Segment Reporting and Significant Expenses- Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	$ 3,587	$ 3,619	$ 10,584	$ 11,001
Labor and Fringe	815	806	2,427	2,377
Purchased Services and Other	730	676	2,214	2,087
Depreciation and Amortization	424	416	1,276	1,236
Fuel	281	276	825	902
Equipment and Other Rents	86	91	267	260
Operating Income	1,087	1,354	3,411	4,139
Expenses	2,500	2,265	7,173	6,862
Impairment	164	0	164	0
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Operating Income	1,256	1,351	3,571	4,123
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	(8)	(2)	(21)	(5)
Expenses	(8)	(2)	(21)	(5)
Rail Operations | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	3,380	3,405	9,964	10,351
Labor and Fringe	758	756	2,268	2,235
Purchased Services and Other	624	556	1,893	1,735
Depreciation and Amortization	408	401	1,228	1,191
Equipment and Other Rents	80	86	252	245
Gains on Property Dispositions	(6)	0	(11)	(10)
Operating Income	1,256	1,351	3,571	4,123
Rail Operations | Operating Segments | Fuel - Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	237	229	688	754
Rail Operations | Operating Segments | Fuel - Non- Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	23	26	75	78
Trucking Operations
Segment Reporting, Asset Reconciling Item [Line Items]
Impairment	164		164
Trucking Operations | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	215	216	641	655
Expenses	384	213	801	639
Trucking Operations | Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	207	214	620	650
Expenses	$ 376	$ 211	$ 780	$ 634