Loans and Allowance for Credit Losses - Summary of Shows the Age Analysis of Past Due Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Total Loans	$ 13,946,676	$ 13,562,528
Total loans	13,961,878	13,575,531
Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	66,039	67,967
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	45,236	42,715
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	5,136	6,360
90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	15,667	18,892
Current
Financing Receivable, Past Due [Line Items]
Total Loans	13,880,637	13,494,561
Commercial and industrial | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	3,325,961	3,132,528
Total loans	3,341,976	3,150,946
Commercial and industrial | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	465	3,759
Commercial and industrial | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	1,300
Commercial and industrial | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	385
Commercial and industrial | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	465	2,074
Commercial and industrial | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	3,325,496	3,128,769
Commercial real estate | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	5,238,472	5,151,363
Total loans	5,242,290	5,155,323
Commercial real estate | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial real estate | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial real estate | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial real estate | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial real estate | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	5,238,472	5,151,363
Commercial construction | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	369,130	334,259
Total loans	371,367	336,276
Commercial construction | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial construction | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial construction | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial construction | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0	0
Commercial construction | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	369,130	334,259
Business banking | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,094,084	1,095,238
Total loans	1,089,548	1,090,492
Business banking | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,447	11,004
Business banking | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	3,384	6,642
Business banking | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,216	845
Business banking | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,847	3,517
Business banking | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,087,637	1,084,234
Residential real estate | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	2,529,219	2,480,055
Total loans	2,510,705	2,460,849
Residential real estate | Total Past Due | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	42,188	36,185
Residential real estate | 30-59 Days Past Due | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	34,598	25,877
Residential real estate | 60-89 Days Past Due | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	1,293	3,852
Residential real estate | 90 or More Days Past Due | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	6,297	6,456
Residential real estate | Current | Residential Real Estate
Financing Receivable, Past Due [Line Items]
Total Loans	2,487,031	2,443,870
Consumer home equity | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,201,624	1,191,307
Total loans	1,198,290	1,187,547
Consumer home equity | Total Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	15,866	15,895
Consumer home equity | 30-59 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,580	8,262
Consumer home equity | 60-89 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,439	1,108
Consumer home equity | 90 or More Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,847	6,525
Consumer home equity | Current | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,185,758	1,175,412
Other Consumer | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	188,186	177,778
Total loans	207,702	194,098
Other Consumer | Total Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,073	1,124
Other Consumer | 30-59 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	674	634
Other Consumer | 60-89 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	188	170
Other Consumer | 90 or More Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	211	320
Other Consumer | Current | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	$ 187,113	$ 176,654