Loans and Credit Quality - Nonaccrual Loans By Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	$ 21,626	$ 13,893
Government guarantees on nonaccrual loans	(467)	(1,413)
Net nonaccrual loans	21,159	12,480
Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	19,917	13,500
Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	1,331	29
Real estate term non-owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	197
Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	378	167
30-59 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	810	8,750
Government guarantees on nonaccrual loans	0	0
Net nonaccrual loans	810	8,750
30-59 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	810	8,750
30-59 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	0
30-59 Days Past Due | Real estate term non-owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans		0
30-59 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	0
60-89 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual 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 nonaccrual loans	0	0
60-89 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	0
60-89 Days Past Due | Real estate term non-owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans		0
60-89 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	0
Greater Than 90 Days Past Due
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	3,030	4,375
Government guarantees on nonaccrual loans	(94)	(1,413)
Net nonaccrual loans	2,936	2,962
Greater Than 90 Days Past Due | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	2,652	4,208
Greater Than 90 Days Past Due | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	0	0
Greater Than 90 Days Past Due | Real estate term non-owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans		0
Greater Than 90 Days Past Due | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	378	167
Current
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	17,786	768
Government guarantees on nonaccrual loans	(373)	0
Net nonaccrual loans	17,413	768
Current | Commercial
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	16,455	542
Current | Real estate term owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	1,331	29
Current | Real estate term non-owner occupied
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans		197
Current | Consumer secured by 1st deeds of trust
Nonaccrual Loans By Major Loan Type [Line Items]
Total nonaccrual loans	$ 0	$ 0