Loans - Impaired Loan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Recorded Investment
Impaired loan, with no related allowance, recorded investment	$ 1,099	$ 1,659
Impaired loan, with related allowance, recorded investment	235	1,558
Impaired loan, total, recorded investment	1,334	3,217
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	1,096	1,659
Impaired loan, with related allowance, unpaid principal balance	231	1,553
Impaired loan, total, unpaid principal balance	1,327	3,212
Impaired loan, total, related allowance	64	167
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	1,571	1,834
Impaired loan, with related allowance, average recorded investment	863	1,762
Impaired loan, total, average recorded investment	2,434	3,596
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	89	123
Impaired loan, with related allowance, interest income recognized	50	55
Impaired loan, total, interest income recognized	139	178
Commercial
Recorded Investment
Impaired loan, with no related allowance, recorded investment	28	4
Impaired loan, with related allowance, recorded investment	62	202
Impaired loan, total, recorded investment	90	206
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	28	4
Impaired loan, with related allowance, unpaid principal balance	58	201
Impaired loan, total, unpaid principal balance	86	205
Impaired loan, total, related allowance	55	154
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	44	19
Impaired loan, with related allowance, average recorded investment	354	150
Impaired loan, total, average recorded investment	398	169
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	14	1
Impaired loan, with related allowance, interest income recognized	40	16
Impaired loan, total, interest income recognized	54	17
Commercial real estate | Construction and land development
Recorded Investment
Impaired loan, with no related allowance, recorded investment	0	0
Impaired loan, with related allowance, recorded investment	0	37
Impaired loan, total, recorded investment	0	37
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	0	0
Impaired loan, with related allowance, unpaid principal balance	0	37
Impaired loan, total, unpaid principal balance	0	37
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	0	56
Impaired loan, with related allowance, average recorded investment	21	56
Impaired loan, total, average recorded investment	21	112
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	0	4
Impaired loan, with related allowance, interest income recognized	0	0
Impaired loan, total, interest income recognized	0	4
Commercial real estate | Real estate
Recorded Investment
Impaired loan, with no related allowance, recorded investment	376	791
Impaired loan, with related allowance, recorded investment	0	34
Impaired loan, total, recorded investment	376	825
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	373	789
Impaired loan, with related allowance, unpaid principal balance	0	32
Impaired loan, total, unpaid principal balance	373	821
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	542	1,069
Impaired loan, with related allowance, average recorded investment	18	126
Impaired loan, total, average recorded investment	560	1,195
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	36	66
Impaired loan, with related allowance, interest income recognized	0	11
Impaired loan, total, interest income recognized	36	77
Residential | Real estate
Recorded Investment
Impaired loan, with no related allowance, recorded investment	646	717
Impaired loan, with related allowance, recorded investment	173	1,022
Impaired loan, total, recorded investment	819	1,739
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	646	719
Impaired loan, with related allowance, unpaid principal balance	173	1,022
Impaired loan, total, unpaid principal balance	819	1,741
Impaired loan, total, related allowance	9	12
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	875	575
Impaired loan, with related allowance, average recorded investment	342	1,174
Impaired loan, total, average recorded investment	1,217	1,749
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	29	41
Impaired loan, with related allowance, interest income recognized	9	27
Impaired loan, total, interest income recognized	38	68
Residential | Home equity
Recorded Investment
Impaired loan, with no related allowance, recorded investment	49	142
Impaired loan, with related allowance, recorded investment	0	263
Impaired loan, total, recorded investment	49	405
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	49	142
Impaired loan, with related allowance, unpaid principal balance	0	261
Impaired loan, total, unpaid principal balance	49	403
Impaired loan, total, related allowance	0	1
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	108	109
Impaired loan, with related allowance, average recorded investment	128	251
Impaired loan, total, average recorded investment	236	360
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	10	10
Impaired loan, with related allowance, interest income recognized	1	1
Impaired loan, total, interest income recognized	11	11
Consumer
Recorded Investment
Impaired loan, with no related allowance, recorded investment	0	5
Impaired loan, with related allowance, recorded investment	0	0
Impaired loan, total, recorded investment	0	5
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	0	5
Impaired loan, with related allowance, unpaid principal balance	0	0
Impaired loan, total, unpaid principal balance	0	5
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	2	6
Impaired loan, with related allowance, average recorded investment	0	5
Impaired loan, total, average recorded investment	2	11
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	0	1
Impaired loan, with related allowance, interest income recognized	0	0
Impaired loan, total, interest income recognized	$ 0	$ 1