Revenues - Revenues Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019		Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 2,255	$ 3,061	[1]	$ 5,110	$ 6,074	[1]
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue	1,508	1,944		3,435	3,823
Chemicals
Disaggregation of Revenue [Line Items]
Revenue	531	592		1,157	1,180
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue	311	358		676	702
Forest Products
Disaggregation of Revenue [Line Items]
Revenue	194	218		411	430
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue	142	188		341	377
Minerals
Disaggregation of Revenue [Line Items]
Revenue	134	147		261	272
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue	103	112		215	222
Automotive
Disaggregation of Revenue [Line Items]
Revenue	93	329		374	640
Coal
Disaggregation of Revenue [Line Items]
Revenue	287	557		692	1,095
Intermodal
Disaggregation of Revenue [Line Items]
Revenue	359	436		781	864
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 101	$ 124		$ 202	$ 292

[1] Certain prior year data has been reclassified to conform to the current presentation.