Loans, Allowance for Loan Losses and Credit Quality (Age Analysis of Past Due Financing Receivables) (Details) $ in Thousands		Jun. 30, 2019 USD ($) loan		Dec. 31, 2018 USD ($) loan
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		389		400
Number of Loans 60-89 Days | loan		49		56
Number of Loans 90 Days or More | loan		107		110
Number of Loans Total Past Due | loan		545		566
Principal Balance Total Past Due		$ 22,047		$ 46,348
Current		8,928,740		6,859,846
Total loans	[1]	8,950,787		6,906,194
Recorded Investment >90 Days and Accruing		$ 2,328		$ 5
Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		1		0
Number of Loans 60-89 Days | loan		0		4
Number of Loans 90 Days or More | loan		4		11
Number of Loans Total Past Due | loan		5		15
Principal Balance Total Past Due		$ 405		$ 26,693
Current		1,400,519		1,066,936
Total loans	[1]	1,400,924		1,093,629
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		5		9
Number of Loans 60-89 Days | loan		2		0
Number of Loans 90 Days or More | loan		1		8
Number of Loans Total Past Due | loan		8		17
Principal Balance Total Past Due		$ 1,070		$ 3,877
Current		4,056,996		3,247,371
Total loans	[1]	4,058,066		3,251,248
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		2		1
Number of Loans 60-89 Days | loan		0		0
Number of Loans 90 Days or More | loan		0		1
Number of Loans Total Past Due | loan		2		2
Principal Balance Total Past Due		$ 706		$ 1,582
Current		490,892		363,583
Total loans	[1]	491,598		365,165
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		2		15
Number of Loans 60-89 Days | loan		5		19
Number of Loans 90 Days or More | loan		9		24
Number of Loans Total Past Due | loan		16		58
Principal Balance Total Past Due		$ 285		$ 755
Current		173,642		163,921
Total loans	[1]	173,927		164,676
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		18		23
Number of Loans 60-89 Days | loan		12		6
Number of Loans 90 Days or More | loan		40		25
Number of Loans Total Past Due | loan		70		54
Principal Balance Total Past Due		$ 13,944		$ 8,389
Current		1,641,238		914,905
Total loans	[1]	1,655,182		923,294
Recorded Investment >90 Days and Accruing		$ 1,776	[2]	$ 0
Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan		25		22
Number of Loans 60-89 Days | loan		10		12
Number of Loans 90 Days or More | loan		34		29
Number of Loans Total Past Due | loan		69		63
Principal Balance Total Past Due		$ 5,242		$ 4,849
Current		1,139,257		1,087,235
Total loans	[1]	1,144,499		1,092,084
Recorded Investment >90 Days and Accruing		$ 541	[2]	$ 0
Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Number of Loans 30-59 Days | loan	[3]	336		330
Number of Loans 60-89 Days | loan	[3]	20		15
Number of Loans 90 Days or More | loan	[3]	19		12
Number of Loans Total Past Due | loan	[3]	375		357
Principal Balance Total Past Due	[3]	$ 395		$ 203
Current	[3]	26,196		15,895
Total loans	[1],[3]	26,591		16,098
Recorded Investment >90 Days and Accruing	[3]	11		5
Financial Asset, 30 to 59 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		6,435		8,402
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		296		0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		637		1,627
Financial Asset, 30 to 59 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		706		1,271
Financial Asset, 30 to 59 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		51		506
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		3,306		3,486
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		1,185		1,331
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due	[3]	254		181
Financial Asset, 60 to 89 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		3,272		1,854
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0		382
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		352		0
Financial Asset, 60 to 89 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0		0
Financial Asset, 60 to 89 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		95		87
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		2,168		521
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		618		855
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due	[3]	39		9
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		12,340		36,092
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial and Industrial [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		109		26,311
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		81		2,250
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Construction Loans [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		0		311
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Small Business [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		139		162
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Real Estate [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		8,470		4,382
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Home Equity [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due		3,439		2,663
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer - Other [Member]
Age Analysis of Past Due Financing Receivables
Principal Balance Total Past Due	[3]	$ 102		$ 13

[1] The amount of net deferred costs on originated loans included in the ending balance was $7.9 million and $7.1 million at June 30, 2019 and December 31, 2018, respectively. Net unamortized discounts on acquired loans not deemed to be purchased credit impaired ("PCI") included in the ending balance was $29.8 million and $15.2 million at June 30, 2019 and December 31, 2018, respectively.

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

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