Loans and Allowance for Credit Losses - Schedule of Company's Loan Portfolio as of the Dates Indicated (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	$ 18,204,485	$ 18,079,084
Allowance for loan losses	(224,310)	(228,952)	$ (149,190)	$ (148,993)
Unearned discounts and deferred fees, net	(288,790)	(300,730)
Loans after the allowance for loan losses and net unearned discounts and deferred fees	17,691,385	17,549,402
Financing receivable, accrued interest, before allowance for credit loss	64,100	66,700
Commercial and industrial \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	3,442,691	3,296,068
Allowance for loan losses	(46,490)	(41,090)	(28,863)	(26,959)
Commercial real estate \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	7,176,744	7,119,523
Allowance for loan losses	(106,634)	(116,175)	(64,629)	(65,475)
Commercial construction \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	461,269	494,842
Allowance for loan losses	(8,514)	(8,462)	(6,204)	(6,666)
Business banking \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	1,419,943	1,448,176
Allowance for loan losses	(20,315)	(19,899)	(14,631)	(14,913)
Residential real estate \| Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	4,038,712	4,063,659
Allowance for loan losses	(31,096)	(32,291)	(25,935)	(25,954)
Consumer home equity \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	1,405,261	1,385,394
Allowance for loan losses	(6,891)	(7,472)	(5,684)	(5,595)
Other Consumer \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unearned discounts and deferred fees, net	259,865	271,422
Allowance for loan losses	$ (4,370)	$ (3,563)	$ (3,244)	$ (3,431)

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

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Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
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-Paragraph c
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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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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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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