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Loans and Allowance for Credit Losses - Summary of Company's Loan Portfolio as of the Dates Indicated (Detail) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 13,961,878		$ 13,575,531
Less: allowance for loan losses	(147,955)	$ (140,938)	(142,211)	$ (125,531)	$ (124,166)	$ (97,787)
Unamortized premiums, net of unearned discounts and deferred fees	(15,202)		(13,003)
Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees	13,798,721		13,420,317
Financing receivable, accrued interest, before allowance for credit loss	49,100		45,200
Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(29,535)	(26,929)
Commercial and industrial \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,341,976		3,150,946
Less: allowance for loan losses	(29,535)		(26,859)	(25,852)	(26,841)	(18,018)
Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(59,524)	(55,193)
Commercial real estate \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	5,242,290		5,155,323
Less: allowance for loan losses	(59,524)		(54,730)	(47,555)	(44,612)	(52,373)
Commercial construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(7,663)	(7,578)
Commercial construction \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	371,367		336,276
Less: allowance for loan losses	(7,663)		(7,085)	(5,474)	(4,414)	(2,585)
Business banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(15,228)	(15,085)
Business banking \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,089,548		1,090,492
Less: allowance for loan losses	(15,228)		(16,189)	(16,699)	(17,269)	(10,983)
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(27,012)	(27,130)
Residential real estate \| Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	2,510,705		2,460,849
Less: allowance for loan losses	(27,012)		(28,129)	(21,663)	(22,243)	(6,556)
Consumer home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(6,044)	(6,182)
Consumer home equity \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,198,290		1,187,547
Less: allowance for loan losses	(6,044)		(6,454)	(5,662)	(6,018)	(3,722)
Other Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Less: allowance for loan losses	(2,949)	$ (2,841)
Other Consumer \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	207,702		194,098
Less: allowance for loan losses	(2,949)		(2,765)	$ (2,626)	$ (2,769)	$ (3,308)
Automobile Loan \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 10,100		$ 18,100