Retirement Plans (Summary Of Reconciliation Of The Beginning And Ending Balances Of Assets Measured At Fair Value On A Recurring Basis Using Level 3 Inputs) (Details) - Guaranteed Deposit Account [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	$ 9
Fair value of plan assets at end of year	12	$ 9
Defined benefit plan investment purchases	15	17
Purchases	(12)	(19)
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	9	11
Fair value of plan assets at end of year	12	9
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	9
Fair value of plan assets at end of year	$ 12	$ 9