v3.25.4
Unpaid losses and loss adjustment expenses - Reconciliation of unpaid losses and allocated loss adjustment expenses to balance sheet liability (Detail) - Insurance Group [Member]
$ in Millions
Dec. 31, 2025
USD ($)
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net $ 110,555
Reinsurance recoverable 4,352
Unallocated LAE 2,396
Other losses and LAE 3,410
Liability for Claims and Claims Adjustment Expense, Total 120,713
GEICO [Member] | Physical Damage [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 914
Reinsurance recoverable 3
GEICO [Member] | Auto Liability [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 23,526
Reinsurance recoverable 899
Berkshire Hathaway Primary Group [Member] | Medical Professional Liability [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 9,721
Reinsurance recoverable 38
Berkshire Hathaway Primary Group [Member] | Workers' Compensation and Other Casualty [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 26,912
Reinsurance recoverable 1,401
Berkshire Hathaway Reinsurance Group [Member] | Property [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 14,944
Reinsurance recoverable 688
Berkshire Hathaway Reinsurance Group [Member] | Casualty [Member]  
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]  
Unpaid losses and ALAE, net 34,538
Reinsurance recoverable $ 1,323