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, 2025 |
Dec. 31, 2024 |
|
| Revenue from Contract with Customer [Abstract] | ||
| Unbilled services (unbilled revenue) | $ 1,244,560 | $ 1,286,274 |
| Change in unbilled services (unbilled revenue) | $ (41,714) | |
| Percentage change in unbilled services (unbilled revenue) | (3.20%) | |
| Unearned revenue (payments on account) | $ (1,514,442) | (1,614,758) |
| Change in unearned revenue (payments on account) | $ 100,316 | |
| Percentage change in unearned revenue (payments on account) | (6.20%) | |
| Net balance | $ (269,882) | $ (328,484) |
| Change in net balance | $ 58,602 | |
| Percentage change in net balance | (17.80%) |