Nature Of Operations (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) mi	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment mi	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commodity Group Information [Line Items]
Other subsidiary revenues									$ 880	$ 881	$ 885
Accessorial revenues									514	502	458
Other revenues									71	65	60
Total operating revenues	$ 5,212	$ 5,516	$ 5,596	$ 5,384	$ 5,757	$ 5,928	$ 5,672	$ 5,475	$ 21,708	22,832	21,240
Network route miles | mi	32,340								32,340
Route miles owned | mi	26,094								26,094
Reportable segments | segment									1
Cargo and Freight [Member]
Commodity Group Information [Line Items]
Freight revenues									$ 20,243	21,384	19,837
Agricultural Products [Member]
Commodity Group Information [Line Items]
Freight revenues									4,444	4,469	4,303
Energy [Member]
Commodity Group Information [Line Items]
Freight revenues									3,761	4,608	4,498
Industrial [Member]
Commodity Group Information [Line Items]
Freight revenues									5,796	5,679	5,204
Premium [Member]
Commodity Group Information [Line Items]
Freight revenues									6,242	6,628	5,832
Mexico [Member]
Commodity Group Information [Line Items]
Freight revenues									$ 2,300	$ 2,500	$ 2,300