Equity Compensation Plans Stock Options (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2013
Shares
Outstanding at September 30, 2013	726
Exercisable at September 30, 2013	422
Expected to Vest at September 30, 2013	290
Weighted-Average Exercise Price
Outstanding at September 30, 2013	$ 9.71
Exercisable at September 30, 2013	$ 9.01
Expected to Vest at September 30, 2013	$ 10.70
Weighted- Average Remaining Contractual Term (years)
Outstanding at September 30, 2013	6 years 1 month 6 days
Exercisable at September 30, 2013	4 years 4 months 24 days
Expected to Vest at September 30, 2013	8 years 4 months 24 days
Aggregate Intrinsic Value
Outstanding at September 30, 2013	$ 5,422
Exercisable at September 30, 2013	3,456
Expected to Vest at September 30, 2013	$ 1,878

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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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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 remaining contractual term for fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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