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Equity-based Compensation and Equity Incentive Plans - Schedule of Stock Option Activity Under 2015 LLC Plan (Detail) - $ / shares | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Granted, Weighted-average grant date fair value | $ 6.35 |
Plan 2015 | Incentive Units |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Beginning balance, Number of Non-vested Units | 0 | 971,906
Vested, Number of Units |  | (73,719)
Forfeited, Number of Units |  | (260,145)
Ending balance, Number of Non-vested Units |  | 0
Vested or expected to vest, Number of Units |  | 0
Beginning balance, Weighted-average price | $ 0 | $ 5.22
Vested, Weighted-average price |  | 4.01
Forfeited, Weighted-average price |  | 4.19
Ending balance, Weighted-average price |  | 0
Weighted-average price, Vested or expected to vest at December 31, 2017 |  | 0
Beginning Balance, Weighted-average grant date fair value | 0 | 1.01
Vested, Weighted-average grant date fair value |  | 0.87
Forfeited, Weighted-average grant date fair value |  | 1.05
Ending balance, Weighted-average grant date fair value |  | 0
Weighted-average grant date fair value, Vested or expected to vest at December 31, 2017 |  | 0
Plan 2015 | Incentive Units | Maximum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Beginning balance, Weighted-average price | $ 0 | 5.93
Granted, Weighted-average price |  | 0
Vested, Weighted-average price |  | 5.53
Forfeited, Weighted-average price |  | 5.57
Ending balance, Weighted-average price |  | 0
Weighted-average price, Vested or expected to vest at December 31, 2017 |  | $ 0
Plan 2015 | Incentive Units | 2017 Reorganization |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Non-vested units cancelled upon 2017 Reorganization, Number of Units |  | (638,042)
Non-vested units cancelled upon 2017 Reorganization, Weighted-average price |  | $ 5.78
Non-vested units cancelled upon 2017 Reorganization, Weighted-average grant date fair value |  | 1.05
Plan 2015 | Incentive Units | 2017 Reorganization | Maximum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Non-vested units cancelled upon 2017 Reorganization, Weighted-average price |  | $ 6.15

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