Commitments and Contingencies - Legal Claims and Insurance (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 |
|
| Rollforward of reserves for legal claims | |||||
| Reserves for legal claims, beginning of period | $ 1,136.7 | $ 991.3 | $ 1,143.6 | $ 949.6 | |
| Increase in reserves | 37.1 | 59.7 | 87.3 | 132.3 | |
| Payments | (34.7) | (14.9) | (91.8) | (45.8) | |
| Reserves for legal claims, end of period | $ 1,139.1 | 1,036.1 | $ 1,139.1 | 1,036.1 | |
| Construction Defect Portion of Loss Contingency Accrual | 99.00% | 99.00% | 98.00% | ||
| Litigation Settlement, Expense | $ 119.4 | 142.5 | |||
| Insurance receivables | $ 123.6 | $ 138.5 | $ 123.6 | $ 138.5 | $ 167.0 |