Loans and Allowance for Credit Losses - Schedule of Company's Loan Portfolio as of the Dates Indicated (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	$ 23,387,994	$ 23,574,496
Allowance for loan losses	(327,892)	(331,841)	$ (224,310)	$ (228,952)
Unearned discounts and deferred fees, net	(463,950)	(489,431)
Net loans	22,596,152	22,753,224
Financing receivable, accrued interest, before allowance for credit loss	81,200	81,900
Commercial and industrial \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	4,373,727	4,324,615
Allowance for loan losses	(59,508)	(65,768)	(46,490)	(41,090)
Commercial real estate \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	9,475,352	9,529,071
Allowance for loan losses	(178,826)	(164,376)	(106,634)	(116,175)
Commercial construction \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	503,192	567,597
Allowance for loan losses	(11,123)	(21,058)	(8,514)	(8,462)
Business banking \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	1,545,197	1,603,489
Allowance for loan losses	(22,159)	(22,921)	(20,315)	(19,899)
Residential real estate \| Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	5,466,975	5,516,114
Allowance for loan losses	(42,641)	(44,177)	(31,096)	(32,291)
Consumer home equity \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	1,765,450	1,758,099
Allowance for loan losses	(9,627)	(9,171)	(6,891)	(7,472)
Other consumer \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	258,101	275,511
Allowance for loan losses	$ (4,008)	$ (4,370)	$ (4,370)	$ (3,563)

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

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Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Amount of unamortized loan commitment, origination, and other costs (fees) and purchase premium (discount) on financing receivable recognized as adjustment to yield. Excludes financing receivable covered under loss sharing agreement.

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