Loans - Impaired Loan Balances By Portfolio Segment (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Recorded Investment
Impaired loan, with no related allowance, recorded investment	$ 1,038	$ 1,099
Impaired loan, with related allowance, recorded investment	316	235
Impaired loan, total, recorded investment	1,354	1,334
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	1,035	1,096
Impaired loan, with related allowance, unpaid principal balance	312	231
Impaired loan, total, unpaid principal balance	1,347	1,327
Impaired loan, total, related allowance	77	64
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	1,060	1,571
Impaired loan, with related allowance, average recorded investment	260	863
Impaired loan, total, average recorded investment	1,320	2,434
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	34	89
Impaired loan, with related allowance, interest income recognized	11	50
Impaired loan, total, interest income recognized	45	139
Commercial
Recorded Investment
Impaired loan, with no related allowance, recorded investment	4	28
Impaired loan, with related allowance, recorded investment	53	62
Impaired loan, total, recorded investment	57	90
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	4	28
Impaired loan, with related allowance, unpaid principal balance	49	58
Impaired loan, total, unpaid principal balance	53	86
Impaired loan, total, related allowance	49	55
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	11	44
Impaired loan, with related allowance, average recorded investment	55	354
Impaired loan, total, average recorded investment	66	398
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	0	14
Impaired loan, with related allowance, interest income recognized	2	40
Impaired loan, total, interest income recognized	2	54
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	0
Impaired loan, total, recorded investment	0	0
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	0	0
Impaired loan, with related allowance, unpaid principal balance	0	0
Impaired loan, total, unpaid principal balance	0	0
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	0	0
Impaired loan, with related allowance, average recorded investment	0	21
Impaired loan, total, average recorded investment	0	21
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	0	0
Impaired loan, with related allowance, interest income recognized	0	0
Impaired loan, total, interest income recognized	0	0
Commercial real estate | Real estate
Recorded Investment
Impaired loan, with no related allowance, recorded investment	348	376
Impaired loan, with related allowance, recorded investment	0	0
Impaired loan, total, recorded investment	348	376
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	346	373
Impaired loan, with related allowance, unpaid principal balance	0	0
Impaired loan, total, unpaid principal balance	346	373
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	362	542
Impaired loan, with related allowance, average recorded investment	0	18
Impaired loan, total, average recorded investment	362	560
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	14	36
Impaired loan, with related allowance, interest income recognized	0	0
Impaired loan, total, interest income recognized	14	36
Residential | Real estate
Recorded Investment
Impaired loan, with no related allowance, recorded investment	641	646
Impaired loan, with related allowance, recorded investment	263	173
Impaired loan, total, recorded investment	904	819
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	640	646
Impaired loan, with related allowance, unpaid principal balance	263	173
Impaired loan, total, unpaid principal balance	903	819
Impaired loan, total, related allowance	28	9
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	640	875
Impaired loan, with related allowance, average recorded investment	205	342
Impaired loan, total, average recorded investment	845	1,217
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	17	29
Impaired loan, with related allowance, interest income recognized	9	9
Impaired loan, total, interest income recognized	26	38
Residential | Home equity
Recorded Investment
Impaired loan, with no related allowance, recorded investment	45	49
Impaired loan, with related allowance, recorded investment	0	0
Impaired loan, total, recorded investment	45	49
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	45	49
Impaired loan, with related allowance, unpaid principal balance	0	0
Impaired loan, total, unpaid principal balance	45	49
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	47	108
Impaired loan, with related allowance, average recorded investment	0	128
Impaired loan, total, average recorded investment	47	236
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	3	10
Impaired loan, with related allowance, interest income recognized	0	1
Impaired loan, total, interest income recognized	3	11
Consumer
Recorded Investment
Impaired loan, with no related allowance, recorded investment	0	0
Impaired loan, with related allowance, recorded investment	0	0
Impaired loan, total, recorded investment	0	0
Unpaid Principal Balance
Impaired loan, with no related allowance, unpaid principal balance	0	0
Impaired loan, with related allowance, unpaid principal balance	0	0
Impaired loan, total, unpaid principal balance	0	0
Impaired loan, total, related allowance	0	0
Average Recorded Investment
Impaired loan, with no related allowance, average recorded investment	0	2
Impaired loan, with related allowance, average recorded investment	0	0
Impaired loan, total, average recorded investment	0	2
Interest Income Recognized
Impaired loan, with no related allowance, interest income recognized	0	0
Impaired loan, with related allowance, interest income recognized	0	0
Impaired loan, total, interest income recognized	$ 0	$ 0