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v3.8.0.1

Salary Deferral Plan - Additional Information (Detail) - USD ($) | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Retirement Benefits [Abstract] |  |
Salary deferral plan, discretionary and matching contribution | $ 374,000 | $ 465,000

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- 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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