | Commercial Real Estate - Land and Construction [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	7,168	7,123
Allowance for loan commitments	6,326	6,894	5,974	6,025
Total allowance for credit losses - loans and commitments	13,494	14,017	11,122	12,762
Collectively-evaluated for credit losses	1,087,649	1,055,865
Total loans	1,087,649	1,055,865
Commercial Real Estate [Member] | Commercial Real Estate - Improved Property [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans individually evaluated for impairment	5,591	5,745
Allowance for loans collectively evaluated for impairment	50,513	53,606
Total allowance for credit losses - loans and commitments	56,104	59,351	54,088	52,659
Individually evaluated for credit loss	36,701	36,929
Collectively-evaluated for credit losses	5,630,583	5,472,654
Total loans	5,667,284	5,509,583
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	21,767	21,218
Allowance for loan commitments	1,285	1,276	2,205	2,215
Total allowance for credit losses - loans and commitments	23,052	22,494	24,908	20,423
Collectively-evaluated for credit losses	2,469,357	2,438,574
Total loans	2,469,357	2,438,574
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	3,851	3,956
Total allowance for credit losses - loans and commitments	3,851	3,956	3,070	3,127
Collectively-evaluated for credit losses	224,732	229,561
Total loans	224,732	229,561
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for loans collectively evaluated for impairment	1,024	1,017
Allowance for loan commitments	11	5	151	128
Total allowance for credit losses - loans and commitments	1,035	1,022	$ 4,348	$ 4,362
Collectively-evaluated for credit losses	740,973	734,219
Total loans	$ 740,973	$ 734,219