Revenues - Disaggregated by Lines of Business (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 2,885	$ 2,978	$ 3,061	$ 3,013	$ 3,143	$ 3,129	$ 3,102	$ 2,876	$ 11,937	$ 12,250	$ 11,408
Chemicals
Disaggregation of Revenue [Line Items]
Revenue									2,343	2,339	2,210
Agricultural and Food Products
Disaggregation of Revenue [Line Items]
Revenue									1,410	1,306	1,262
Automotive
Disaggregation of Revenue [Line Items]
Revenue									1,236	1,267	1,195
Forest Products
Disaggregation of Revenue [Line Items]
Revenue									878	850	755
Metals and Equipment
Disaggregation of Revenue [Line Items]
Revenue									741	769	703
Minerals
Disaggregation of Revenue [Line Items]
Revenue									550	518	477
Fertilizers
Disaggregation of Revenue [Line Items]
Revenue									431	442	466
Total Merchandise
Disaggregation of Revenue [Line Items]
Revenue									7,589	7,491	7,068
Coal
Disaggregation of Revenue [Line Items]
Revenue									2,070	2,246	2,107
Intermodal
Disaggregation of Revenue [Line Items]
Revenue									1,760	1,931	1,799
Other
Disaggregation of Revenue [Line Items]
Revenue									$ 518	$ 582	$ 434