Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 2,978	$ 3,129	$ 9,052	$ 9,107
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,906	1,890	5,729	5,576
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	589	596	1,766	1,741
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	354	325	1,056	959
Automotive
Disaggregation of Revenue [Line Items]
Revenue	297	300	937	934
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	225	223	664	633
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	195	205	571	589
Minerals
Disaggregation of Revenue [Line Items]
Revenue	145	137	412	388
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	101	104	323	332
Coal
Disaggregation of Revenue [Line Items]
Revenue	516	588	1,611	1,660
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	447	500	1,311	1,439
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 109	$ 151	$ 401	$ 432