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v3.8.0.1

Employee 401(k) Plan (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Employee 401(k) Plan |  |  |
Maximum percentage of pretax salary, which can be deferred by employees | 20.00% |  |
Maximum amount of wages, which can be deferred by employees | $ 18,000 |  |
Maximum amount of wages, which can be deferred by employees at least 50 years of age | $ 24,000 |  |
Minimum age of employees for a specified contribution amount of wages | 50 years |  |
Percentage of employee's salary for which the company contributes a matching contribution | 50.00% | 50.00% | 50.00%
Maximum percentage of employee's salary for which the company contributes a matching contribution | 8.00% | 8.00% | 8.00%
Maximum amount of employee's salary for which the company contributes a matching contribution | $ 12,000,000 | $ 12,000,000 | $ 12,000,000
Amount of employer contribution | $ 400,000 | $ 400,000 | $ 400,000

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- Definition Represents the maximum amount of pretax salary, which can be deferred by participants of the defined contribution plans. + References No definition available. + Details
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- Definition Represents the maximum amount of wages, which can be deferred by participants with a specified age, for defined contribution plans. + References No definition available. + Details
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