Segment Reporting and Significant Expenses- Schedule of Segment Reporting Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	$ 3,574	$ 3,701	$ 6,997	$ 7,382
Labor and Fringe	791	766	1,612	1,571
Purchased Services and Other	710	691	1,484	1,411
Depreciation and Amortization	427	410	852	820
Fuel	269	301	544	626
Equipment and Other Rents	94	85	181	169
Operating Income	1,283	1,448	2,324	2,785
Expenses	2,291	2,253	4,673	4,597
Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Operating Income	1,277	1,441	2,315	2,772
Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	(8)	(2)	(13)	(4)
Expenses	(8)	(2)	(13)	(4)
Rail Operations | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	3,363	3,480	6,584	6,946
Labor and Fringe	736	719	1,510	1,478
Purchased Services and Other	605	577	1,269	1,178
Depreciation and Amortization	410	396	820	791
Equipment and Other Rents	90	80	172	159
Gains on Property Dispositions	(4)	(9)	(5)	(10)
Operating Income	1,277	1,441	2,315	2,772
Rail Operations | Operating Segments | Fuel - Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	226	249	451	525
Rail Operations | Operating Segments | Fuel - Non- Locomotive
Segment Reporting, Asset Reconciling Item [Line Items]
Fuel	23	27	52	53
Trucking Operating Segment | Operating Segments
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	219	223	426	440
Expenses	213	216	417	427
Trucking Operating Segment | Eliminations
Segment Reporting, Asset Reconciling Item [Line Items]
Revenue	211	221	413	436
Expenses	$ 205	$ 214	$ 404	$ 423