Guarantees (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Commitments to Extend Credit
Loan Commitments and Letters of Credit [Line Items]
Notional Amount	$ 335,587	$ 315,256	$ 316,449
Fair Value	0	0	0
Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Notional Amount	4,016	3,526	3,672
Fair Value	$ 4	$ 23	$ 18
Minimum | Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Loan commitments, fixed fee percent	1.00%
Maximum | Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Loan commitments, fixed fee percent	3.00%