Summary of Changes in Outstanding Options (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013
Number of Shares
Number of Shares, Outstanding at January 1, 2013	1,487,000
Number of Shares, Exercised	(1,014,956)
Number of Shares, Forfeited and expired	(27,624)
Number of Shares, Outstanding at December 31, 2013	444,420
Number of Shares, Vested or expected to vest at December 31, 2013	444,420
Number of Shares, Exercisable at December 31, 2013	444,420
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding at January 1, 2013	$ 5.53
Weighted Average Exercise Price, Exercised	$ 5.67
Weighted Average Exercise Price, Forfeited and expired	$ 5.25
Weighted Average Exercise Price, Outstanding at December 31, 2013	$ 5.23
Weighted Average Exercise Price, Vested or expected to vest at December 31, 2013	$ 5.23
Weighted Average Exercise Price, Exercisable at December 31, 2013	$ 5.23
Weighted Average Remaining Contractual Term/Average Intrinsic Value, Outstanding
Weighted Average Remaining Contractual Term, Outstanding at December 31, 2013	1 year 8 months 12 days
Weighted Average Remaining Contractual Term, Vested or expected to vest at December 31, 2013	1 year 8 months 12 days
Weighted Average Remaining Contractual Term, Exercisable at December 31, 2013	1 year 8 months 12 days
Average Intrinsic Value, Outstanding at December 31, 2013	$ 10,726
Average Intrinsic Value, Vested or expected to vest at December 31, 2013	10,726
Average Intrinsic Value, Exercisable at December 31, 2013	$ 10,726

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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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.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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For presentations that combine terminations, 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 or that expired.

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Weighted average price of options that were either forfeited or expired.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-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 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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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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

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

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