Short-Term and Long-Term Debt (Schedule of Extinguishment of Debt) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Principal balance outstanding prior to payoff	[1]	$ 287		$ 350
Unamortized debt issuance costs and discounts prior to payoff		(1)	$ 5	(3)
Amount paid to retire debt		(309)		(410)
Gain (loss) on extinguishment of debt, pre-tax		(23)	$ 5	(63)
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%
Senior Notes Due 2019 [Member]
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Debt Instrument Repurchase Amount				$ 200
Interest rate				8.75%
Senior Notes Due 2036 [Member]
Details underlying the recognition of gain or loss on extinguishment of debt [Abstract]
Debt Instrument Repurchase Amount				$ 150
Interest rate				6.15%

[1] During the first quarter of 2018, we repurchased $287 million of our 8.75% senior notes due 2019. During the fourth quarter of 2016, we repurchased $200 million of our 8.75% senior notes due 2019 and $150 million of our 6.15% senior notes due 2036.