v3.25.2
Unpaid losses and loss adjustment expenses - Reconciliation of changes in claim liabilities (Detail) - Property and Casualty Insurance and Reinsurance, Excluding Retroactive Reinsurance [Member] - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Liability for Claims and Claims Adjustment Expense [Line Items]    
Gross liabilities at the beginning of the year $ 115,151 $ 111,082
Reinsurance recoverable on unpaid losses at the beginning of the year (4,593) (4,893)
Net liabilities at the beginning of the year 110,558 106,189
Losses and loss adjustment expenses incurred, current accident year 28,607 28,359
Losses and loss adjustment expenses incurred, prior accident years (240) (1,167)
Total losses and loss adjustment expenses incurred 28,367 27,192
Losses and loss adjustment expenses paid, current accident year (9,253) (9,491)
Losses and loss adjustment expenses paid, prior accident years (16,283) (15,626)
Total losses and loss adjustment expenses paid (25,536) (25,117)
Foreign currency effect 712 (110)
Net liabilities at end of period 114,101 108,154
Reinsurance recoverable on unpaid losses at end of period 4,687 4,650
Gross liabilities at end of period $ 118,788 $ 112,804