Loans and Allowance for Credit Losses - Schedule of Changes in Allowance for Loan Losses by Loan Category (Details) - USD ($) $ in Thousands		12 Months Ended
Jan. 01, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 97,787	$ 148,993	$ 142,211	$ 97,787
Initial reserve on PCD loans at merger		55,830
Charge-offs		(47,757)	(15,092)	(4,831)
Recoveries		4,506	2,965	4,244
Provision (release)		67,380	20,052	17,925
Ending balance		228,952	148,993	142,211
Allowance for loan losses		228,952	148,993	142,211
Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	27,086		(1,143)	27,086
Ending balance				(1,143)
Allowance for loan losses				(1,143)
Cumulative effect accounting adjustment \| Accounting Standards Update 2022-02
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance			(1,100)
Ending balance				(1,100)
Allowance for loan losses				(1,100)
Cumulative effect accounting adjustment \| Accounting Standards Update 2016-13
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	27,100			27,100
Initial reserve on PCD loans at merger	100
Allowance for loan losses
Commercial Portfolio Segment \| Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	18,018	26,959	26,859	18,018
Initial reserve on PCD loans at merger		6,589
Charge-offs		(40)	(13)	(269)
Recoveries		99	296	1,322
Provision (release)		7,483	(230)	(3,745)
Ending balance		41,090	26,959	26,859
Allowance for loan losses		41,090	26,959	26,859
Commercial Portfolio Segment \| Commercial and industrial \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	11,533		47	11,533
Ending balance				47
Allowance for loan losses				47
Commercial Portfolio Segment \| Commercial real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	52,373	65,475	54,730	52,373
Initial reserve on PCD loans at merger		45,656
Charge-offs		(42,556)	(8,008)	0
Recoveries		2,207	198	91
Provision (release)		45,393	18,555	8,921
Ending balance		116,175	65,475	54,730
Allowance for loan losses		116,175	65,475	54,730
Commercial Portfolio Segment \| Commercial real estate \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(6,655)		0	(6,655)
Ending balance				0
Allowance for loan losses				0
Commercial Portfolio Segment \| Commercial construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	2,585	6,666	7,085	2,585
Initial reserve on PCD loans at merger		26
Charge-offs		0	0	0
Recoveries		0	0	0
Provision (release)		1,770	(419)	3,015
Ending balance		8,462	6,666	7,085
Allowance for loan losses		8,462	6,666	7,085
Commercial Portfolio Segment \| Commercial construction \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,485		0	1,485
Ending balance				0
Allowance for loan losses				0
Commercial Portfolio Segment \| Business banking
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	10,983	14,913	16,189	10,983
Initial reserve on PCD loans at merger		581
Charge-offs		(2,498)	(4,645)	(2,292)
Recoveries		1,189	1,867	2,069
Provision (release)		5,714	1,642	(731)
Ending balance		19,899	14,913	16,189
Allowance for loan losses		19,899	14,913	16,189
Commercial Portfolio Segment \| Business banking \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,160		(140)	6,160
Ending balance				(140)
Allowance for loan losses				(140)
Residential Portfolio Segment \| Residential real estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	6,556	25,954	28,129	6,556
Initial reserve on PCD loans at merger		2,919
Charge-offs		(28)	0	0
Recoveries		205	97	94
Provision (release)		3,241	(1,423)	7,990
Ending balance		32,291	25,954	28,129
Allowance for loan losses		32,291	25,954	28,129
Residential Portfolio Segment \| Residential real estate \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	13,489		(849)	13,489
Ending balance				(849)
Allowance for loan losses				(849)
Consumer Portfolio Segment \| Consumer home equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,722	5,595	6,454	3,722
Initial reserve on PCD loans at merger		40
Charge-offs		(59)	(7)	(1)
Recoveries		136	41	24
Provision (release)		1,760	(692)	852
Ending balance		7,472	5,595	6,454
Allowance for loan losses		7,472	5,595	6,454
Consumer Portfolio Segment \| Consumer home equity \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,857		(201)	1,857
Ending balance				(201)
Allowance for loan losses				(201)
Consumer Portfolio Segment \| Other Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,308	3,431	2,765	3,308
Initial reserve on PCD loans at merger		19
Charge-offs		(2,576)	(2,419)	(2,269)
Recoveries		670	466	644
Provision (release)		2,019	2,619	1,623
Ending balance		3,563	3,431	2,765
Allowance for loan losses		$ 3,563	3,431	2,765
Consumer Portfolio Segment \| Other Consumer \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(541)		0	(541)
Ending balance				0
Allowance for loan losses				0
Consumer Portfolio Segment \| Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	242		$ 0	242
Charge-offs				0
Recoveries				0
Provision (release)				0
Ending balance				0
Allowance for loan losses				0
Consumer Portfolio Segment \| Other \| Cumulative effect accounting adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ (242)			$ (242)
Allowance for loan losses

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
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Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

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

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