Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 2,648	$ 2,978	[1]	$ 7,758	$ 9,052	[1]
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,777	1,906		5,212	5,729
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	566	590		1,723	1,770
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	335	354		1,011	1,056
Automotive
Disaggregation of Revenue [Line Items]
Revenue	271	297		645	937
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	206	222		617	652
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	159	195		500	572
Minerals
Disaggregation of Revenue [Line Items]
Revenue	144	147		405	419
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	96	101		311	323
Coal
Disaggregation of Revenue [Line Items]
Revenue	330	516		1,022	1,611
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	445	447		1,226	1,311
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 96	$ 109		$ 298	$ 401

[1] Certain prior year data has been reclassified to conform to the current presentation.