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Stock-Based Compensation - Additional Information (Detail) (USD $) | 3 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2013 | Mar. 31, 2012 | Mar. 31, 2013 2008 Equity Incentive Plan | Jun. 06, 2012 2008 Equity Incentive Plan | Mar. 31, 2013 Employee Stock Purchase Plan | Jun. 06, 2012 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Increase in shares of common stock authorized for issuance |  |  |  | 3,000,000 |  | 500,000
Maximum number of shares of common stock authorized for issuance |  |  |  | 13,540,940 |  | 1,320,500
Aggregate number of shares of common stock reserved for future issuance | 12,800,000 |  |  |  |  |
Outstanding options and other stock based awards | 10,700,000 |  |  |  |  |
Number of shares available for future issuance |  |  | 2,100,000 |  | 600,000 |
Restricted stock units vesting Description | The restricted stock units generally vest in three annual installments from the date of grant and are generally issuable at the end of the three-year vesting term. |  |  |  |  |
Performance-based stock options awards | $ 0 | $ 0 |  |  |  |
Performance-based stock options, outstanding | 50,000 |  |  |  |  |

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