v3.25.4
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
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]      
Gross liabilities at the beginning of the year $ 115,151 $ 111,082 $ 107,472
Reinsurance recoverable on unpaid losses at the beginning of the year (4,593) (4,893) (5,025)
Net liabilities at the beginning of the year 110,558 106,189 102,447
Losses and loss adjustment expenses incurred, current accident year 58,207 57,563 59,244
Losses and loss adjustment expenses incurred, prior accident years (1,854) (2,322) (3,541)
Total Losses and loss adjustment expenses incurred 56,353 55,241 55,703
Losses and loss adjustment expenses paid, current accident year (23,762) (24,139) (25,184)
Losses and loss adjustment expenses paid, prior accident years (27,709) (26,436) (27,065)
Total Losses and loss adjustment expenses paid (51,471) (50,575) (52,249)
Foreign currency effect 817 (297) 288
Net liabilities at end of year 116,257 110,558 106,189
Reinsurance recoverable on unpaid losses at end of year 4,456 4,593 4,893
Gross liabilities at end of year $ 120,713 $ 115,151 $ 111,082