Status of Options (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Shares
Outstanding and exercisable	3,451,178
Vested and expected to vest	3,387,447
Vested	2,229,151
Weighted-Average Exercise Price Per Share
Outstanding and exercisable	$ 6.35
Vested and expected to vest	$ 6.33
Vested	$ 5.51
Remaining Contractual Life
Outstanding and exercisable	6 years 2 months 12 days
Vested and expected to vest	6 years 2 months 12 days
Vested	4 years 10 months 24 days
Aggregate Instrinsic Value
Outstanding and exercisable	$ 11,891
Vested and expected to vest	11,762
Vested	$ 9,568

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Share Based Compensation Arrangement By Share Based Payment Award Options Vested Number

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Share Based Compensation Arrangement By Share Based Payment Award Options Vested Weighted Average Exercise Price

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Share Based Compensation Arrangement By Share Based Payment Award Options Vested Weighted Average Remaining Contractual Life

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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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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

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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 of difference between fair value of the underlying shares reserved for issuance and exercise price of fully vested and expected to vest options that are exercisable.

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The number of exercisable share options (fully vested and expected to vest) that may be converted as of the balance sheet date.

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As of the balance sheet date, the weighted-average exercise price (at which grantees can acquire the shares reserved for issuance) for exercisable 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 that are 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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