Loans, Allowance for Loan Losses and Credit Quality (Age Analysis of Past Due Financing Receivables) (Details) $ in Thousands		Jun. 30, 2018 USD ($) loan	Dec. 31, 2017 USD ($) loan
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		266	319
Number of Loans 60-89 Days | loan		40	48
Number of Loans 90 Days or More | loan		87	92
Number of Loans Total Past Due | loan		393	459
Principal Balance Total Past Due		$ 57,838	$ 48,746
Current		6,421,433	6,306,807
Total loans	[1]	6,479,271	6,355,553
Recorded Investment >90 Days and Accruing		$ 14	$ 8
Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		5	2
Number of Loans 60-89 Days | loan		2	2
Number of Loans 90 Days or More | loan		12	14
Number of Loans Total Past Due | loan		19	18
Principal Balance Total Past Due		$ 30,701	$ 32,572
Current		945,563	855,956
Total loans	[1]	976,264	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		12	7
Number of Loans 60-89 Days | loan		3	0
Number of Loans 90 Days or More | loan		9	9
Number of Loans Total Past Due | loan		24	16
Principal Balance Total Past Due		$ 14,481	$ 4,853
Current		3,116,856	3,111,708
Total loans	[1]	3,131,337	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		364,225	401,797
Total loans	[1]	364,225	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		8	17
Number of Loans 60-89 Days | loan		8	11
Number of Loans 90 Days or More | loan		14	10
Number of Loans Total Past Due | loan		30	38
Principal Balance Total Past Due		$ 465	$ 540
Current		146,672	131,830
Total loans	[1]	147,137	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		15	6
Number of Loans 60-89 Days | loan		7	13
Number of Loans 90 Days or More | loan		18	22
Number of Loans Total Past Due | loan		40	41
Principal Balance Total Past Due		$ 6,880	$ 6,726
Current		772,541	747,603
Total loans	[1]	779,421	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		21	22
Number of Loans 60-89 Days | loan		11	6
Number of Loans 90 Days or More | loan		24	20
Number of Loans Total Past Due | loan		56	48
Principal Balance Total Past Due		$ 5,197	$ 3,786
Current		1,064,100	1,048,302
Total loans	[1]	1,069,297	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		205	265	[2]
Number of Loans 60-89 Days | loan		9	16	[2]
Number of Loans 90 Days or More | loan		10	17	[2]
Number of Loans Total Past Due | loan		224	298	[2]
Principal Balance Total Past Due		$ 114	$ 269	[2]
Current		11,476	9,611	[2]
Total loans	[1]	11,590	9,880	[2]
Recorded Investment >90 Days and Accruing		14	8
Financing Receivables, 30 to 59 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		14,122	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		291	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		9,675	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		120	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		2,567	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		1,388	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		81	197	[2]
Financing Receivables, 60 to 89 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		5,071	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		368	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		2,534	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		59	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		908	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		1,191	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		11	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		38,645	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		30,042	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		2,272	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		286	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		3,405	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		2,618	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		$ 22	$ 45	[2]

[1] The amount of net deferred costs on originated loans included in the ending balance was $6.7 million and $6.1 million at June 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 $8.8 million and $9.4 million at June 30, 2018 and December 31, 2017, respectively.

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