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Loans and Allowance for Credit Losses - Schedule of Company's Loan Portfolio as of the Dates Indicated (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 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	$ 14,145,520		$ 13,973,428
Allowance for loan losses	(156,146)	$ (149,190)	(148,993)	$ (147,955)	$ (140,938)	$ (142,211)
Unamortized premiums, net of unearned discounts and deferred fees	(35,601)		(25,068)
Loans after the allowance for loan losses, unamortized premiums, unearned discounts and deferred fees	13,953,773		13,799,367
Financing receivable, accrued interest, before allowance for credit loss	55,800		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	3,084,186		3,034,068
Allowance for loan losses	(28,916)	(28,863)	(26,959)	(29,535)	(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	5,440,411		5,457,349
Allowance for loan losses	(69,079)	(64,629)	(65,475)	(59,524)	(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	447,157		386,999
Allowance for loan losses	(6,388)	(6,204)	(6,666)	(7,663)	(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	1,108,163		1,085,763
Allowance for loan losses	(16,748)	(14,631)	(14,913)	(15,228)	(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	2,562,808		2,565,485
Allowance for loan losses	(25,829)	(25,935)	(25,954)	(27,012)	(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	1,254,105		1,208,231
Allowance for loan losses	(5,781)	(5,684)	(5,595)	(6,044)	(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	248,690		235,533
Allowance for loan losses	$ (3,405)	$ (3,244)	$ (3,431)	$ (2,949)	$ (2,841)	$ (2,765)