Loans and Credit Quality - Nonaccrual Loans by Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	$ 16,635	$ 21,626
Government guarantees on nonaccrual loans	(327)	(467)
Net nonaccrual loans	16,308	21,159
Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	15,234	19,917
Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,331	1,331
Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	70	0
Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	378
30-59 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	810
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	0	810
30-59 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	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 other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	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
60-89 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	41	0
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	41	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 other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	41
60-89 Days Past Due | Consumer secured by 1st deeds of trust
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	1,789	3,030
Government guarantees on nonaccrual loans	(73)	(94)
Net nonaccrual loans	1,716	2,936
Greater Than 90 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,769	2,652
Greater Than 90 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	0
Greater Than 90 Days Past Due | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	20
Greater Than 90 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans		378
Current
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	14,805	17,786
Government guarantees on nonaccrual loans	(254)	(373)
Net nonaccrual loans	14,551	17,413
Current | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	13,465	16,455
Current | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,331	1,331
Current | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	$ 9
Current | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans		$ 0