Properties - Schedule of Net Properties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 46,505	$ 45,530
Accumulated Depreciation	(13,490)	(13,086)
Properties - Net (Note 6)	33,015	32,444
Total Road
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	34,076	33,109
Accumulated Depreciation	(9,694)	(9,138)
Properties - Net (Note 6)	24,382	23,971
Rail and Other Track Material
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	8,761	8,449
Accumulated Depreciation	(1,835)	(1,739)
Properties - Net (Note 6)	$ 6,926	$ 6,710
Annual Depreciation Rate	2.50%	2.50%
Estimated useful life (Avg. Years)	41 years	41 years
Ties
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 6,522	$ 6,284
Accumulated Depreciation	(1,923)	(1,780)
Properties - Net (Note 6)	$ 4,599	$ 4,504
Annual Depreciation Rate	3.50%	3.50%
Estimated useful life (Avg. Years)	28 years	28 years
Grading
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,751	$ 2,768
Accumulated Depreciation	(624)	(614)
Properties - Net (Note 6)	$ 2,127	$ 2,154
Annual Depreciation Rate	1.30%	1.30%
Estimated useful life (Avg. Years)	75 years	75 years
Ballast
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 3,289	$ 3,238
Accumulated Depreciation	(1,094)	(1,051)
Properties - Net (Note 6)	$ 2,195	$ 2,187
Annual Depreciation Rate	2.60%	2.60%
Estimated useful life (Avg. Years)	38 years	38 years
Bridges, Trestles, and Culverts
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,794	$ 2,688
Accumulated Depreciation	(411)	(380)
Properties - Net (Note 6)	$ 2,383	$ 2,308
Annual Depreciation Rate	1.70%	1.70%
Estimated useful life (Avg. Years)	60 years	60 years
Signals and Interlockers
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 3,266	$ 3,170
Accumulated Depreciation	(1,086)	(944)
Properties - Net (Note 6)	$ 2,180	$ 2,226
Annual Depreciation Rate	4.10%	4.10%
Estimated useful life (Avg. Years)	24 years	24 years
Buildings
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 1,388	$ 1,366
Accumulated Depreciation	(514)	(529)
Properties - Net (Note 6)	$ 874	$ 837
Annual Depreciation Rate	2.50%	2.50%
Estimated useful life (Avg. Years)	40 years	40 years
Other
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 5,305	$ 5,146
Accumulated Depreciation	(2,207)	(2,101)
Properties - Net (Note 6)	$ 3,098	$ 3,045
Annual Depreciation Rate	4.10%	4.10%
Estimated useful life (Avg. Years)	25 years	25 years
Total Equipment
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 10,125	$ 10,227
Accumulated Depreciation	(3,796)	(3,948)
Properties - Net (Note 6)	6,329	6,279
Locomotive
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	4,912	5,085
Accumulated Depreciation	(1,732)	(1,849)
Properties - Net (Note 6)	$ 3,180	$ 3,236
Annual Depreciation Rate	3.60%	3.60%
Estimated useful life (Avg. Years)	27 years	27 years
Freight Cars
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,322	$ 2,557
Accumulated Depreciation	(358)	(540)
Properties - Net (Note 6)	$ 1,964	$ 2,017
Annual Depreciation Rate	2.90%	2.90%
Estimated useful life (Avg. Years)	35 years	35 years
Work Equipment and Other
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,891	$ 2,585
Accumulated Depreciation	(1,706)	(1,559)
Properties - Net (Note 6)	$ 1,185	$ 1,026
Annual Depreciation Rate	8.20%	8.20%
Estimated useful life (Avg. Years)	12 years	12 years
Land
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 1,885	$ 1,823
Properties - Net (Note 6)	1,885	1,823
Construction In Progress
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	419	371
Properties - Net (Note 6)	$ 419	$ 371