Retirement Plans (Projected Benefit Obligation, Fair Values Of Plan Assets And Amounts Recognized In The Balance Sheet) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in projected benefit obligation (PBO) [Roll Forward]
Benefits paid	$ (317)
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	2,674
Actual return on plan assets	(159)
Fair value of plan assets at end of year	2,348	$ 2,674
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - current	(39)	(29)
Pension and other postretirement benefits - noncurrent	(1,750)	(1,676)
Pension Benefits [Member]
Change in projected benefit obligation (PBO) [Roll Forward]
PBO at beginning of year	3,363	3,465
Service cost	90	97	$ 88
Interest cost	125	127	122
Actuarial (gain) loss	(88)	214
Benefits paid	(63)	(59)
Settlements	(254)	(486)
Special termination benefits		5
PBO at end of year	3,173	3,363	3,465
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	2,674	2,766
Actual return on plan assets	(159)	378
Employer contributions	150	206	28
Settlements	(254)	(486)
Differential payment received from Verizon		(131)
Benefits paid	(63)	(59)
Fair value of plan assets at end of year	2,348	2,674	2,766
Funded status	(825)	(689)
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - noncurrent	(825)	(689)
Accumulated other comprehensive (gain) loss	754	556	647
Postretirement Benefits Other Than Pensions (OPEB) [Member]
Change in projected benefit obligation (PBO) [Roll Forward]
PBO at beginning of year	1,016	925
Service cost	21	21	19
Interest cost	38	40	37
Plan participants' contributions	7	7
Actuarial (gain) loss	(79)	54
Benefits paid	(38)	(31)
PBO at end of year	965	1,016	925
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year
Plan participants' contributions	7	7
Employer contributions	31	24
Benefits paid	(38)	(31)
Fair value of plan assets at end of year
Funded status	(965)	(1,016)
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - current	(39)	(29)
Pension and other postretirement benefits - noncurrent	(926)	(987)
Accumulated other comprehensive (gain) loss	$ (41)	$ 33	$ (29)