Stock-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Oct. 25, 2018
2008 Equity Inventive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued	0
2018 Equity Inventive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued	5,975	0
Options granted in period (in shares)	0	0
Number of shares authorized (in shares)			200,000
Number of shares available for grant (in shares)	194,025
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Number of options outstanding (in shares)	20,500	28,000
Options outstanding and exercisable, intrinsic value	$ 826	$ 725
Options, weighted average remaining term	1 year 3 months 25 days	1 year 9 months
Options, vested in period (in shares)	0	0
Options | Year 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Options | Year 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Options | Year 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Options | Year 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Options | Year 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Options | 2018 Equity Inventive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration term	10 years
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	5 years
Granted (in shares)	5,975	6,750
Fair value of stock award granted (in dollars per share)	$ 48.15	$ 37.49
Share-based board compensation earned	$ 227	$ 193
Unrecognized compensation cost	$ 641	$ 568
Expected weighted average period of compensation cost recognition	4 years 6 months	4 years 6 months
Restricted Stock | Year 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Restricted Stock | Year 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Restricted Stock | Year 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Restricted Stock | Year 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%
Restricted Stock | Year 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	20.00%