Summary of Option Activity (Detail) (USD $)	3 Months Ended
Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Exercised, Exercise price	$ 7.50
Incentive Stock Option Plans, Beginning balance	705,345
Incentive Stock Option Plans, Options granted
Incentive Stock Option Plans, Option exercised	(6,666)
Incentive Stock Option Plans, Options forfeited	(6,667)
Incentive Stock Option Plans, Ending balance	692,012
Weighted Average Price Per Share, Beginning balance	$ 7.70
Weighted Average Price Per Share, Option granted
Weighted Average Price Per Share, Option exercised	$ 7.50
Weighted Average Price Per Share, Options forfeited	$ 7.50
Weighted Average Price Per Share, Ending balance	$ 7.71
Exercisable Weighted Average Price Per Share, Beginning balance	$ 7.95
Exercisable Weighted Average Price Per Share, Ending balance	$ 7.96

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ References

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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

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No definition available.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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No definition available.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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Weighted average price at which grantees can acquire the shares reserved for issuance on stock options awarded.

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

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