v3.25.4
Goodwill and other intangible assets - Intangible assets (Detail) - USD ($)
$ in Millions
Dec. 31, 2025
Dec. 31, 2024
Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount $ 51,067 $ 50,874
Accumulated amortization 17,265 16,236
Net carrying value 33,802 34,638
Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount [1] 1,983 1,990
Accumulated amortization [1] 943 854
Net carrying value [1] 1,040 1,136
Trademarks and trade names [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 9,007 9,007
Accumulated amortization 1,143 1,041
Net carrying value 7,864 7,966
Customer relationships [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 31,215 30,941
Accumulated amortization 9,638 8,840
Net carrying value 21,577 22,101
Other intangible assets [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 5,608 5,551
Accumulated amortization 2,288 1,996
Net carrying value 3,320 3,555
Other intangible assets [Member] | Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount [1] 442 437
Accumulated amortization [1] 134 126
Net carrying value [1] 308 311
Customer relationships and contracts [Member] | Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount [1] 1,541 1,553
Accumulated amortization [1] 809 728
Net carrying value [1] 732 825
Patents and technology [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 5,237 5,375
Accumulated amortization 4,196 4,359
Net carrying value $ 1,041 $ 1,016
[1] Included in other assets.