Revenues - Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 10,583	$ 11,937	[1]	$ 12,250	[1]
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	7,076	7,589		7,491
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	2,309	2,349		2,344
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	1,386	1,410		1,306
Automotive
Disaggregation of Revenue [Line Items]
Revenue	920	1,236		1,267
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	824	862		834
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	675	742		771
Minerals
Disaggregation of Revenue [Line Items]
Revenue	538	559		527
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	424	431		442
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	1,702	1,760		1,931
Coal
Disaggregation of Revenue [Line Items]
Revenue	1,397	2,070		2,246
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 408	$ 518		$ 582

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