Stockholders' Equity - Activity Under Stock Option Plans (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
Sep. 30, 2017 USD ($) $ / shares shares
Number of Shares Underlying Stock Options
Outstanding as of December 31, 2016 \| shares	222
Exercised \| shares	(110)
Cancelled or expired \| shares	(4)
Outstanding as of September 30, 2017 \| shares	108
Vested and expected to vest at September 30, 2017 \| shares	108
Exercisable at September 30, 2017 \| shares	108
Weighted Average Exercise Price per Share
Outstanding as of December 31, 2016 \| $ / shares	$ 14.90
Exercised \| $ / shares	16.19
Cancelled or expired \| $ / shares	18.16
Outstanding as of September 30, 2017 \| $ / shares	13.47
Vested and expected to vest at September 30, 2017 \| $ / shares	13.47
Exercisable at September 30, 2017 \| $ / shares	$ 13.47
Weighted Average Remaining Contractual Term
Outstanding as of September 30, 2017	10 months 24 days
Vested and expected to vest at September 30, 2017	10 months 24 days
Exercisable at September 30, 2017	10 months 24 days
Aggregate Intrinsic Value
Outstanding as of September 30, 2017 \| $	$ 18,711
Vested and expected to vest at September 30, 2017 \| $	18,711
Exercisable at September 30, 2017 \| $	$ 18,711

Share-based Compensation Arrangement by Share-based Payment Award, Options, Aggregate Intrinsic Value [Abstract]

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Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Remaining Contractual Term [Abstract]

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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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-Publisher FASB
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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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For presentations that combine terminations, 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 or that expired.

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

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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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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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 the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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As of the balance sheet date, the number of shares into which fully vested and expected to vest stock options outstanding can be converted under the option plan.

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As of the balance sheet date, the weighted-average exercise price for outstanding stock options that are fully vested or expected to vest.

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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 the reported fact of one year, five months, and thirteen days.

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

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