Revenues - Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 3,427	$ 3,292	$ 2,990	$ 2,813	$ 2,825	$ 2,648	$ 2,255	$ 2,855	$ 12,522	$ 10,583	$ 11,937
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue									7,539	7,076	7,589
Chemicals
Disaggregation of Revenue [Line Items]
Revenue									2,421	2,309	2,349
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue									1,461	1,386	1,410
Forest Products
Disaggregation of Revenue [Line Items]
Revenue									918	834	870
Automotive
Disaggregation of Revenue [Line Items]
Revenue									886	920	1,236
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue									796	675	742
Minerals
Disaggregation of Revenue [Line Items]
Revenue									587	538	559
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue									470	414	423
Intermodal
Disaggregation of Revenue [Line Items]
Revenue									2,039	1,702	1,760
Coal
Disaggregation of Revenue [Line Items]
Revenue									1,790	1,397	2,070
Trucking
Disaggregation of Revenue [Line Items]
Revenue									410	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue									$ 744	$ 408	$ 518