Loans, Allowance for Credit Losses and Credit Quality Financing Receivable Past Due (Details) $ in Thousands	Sep. 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	274	447
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 1	$ 2,157
Financing Receivable, Past Due	29,589	25,485
Financing Receivable, Not Past Due	9,375,604	8,848,154
Loans and Leases Receivable, Gross	$ 9,405,193	$ 8,873,639
Number Of Financing Receivables Total Past Due | loan	411	603
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	30	43
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	107	113
Commercial And Industrial [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	1	1
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0
Financing Receivable, Past Due	4,590	1,336
Financing Receivable, Not Past Due	2,057,755	1,393,700
Loans and Leases Receivable, Gross	$ 2,062,345	$ 1,395,036
Number Of Financing Receivables Total Past Due | loan	12	8
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	6	2
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	5	5
Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	1	7
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 218	[1]
Financing Receivable, Past Due	9,723	3,922
Financing Receivable, Not Past Due	4,115,741	3,998,437
Loans and Leases Receivable, Gross	$ 4,125,464	$ 4,002,359
Number Of Financing Receivables Total Past Due | loan	8	16
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	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	0	560
Financing Receivable, Not Past Due	573,334	546,733
Loans and Leases Receivable, Gross	$ 573,334	$ 547,293
Number Of Financing Receivables Total Past Due | loan	0	1
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
Small Business [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	6	11
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0
Financing Receivable, Past Due	1,093	967
Financing Receivable, Not Past Due	166,539	173,530
Loans and Leases Receivable, Gross	$ 167,632	$ 174,497
Number Of Financing Receivables Total Past Due | loan	22	20
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	12	6
Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	11	17
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 1,652	[1]
Financing Receivable, Past Due	9,293	12,312
Financing Receivable, Not Past Due	1,343,012	1,578,257
Loans and Leases Receivable, Gross	$ 1,352,305	$ 1,590,569
Number Of Financing Receivables Total Past Due | loan	55	72
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	7	17
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	37	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	18	23
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 265	[1]
Financing Receivable, Past Due	4,615	6,067
Financing Receivable, Not Past Due	1,096,439	1,127,731
Loans and Leases Receivable, Gross	$ 1,101,054	$ 1,133,798
Number Of Financing Receivables Total Past Due | loan	62	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	36	40
Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	237	387	[2]
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 1	$ 22	[2]
Financing Receivable, Past Due	275	321	[2]
Financing Receivable, Not Past Due	22,784	29,766	[2]
Loans and Leases Receivable, Gross	$ 23,059	$ 30,087	[2]
Number Of Financing Receivables Total Past Due | loan	252	415	[2]
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	3	12	[2]
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	12	16	[2]
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 14,432	$ 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	3,608	323
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	8,269	194
Financial Asset, 60 to 89 Days Past Due [Member] | Construction Loans [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Small Business [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	455	15
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,631	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	468	524
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1	44	[2]
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	10,902	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	930	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	1,355	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	124	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	5,870	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	2,566	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	57	32	[2]
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,255	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	52	253
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	99	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	514	837
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Real Estate [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,792	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	1,581	1,689
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer - Other [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 217	$ 245	[2]

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

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