Revenue Recognition - Disaggregated revenues (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2024 |
Jun. 30, 2023 |
Jun. 30, 2024 |
Jun. 30, 2023 |
|
| Revenue Recognition | ||||
| Total revenue | $ 4,151.2 | $ 3,663.6 | $ 11,995.0 | $ 10,536.1 |
| Americas | ||||
| Revenue Recognition | ||||
| Total revenue | 3,247.0 | 2,829.4 | 9,325.0 | 8,039.3 |
| Europe, Middle East, India, Africa | ||||
| Revenue Recognition | ||||
| Total revenue | 530.1 | 476.0 | 1,645.3 | 1,418.1 |
| Asia-Australia-Pacific | ||||
| Revenue Recognition | ||||
| Total revenue | 374.1 | 358.2 | 1,024.7 | 1,078.7 |
| Cost reimbursable | ||||
| Revenue Recognition | ||||
| Total revenue | 1,594.7 | 1,500.2 | 4,817.0 | 4,526.4 |
| Guaranteed maximum price | ||||
| Revenue Recognition | ||||
| Total revenue | 1,597.5 | 1,325.5 | 4,433.1 | 3,564.7 |
| Fixed-price | ||||
| Revenue Recognition | ||||
| Total revenue | $ 959.0 | $ 837.9 | $ 2,744.9 | $ 2,445.0 |