Employee Benefit Plan (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Retirement Benefits [Abstract] | |||
| Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent | 100.00% | ||
| Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00% | ||
| Defined Contribution Plan, Contributions | $ 7,000,000 | $ 6,000,000 | $ 5,000,000 |
| Defined Contribution Plan, Employer Discretionary Contribution Amount | $ 0 | ||
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- References No definition available.
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- Definition Amount of cost for defined contribution plan. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. No definition available.
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| X | ||||||||||
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. No definition available.
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| X | ||||||||||
- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. No definition available.
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