Loans and Allowance for Loan Losses - Summary of Shows the Age Analysis of Past Due Loans (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Total Loans	$ 12,157,769
Total loans	12,182,203	$ 12,281,510
Total Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	49,963
Total loans		79,414
30-59 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	25,960
Total loans		53,510
60-89 Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	4,604
Total loans		7,393
90 or More Days Past Due
Financing Receivable, Past Due [Line Items]
Total Loans	19,399
Total loans		18,511
Current
Financing Receivable, Past Due [Line Items]
Total Loans	12,107,806
Total loans		12,202,096
Commercial and industrial | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,866,078
Total loans	2,886,560	2,960,527
Commercial and industrial | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,140
Total loans		1,748
Commercial and industrial | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	146
Total loans		45
Commercial and industrial | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0
Total loans		31
Commercial and industrial | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,994
Total loans		1,672
Commercial and industrial | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,863,938
Total loans		2,958,779
Commercial real estate | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	4,607,185
Total loans	4,609,824	4,522,513
Commercial real estate | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,101
Total loans		27,127
Commercial real estate | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	600
Total loans		25,931
Commercial real estate | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0
Total loans		0
Commercial real estate | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	501
Total loans		1,196
Commercial real estate | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	4,606,084
Total loans		4,495,386
Commercial construction | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	245,038
Total loans	246,093	222,328
Commercial construction | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,743
Total loans		0
Commercial construction | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,743
Total loans		0
Commercial construction | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0
Total loans		0
Commercial construction | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	0
Total loans		0
Commercial construction | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	238,295
Total loans		222,328
Business Banking | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,203,668
Total loans	1,201,007	1,334,694
Business Banking | Total Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	8,768
Total loans		11,476
Business Banking | 30-59 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	4,599
Total loans		5,043
Business Banking | 60-89 Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	875
Total loans		1,793
Business Banking | 90 or More Days Past Due | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	3,294
Total loans		4,640
Business Banking | Current | Commercial Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,194,900
Total loans		1,323,218
Residential real estate | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,945,842
Total loans	1,936,182	1,926,810
Residential real estate | Total Past Due | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	18,925
Total loans		26,577
Residential real estate | 30-59 Days Past Due | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	10,384
Total loans		17,523
Residential real estate | 60-89 Days Past Due | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,162
Total loans		3,511
Residential real estate | 90 or More Days Past Due | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,379
Total loans		5,543
Residential real estate | Current | Residential Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,926,917
Total loans		1,900,233
Consumer home equity | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,101,752
Total loans	1,099,211	1,100,153
Consumer home equity | Total Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	10,591
Total loans		9,855
Consumer home equity | 30-59 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	2,517
Total loans		3,774
Consumer home equity | 60-89 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,348
Total loans		1,510
Consumer home equity | 90 or More Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	6,726
Total loans		4,571
Consumer home equity | Current | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,091,161
Total loans		1,090,298
Other Consumer | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	188,206
Total loans	203,326	214,485
Other Consumer | Total Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	1,695
Total loans		2,631
Other Consumer | 30-59 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	971
Total loans		1,194
Other Consumer | 60-89 Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	219
Total loans		548
Other Consumer | 90 or More Days Past Due | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	505
Total loans		889
Other Consumer | Current | Consumer Portfolio Segment
Financing Receivable, Past Due [Line Items]
Total Loans	$ 186,511
Total loans		$ 211,854