Commitments and Contingencies - Warranty Claims (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Mar. 31, 2026 |
Sep. 30, 2025 |
Mar. 31, 2025 |
Sep. 30, 2024 |
|
| Movement in Standard Product Warranty Accrual [Roll Forward] | ||||||||
| Standard Product Warranty Accrual | $ 550.7 | $ 564.7 | $ 550.7 | $ 564.7 | $ 546.5 | $ 566.2 | $ 557.3 | $ 566.9 |
| Standard Product Warranty Accrual, Increase for Warranties Issued | 49.6 | 51.5 | 129.5 | 138.5 | ||||
| Standard Product Warranty Accrual, Increase (Decrease) for Preexisting Warranties | (26.2) | (13.4) | (85.8) | (51.4) | ||||
| Standard Product Warranty Accrual, Decrease for Payments | $ 19.2 | $ 30.7 | $ 59.2 | $ 89.3 | ||||