Employee Retirement Plans (Net Periodic Benefit Expense) (Details) - Pension Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 103	$ 92	$ 85
Interest cost	132	126	124
Expected return on plan assets	(189)	(174)	(165)
Amortization of prior service cost (credit)	6	5	6
Recognition of actuarial loss	145	21	67
Total net periodic benefit expense	197	70	117
Settlement charge	(1)		1
Total expense	196	70	118
Settlements	1		(2)
Current year actuarial loss (gain)	180	(30)	84
Recognition of actuarial loss	(145)	(21)	(64)
Current year prior service cost/credit	20
Amortization of prior service (cost) credit	(6)	(5)	(6)
Total recognized in other comprehensive loss (income)	50	(56)	12
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	78	66	61
Interest cost	116	112	111
Expected return on plan assets	(178)	(163)	(153)
Amortization of prior service cost (credit)	7	6	6
Recognition of actuarial loss	143	18	55
Total net periodic benefit expense	166	39	80
Settlement charge			1
Total expense	166	39	81
Settlements			(2)
Current year actuarial loss (gain)	182	(8)	63
Recognition of actuarial loss	(143)	(18)	(55)
Current year prior service cost/credit	20
Amortization of prior service (cost) credit	(7)	(6)	(6)
Total recognized in other comprehensive loss (income)	52	(32)	0
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	25	26	24
Interest cost	16	14	13
Expected return on plan assets	(11)	(11)	(12)
Amortization of prior service cost (credit)	(1)	(1)
Recognition of actuarial loss	2	3	12
Total net periodic benefit expense	31	31	37
Settlement charge	(1)
Total expense	30	31	37
Settlements	1
Current year actuarial loss (gain)	(2)	(22)	21
Recognition of actuarial loss	(2)	(3)	(9)
Amortization of prior service (cost) credit	1	1
Total recognized in other comprehensive loss (income)	$ (2)	$ (24)	$ 12