Properties - Schedule of Net Properties (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023		Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	$ 52,191	$ 50,281	[1]	$ 50,617	$ 49,691	$ 49,241	$ 48,780	$ 48,463
Accumulated Depreciation	(16,533)	(15,560)	[1]	(15,792)	(15,250)	(14,974)	(14,681)	(14,393)
Properties - Net (Note 6)	35,658	34,721	[1]	$ 34,825	$ 34,441	$ 34,267	$ 34,099	$ 34,070
Total Road
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	37,684	36,551
Accumulated Depreciation	(11,648)	(11,101)
Properties - Net (Note 6)	26,036	25,450
Rail and Other Track Material
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	9,883	9,498
Accumulated Depreciation	(2,199)	(2,153)
Properties - Net (Note 6)	$ 7,684	$ 7,345
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	$ 7,269	$ 7,020
Accumulated Depreciation	(2,252)	(2,131)
Properties - Net (Note 6)	$ 5,017	$ 4,889
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	$ 2,813	$ 2,796
Accumulated Depreciation	(699)	(668)
Properties - Net (Note 6)	$ 2,114	$ 2,128
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	$ 3,494	$ 3,424
Accumulated Depreciation	(1,159)	(1,119)
Properties - Net (Note 6)	$ 2,335	$ 2,305
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	$ 3,234	$ 3,121
Accumulated Depreciation	(572)	(525)
Properties - Net (Note 6)	$ 2,662	$ 2,596
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	$ 3,476	$ 3,376
Accumulated Depreciation	(1,480)	(1,351)
Properties - Net (Note 6)	$ 1,996	$ 2,025
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	$ 1,498	$ 1,530
Accumulated Depreciation	(568)	(608)
Properties - Net (Note 6)	$ 930	$ 922
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	$ 6,017	$ 5,786
Accumulated Depreciation	(2,719)	(2,546)
Properties - Net (Note 6)	$ 3,298	$ 3,240
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	$ 11,162	$ 10,643
Accumulated Depreciation	(4,885)	(4,459)
Properties - Net (Note 6)	6,277	6,184
Locomotive
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	5,252	4,952
Accumulated Depreciation	(2,175)	(1,981)
Properties - Net (Note 6)	$ 3,077	$ 2,971
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	$ 2,311	$ 2,300
Accumulated Depreciation	(407)	(378)
Properties - Net (Note 6)	$ 1,904	$ 1,922
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	$ 3,599	$ 3,391
Accumulated Depreciation	(2,303)	(2,100)
Properties - Net (Note 6)	$ 1,296	$ 1,291
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	$ 2,276	$ 2,272
Properties - Net (Note 6)	2,276	2,272
Construction In Progress
Property, Plant and Equipment, Net, by Type [Abstract]
Cost	1,069	815
Properties - Net (Note 6)	$ 1,069	$ 815

[1] See Note 20, Revision of Prior Period Financial Statements.