Properties (Details) $ in Millions		12 Months Ended
		Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment [Line Items]
Cost		$ 74,246	$ 72,805
Accumulated depreciation		20,330	20,126
Net book value		$ 53,916	52,679
Depreciable asset classes description		We currently have more than 60 depreciable asset classes, and we may increase or decrease the number of asset classes due to changes in technology, asset strategies, or other factors.
Total repairs and maintenance expense		$ 2,300	2,500	$ 2,500
Land [Member]
Property, Plant and Equipment [Line Items]
Cost		5,276	5,264
Accumulated depreciation
Net book value		5,276	5,264
Road: Rail and Other Track Material [Member]
Property, Plant and Equipment [Line Items]
Cost		17,178	16,785
Accumulated depreciation		6,381	6,156
Net book value		$ 10,797	$ 10,629
Estimated useful life		42 years	43 years
Road: Ties [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 10,693	$ 10,409
Accumulated depreciation		3,186	3,025
Net book value		$ 7,507	$ 7,384
Estimated useful life		34 years	34 years
Road: Ballast [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 5,752	$ 5,561
Accumulated depreciation		1,669	1,595
Net book value		$ 4,083	$ 3,966
Estimated useful life		34 years	34 years
Road: Other Roadway [Member]
Property, Plant and Equipment [Line Items]
Cost	[1]	$ 20,331	$ 19,584
Accumulated depreciation	[1]	4,056	3,766
Net book value	[1]	$ 16,275	$ 15,818
Estimated useful life	[1]	48 years	48 years
Total Road [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 53,954	$ 52,339
Accumulated depreciation		15,292	14,542
Net book value		$ 38,662	37,797
Term of Depreciation Studies		6 years
Equipment: Locomotives [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 9,467	9,792
Accumulated depreciation		3,434	3,861
Net book value		$ 6,033	$ 5,931
Estimated useful life		18 years	19 years
Equipment: Freight Cars [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 2,083	$ 2,229
Accumulated depreciation		779	929
Net book value		$ 1,304	$ 1,300
Estimated useful life		25 years	24 years
Equipment: Work Equipment and Other [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 1,081	$ 1,040
Accumulated depreciation		322	301
Net book value		$ 759	$ 739
Estimated useful life		18 years	19 years
Total Equipment [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 12,631	$ 13,061
Accumulated depreciation		4,535	5,091
Net book value		$ 8,096	7,970
Term of Depreciation Studies		3 years
Technology and Other [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 1,136	1,117
Accumulated depreciation		503	493
Net book value		$ 633	$ 624
Estimated useful life		12 years	12 years
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Cost		$ 1,249	$ 1,024
Accumulated depreciation
Net book value		$ 1,249	$ 1,024
Minimum [Member]
Property, Plant and Equipment [Line Items]
Number of depreciable asset classes | item		60

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