Stock Plans (Details 4) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Supplemental disclosure of stock options
Options exercisable, Shares	639,185
Options exercisable, Weighted- Average Exercise Price	$ 3.42
Options exercisable, Weighted- Average Remaining Contractual Life (Years)	6 years 11 months 12 days
Options exercisable, Aggregate Intrinsic Value	$ 21,460
Options outstanding, Shares	2,213,529
Options outstanding, Weighted- Average Exercise Price	$ 11.97
Options outstanding, Weighted- Average Remaining Contractual Life (Years)	8 years 2 months 5 days
Options outstanding, Aggregate Exercise Price Intrinsic Value	$ 55,431

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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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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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