Properties - Schedule of Net Properties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 50,320	$ 48,105
Accumulated depreciation	(15,385)	(13,863)
Net book value	34,935	34,242
Total Road
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	36,590	34,792
Accumulated depreciation	(10,926)	(9,727)
Net book value	25,664	25,065
Rail and Other Track Material
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	9,537	8,660
Accumulated depreciation	(1,978)	(1,405)
Net book value	$ 7,559	$ 7,255
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	$ 7,020	$ 6,763
Accumulated depreciation	(2,131)	(2,010)
Net book value	$ 4,889	$ 4,753
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	$ 2,796	$ 2,741
Accumulated depreciation	(668)	(637)
Net book value	$ 2,128	$ 2,104
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	$ 3,424	$ 3,383
Accumulated depreciation	(1,119)	(1,130)
Net book value	$ 2,305	$ 2,253
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	$ 3,121	$ 2,989
Accumulated depreciation	(525)	(454)
Net book value	$ 2,596	$ 2,535
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	$ 3,376	$ 3,299
Accumulated depreciation	(1,351)	(1,210)
Net book value	$ 2,025	$ 2,089
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	$ 1,530	$ 1,416
Accumulated depreciation	(608)	(558)
Net book value	$ 922	$ 858
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	$ 5,786	$ 5,541
Accumulated depreciation	(2,546)	(2,323)
Net book value	$ 3,240	$ 3,218
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	$ 10,643	$ 10,296
Accumulated depreciation	(4,459)	(4,136)
Net book value	6,184	6,160
Locomotive
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	4,952	4,848
Accumulated depreciation	(1,981)	(1,856)
Net book value	$ 2,971	$ 2,992
Annual depreciation rate	3.80%	3.80%
Estimated useful life (avg. years)	26 years	26 years
Freight Cars
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,300	$ 2,316
Accumulated depreciation	(378)	(369)
Net book value	$ 1,922	$ 1,947
Annual depreciation rate	3.10%	3.10%
Estimated useful life (avg. years)	32 years	32 years
Work Equipment and Other
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 3,391	$ 3,132
Accumulated depreciation	(2,100)	(1,911)
Net book value	$ 1,291	$ 1,221
Annual depreciation rate	8.90%	8.90%
Estimated useful life (avg. years)	11 years	11 years
Land
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 2,272	$ 2,272
Net book value	2,272	2,272
Construction In Progress
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	815	745
Net book value	$ 815	$ 745