Summary of Significant Accounting Policies - Schedule of Cost and Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Railway operating revenues	$ 12,180	$ 12,123	$ 12,156
Railway operating expenses
Compensation and benefits	2,922	2,823	2,819
Fuel	932	987	1,170
Depreciation	1,393	1,353	1,298
Merger-related expenses	80	0	0
Restructuring and other charges	22	183	0
Eastern Ohio incident	(254)
Eastern Ohio incident		325	1,116
Total railway operating expenses	7,824	8,052	9,305
Income from railway operations	4,356	4,071	2,851
Other income – net	101	65	191
Income before income taxes	3,665	3,329	2,320
Income taxes	792	707	493
Net income	2,873	2,622	1,827
Reportable Segment
Segment Reporting Information [Line Items]
Railway operating revenues	12,180	12,123	12,156
Railway operating expenses
Compensation and benefits	2,922	2,823	2,819
Purchased services	1,675	1,655	1,683
Equipment rents	420	393	387
Fuel	932	987	1,170
Depreciation	1,393	1,353	1,298
Materials	411	369	364
Claims	281	237	242
Other	(58)	(273)	226
Merger-related expenses	80	0	0
Restructuring and other charges	22	183	0
Eastern Ohio incident	(254)
Eastern Ohio incident		325	1,116
Total railway operating expenses	7,824	8,052	9,305
Income from railway operations	4,356	4,071	2,851
Other income – net	101	65	191
Interest expense on debt	792	807	722
Income before income taxes	3,665	3,329	2,320
Income taxes	792	707	493
Net income	$ 2,873	$ 2,622	$ 1,827