Loans and Credit Quality - Nonaccrual Loans by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	$ 16,728	$ 21,626
Government guarantees on nonaccrual loans	(279)	(467)
Net nonaccrual loans	16,449	21,159
Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	14,734	19,917
Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,694	1,331
Real estate term other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	26	0
Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	226	378
Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	48	0
30-59 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	121	810
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	121	810
30-59 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	121	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 | Real estate term 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	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	600	0
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	600	0
60-89 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	600	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 | Real estate term other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	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	4,728	3,030
Government guarantees on nonaccrual loans	(62)	(94)
Net nonaccrual loans	4,666	2,936
Greater Than 90 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	2,742	2,652
Greater Than 90 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	1,694	0
Greater Than 90 Days Past Due | Real estate term other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	26
Greater Than 90 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	226	378
Greater Than 90 Days Past Due | Consumer other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	40
Current
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	11,279	17,786
Government guarantees on nonaccrual loans	(217)	(373)
Net nonaccrual loans	11,062	17,413
Current | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	11,271	16,455
Current | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0	1,331
Current | Real estate term other
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonperforming loans	0
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	$ 8