Business segment data - Narrative (Detail) $ in Millions	12 Months Ended
Dec. 31, 2024 USD ($) Activity	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of insurance segment activities \| Activity	2
Sales	$ 371,433	$ 364,482	$ 302,020
Sales, Service and Leasing Revenues [Member]
Segment Reporting Information [Line Items]
Sales	$ 211,600	$ 215,600	$ 165,000
United States [Member] \| Geographic Concentration [Member] \| Sales, Service and Leasing Revenues [Member]
Segment Reporting Information [Line Items]
Concentration percentage	86.00%	87.00%	86.00%
United States [Member] \| Geographic Concentration [Member] \| Property, Plant and Equipment and Equipment Held for Lease [Member]
Segment Reporting Information [Line Items]
Concentration percentage	91.00%
Railroad, Utilities and Energy [Member]
Segment Reporting Information [Line Items]
Sales	$ 49,790	$ 49,751	$ 52,149
Railroad, Utilities and Energy [Member] \| United States [Member] \| Geographic Concentration [Member] \| Revenues [Member]
Segment Reporting Information [Line Items]
Concentration percentage	95.00%	96.00%	96.00%

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration