Short-Term and Long-Term Debt (Schedule of Extinguishment of Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Principal balance outstanding prior to payoff	[1]	$ 109	$ 287
Unamortized debt issuance costs and discounts		(1)	(1)	$ 5
Amount paid to retire debt		(150)	(309)
Gain (loss) on early extinguishment of debt, pre-tax		(42)	(23)	$ 5
6.15% Notes, Due 2036 [Member]
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Debt Instrument Repurchase Amount		$ 105
Interest rate		6.15%
4.85% Notes, Due 2021 [Member]
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Debt Instrument Repurchase Amount		$ 4
Interest rate		4.85%
8.75% notes, due 2019 [Member]
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Debt Instrument Repurchase Amount			$ 287
Interest rate			8.75%

[1] During the third quarter of 2019, we repurchased $105 million of our 6.15% senior notes due 2036 and $4 million of our 4.85% senior notes due 2021. During the first quarter of 2018, we repurchased $287 million of our 8.75% senior notes due 2019.