Guarantees (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Commitments to Extend Credit
Loan Commitments and Letters of Credit [Line Items]
Notional Amount	$ 316,449	$ 296,442	$ 300,439
Fair Value	0	0	0
Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Notional Amount	3,672	3,445	3,483
Fair Value	$ 18	$ 30	$ 31
Minimum | Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Loans And Leases Receivable, Loan Commitments, Fixed Fees, Percent	1.00%
Maximum | Standby Letters of Credit
Loan Commitments and Letters of Credit [Line Items]
Loans And Leases Receivable, Loan Commitments, Fixed Fees, Percent	3.00%