Employee Retirement Plans (Net Periodic Benefit Expense) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 101	$ 103	$ 92
Interest cost	148	132	126
Expected return on plan assets	(171)	(189)	(174)
Amortization of prior service cost (credit)	6	6	5
Recognition of actuarial gain	90	145	21
Total pension and postretirement benefit expense	174	197	70
Settlement charge		(1)
Special termination benefit charge	6
Total expense	180	196	70
Settlements		1
Current year actuarial loss (gain)	88	180	(30)
Amortization of actuarial gain	90	145	21
Current year prior service cost		20
Amortization of prior service (cost) credit	(6)	(6)	(5)
Total recognized in other comprehensive loss (income)	(8)	50	(56)
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	76	78	66
Interest cost	133	116	112
Expected return on plan assets	(161)	(178)	(163)
Amortization of prior service cost (credit)	7	7	6
Recognition of actuarial gain	66	143	18
Total pension and postretirement benefit expense	121	166	39
Special termination benefit charge	6
Total expense	127	166	39
Current year actuarial loss (gain)	47	182	(8)
Amortization of actuarial gain	66	143	18
Current year prior service cost		20
Amortization of prior service (cost) credit	(7)	(7)	(6)
Total recognized in other comprehensive loss (income)	(26)	52	(32)
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	25	26
Interest cost	15	16	14
Expected return on plan assets	(10)	(11)	(11)
Amortization of prior service cost (credit)	(1)	(1)	(1)
Recognition of actuarial gain	24	2	3
Total pension and postretirement benefit expense	53	31	31
Settlement charge		(1)
Total expense	53	30	31
Settlements		1
Current year actuarial loss (gain)	41	(2)	(22)
Amortization of actuarial gain	24	2	3
Amortization of prior service (cost) credit	1	1	1
Total recognized in other comprehensive loss (income)	$ 18	$ (2)	$ (24)