Loans, Allowance for Credit Losses and Credit Quality Financing Receivable Past Due (Details) $ in Thousands	Jun. 30, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	206	447
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 58	$ 2,157
Financing Receivable, Past Due	22,770	25,485
Financing Receivable, Not Past Due	9,336,878	8,848,154
Loans and Leases Receivable, Gross	$ 9,359,648	$ 8,873,639
Number Of Financing Receivables Total Past Due | loan	367	603
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	48	43
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	113	113
Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	2	1
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0
Financing Receivable, Past Due	1,077	1,336
Financing Receivable, Not Past Due	2,003,568	1,393,700
Loans and Leases Receivable, Gross	$ 2,004,645	$ 1,395,036
Number Of Financing Receivables Total Past Due | loan	8	8
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	0	2
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	6	5
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	5	7
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 218	[1]
Financing Receivable, Past Due	4,553	3,922
Financing Receivable, Not Past Due	4,066,494	3,998,437
Loans and Leases Receivable, Gross	$ 4,071,047	$ 4,002,359
Number Of Financing Receivables Total Past Due | loan	11	16
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	1	1
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	5	8
Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	0	1
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0
Financing Receivable, Past Due	510	560
Financing Receivable, Not Past Due	537,278	546,733
Loans and Leases Receivable, Gross	$ 537,788	$ 547,293
Number Of Financing Receivables Total Past Due | loan	1	1
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	1	0
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	0	0
Small Business [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	13	11
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0
Financing Receivable, Past Due	1,493	967
Financing Receivable, Not Past Due	168,795	173,530
Loans and Leases Receivable, Gross	$ 170,288	$ 174,497
Number Of Financing Receivables Total Past Due | loan	41	20
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	17	3
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	11	6
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	15	17
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 1,652	[1]
Financing Receivable, Past Due	10,399	12,312
Financing Receivable, Not Past Due	1,420,730	1,578,257
Loans and Leases Receivable, Gross	$ 1,431,129	$ 1,590,569
Number Of Financing Receivables Total Past Due | loan	61	72
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	8	17
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	38	38
Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	8	23
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 265	[1]
Financing Receivable, Past Due	4,428	6,067
Financing Receivable, Not Past Due	1,116,095	1,127,731
Loans and Leases Receivable, Gross	$ 1,120,523	$ 1,133,798
Number Of Financing Receivables Total Past Due | loan	56	71
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	40	40
Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	163	387	[2]
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 58	$ 22	[2]
Financing Receivable, Past Due	310	321	[2]
Financing Receivable, Not Past Due	23,918	29,766	[2]
Loans and Leases Receivable, Gross	$ 24,228	$ 30,087	[2]
Number Of Financing Receivables Total Past Due | loan	189	415	[2]
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	13	12	[2]
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	13	16	[2]
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 2,976	$ 4,155
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	323
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	68	194
Financial Asset, 60 to 89 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	510	0
Financial Asset, 60 to 89 Days Past Due [Member] | Small Business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	453	15
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,247	3,055
Financial Asset, 60 to 89 Days Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	671	524
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	27	44	[2]
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	11,733	13,819
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,045	760
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	935	2,038
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Small Business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	123	115
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	6,333	7,020
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	3,203	3,854
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	94	32	[2]
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	8,061	7,511
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	32	253
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	3,550	1,690
Financial Asset, 30 to 59 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	560
Financial Asset, 30 to 59 Days Past Due [Member] | Small Business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	917	837
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2,819	2,237
Financial Asset, 30 to 59 Days Past Due [Member] | Home Equity Line of Credit [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	554	1,689
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 189	$ 245	[2]

[1] (2) Represents purchased credit impaired loans that were accruing interest due to expectations of future cash collections.

[2] (1) Other consumer portfolio is inclusive of deposit account overdrafts recorded as loan balances.