Claim and Claim Adjustment Expense Reserves - Narratives (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] | ||||
| Loss from catastrophes, net of reinsurance | $ 62 | $ 82 | $ 159 | $ 170 |
| Property and casualty operations | ||||
| Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] | ||||
| Pretax (favorable) unfavorable development | (4) | (12) | 57 | (19) |
| Property and casualty operations | CNA Financial | ||||
| Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] | ||||
| Pretax (favorable) unfavorable development | (4) | (12) | 57 | (19) |
| Other insurance operations | ||||
| Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] | ||||
| Pretax (favorable) unfavorable development | $ 112 | $ 35 | $ 134 | $ 35 |