Allowance for Loan and Lease Loss and Credit Quality (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) risk_code	Dec. 31, 2016 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Unallocated Allowance | $	$ 0	$ 0
Provision for loan and lease losses, subsequent deterioration of purchased impaired loans | $	396,000	1,400,000
Allowance for loan and lease losses, purchased impaired loans, period increase (decrease) | $	733,000	1,100,000
Financing receivables modified as troubled debt restructurings within the previous 12 months for which there was a payment default | $	$ 118,000	926,000
Homogeneous | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Duration of time account is past due before risk rating is applied	30 days
Restructured Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired loans | $	$ 32,200,000	40,700,000
Percentage of loan collateral balance, greater than or equal to	100.00%
Available commitments for troubled debt restructurings outstanding | $	$ 917,000	$ 0
Minimal Risk | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	1
Loss | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	10
Loss | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	180 days
Loss | Homogeneous Retail | Minimum | Open-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	180 days
Loss | Homogeneous Retail | Minimum | Closed-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	120 days
Low Risk | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	2
Modest Risk | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	3
Average Risk | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	4
Acceptable Risk | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	5
Pass/Watch | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	6
Special Mention | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	7
Special Mention | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	30 days
Special Mention | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	59 days
Special Mention | Homogeneous Retail | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	30 days
Special Mention | Homogeneous Retail | Maximum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	89 days
Substandard | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	8
Substandard | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	60 days
Substandard | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	89 days
Substandard | Homogeneous Retail | Minimum | Open-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	90 days
Substandard | Homogeneous Retail | Minimum | Closed-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	90 days
Substandard | Homogeneous Retail | Maximum | Open-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	180 days
Substandard | Homogeneous Retail | Maximum | Closed-End Loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	120 days
Doubtful | Non Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	9
Doubtful | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	90 days
Doubtful | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	179 days