Note 10 - Properties - Schedule of Property and Equipment Major Categories (Details) - USD ($) $ in Millions		Mar. 31, 2024		Dec. 31, 2023
Property, Plant and Equipment, Cost		$ 82,271		$ 81,733
Property, Plant and Equipment, Net		57,590		57,398
Property, Plant and Equipment, Accumulated Depreciation		24,681		24,335
Land [Member]
Property, Plant and Equipment, Cost		5,429		5,426
Property, Plant and Equipment, Net		5,429		5,426
Roadrail and Other Track Material [Member]
Property, Plant and Equipment, Cost		18,952		18,837
Property, Plant and Equipment, Net		11,532		11,493
Property, Plant and Equipment, Accumulated Depreciation		$ 7,420		$ 7,344
Property, Plant and Equipment, Useful Life (Year)		46 years		42 years
Road Ties [Member]
Property, Plant and Equipment, Cost		$ 12,064		$ 11,985
Property, Plant and Equipment, Net		8,106		8,090
Property, Plant and Equipment, Accumulated Depreciation		$ 3,958		$ 3,895
Property, Plant and Equipment, Useful Life (Year)		34 years		34 years
Road Ballast [Member]
Property, Plant and Equipment, Cost		$ 6,373		$ 6,345
Property, Plant and Equipment, Net		4,278		4,284
Property, Plant and Equipment, Accumulated Depreciation		$ 2,095		$ 2,061
Property, Plant and Equipment, Useful Life (Year)		34 years		34 years
Road, Other [Member]
Property, Plant and Equipment, Cost	[1]	$ 23,290		$ 23,175
Property, Plant and Equipment, Net		17,840	[1]	17,807
Property, Plant and Equipment, Accumulated Depreciation		$ 5,450	[1]	$ 5,368
Property, Plant and Equipment, Useful Life (Year)		47 years	[1]	47 years
Road [Member]
Property, Plant and Equipment, Cost		$ 60,679		$ 60,342
Property, Plant and Equipment, Net		41,756		41,674
Property, Plant and Equipment, Accumulated Depreciation		18,923		18,668
Equipment, Locomotives [Member]
Property, Plant and Equipment, Cost		9,481		9,295
Property, Plant and Equipment, Net		5,839		5,704
Property, Plant and Equipment, Accumulated Depreciation		$ 3,642		$ 3,591
Property, Plant and Equipment, Useful Life (Year)		18 years		18 years
Equipment, Freight Cars [Member]
Property, Plant and Equipment, Cost		$ 2,789		$ 2,765
Property, Plant and Equipment, Net		1,806		1,809
Property, Plant and Equipment, Accumulated Depreciation		$ 983		$ 956
Property, Plant and Equipment, Useful Life (Year)		23 years		23 years
Equipment, Work Equipment and Other [Member]
Property, Plant and Equipment, Cost		$ 1,335		$ 1,344
Property, Plant and Equipment, Net		790		798
Property, Plant and Equipment, Accumulated Depreciation		$ 545		$ 546
Property, Plant and Equipment, Useful Life (Year)		17 years		17 years
Equipment [Member]
Property, Plant and Equipment, Cost		$ 13,605		$ 13,404
Property, Plant and Equipment, Net		8,435		8,311
Property, Plant and Equipment, Accumulated Depreciation		5,170		5,093
Technology Equipment [Member]
Property, Plant and Equipment, Cost		1,394		1,388
Property, Plant and Equipment, Net		806		814
Property, Plant and Equipment, Accumulated Depreciation		$ 588		$ 574
Property, Plant and Equipment, Useful Life (Year)		12 years		12 years
Construction in Progress [Member]
Property, Plant and Equipment, Cost		$ 1,164		$ 1,173
Property, Plant and Equipment, Net		1,164		1,173
Property, Plant and Equipment, Accumulated Depreciation		$ 0		$ 0

[1] Other roadway includes grading, bridges and tunnels, signals, buildings, and other road assets.