REVENUE FROM CONTRACTS WITH CUSTOMERS - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Sep. 30, 2025 |
|
| Revenue from Contract with Customer [Abstract] | |||||
| Revenue from performance contracts | $ 311.5 | $ 309.8 | $ 884.8 | $ 941.4 | |
| Performance bonuses recognized | 14.7 | $ 14.1 | 42.5 | $ 48.1 | |
| Capitalized fulfillment costs | $ 31.2 | $ 31.2 | $ 34.8 | ||