Benefit Plans (Movements in Other Comprehensive Earnings/Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2018	Jan. 01, 2018	[1]
Amortization:
Net loss	$ 263	$ 239	$ 214
Prior service cost/credit	(38)	(34)	(34)
Other expense:
Net loss	13	86	9
Prior service cost/credit	3		(11)
Deferred income taxes	(61)	(113)	(65)
Amounts reclassified to net earnings as components of net periodic benefit cost	180	178	113
Other movements during the year:
Adoption of ASU No. 2018-02	(397)			$ 408	$ 0
Net loss	(74)	14	(259)
Prior service cost/credit	(77)	38	12
Deferred income taxes	39	(21)	96
Other movements	(509)	31	(151)
Total movements in other comprehensive earnings/losses, including cumulative effect adjustment	(329)
Total movements in other comprehensive earnings/losses	68	209	(38)
Pension [Member]
Amortization:
Net loss	225	197	171
Prior service cost/credit	4	4	5
Other expense:
Net loss	13	86	9
Prior service cost/credit	3		2
Deferred income taxes	(61)	(113)	(69)
Amounts reclassified to net earnings as components of net periodic benefit cost	184	174	118
Other movements during the year:
Adoption of ASU No. 2018-02	(330)
Net loss	(336)	81	(232)
Prior service cost/credit	(26)	0	(4)
Deferred income taxes	91	(32)	92
Other movements	(601)	49	(144)
Total movements in other comprehensive earnings/losses, including cumulative effect adjustment	(417)
Total movements in other comprehensive earnings/losses		223	(26)
Postretirement Benefit Plan [Member]
Amortization:
Net loss	21	25	25
Prior service cost/credit	(42)	(38)	(39)
Other expense:
Net loss	0	0	0
Prior service cost/credit	0		(13)
Deferred income taxes	4	6	11
Amounts reclassified to net earnings as components of net periodic benefit cost	(17)	(7)	(16)
Other movements during the year:
Adoption of ASU No. 2018-02	(55)
Net loss	264	(56)	(18)
Prior service cost/credit	(45)	38	16
Deferred income taxes	(54)	7	1
Other movements	110	(11)	(1)
Total movements in other comprehensive earnings/losses, including cumulative effect adjustment	93
Total movements in other comprehensive earnings/losses		(18)	(17)
Postemployment Retirement Benefits [Member]
Amortization:
Net loss	17	17	18
Prior service cost/credit	0	0	0
Other expense:
Net loss	0	0	0
Prior service cost/credit	0		0
Deferred income taxes	(4)	(6)	(7)
Amounts reclassified to net earnings as components of net periodic benefit cost	13	11	11
Other movements during the year:
Adoption of ASU No. 2018-02	(12)
Net loss	(2)	(11)	(9)
Prior service cost/credit	(6)	0	0
Deferred income taxes	2	4	3
Other movements	(18)	(7)	(6)
Total movements in other comprehensive earnings/losses, including cumulative effect adjustment	$ (5)
Total movements in other comprehensive earnings/losses		$ 4	$ 5

[1] For further discussion, see Note 15. Income Taxes.