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, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in projected benefit obligation (PBO) [Roll Forward]
Benefits paid	$ (300)
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	2,348
Actual return on plan assets	(516)
Fair value of plan assets at end of year	2,730	$ 2,348
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - current	(43)	(39)
Pension and other postretirement benefits - noncurrent	(1,896)	(1,750)
Pension and other postretirement benefits - AHFS	(29)
Pension Benefits [Member]
Change in projected benefit obligation (PBO) [Roll Forward]
PBO at beginning of year	3,173	3,363
Service cost	82	90	$ 97
Interest cost	130	125	127
Actuarial (gain) loss	603	(88)
Benefits paid	(65)	(63)
Settlements	(235)	(254)
Special termination benefits	38
PBO at end of year	3,726	3,173	3,363
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	2,348	2,674
Actual return on plan assets	516	(159)
Employer contribution	166	150
Settlements	(235)	(254)
Benefits paid	(65)	(63)
Fair value of plan assets at end of year	2,730	2,348	2,674
Funded status	(996)	(825)
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - noncurrent	(996)	(825)
Accumulated other comprehensive (gain) loss	899	754	556
Postretirement Benefits Other Than Pensions (OPEB) [Member]
Change in projected benefit obligation (PBO) [Roll Forward]
PBO at beginning of year	965	1,016
Service cost	20	21	21
Interest cost	41	38	40
Plan participants' contributions	7	7
Actuarial (gain) loss	129	(79)
Benefits paid	(47)	(38)
Special termination benefits	6
Plan change	(149)
PBO at end of year	972	965	1,016
Change in plan assets [Roll Forward]
Plan participants' contributions	7	7
Employer contribution	40	31
Benefits paid	(47)	(38)
Funded status	(972)	(965)
Amounts recognized in the consolidated balance sheet [Abstract]
Pension and other postretirement benefits - current	(43)	(39)
Pension and other postretirement benefits - noncurrent	(900)	(926)
Pension and other postretirement benefits - AHFS	(29)
Accumulated other comprehensive (gain) loss	$ (45)	$ (41)	$ 33