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Fair Value Measurement - Summary of Valuation Technique, Unobservable Inputs and Qualitative Information of Assets and Liabilities Measured at Fair Value on Non-recurring Basis (Details) - Level 3 - Fair Value Measurements, Non-recurring	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Impaired Loans
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Valuation Technique	Appraisals	Appraisals
Impact to Valuation from an Increased or Higher Input Value	Decrease	Decrease
Impaired Loans | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Appraisal adjustments, sales costs and other discount adjsutments for market conditions	6.00%	6.00%
Impaired Loans | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Appraisal adjustments, sales costs and other discount adjsutments for market conditions	10.00%	10.00%
Asset Held For Sale
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Valuation Technique	List price, contract price	List price, contract price
Appraisal adjustments, sales costs and other discount adjsutments for market conditions	7.00%	7.00%
Impact to Valuation from an Increased or Higher Input Value	Decrease	Decrease
Other Real Estate Owned
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Valuation Technique	Appraisals	Appraisals
Impact to Valuation from an Increased or Higher Input Value	Decrease	Decrease
Other Real Estate Owned | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Appraisal adjustments, sales costs and other discount adjsutments for market conditions	7.00%	7.00%
Other Real Estate Owned | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Appraisal adjustments, sales costs and other discount adjsutments for market conditions	20.00%	20.00%

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Fair Value Inputs appraisal adjustments, sales costs and other discount adjustments for market conditions.

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Description of the changes in significant assumptions used by management to measure fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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Description of the inputs and valuation technique(s) used to measure fair value.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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