Employee Benefit Plans (Details 4) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes Recognized in Comprehensive Income
Prior service (credits) costs during period	$ 1	$ (345)	$ (6)
Amortization of prior service (costs) credits	20	(19)	(30)
Other Benefits
Net Periodic Benefit Cost
Service cost	32	60	72
Interest cost	95	128	151
Expected return on plan assets	0	0	0
Amortization of prior service costs (credits)	(28)	14	14
Recognized actuarial losses	(5)	19	34
Settlement losses	0	0	0
Curtailment losses (gains)	0	0	0
Total net periodic benefit cost	94	221	271
Changes Recognized in Comprehensive Income
Net actuarial (gain) loss during period	284	(430)	(362)
Amortization of actuarial loss	5	(19)	(34)
Prior service (credits) costs during period	0	(345)	0
Amortization of prior service (costs) credits	28	(14)	(14)
Total changes recognized in other comprehensive income	317	(808)	(410)
Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	411	(587)	(139)
U.S. | Pension Benefits
Net Periodic Benefit Cost
Service cost	489	494	538
Interest cost	366	377	502
Expected return on plan assets	(597)	(723)	(783)
Amortization of prior service costs (credits)	(5)	(9)	(8)
Recognized actuarial losses	340	335	356
Settlement losses	436	511	320
Curtailment losses (gains)	0	0	0
Total net periodic benefit cost	1,029	985	925
Changes Recognized in Comprehensive Income
Net actuarial (gain) loss during period	381	690	513
Amortization of actuarial loss	(776)	(846)	(676)
Prior service (credits) costs during period	0	0	0
Amortization of prior service (costs) credits	5	9	8
Total changes recognized in other comprehensive income	(390)	(147)	(155)
Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	639	838	770
Int’l. | Pension Benefits
Net Periodic Benefit Cost
Service cost	151	159	185
Interest cost	219	261	277
Expected return on plan assets	(239)	(243)	(262)
Amortization of prior service costs (credits)	13	14	22
Recognized actuarial losses	44	47	78
Settlement losses	2	6	6
Curtailment losses (gains)	0	0	(14)
Total net periodic benefit cost	190	244	292
Changes Recognized in Comprehensive Income
Net actuarial (gain) loss during period	(94)	55	(260)
Amortization of actuarial loss	(46)	(53)	(84)
Prior service (credits) costs during period	1	0	(6)
Amortization of prior service (costs) credits	(13)	(14)	(24)
Total changes recognized in other comprehensive income	(152)	(12)	(374)
Recognized in Net Periodic Benefit Cost and Other Comprehensive Income	$ 38	$ 232	$ (82)