Loans and Allowance for Credit Losses - Schedule of Accounts, Notes, Loans and Financing Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	$ 14,088,747	$ 13,973,428
Allowance for loan losses	(149,190)	(148,993)	$ (140,938)	$ (142,211)
Unamortized premiums, net of unearned discounts and deferred fees, net of costs	(32,947)	(25,068)
Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees and costs	13,906,610	13,799,367
Financing receivable, accrued interest, before allowance for credit loss	54,200	53,900
Commercial and industrial \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	3,084,580	3,034,068
Allowance for loan losses	(28,863)	(26,959)	(26,929)	(26,859)
Commercial real estate \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	5,519,505	5,457,349
Allowance for loan losses	(64,629)	(65,475)	(55,193)	(54,730)
Commercial construction \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	388,024	386,999
Allowance for loan losses	(6,204)	(6,666)	(7,578)	(7,085)
Business banking \| Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,100,637	1,085,763
Allowance for loan losses	(14,631)	(14,913)	(15,085)	(16,189)
Residential real estate \| Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	2,544,462	2,565,485
Allowance for loan losses	(25,935)	(25,954)	(27,130)	(28,129)
Consumer home equity \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	1,217,141	1,208,231
Allowance for loan losses	(5,684)	(5,595)	(6,182)	(6,454)
Other Consumer \| Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Line Items]
Gross loans before unamortized premiums, unearned discounts and deferred fees	234,398	235,533
Allowance for loan losses	$ (3,244)	$ (3,431)	$ (2,841)	$ (2,765)

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
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-SubTopic 20
-Name Accounting Standards Codification
-Section 45
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Reference 1: 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/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes 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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
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