Equity Incentive Plans - Summary of Stock Option Activity (Details) - Stock Option $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($) $ / shares shares
Options Outstanding
Outstanding at beginning of period \| shares	7,490,000
Options exercised \| shares	(2,148,000)
Options forfeited or canceled \| shares	(314,000)
Outstanding at end of period \| shares	5,028,000
Vested and expected to vest at end of period \| shares	4,923,000
Exercisable at end of period \| shares	3,628,000
Weighted Average Exercise Price per Share
Outstanding at beginning of period \| $ / shares	$ 10.76
Options exercised \| $ / shares	8.40
Options forfeited or canceled \| $ / shares	15.03
Outstanding at end of period \| $ / shares	11.51
Vested and expected to vest at end of period \| $ / shares	11.43
Exercisable at end of period \| $ / shares	$ 10.11
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding	6 years 1 month 16 days
Vested and expected to vest at end of period	6 years 1 month 6 days
Exercisable at end of period	5 years 6 months 10 days
Total Intrinsic Value \| $	$ 127,969
Vested and expected to vest at end of period \| $	125,678
Exercisable at end of period \| $	$ 97,415

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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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Weighted average price of options that were either forfeited or expired.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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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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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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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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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 outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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