Allowance for Loan and Lease Loss and Credit Quality (Narrative) (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) risk_code	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Unallocated Allowance | $	$ 0		$ 0
Financing receivables modified as troubled debt restructurings within the previous 12 months for which there was a payment default | $	$ 0	$ 10,200,000
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 | $	$ 15,700,000		13,900,000
Percentage of loan collateral balance, greater than or equal to	100.00%
Available commitments for troubled debt restructurings outstanding | $	$ 1,100,000		$ 338,000
Minimal Risk | Non-Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	1
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
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
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
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	8
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
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
Loss | Non-Homogeneous
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	10
Loss | 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
Financing Receivable, Allowance for Credit Losses [Line Items]
Internal risk rating code	10
Loss | Homogeneous Retail | Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Days past due on account for qualifying credit quality indicator	120 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