Loans and Credit Quality - Nonaccrual Loans by Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	$ 18,895	$ 21,626
Government guarantees on nonaccrual loans	(412)	(467)
Net nonaccrual loans	18,483	21,159
Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	17,268	19,917
Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,331	1,331
Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	285	378
Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	11	0
30-59 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	15	810
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	15	810
30-59 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	15	810
30-59 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
30-59 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
30-59 Days Past Due | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0
60-89 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	0	0
60-89 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
60-89 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
60-89 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
60-89 Days Past Due | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0
Greater Than 90 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	3,560	3,030
Government guarantees on nonaccrual loans	(73)	(94)
Net nonaccrual loans	3,487	2,936
Greater Than 90 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,933	2,652
Greater Than 90 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,331	0
Greater Than 90 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	285	378
Greater Than 90 Days Past Due | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	11
Current
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	15,320	17,786
Government guarantees on nonaccrual loans	(339)	(373)
Net nonaccrual loans	14,981	17,413
Current | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	15,320	16,455
Current | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	1,331
Current | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	$ 0
Current | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	$ 0