Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 3,292	$ 2,648	$ 9,095	$ 7,758
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,881	1,777	5,602	5,212
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	624	566	1,810	1,723
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	343	335	1,062	1,011
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	231	209	684	625
Automotive
Disaggregation of Revenue [Line Items]
Revenue	209	271	661	645
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	206	159	596	500
Minerals
Disaggregation of Revenue [Line Items]
Revenue	162	144	439	405
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	106	93	350	303
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	509	445	1,488	1,226
Coal
Disaggregation of Revenue [Line Items]
Revenue	460	330	1,267	1,022
Trucking
Disaggregation of Revenue [Line Items]
Revenue	200	0	200	0
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 242	$ 96	$ 538	$ 298