Fiduciary Assets and Liabilities (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2025 |
|
| Fiduciary Assets and Liabilities [Line Items] | |||||
| Net uncollected premiums and claims receivable and payable | $ 15,400 | $ 15,400 | $ 14,600 | ||
| Operating Segments | Risk and Insurance Services | |||||
| Fiduciary Assets and Liabilities [Line Items] | |||||
| Interest on fiduciary funds | $ 100 | $ 109 | $ 273 | $ 311 | |