Long-Term Debt (Schedule Of Changes In Long Term Debt) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Debt Instrument [Line Items]
Balance as of beginning-of-year	$ 4,894
Notes issued	1,094
Early extinguishment of notes	(487)
Unamortized premium (discount)	4
Unamortized debt issuance costs	(9)
Fair value hedge-interest rate swap	(54)
Balance as of end-of-period	5,648
4.00% Notes, Due 2023 [Member]
Debt Instrument [Line Items]
Notes issued	$ 150
Interest rate	4.00%
3.80% Notes, Due 2028 [Member]
Debt Instrument [Line Items]
Notes issued	$ 500
Interest rate	3.80%
4.35% Notes Due 2048 [Member]
Debt Instrument [Line Items]
Notes issued	$ 450
Interest rate	4.35%
8.75% notes, due 2019 [Member]
Debt Instrument [Line Items]
Early extinguishment of notes	$ (287)
Interest rate	8.75%