Loans, Allowance for Loan Losses and Credit Quality (Age Analysis of Past Due Financing Receivables) (Details) $ in Thousands		Sep. 30, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		317	319
Number of Loans 60-89 Days | loan		45	48
Number of Loans 90 Days or More | loan		90	92
Number of Loans Total Past Due | loan		452	459
Principal Balance Total Past Due		$ 46,117	$ 48,746
Current		6,481,285	6,306,807
Total loans	[1]	6,527,402	6,355,553
Recorded Investment >90 Days and Accruing		$ 9	$ 8
Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		3	2
Number of Loans 60-89 Days | loan		5	2
Number of Loans 90 Days or More | loan		10	14
Number of Loans Total Past Due | loan		18	18
Principal Balance Total Past Due		$ 29,390	$ 32,572
Current		974,390	855,956
Total loans	[1]	1,003,780	888,528
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		7	7
Number of Loans 60-89 Days | loan		5	0
Number of Loans 90 Days or More | loan		6	9
Number of Loans Total Past Due | loan		18	16
Principal Balance Total Past Due		$ 4,467	$ 4,853
Current		3,128,024	3,111,708
Total loans	[1]	3,132,491	3,116,561
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		0	0
Number of Loans 60-89 Days | loan		0	0
Number of Loans 90 Days or More | loan		0	0
Number of Loans Total Past Due | loan		0	0
Principal Balance Total Past Due		$ 0	$ 0
Current		352,491	401,797
Total loans	[1]	352,491	401,797
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Small Business [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		9	17
Number of Loans 60-89 Days | loan		6	11
Number of Loans 90 Days or More | loan		17	10
Number of Loans Total Past Due | loan		32	38
Principal Balance Total Past Due		$ 682	$ 540
Current		148,518	131,830
Total loans	[1]	149,200	132,370
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		10	6
Number of Loans 60-89 Days | loan		12	13
Number of Loans 90 Days or More | loan		19	22
Number of Loans Total Past Due | loan		41	41
Principal Balance Total Past Due		$ 6,863	$ 6,726
Current		794,947	747,603
Total loans	[1]	801,810	754,329
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		16	22
Number of Loans 60-89 Days | loan		9	6
Number of Loans 90 Days or More | loan		25	20
Number of Loans Total Past Due | loan		50	48
Principal Balance Total Past Due		$ 4,531	$ 3,786
Current		1,069,430	1,048,302
Total loans	[1]	1,073,961	1,052,088
Recorded Investment >90 Days and Accruing		$ 0	$ 0
Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		272	265	[2]
Number of Loans 60-89 Days | loan		8	16	[2]
Number of Loans 90 Days or More | loan		13	17	[2]
Number of Loans Total Past Due | loan		293	298	[2]
Principal Balance Total Past Due		$ 184	$ 269	[2]
Current		13,485	9,611	[2]
Total loans	[1]	13,669	9,880	[2]
Recorded Investment >90 Days and Accruing		9	8
Financing Receivables, 30 to 59 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		5,092	5,971
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		265	195
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		2,188	3,060
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		483	339
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		1,129	870
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		909	1,310
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		118	197	[2]
Financing Receivables, 60 to 89 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		4,524	3,377
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		431	370
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		849	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		60	144
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		2,367	2,385
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		797	451
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		20	27	[2]
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		36,501	39,398
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		28,694	32,007
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		1,430	1,793
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		139	57
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		3,367	3,471
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		2,825	2,025
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		$ 46	$ 45	[2]

[1] The amount of net deferred costs on originated loans included in the ending balance was $6.9 million and $6.1 million at September 30, 2018 and December 31, 2017, respectively. Net unamortized discounts on acquired loans not deemed to be purchased credit impaired ("PCI") included in the ending balance was $8.6 million and $9.4 million at September 30, 2018 and December 31, 2017, respectively.

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