Loans and Allowance for Loan Losses - Summary of Company's Loan Portfolio as of the Dates Indicated (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 12,281,510	$ 9,730,525	$ 8,987,046
Allowance for loan losses	(97,787)	(113,031)	(82,297)	$ (80,655)
Unamortized premiums, net of unearned discounts and deferred fees	(26,442)	(23,536)
Loans, net of allowance for loan losses	12,157,281	9,593,958
Commercial and industrial \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	2,960,527	1,995,016	1,642,184
Allowance for loan losses	(18,018)	(26,617)	(20,919)	(19,321)
Commercial real estate \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	4,522,513	3,573,630	3,535,441
Allowance for loan losses	(52,373)	(54,569)	(34,730)	(32,400)
Commercial construction \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	222,328	305,708	273,774
Allowance for loan losses	(2,585)	(4,553)	(3,424)	(4,606)
Business banking \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,334,694	1,339,164	771,498
Allowance for loan losses	(10,983)	(13,152)	(8,260)	(8,167)
Residential real estate \| Residential Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,926,810	1,370,957	1,428,630
Allowance for loan losses	(6,556)	(6,435)	(6,380)	(7,059)
Consumer home equity \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,100,153	868,270	933,088
Allowance for loan losses	(3,722)	(3,744)	(4,027)	(4,113)
Other consumer \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	214,485	277,780	402,431
Allowance for loan losses	(3,308)	(3,467)	$ (4,173)	$ (4,600)
Home Improvement Loan \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	104,400	81,800
Automobile loans \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 53,300	$ 126,700

Amount excluding accrued interest, of allowance for credit loss on financing receivable.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
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Amount, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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