Accounts receivable, unbilled revenue (contract assets) and unearned revenue or payments on account (contract liabilities) - Schedule of Unbilled Services and Unearned Revenue or Payments on Account (Details) - USD ($) $ in Thousands |
9 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Dec. 31, 2025 |
|
| Revenue from Contract with Customer [Abstract] | ||
| Unbilled revenue (Unbilled services) | $ 1,023,170 | $ 1,096,592 |
| Change in unbilled revenue (Unbilled services) | $ (73,422) | |
| Percentage change in unbilled revenue (unbilled services) | (6.70%) | |
| Unearned revenue (Payments on account) | $ (1,727,355) | $ (1,550,471) |
| Change in unearned revenue (Payments on account) | $ (176,884) | |
| Percentage change in unearned revenue (Payments on account) | 11.40% |