Long-Term Debt (Schedule Of Senior Medium-Term Notes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 165
Senior medium-term notes	$ 135	288
Long-term Senior notes redeemed		100
Debt Redemptions and Repurchases, Par		265
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	June 1, 2023
Long-Term Debt, Senior Note at 3.60% [Member]
Debt Instrument [Line Items]
Long-term Senior notes redeemed		11
Long-Term Debt, Senior Note at 4.00% [Member]
Debt Instrument [Line Items]
Long-term Senior notes redeemed		$ 89