Fair Values of Financial Instruments - Unobservable Inputs Used in Recurring and Nonrecurring Level 3 Fair Value Measurements Other Than Goodwill (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Discounted cash flow | State and municipal securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 3,293	$ 3,943
Discounted cash flow | State and municipal securities | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Maturity Call Date	1 month	1 month
US Muni BQ curve	A-	A-
Discounted cash flow | State and municipal securities | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Maturity Call Date	20 years	20 years
US Muni BQ curve	BBB-	BBB-
Discounted cash flow | State and municipal securities | Maturity Call Date US Muni BQ curve Discount rate | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0069	0.0069
Discounted cash flow | State and municipal securities | Maturity Call Date US Muni BQ curve Discount rate | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.05	0.05
Discounted cash flow | Corporate obligations and U.S. Government-sponsored mortgage backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 35	$ 35
Discounted cash flow | Corporate obligations and U.S. Government-sponsored mortgage backed securities | Risk free rate plus Premium for illiquidity | Three-Month LIBOR
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount rate	0.0200	0.0200
Collateral based measurements | Impaired loans (collateral dependent)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 11,866	$ 9,576
Collateral based measurements | Impaired loans (collateral dependent) | Discount to reflect current market conditions and ultimate collectability | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	0.00	0.00
Collateral based measurements | Impaired loans (collateral dependent) | Discount to reflect current market conditions and ultimate collectability | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	0.10	0.10
Collateral based measurements | Impaired loans (collateral dependent) | Discount to reflect current market conditions and ultimate collectability | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions and ultimate collectability	0.06	0.01
Appraisals | Other real estate owned
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 657	$ 859
Appraisals | Other real estate owned | Discount to reflect current market conditions | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	0.00	0.00
Appraisals | Other real estate owned | Discount to reflect current market conditions | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	0.10	0.10
Appraisals | Other real estate owned | Discount to reflect current market conditions | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Discount to reflect current market conditions (percent)	0.04	0.02