Fair Value - Fair Value on Nonrecurring Basis - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired financing receivable, related allowance	$ 447	$ 332
Increase in valuation allowance for impaired loans	115
Standby Letters of Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Standby letter of credit	$ 5,600
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Post modification recorded investment discount for selling and closing costs	8.00%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Post modification recorded investment discount for selling and closing costs	10.00%
Measurement Input, Discount Rate | Minimum | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, discount rate	0.10
Measurement Input, Discount Rate | Maximum | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value inputs, discount rate	0.25