Goodwill and other intangible assets - Intangible assets (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Insurance and Other [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 42,461	$ 40,664
Accumulated amortization	13,274	12,178
Net carrying value	29,187	28,486
Trademarks and trade names [Member] | Insurance and Other [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	5,603	5,176
Accumulated amortization	822	802
Net carrying value	4,781	4,374
Customer relationships [Member] | Insurance and Other [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	27,765	27,335
Accumulated amortization	7,174	6,450
Net carrying value	20,591	20,885
Other intangible assets [Member] | Insurance and Other [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	4,150	3,390
Accumulated amortization	1,530	1,442
Net carrying value	2,620	1,948
Customer Relationships and Contracts and Other [Member] | Railroad, Utilities and Energy [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	1,914	1,693
Accumulated amortization	622	542
Net carrying value	1,292	1,151
Patents and technology [Member] | Insurance and Other [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Gross carrying amount	4,943	4,763
Accumulated amortization	3,748	3,484
Net carrying value	$ 1,195	$ 1,279