Stock-Based Awards - Summary of Stock Option Activity (Details) shares in Thousands	3 Months Ended
Mar. 31, 2019 shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding, Beginning balance	3,603
Number of Shares, Granted	57
Number of Shares, Exercised	(28)
Number of Shares, Forfeited or expired	(178)
Number of Shares, Outstanding, Ending balance	3,454
Number of Shares, Vested and exercisable	1,066

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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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- Definition

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

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Number of options outstanding, including both vested and non-vested options.

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Number of fully vested and expected to vest exercisable options that may 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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Number of share options (or share units) exercised during the current period.

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