Debt (Debt Redemption) (Narrative) (Details) - USD ($) $ in Millions			2 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Oct. 15, 2019	Mar. 15, 2018	Mar. 15, 2018	Dec. 31, 2019	Mar. 31, 2018	Oct. 15, 2019	Dec. 31, 2019	[1]	Dec. 31, 2018	[1]
Extinguishment of Debt [Line Items]
Debt Instrument, Repurchase Date	Oct. 15, 2019	Mar. 15, 2018
Weighted average interest rate of bonds and debentures		4.90%	4.90%
Fixed rate debt securities carrying value		$ 70	$ 70
Early extinguishment of debt				$ (2)	$ (85)		$ (2)		$ (85)
Missiouri Pacific 5 Percent Income Debentures due 2045 [Member]
Extinguishment of Debt [Line Items]
Interest rate on note		5.00%	5.00%
Due date of debt			Jan. 01, 2045
Principal outstanding		$ 96	$ 96
Chicago and Eastern Illinois 5 Percent Income Debentures Due 2054 [Member]
Extinguishment of Debt [Line Items]
Interest rate on note		5.00%	5.00%
Due date of debt			Jan. 01, 2054
Principal outstanding		$ 2	$ 2
Missouri Pacific 4.75 Percent General Mortgage Income Bonds Series A Due 2020 [Member]
Extinguishment of Debt [Line Items]
Interest rate on note		4.75%	4.75%
Due date of debt			Jan. 01, 2020
Principal outstanding		$ 30	$ 30
Missouri Pacific 4.75 Percent General Mortgage Income Bonds Series B Due 2020 [Member]
Extinguishment of Debt [Line Items]
Interest rate on note		4.75%	4.75%
Due date of debt			Jan. 01, 2030
Principal outstanding		$ 27	$ 27
6.125% Notes Due 2020 [Member]
Extinguishment of Debt [Line Items]
Interest rate on note	6.125%					6.125%
Due date of debt						Feb. 15, 2020
Principal outstanding	$ 163					$ 163

[1] 2019 includes a debt extinguishment charge for the early redemption of certain notes in the fourth quarter. 2018 includes a debt extinguishment charge for the early redemption of certain bonds and debentures in the first quarter (Note 15).