Long-Term Debt (Schedule Of Senior Medium-Term Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, interest rate 4.5%	4.50%
Senior medium-term notes	$ 637	$ 135
Senior Medium Term Notes, Par Amount	$ 636
Long-term debt, interest rate 3.5%	3.50%
Senior Medium-Term Notes four point five zero percent with maturity of June 2023 [Member]
Debt Instrument [Line Items]
Senior medium-term notes	$ 135
Senior Medium Term Notes, Par Amount	$ 136
Schedule Of Maturities On Long-Term Debt	45078
Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Senior medium-term notes	$ 502
Senior Medium Term Notes, Par Amount	$ 500
Schedule Of Maturities On Long-Term Debt	44435