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Share based compensation arrangement by share based payment award equity instruments other than options granted fair value.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of cost to be recognized for option under share-based payment arrangement.

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The cash inflow associated with the amount received from the stock plan during the period.

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Amount of noncash expense for share-based payment arrangement.

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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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Number of shares authorized for issuance under share-based payment arrangement.

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Gross number of share options (or share units) granted during the period.

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Number of shares issued under share-based payment arrangement.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Number of share options (or share units) exercised during the current period.

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Share-Based Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,000	$ 1,000	$ 3,000
Stock-based compensation tax benefit recognized	$ 315,000	$ 299,000
Share-based compensation, number of options exercised	0	0	0
Options granted to employees on grant date	0	0
Unrecognized compensation cost related to nonvested options	$ 0
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of RSUs granted	0	$ 0	$ 0
Unrecognized compensation cost related to nonvested RSUs	0	0
Cash received from employee stock award vesting and the forfeiture of RSUs	$ 0	$ 0	0
2004 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	1,400,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2006 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	200,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2007 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	400,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2008 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	200,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2008 Employee Share Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares subscribed by qualified employees	0
2008 Employee Share Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	40,000
2009 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	300,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2009 Employee Share Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	40,000
Share-based compensation, number of shares issued		0
2010 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	200,000
Share-based compensation, number of shares reserved for issuance, contractual terms		10 years
2010 Employee Share Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, number of shares reserved for issuance	40,000
Share-based compensation, number of shares issued		0
Capitalized stock-based compensation
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 0	$ 0
Stock-based compensation tax benefit recognized	0	0	0
General and Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 1,000	$ 1,000	$ 3,000