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Share-Based Compensation - Summary of Incentive Unit Activity (Detail) - Incentive Units [Member] - USD ($) $ / shares in Units, $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Number of Units |  |  |
Outstanding Beginning Balance |  | 413,266 |
Granted |  | 9,132 |
Forfeited |  | (19,541) |
Cancelled | (402,857) | (402,857) |
Outstanding Ending Balance |  |  | 413,266
Weighted Average Strike Price |  |  |
Outstanding Beginning Balance |  | $ 2.75 |
Granted |  | 1.28 |
Forfeited |  | 4.99 |
Cancelled |  | $ 2.62 |
Outstanding Ending Balance |  |  | $ 2.75
Weighted Average Contractual Term |  |  |
Outstanding Beginning Balance |  |  | 9 years 1 month 6 days
Aggregate Intrinsic Value |  |  |
Outstanding Beginning Balance |  | $ 779 |
Outstanding Ending Balance |  |  | $ 779

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