Loans, Allowance for Credit Losses and Credit Quality - Financing Receivable Past Due (Details) $ in Thousands		Sep. 30, 2023 USD ($) loan		Dec. 31, 2022 USD ($) loan	Sep. 30, 2022 USD ($)
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		445		481
Total loans		$ 14,224,235	[1]	$ 13,928,675
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		31		35
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		51		46
Number Of Financing Receivables Total Past Due | loan		527		562
Total		$ 14,224,235		$ 13,928,675	$ 13,700,350
Financing Receivable, 90 Days or More Past Due, Still Accruing		3		0
Financing receivable, net deferred costs		6,100		5,000
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		12,404		5,934
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		2,928		6,560
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		15,804		29,426
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		31,136		41,920
Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 14,193,099		$ 13,886,755
Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		1		3
Total loans		$ 1,653,003	[1]	$ 1,635,103
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		2		1
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		3		3
Number Of Financing Receivables Total Past Due | loan		6		7
Total		$ 1,653,003		$ 1,635,103	1,548,349	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Commercial And Industrial [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		63		49
Commercial And Industrial [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		527		175
Commercial And Industrial [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		390		23,726
Commercial And Industrial [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		980		23,950
Commercial And Industrial [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 1,652,023		$ 1,611,153
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		2		7
Total loans		$ 7,896,230	[1]	$ 7,760,230
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		1		5
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		2		3
Number Of Financing Receivables Total Past Due | loan		5		15
Total		$ 7,896,230		$ 7,760,230	7,677,917	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Commercial Real Estate [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		736		2,052
Commercial Real Estate [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		659		4,971
Commercial Real Estate [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		11,688		2,977
Commercial Real Estate [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		13,083		10,000
Commercial Real Estate [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 7,883,147		$ 7,750,230
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		1		0
Total loans		$ 965,442	[1]	$ 1,154,413
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		0		0
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		0		0
Number Of Financing Receivables Total Past Due | loan		1		0
Total		$ 965,442		$ 1,154,413	1,185,157	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Construction Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		7,499		0
Construction Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		0		0
Construction Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		0		0
Construction Loans [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		7,499		0
Construction Loans [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 957,943		$ 1,154,413
Small Business [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		7		12
Total loans		$ 245,335	[1]	$ 219,102
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		4		3
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		11		3
Number Of Financing Receivables Total Past Due | loan		22		18
Total		$ 245,335		$ 219,102	209,567	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Small Business [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		91		111
Small Business [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		69		25
Small Business [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		204		5
Small Business [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		364		141
Small Business [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 244,971		$ 218,961
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		14		8
Total loans		$ 2,338,102	[1]	$ 2,035,524
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		8		8
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		14		16
Number Of Financing Receivables Total Past Due | loan		36		32
Total		$ 2,338,102		$ 2,035,524	1,959,254	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Residential Real Estate [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		2,405		1,654
Residential Real Estate [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		1,446		1,105
Residential Real Estate [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		2,067		1,725
Residential Real Estate [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		5,918		4,484
Residential Real Estate [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 2,332,184		$ 2,031,040
Home Equity Loan [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan		11		19
Total loans	[1]	$ 1,095,555
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan		4		3
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan		17		17
Number Of Financing Receivables Total Past Due | loan		32		39
Total		$ 1,095,555		$ 1,088,750	$ 1,087,170	[1]
Financing Receivable, 90 Days or More Past Due, Still Accruing		0		0
Home Equity Loan [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		919		1,647
Home Equity Loan [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		185		201
Home Equity Loan [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans		1,431		965
Home Equity Loan [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans		2,535		2,813
Home Equity Loan [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans		$ 1,093,020		$ 1,085,937
Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	[2]	409		432
Total loans		$ 30,568		$ 35,553
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	[2]	12		15
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	[2]	4		4
Number Of Financing Receivables Total Past Due | loan	[2]	425		451
Total	[2]	$ 30,568		$ 35,553
Financing Receivable, 90 Days or More Past Due, Still Accruing	[2]	3		0
Consumer - Other [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans	[2]	691		421
Consumer - Other [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans	[2]	42		83
Consumer - Other [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Total loans	[2]	24		28
Consumer - Other [Member] | Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Total loans	[2]	757		532
Consumer - Other [Member] | Financial Asset, Not Past Due
Financing Receivable, Past Due [Line Items]
Total loans	[2]	$ 29,811		$ 35,021

[1] Loan origination dates in the tables above reflect the original origination date, or the date of a material modification of a previously originated loan.(2)Loans originated as part of the Paycheck Protection Program ("PPP") established by the Coronavirus Aid, Relief and Economic Security Act (the "CARES Act") are included within commercial and industrial under the 2021 and 2020 vintage year and "pass" category as these loans are 100% guaranteed by the U.S. Government. Outstanding PPP loans totaled $5.1 million and $11.1 million as of September 30, 2023 and 2022, respectively.

[2] Other consumer portfolio is inclusive of deposit account overdrafts recorded as loan balances. (2)The amount of net deferred costs on originated loans included in the ending balance was $6.1 million and $5.0 million at September 30, 2023 and December 31, 2022, respectively.