Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 3,061	$ 3,102	$ 6,074	$ 5,978
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,944	1,907	3,823	3,686
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	591	588	1,177	1,145
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	358	327	702	634
Automotive
Disaggregation of Revenue [Line Items]
Revenue	329	330	640	634
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	223	215	439	410
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	187	198	376	384
Minerals
Disaggregation of Revenue [Line Items]
Revenue	144	137	267	251
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	112	112	222	228
Coal
Disaggregation of Revenue [Line Items]
Revenue	557	569	1,095	1,072
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	436	490	864	939
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 124	$ 136	$ 292	$ 281