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Summary of Stock Options Summarized by Exercise Price (Detail) - Incentive Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Weighted Average, Shares	123,087
Outstanding Weighted Average, Remaining Life (Months)		46 months
Outstanding Weighted Average, Exercise Price	$ 11.48	$ 9.14	$ 9.10	$ 9.38
Range One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Per Share, Lower Range	$ 7.50
Outstanding Weighted Average, Shares	7,200
Outstanding Weighted Average, Remaining Life (Months)		5 months
Outstanding Weighted Average, Exercise Price	$ 11.32
Range Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Per Share, Lower Range	11.32
Exercise Price Per Share, Upper Range	$ 14.75
Outstanding Weighted Average, Shares	115,887
Outstanding Weighted Average, Remaining Life (Months)		48 months
Outstanding Weighted Average, Exercise Price	$ 11.49

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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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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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