Segment Reporting and Significant Expenses- Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	$ 3,423	$ 3,681	[1]
Labor and Fringe	821	805	[1]
Purchased Services and Other	774	720	[1]
Depreciation and Amortization	425	410	[1]
Fuel	275	325	[1]
Equipment and Other Rents	87	84	[1]
Operating Income	1,041	1,337	[1]
Expenses	2,382	2,344	[1]
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Operating Income	1,038	1,331
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	(5)	(2)
Expenses	(5)	(2)
Trucking Operating Segment | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	207	217
Expenses	204	211
Trucking Operating Segment | Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	202	215
Expenses	199	209
Rail Operations | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	3,221	3,466
Labor and Fringe	774	760
Purchased Services and Other	662	602
Depreciation and Amortization	410	395
Equipment and Other Rents	82	78
Gain on Property Disposition	0	1
Operating Income	1,038	1,331
Rail Operations | Operating Segments | Fuel - Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	225	276
Rail Operations | Operating Segments | Fuel - Non- Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	$ 30	$ 25

[1] See the 2024 annual report filed on Form 10-K for revision of prior period financial statements.