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Loans and Loans Held for Sale - Summary of Restructured Loans (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	$ 5,155	$ 2,665	$ 11,685	$ 3,103
Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	0	100	0	100
Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	5,034	2,229	10,845	2,229
Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	0	0	0	0
Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	41	33	196	33
Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	73	269	621	707
Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans	[1]	$ 7	$ 34	23	$ 34
Performing TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans				24,454		$ 14,901
Performing TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans				2,136		2,579
Performing TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans				14,149		3,946
Performing TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans				2,400		2,420
Performing TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans				2,157		2,039
Performing TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans				3,569		3,885
Performing TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans				43		32
Nonperforming TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans				7,395		11,150
Nonperforming TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans				925		967
Nonperforming TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans				2,599		3,197
Nonperforming TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans				410		2,413
Nonperforming TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans				1,924		3,585
Nonperforming TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans				1,536		979
Nonperforming TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans				1		9
Total TDRs
Financing Receivable, Modifications [Line Items]
Restructured loans				31,849		26,051
Total TDRs | Commercial real estate
Financing Receivable, Modifications [Line Items]
Restructured loans				3,061		3,546
Total TDRs | Commercial and industrial
Financing Receivable, Modifications [Line Items]
Restructured loans				16,748		7,143
Total TDRs | Commercial construction
Financing Receivable, Modifications [Line Items]
Restructured loans				2,810		4,833
Total TDRs | Residential mortgage
Financing Receivable, Modifications [Line Items]
Restructured loans				4,081		5,624
Total TDRs | Home equity
Financing Receivable, Modifications [Line Items]
Restructured loans				5,105		4,864
Total TDRs | Installment and other consumer
Financing Receivable, Modifications [Line Items]
Restructured loans				$ 44		$ 41
[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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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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