v3.25.2
Goodwill and other intangible assets - Intangible assets (Detail) - USD ($)
$ in Millions
Jun. 30, 2025
Dec. 31, 2024
Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount $ 51,149 $ 50,874
Accumulated amortization 17,070 16,236
Net carrying value 34,079 34,638
Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 1,983 1,990
Accumulated amortization 892 854
Net carrying value 1,091 1,136
Customer relationships [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 30,939 30,941
Accumulated amortization 9,224 8,840
Net carrying value 21,715 22,101
Trademarks and trade names [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 9,031 9,007
Accumulated amortization 1,111 1,041
Net carrying value 7,920 7,966
Customer relationships and contracts [Member] | Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 1,540 1,553
Accumulated amortization 762 728
Net carrying value 778 825
Other intangible assets [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 5,607 5,551
Accumulated amortization 2,156 1,996
Net carrying value 3,451 3,555
Other intangible assets [Member] | Railroad, Utilities and Energy [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 443 437
Accumulated amortization 130 126
Net carrying value 313 311
Patents and technology [Member] | Insurance and Other [Member]    
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]    
Gross carrying amount 5,572 5,375
Accumulated amortization 4,579 4,359
Net carrying value $ 993 $ 1,016