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Fair Value Measurements - Narrative (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Loans held for sale | Nonrecurring basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non recurring fair value adjustments on loans held for sale	$ 0	$ 0
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period under consideration for valuation of real estate collateral	12 months
Period under consideration for valuation of business equipment	1 year
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Period under consideration for valuation of house or building in the process of construction	1 year

X

- Definition

Period of appraisal of property to consider different method to measure fair value.

+ References

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- Definition

Period used to determine value of business equipment.

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- Definition

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- Definition

Amount of addition (reduction) to the amount at which an asset could be incurred (settled) in a current transaction between willing parties.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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