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401(k) Savings Plan - Additional Information (Detail) | 12 Months Ended
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Dec. 31, 2017 USD ($) h | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Compensation And Retirement Disclosure [Abstract] |  |  |
Age to participate in the savings plan | 21 years |  |
Time to participate in the savings plan | h | 1,000 |  |
Consecutive period to participate in the savings plan | 12 months |  |
Discretionary Company contributions | $ | $ 0 | $ 0 | $ 0
Contributions by management | 100.00% |  |
Percentage of each participating employee annual cash compensation | 3.00% |  |
Employee's contributions | 50.00% |  |
Additional annual cash compensation | 2.00% |  |

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- Definition Age to participate in the savings plan. + References No definition available. + Details
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- Definition Consecutive period of service following initial date of employment for saving plan valuation. + References No definition available. + Details
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- Definition Defined contribution employee contribution percent. + References No definition available. + Details
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- Definition Employee contribution portion of annual cash compensation. + References No definition available. + Details
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- Definition Time to participate in the savings plan. + References No definition available. + Details
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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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