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Equity-Based Compensation (Detail) - Restricted Stock - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2020 | Mar. 31, 2020 | Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Aggregate grant date fair value |  |  | $ 3.8
Compensation expense | $ 0.4 | $ 0.8 |
Unrecognized compensation expense | $ 2.4 | $ 2.4 |
Class A Common Stock |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Options granted (in shares) |  |  | 292,534

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