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Stock-Based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands | 1 Months Ended | 3 Months Ended
--- | --- | ---
May 31, 2021 $ / shares | Nov. 30, 2020 $ / shares | May 31, 2020 tranche shares | Mar. 31, 2025 USD ($) $ / shares shares | Sep. 30, 2024 USD ($) $ / shares shares | Mar. 31, 2024 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted average grant date fair value, grants in period (in usd per share) | $ / shares |  |  |  | $ 27.05 |  | $ 12.92
Stock based compensation not recognized, options |  |  |  | $ 48,800 |  |
Stock based compensation not recognized, period for recognition (in years) |  |  |  | 2 years 3 months 18 days |  |
Compensation expense |  |  |  | $ 37,757 |  | $ 27,041
Granted (in shares) | shares |  |  |  | 524,770 |  |
Stock options |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Exercises in period, intrinsic value |  |  |  | $ 1,100 |  | $ 600
Expected dividend yield |  |  |  | 0.00% |  | 0.00%
Shares underlying unvested restricted stock units |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock based compensation not recognized, period for recognition (in years) |  |  |  | 2 years 4 months 24 days |  |
Stock based compensation not recognized, other than options |  |  |  | $ 241,400 |  |
Shares underlying unvested performance-based restricted stock units |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted average grant date fair value, grants in period (in usd per share) | $ / shares |  | $ 113.40 |  |  | $ 113.40 |
Stock based compensation not recognized, period for recognition (in years) |  |  |  | 2 years 3 months 18 days |  |
Stock based compensation not recognized, other than options |  |  |  | $ 26,700 |  |
Additional service period requirement |  | 2 years |  |  |  |
Weighted average grant date fair value, Vested in period (in usd per share) | $ / shares | $ 148.19 |  |  |  | $ 148.19 |
Cumulative charge |  |  |  |  | $ 24,800 |
Compensation expense |  |  |  | $ 4,300 |  | $ 1,400
Granted (in shares) | shares |  |  |  |  | 219,161 |
Total market-based restricted stock units approved and granted (in shares) | shares |  |  |  | 281,378 |  |
Shares underlying unvested performance-based restricted stock units | Minimum |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average derivative service period |  | 7 months 6 days |  |  |  |
Market-based stock unit vesting period |  | 7 months 6 days |  |  |  |
Shares underlying unvested performance-based restricted stock units | Maximum |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average derivative service period |  | 3 years |  |  |  |
Market-based stock unit vesting period |  | 3 years 1 month 6 days |  |  |  |
MSUs |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Number of tranches | tranche |  |  | 3 |  |  |
Market-based restricted stock share price goal |  |  | 30 days |  |  |
MSUs | Chief Executive Officer |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total market-based restricted stock units approved and granted (in shares) | shares |  |  | 1,695,574 |  |  |
Shares available for issuance under the 2018 Employee Stock Purchase Plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock based compensation not recognized, period for recognition (in years) |  |  |  | 1 month 6 days |  |
Stock based compensation not recognized, other than options |  |  |  | $ 800 |  |
Compensation expense |  |  |  | $ 1,600 |  | $ 1,400
Maximum employee subscription rate, ESPP |  |  |  | 10.00% |  |
Purchase price of common stock (as a percent of the fair value of common stock) |  |  |  | 85.00% |  |
Purchase period |  |  |  | 6 months |  |
Common stock issued under employee stock purchase plan (in shares) | shares |  |  |  | 0 |  | 0
Phantom Share Units (PSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Weighted-average derivative service period | 4 years | 4 years |  |  |  |
Market-based stock unit vesting period | 6 months | 6 months |  |  |  |

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