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 |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
|
| Revenue from Contract with Customer [Abstract] | ||
| Unbilled revenue (Unbilled services) | $ 1,054,478 | $ 1,096,592 |
| Change in unbilled revenue (unbilled services) | $ (42,114) | |
| Percentage change in unbilled revenue (unbilled services) | (3.80%) | |
| Unearned revenue (Payments on account) | $ (1,603,204) | $ (1,550,471) |
| Change in unearned revenue (payments on account) | $ (52,733) | |
| Percentage change in unearned revenue (payments on account) | 3.40% |