Stock-based Compensation Plans and Awards - ESPP narrative (Details) - USD ($) $ / shares in Units, $ in Thousands |
12 Months Ended | ||
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Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Stock-based compensation expense | $ 128,431 | $ 138,458 | $ 111,645 |
| ESPP shares issued (in shares) | 1,287,687 | ||
| ESPP | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| ESPP shares issued (in shares) | 1,287,687 | ||
| ESPP | Shares issuable pursuant to the ESPP | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Amounts withheld in contributions from employees | $ 10,900 | 9,700 | 7,600 |
| Stock-based compensation expense | $ 4,000 | $ 3,400 | $ 3,300 |
| ESPP shares issued (in shares) | 1,287,687 | 1,254,910 | 538,398 |
| Weighted average purchase price (in dollars per share) | $ 8.84 | $ 6.76 | $ 17.80 |
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- Definition Represents the amount of contributions from employees withheld. No definition available.
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. 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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- Definition Per share or per unit amount of equity securities issued. No definition available.
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- Definition Number of shares issued during the period as a result of an employee stock purchase plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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