Loans, Allowance for Credit Losses and Credit Quality Financing Receivable Past Due (Details) $ in Thousands	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan		Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	301	447
Principal Balance Total Past Due | $	$ 21,396	$ 25,485
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	25	43
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	82	113
Number Of Financing Receivables Total Past Due | loan	408	603
Financing Receivable, Not Past Due | $	$ 9,371,470	$ 8,848,154
Total loans | $	9,392,866	8,873,639		$ 6,906,194
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 1	$ 2,157
Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	2	1
Principal Balance Total Past Due | $	$ 1,775	$ 1,336
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	1	2
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	8	5
Number Of Financing Receivables Total Past Due | loan	11	8
Financing Receivable, Not Past Due | $	$ 2,101,377	$ 1,393,700
Total loans | $	2,103,152	1,395,036		1,093,629
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	3	7
Principal Balance Total Past Due | $	$ 924	$ 3,922
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	0	1
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	4	8
Number Of Financing Receivables Total Past Due | loan	7	16
Financing Receivable, Not Past Due | $	$ 4,173,003	$ 3,998,437
Total loans | $	4,173,927	4,002,359		3,251,248
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 218	[1]
Construction Loans [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	0	1
Principal Balance Total Past Due | $	$ 2,794	$ 560
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	2	0
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	0	0
Number Of Financing Receivables Total Past Due | loan	2	1
Financing Receivable, Not Past Due | $	$ 551,135	$ 546,733
Total loans | $	553,929	547,293		365,165
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 0
Small Business [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	14	11
Principal Balance Total Past Due | $	$ 753	$ 967
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	6	3
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	4	6
Number Of Financing Receivables Total Past Due | loan	24	20
Financing Receivable, Not Past Due | $	$ 174,270	$ 173,530
Total loans | $	175,023	174,497		164,676
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 0
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	12	17
Principal Balance Total Past Due | $	$ 11,305	$ 12,312
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	27	38
Number Of Financing Receivables Total Past Due | loan	47	72
Financing Receivable, Not Past Due | $	$ 1,284,878	$ 1,578,257
Total loans | $	1,296,183	1,590,569		923,294
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 1,652	[1]
Home Equity Line of Credit [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	10	23
Principal Balance Total Past Due | $	$ 3,569	$ 6,067
Number of Financing Receivables Sixty to Eighty Nine Days Past Due | loan	5	8
Number Of Financing Receivables Equal To Greater Than Ninety Days | loan	33	40
Number Of Financing Receivables Total Past Due | loan	48	71
Financing Receivable, Not Past Due | $	$ 1,065,221	$ 1,127,731
Total loans | $	1,068,790	1,133,798		1,092,084
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 0	$ 265	[1]
Consumer Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Number Of Financing Receivables Thirty To Fifty Nine Days Past Due | loan	260	387	[2]
Principal Balance Total Past Due | $	$ 276	$ 321	[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	6	16	[2]
Number Of Financing Receivables Total Past Due | loan	269	415	[2]
Financing Receivable, Not Past Due | $	$ 21,586	$ 29,766	[2]
Total loans | $	21,862	30,087	[2]	$ 16,098
Financing Receivable, 90 Days or More Past Due, Still Accruing | $	$ 1	$ 22	[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.