Credit Facilities and Long-Term Debt (Summary of Debt Outstanding) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Credit Facilities and Long-Term Debt :
Debt issuance costs and unamortized discount	$ (17)	$ (19)
Total debt	2,316	2,308
Less: short-term borrowings and current maturities of long-term debt	276	257
Long-term debt, net	2,040	2,051
4.875% Senior Notes Due 2021
Credit Facilities and Long-Term Debt :
Outstanding balances	600	600
2.250% Senior Notes Due 2023
Credit Facilities and Long-Term Debt :
Outstanding balances	557	570
Debt fair value	591	599
3.250% Senior Notes Due 2026
Credit Facilities and Long-Term Debt :
Outstanding balances	500	500
Debt fair value	518	476
4.375% Senior Notes Due 2046
Credit Facilities and Long-Term Debt :
Outstanding balances	400	400
Debt fair value	431	397
Commercial paper
Credit Facilities and Long-Term Debt :
Outstanding balances	276	0
Term loan
Credit Facilities and Long-Term Debt :
Outstanding balances	0	257
Level 1 \| 4.875% Senior Notes Due 2021
Credit Facilities and Long-Term Debt :
Debt fair value	$ 629	$ 620

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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