Stock-based Compensation - Shares Available for Future Grant (Details) shares in Thousands |
12 Months Ended |
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Dec. 31, 2018
shares
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| Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward] | |
| Beginning balance (in shares) | 4,838 |
| Granted (in shares) | (4,279) |
| Forfeited (in shares) | 523 |
| Expired (in shares) | 185 |
| Ending balance (in shares) | 1,267 |
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- Definition Number of shares under non-option equity instrument agreements for which rights to exercise lapsed. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Number of share instruments newly issued under a share-based compensation plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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