Stock-Based Compensation (Narrative) (Details) - USD ($) |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
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| Employee Stock Options [Member] | ||
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ||
| Stock options granted (in shares) | 361,135 | 455,342 |
| Unrecognized costs related to share based compensation | $ 11,624,000 | |
| Weighted average period of recognition of unrecognized costs related to stock options, years | 2 years 11 months 5 days | |
| Restricted Stock Units [Member] | ||
| Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] | ||
| Unrecognized costs related to share based compensation | $ 21,960,000 | |
| Weighted average period of recognition of unrecognized costs related to stock options, years | 2 years 11 months 5 days | |
| Restricted stock units granted (in shares) | 165,235 | 233,175 |
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- Definition Unrecognized cost of unvested share-based compensation awards. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Net number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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