Allowance for Loan Losses - Weighted Average Annualized Balance of Recorded Investment and Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Financing Receivable Modifications [Line Items]
Average Recorded Investment	$ 13,381	$ 9,229
Interest Income after Impairment	34	75
Residential Properties
Financing Receivable Modifications [Line Items]
Average Recorded Investment		1,323
Interest Income after Impairment		20
Commercial Real Estate
Financing Receivable Modifications [Line Items]
Average Recorded Investment	4,021	2,403
Interest Income after Impairment	34	50
Commercial and Industrial Loans
Financing Receivable Modifications [Line Items]
Average Recorded Investment	$ 9,360	5,503
Interest Income after Impairment		$ 5

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

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