Other Income (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Other Income [Abstract]
Rental income					$ 124		$ 122		$ 178	[1]
Net periodic pension and OPEB costs					37		13		(45)
Interest income					32		30		16
Interest income due to employment tax refund					31
Net gain on non-operating asset dispositions.					20		30		111	[2]
Early extinguishment of debt	$ (2)	$ (85)			(2)	[3]	(85)	[3]
Non-operating environmental costs and other					1		(16)		(15)
Total					$ 243		$ 94		$ 245
Gain (Loss) Related to Litigation Settlement			$ 65
Real estate sale			$ 57	$ 26

[1] 2017 includes $65 million related to a favorable litigation settlement in the third quarter.

[2] 2017 includes $26 million and $57 million related to a real estate sale in the first quarter and in the third quarter, respectively.

[3] 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).