Allowance for Loan and Lease Loss and Credit Quality (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($) risk_code	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) risk_code	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Unallocated allowance | $	$ 0		$ 0		$ 0
Financing receivables modified as troubled debt restructurings within the previous 12 months | $	0	$ 0	$ 0	$ 0
Homogeneous | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are considered past due			30 days
Restructured Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Impaired loans classified as accruing restructured loans | $	$ 14,300		$ 14,300		13,900
Loan collateral coverage (as a percent) (greater than or equal to)			100.00%
Available commitments for troubled debt restructurings outstanding | $			$ 500		$ 338
Minimal Risk | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	1		1
Low Risk | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	2		2
Modest Risk | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	3		3
Average Risk | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	4		4
Acceptable Risk | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	5		5
Pass/Watch | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	6		6
Special Mention | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	7		7
Special Mention | Homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	7		7
Special Mention | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			30 days
Special Mention | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			59 days
Special Mention | Homogeneous Retail | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			30 days
Special Mention | Homogeneous Retail | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			89 days
Substandard | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	8		8
Substandard | Homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	8		8
Substandard | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			60 days
Substandard | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			89 days
Substandard | Homogeneous Retail
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	8		8
Substandard | Homogeneous Retail | Minimum | Open End Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			90 days
Substandard | Homogeneous Retail | Minimum | Closed End Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			90 days
Substandard | Homogeneous Retail | Maximum | Open End Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			180 days
Substandard | Homogeneous Retail | Maximum | Closed End Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			120 days
Doubtful | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	9		9
Doubtful | Homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	9		9
Doubtful | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			90 days
Doubtful | Homogeneous | Maximum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			179 days
Loss | Non homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	10		10
Loss | Homogeneous
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	10		10
Loss | Homogeneous | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			180 days
Loss | Homogeneous Retail
Financing Receivable, Allowance for Credit Loss [Line Items]
Internal risk rating code (number)	10		10
Loss | Homogeneous Retail | Minimum
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			120 days
Loss | Homogeneous Retail | Minimum | Closed End Loan
Financing Receivable, Allowance for Credit Loss [Line Items]
Period before loans and leases are classified as substandard			120 days