Credit Facilities and Long-Term Debt (Summary of Debt Outstanding) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jun. 26, 2020	Dec. 31, 2019	Oct. 11, 2016	Sep. 20, 2011
Credit Facilities and Long-Term Debt :
Debt issuance costs and unamortized discount	$ (28)		$ (17)
Total debt	3,084		2,316
Less: short-term borrowings and current maturities of long-term debt	600		276
Long-term debt, net	$ 2,484		2,040
4.875% Senior Notes Due 2021
Credit Facilities and Long-Term Debt :
Interest rate	4.875%				4.875%
Outstanding balances	$ 600		600
2.250% Senior Notes Due 2023
Credit Facilities and Long-Term Debt :
Interest rate	2.25%
Outstanding balances	$ 612		557
Debt fair value	$ 640		591
3.250% Senior Notes Due 2026
Credit Facilities and Long-Term Debt :
Interest rate	3.25%			3.25%
Outstanding balances	$ 500		500
Debt fair value	$ 563		518
Senior Notes Due Twenty Twenty Eight
Credit Facilities and Long-Term Debt :
Interest rate	1.95%	1.95%
Outstanding balances	$ 500		0
Senior Notes Due Twenty Thirty One
Credit Facilities and Long-Term Debt :
Interest rate	2.25%	2.25%
Outstanding balances	$ 500		0
4.375% Senior Notes Due 2046
Credit Facilities and Long-Term Debt :
Interest rate	4.375%			4.375%
Outstanding balances	$ 400		400
Debt fair value	496		431
Commercial paper
Credit Facilities and Long-Term Debt :
Outstanding balances	0		276
Level 1 | 4.875% Senior Notes Due 2021
Credit Facilities and Long-Term Debt :
Debt fair value	620		$ 629
Level 1 | Senior Notes Due Twenty Twenty Eight
Credit Facilities and Long-Term Debt :
Debt fair value	529
Level 1 | Senior Notes Due Twenty Thirty One
Credit Facilities and Long-Term Debt :
Debt fair value	$ 527