Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 2,813	$ 2,855
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,818	1,927
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	580	626
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	349	365
Automotive
Disaggregation of Revenue [Line Items]
Revenue	236	281
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	220	219
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	186	199
Minerals
Disaggregation of Revenue [Line Items]
Revenue	125	127
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	122	110
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	468	422
Coal
Disaggregation of Revenue [Line Items]
Revenue	384	405
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 143	$ 101