Revenue Recognition - Disaggregated revenues (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2024 |
Mar. 31, 2023 |
Mar. 31, 2024 |
Mar. 31, 2023 |
|
| Revenue Recognition | ||||
| Total revenue | $ 3,943.9 | $ 3,490.1 | $ 7,843.8 | $ 6,872.5 |
| Americas | ||||
| Revenue Recognition | ||||
| Total revenue | 3,039.1 | 2,630.3 | 6,077.9 | 5,209.9 |
| Europe, Middle East, India, Africa | ||||
| Revenue Recognition | ||||
| Total revenue | 619.8 | 494.1 | 1,115.2 | 942.1 |
| Asia-Australia-Pacific | ||||
| Revenue Recognition | ||||
| Total revenue | 285.0 | 365.7 | 650.7 | 720.5 |
| Cost reimbursable | ||||
| Revenue Recognition | ||||
| Total revenue | 1,605.1 | 1,511.3 | 3,222.3 | 3,026.2 |
| Guaranteed maximum price | ||||
| Revenue Recognition | ||||
| Total revenue | 1,420.7 | 1,151.0 | 2,835.6 | 2,239.2 |
| Fixed-price | ||||
| Revenue Recognition | ||||
| Total revenue | $ 918.1 | $ 827.8 | $ 1,785.9 | $ 1,607.1 |