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Loans and Loans Held for Sale - Restructured Loans for Periods Presented (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	$ 6,142	$ 12,192
Performing TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans		14,901	13,423
Performing TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans		2,579	2,994
Performing TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans		3,946	1,387
Performing TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans		2,420	2,966
Performing TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans		2,039	2,375
Performing TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans		3,885	3,683
Performing TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans		32	18
Nonperforming TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans		11,150	11,598
Nonperforming TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans		967	646
Nonperforming TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans		3,197	4,493
Nonperforming TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans		2,413	430
Nonperforming TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans		3,585	5,068
Nonperforming TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans		979	954
Nonperforming TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans		9	7
Total TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans		26,051	25,021
Total TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans		3,546	3,640
Total TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans		7,143	5,880
Total TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans		4,833	3,396
Total TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans		5,624	7,443
Total TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans		4,864	4,637
Total TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans		$ 41	$ 25
[1] Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end

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- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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