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Loans and Allowance for Credit Losses - Summary of Company's Loan Portfolio as of the Dates Indicated (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	$ 13,973,428	$ 13,575,531
Allowance for loan losses	(148,993)	(142,211)	$ (97,787)	$ (113,031)
Unamortized premiums, net of unearned discounts and deferred fees, net of costs	(25,068)	(13,003)
Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees and costs	13,799,367	13,420,317
Financing receivable, accrued interest, before allowance for credit loss	53,900	45,200
Commercial Portfolio Segment \| Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	3,034,068	3,150,946
Allowance for loan losses	(26,959)	(26,859)	(18,018)	(26,617)
Commercial Portfolio Segment \| Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	5,457,349	5,155,323
Allowance for loan losses	(65,475)	(54,730)	(52,373)	(54,569)
Commercial Portfolio Segment \| Commercial construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	386,999	336,276
Allowance for loan losses	(6,666)	(7,085)	(2,585)	(4,553)
Commercial Portfolio Segment \| Business banking
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	1,085,763	1,090,492
Allowance for loan losses	(14,913)	(16,189)	(10,983)	(13,152)
Residential Portfolio Segment \| Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	2,565,485	2,460,849
Allowance for loan losses	(25,954)	(28,129)	(6,556)	(6,435)
Consumer Portfolio Segment \| Consumer home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	1,208,231	1,187,547
Allowance for loan losses	(5,595)	(6,454)	(3,722)	(3,744)
Consumer Portfolio Segment \| Other Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	235,533	194,098
Allowance for loan losses	(3,431)	(2,765)	$ (3,308)	$ (3,467)
Consumer Portfolio Segment \| Automobile loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	7,200	18,100
Consumer Portfolio Segment \| Home Improvement Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees and costs	$ 178,900	$ 121,100