Retirement Plans (Schedule Of Changes In Defined Benefit Plan Obligations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	$ 924	$ 916
Service cost	5	7	$ 9
Interest cost	25	32	38
Actuarial loss (gain)	116	91
Plan amendments	2	3
Plan curtailments	(14)	(3)
Plan settlements	(28)	(75)
Benefits paid	(49)	(47)
Benefit obligation at end of year	981	924	916
Change in plan assets:
Fair value of plan assets at beginning of year	694	685
Actual return on plan assets	114	118
Employer contributions	14	13
Plan settlements	(28)	(75)
Benefits paid	(49)	(47)
Fair value of plan assets at end of year	745	694	685
Funded status at end of year	(236)	(230)
Amounts recognized in balance sheet:
Other long-term assets	10
Other current liabilities	(14)	(13)
Other long-term liabilities	(232)	(217)
Net amount	(236)	(230)
Amounts recognized in accumulated other comprehensive earnings:
Net actuarial loss (gain)	201	183
Prior service cost (credit)		5
Total	201	188
Postretirement Benefits [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	14	17
Actuarial loss (gain)	(1)	(3)
Plan curtailments	1	1
Participant contributions	2	2
Benefits paid	(3)	(3)
Benefit obligation at end of year	13	14	$ 17
Change in plan assets:
Employer contributions	1	1
Participant contributions	2	2
Benefits paid	(3)	(3)
Funded status at end of year	(13)	(14)
Amounts recognized in balance sheet:
Other current liabilities	(2)
Other current liabilities		(2)
Other long-term liabilities	(11)
Other long-term liabilities		(12)
Net amount	(13)	(14)
Amounts recognized in accumulated other comprehensive earnings:
Net actuarial loss (gain)	(12)	(12)
Prior service cost (credit)		(1)
Total	$ (12)	$ (13)