Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions |
9 Months Ended | |
|---|---|---|
Sep. 30, 2025 |
Dec. 31, 2024 |
|
| Property, Plant and Equipment [Line Items] | ||
| Receivables | $ 3,515 | $ 3,299 |
| Minimum MLR, medical cost corridors and profit sharing liability | $ 641 | $ 1,006 |
| Percent due to medicare, medical loss ratio | 85.00% | 85.00% |
| Government agencies liability | $ 38 | $ 32 |
| Percent due to medicare, medical loss ratio of marketplace | 80.00% | 80.00% |
| Medical loss ratio of marketplace | $ 18 | $ 30 |
| Risk adjustments liability | 128 | 115 |
| Risk adjustment receivable (payable) | (353) | (290) |
| Risk adjustment receivable | 183 | 192 |
| Risk adjustment, net receivable (payable) | $ (170) | (98) |
| Maturity period (less than) | 15 years | |
| Structured Securities | ||
| Property, Plant and Equipment [Line Items] | ||
| Average maturity period (less than) | 15 years | |
| Government Receivables | ||
| Property, Plant and Equipment [Line Items] | ||
| Receivables | $ 2,241 | $ 2,223 |