Loan Portfolio and Credit Quality Impaired Loans With and Without Related Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Recorded Investment:
Recorded investment, With no related allowance recorded	$ 11,374	$ 14,491
Recorded investment, With an allowance recorded	4,269	8,086
Recorded investment, Total	15,643	22,577
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	13,051	17,288
Unpaid principal balance, With an allowance recorded	4,471	8,640
Unpaid principal balance, Total	17,522	25,928
Related Allowance	1,235	654
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	14,345	15,311
Average recorded investment, With an allowance recorded	6,472	9,651
Average recorded investment, Total	20,817	24,962
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	2,061	2,036
Interest income recognized while impaired, With an allowance recorded	756	416
Interest income recognized while impaired, Total	2,817	2,452
Commercial and industrial
Recorded Investment:
Recorded investment, With no related allowance recorded	1,435	1,434
Recorded investment, With an allowance recorded	1,770	242
Recorded investment, Total	3,205	1,676
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	2,397	2,238
Unpaid principal balance, With an allowance recorded	1,972	242
Unpaid principal balance, Total	4,369	2,480
Related Allowance	598	58
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	1,614	1,594
Average recorded investment, With an allowance recorded	631	156
Average recorded investment, Total	2,245	1,750
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	69	50
Interest income recognized while impaired, With an allowance recorded	15	4
Interest income recognized while impaired, Total	84	54
Commercial tax-exempt
Recorded Investment:
Recorded investment, With no related allowance recorded	0	0
Recorded investment, With an allowance recorded	0	0
Recorded investment, Total	0	0
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	0	0
Unpaid principal balance, With an allowance recorded	0	0
Unpaid principal balance, Total	0	0
Related Allowance	0	0
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	0	1,001
Average recorded investment, With an allowance recorded	0	0
Average recorded investment, Total	0	1,001
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	0	80
Interest income recognized while impaired, With an allowance recorded	0	0
Interest income recognized while impaired, Total	0	80
Commercial real estate
Recorded Investment:
Recorded investment, With no related allowance recorded	546	1,832
Recorded investment, With an allowance recorded	0	6,855
Recorded investment, Total	546	8,687
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	900	3,453
Unpaid principal balance, With an allowance recorded	0	7,284
Unpaid principal balance, Total	900	10,737
Related Allowance	0	362
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	2,002	3,098
Average recorded investment, With an allowance recorded	4,087	6,980
Average recorded investment, Total	6,089	10,078
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	1,544	1,546
Interest income recognized while impaired, With an allowance recorded	705	322
Interest income recognized while impaired, Total	2,249	1,868
Construction and land
Recorded Investment:
Recorded investment, With no related allowance recorded	0	109
Recorded investment, With an allowance recorded	0	0
Recorded investment, Total	0	109
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	0	109
Unpaid principal balance, With an allowance recorded	0	0
Unpaid principal balance, Total	0	109
Related Allowance	0	0
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	50	172
Average recorded investment, With an allowance recorded	0	0
Average recorded investment, Total	50	172
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	16	0
Interest income recognized while impaired, With an allowance recorded	0	0
Interest income recognized while impaired, Total	16	0
Residential
Recorded Investment:
Recorded investment, With no related allowance recorded	8,403	9,337
Recorded investment, With an allowance recorded	780	828
Recorded investment, Total	9,183	10,165
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	8,764	9,709
Unpaid principal balance, With an allowance recorded	780	828
Unpaid principal balance, Total	9,544	10,537
Related Allowance	75	89
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	9,638	9,033
Average recorded investment, With an allowance recorded	785	2,469
Average recorded investment, Total	10,423	11,502
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	408	360
Interest income recognized while impaired, With an allowance recorded	22	89
Interest income recognized while impaired, Total	430	449
Home equity
Recorded Investment:
Recorded investment, With no related allowance recorded	990	1,779
Recorded investment, With an allowance recorded	1,719	36
Recorded investment, Total	2,709	1,815
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	990	1,779
Unpaid principal balance, With an allowance recorded	1,719	36
Unpaid principal balance, Total	2,709	1,815
Related Allowance	562	20
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	1,041	413
Average recorded investment, With an allowance recorded	959	36
Average recorded investment, Total	2,000	449
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	24	0
Interest income recognized while impaired, With an allowance recorded	11	1
Interest income recognized while impaired, Total	35	1
Consumer and other
Recorded Investment:
Recorded investment, With no related allowance recorded	0	0
Recorded investment, With an allowance recorded	0	125
Recorded investment, Total	0	125
Unpaid principal balance:
Unpaid principal balance, With no related allowance recorded	0	0
Unpaid principal balance, With an allowance recorded	0	250
Unpaid principal balance, Total	0	250
Related Allowance	0	125
Average Recorded Investment:
Average recorded investment, With no related allowance recorded	0	0
Average recorded investment, With an allowance recorded	10	10
Average recorded investment, Total	10	10
Interest Income Recognized while Impaired:
Interest income recognized while impaired, With no related allowance recorded	0	0
Interest income recognized while impaired, With an allowance recorded	3	0
Interest income recognized while impaired, Total	$ 3	$ 0