Stock Based Compensation (Additional Information) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price, granted	$ 1.98	$ 0.70
Averages contractual term	10 years
Estimated annualized forfeiture rate for options granted to employees	15.00%
Estimated annualized forfeiture rate for options granted to senior management	8.00%
Unrecognized compensation cost	$ 12,033
Operating expenses weighted average period	2 years 9 months 11 days
Shares subject to outstanding common stock options granted	7,113,000
Weighted average contractual term for options outstanding	8 years 1 month 2 days	7 years 10 months 13 days	7 years 6 months 22 days
Weighted average contractual term for options exercisable	6 years 9 months 4 days	7 years 4 months 17 days	6 years 10 months 13 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	30,537	2,288
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	16,376	1,394
Aggregate Intrinsic Value Of Stock Options Exercisable	$ 890	$ 18
Issuance of common stock in connection with employee stock purchase plan, shares	243,510
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average vesting term	4 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average vesting term	6 years
2007 Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance	16,500,000
Shares subject to outstanding common stock options granted	13,159,000
Shares available for future grants	1,927,000
Vesting periods of options granted	4 years
Options expire from date of grant	10 years
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock reserved for issuance	756,490
Share Based Compensation Arrangement By Share Based Payment Award Percentage Earning Of Participants		15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent		85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	250,000
Percentage Increase In Number Of Shares Available For Future Issuance Under Stock Based Awards	1.00%
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Issued	1,000,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instrument granted	0	0	220,729
Intrinsic value of equity instrument			256,000

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Employee Service Share Based Compensation Unrecognized Compensation Costs

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Percentage Increase In Number Of Shares Available For Future Issuance Under Stock Based Awards

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The intrinsic value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units, as calculated by applying the disclosed pricing methodology.

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Number of additional shares authorized for issuance under an established share-based compensation plan.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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

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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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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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Purchase price of common stock expressed as a percentage of its fair market value.

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

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Number of shares issued during the period as a result of an employee stock purchase plan.

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