Employee Retirement Plans (Obligations and Funded Status Schedule) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Change in benefit obligation
Benefit obligation at beginning of year	$ 4,003	$ 4,188
Service cost	101	103	$ 92
Interest cost	148	132	126
Plan participants’ contributions	1	1
Plan amendments		21
Actuarial loss (gain)	533	(210)
Other	6	(1)
Benefits paid	(214)	(202)
Foreign currency translation	3	(29)
Benefit obligation at end of year	4,581	4,003	4,188
Change in plan assets
Fair value of plan assets at beginning of year	3,239	3,539
Actual gain (loss) on plan assets	615	(201)
Employer contributions	22	135
Plan participants’ contributions	1	1
Benefits paid	(214)	(208)
Foreign currency translation	8	(27)
Fair value of plan assets at end of year	3,671	3,239	3,539
Funded status at end of year
Fair value of plan assets	3,239	3,239	3,539	$ 3,671	$ 3,239
Benefit obligations	(4,581)	(4,188)	(4,188)	(4,581)	(4,003)
Funded status of plans				(910)	(764)
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset				82	81
Current liability				(20)	(29)
Noncurrent liability				(972)	(816)
Recognized liability				(910)	(764)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss				338	338
Prior service cost (credit)				29	36
Amount recognized at end of year				367	374
United States [Member]
Change in benefit obligation
Benefit obligation at beginning of year	3,358	3,522
Service cost	76	78	66
Interest cost	133	116	112
Plan participants’ contributions	1	1
Plan amendments		20
Actuarial loss (gain)	462	(200)
Other	6
Benefits paid	(180)	(179)
Benefit obligation at end of year	3,856	3,358	3,522
Change in plan assets
Fair value of plan assets at beginning of year	2,742	3,004
Actual gain (loss) on plan assets	576	(202)
Employer contributions	14	118
Plan participants’ contributions	1	1
Benefits paid	(180)	(179)
Fair value of plan assets at end of year	3,153	2,742	3,004
Funded status at end of year
Fair value of plan assets	2,742	2,742	3,004	3,153	2,742
Benefit obligations	(3,856)	(3,522)	(3,522)	(3,856)	(3,358)
Funded status of plans				(703)	(616)
Amounts recognized in the consolidated balance sheets consist of:
Current liability				(13)	(13)
Noncurrent liability				(690)	(603)
Recognized liability				(703)	(616)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss				306	324
Prior service cost (credit)				30	37
Amount recognized at end of year				336	361
International [Member]
Change in benefit obligation
Benefit obligation at beginning of year	645	666
Service cost	25	25	26
Interest cost	15	16	14
Plan amendments		1
Actuarial loss (gain)	71	(10)
Other		(1)
Benefits paid	(34)	(23)
Foreign currency translation	3	(29)
Benefit obligation at end of year	725	645	666
Change in plan assets
Fair value of plan assets at beginning of year	497	535
Actual gain (loss) on plan assets	39	1
Employer contributions	8	17
Benefits paid	(34)	(29)
Foreign currency translation	8	(27)
Fair value of plan assets at end of year	518	497	535
Funded status at end of year
Fair value of plan assets	497	497	535	518	497
Benefit obligations	$ (645)	$ (645)	$ (666)	(725)	(645)
Funded status of plans				(207)	(148)
Amounts recognized in the consolidated balance sheets consist of:
Noncurrent asset				82	81
Current liability				(7)	(16)
Noncurrent liability				(282)	(213)
Recognized liability				(207)	(148)
Amounts recognized in accumulated other comprehensive income consist of:
Net actuarial loss				32	14
Prior service cost (credit)				(1)	(1)
Amount recognized at end of year				$ 31	$ 13