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Goodwill - Narrative (Details) - USD ($) $ in Thousands |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | ---
Aug. 19, 2025 | Aug. 19, 2024 | Jan. 09, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024 | Dec. 31, 2023
Goodwill [Line Items] |  |  |  |  |  |  |  |  |
Goodwill impairment |  |  |  | $ 165,300 | $ 0 | $ 165,300 | $ 0 | $ 0 |
Purchase of subsidiary undertakings (net of cash acquired) |  |  |  |  |  | 2,537 | $ 85,629 |  |
Goodwill |  |  |  | $ 8,927,323 |  | 8,927,323 |  | 9,051,410 | $ 9,022,075
Prior period acquisitions |  |  |  |  |  | 5,108 |  | $ 0 |
KCR S.A Group |  |  |  |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |  |  |  |
Business combination, consideration transferred |  | $ 92,500 |  |  |  |  |  |  |
Purchase of subsidiary undertakings (net of cash acquired) |  |  |  |  |  | 1,300 |  |  |
Goodwill |  | 43,400 |  |  |  |  |  |  |
Intangible assets acquired |  | 45,100 |  |  |  |  |  |  |
Prior period acquisitions | $ 5,100 |  |  |  |  |  |  |  |
KCR S.A Group | Customer relationships |  |  |  |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |  |  |  |
Intangible assets acquired |  | 41,400 |  |  |  |  |  |  |
KCR S.A Group | Order backlog |  |  |  |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |  |  |  |
Intangible assets acquired |  | $ 3,700 |  |  |  |  |  |  |
HumanFirst Inc |  |  |  |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |  |  |  |
Business combination, consideration transferred |  |  | $ 13,300 |  |  |  |  |  |
Purchase of subsidiary undertakings (net of cash acquired) |  |  |  |  |  | $ 1,200 |  |  |
Goodwill |  |  | 2,700 |  |  |  |  |  |
Intangible assets acquired |  |  | $ 9,900 |  |  |  |  |  |

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