Benefit Plans (Movements in Other Comprehensive Earnings/Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortization:
Net loss	$ 239	$ 214	$ 296
Prior service cost/credit	(34)	(34)	(32)
Other expense:
Net loss, other expense (income)	86	9	8
Other		(11)
Deferred income taxes	(113)	(65)	(105)
Amounts reclassified to net earnings as components of net periodic benefit cost	178	113	167
Other movements during the year:
Net loss, Other movements during the year	14	(259)	(223)
Prior service cost/credit, Other movements during the year	38	12	0
Deferred income taxes, Other movements during the year	(21)	96	86
Other movements	31	(151)	(137)
Total movements in other comprehensive earnings/losses	209	(38)	30
Pension [Member]
Amortization:
Net loss	197	171	234
Prior service cost/credit	4	5	7
Other expense:
Net loss, other expense (income)	86	9	8
Other		2
Deferred income taxes	(113)	(69)	(96)
Amounts reclassified to net earnings as components of net periodic benefit cost	174	118	153
Other movements during the year:
Net loss, Other movements during the year	81	(232)	(410)
Prior service cost/credit, Other movements during the year	0	(4)	(6)
Deferred income taxes, Other movements during the year	(32)	92	160
Other movements	49	(144)	(256)
Total movements in other comprehensive earnings/losses	223	(26)	(103)
Postretirement Benefit Plan [Member]
Amortization:
Net loss	25	25	43
Prior service cost/credit	(38)	(39)	(39)
Other expense:
Net loss, other expense (income)	0	0	0
Other		(13)
Deferred income taxes	6	11	(2)
Amounts reclassified to net earnings as components of net periodic benefit cost	(7)	(16)	2
Other movements during the year:
Net loss, Other movements during the year	(56)	(18)	192
Prior service cost/credit, Other movements during the year	38	16	6
Deferred income taxes, Other movements during the year	7	1	(75)
Other movements	(11)	(1)	123
Total movements in other comprehensive earnings/losses	(18)	(17)	125
Postemployment Retirement Benefits [Member]
Amortization:
Net loss	17	18	19
Prior service cost/credit	0	0	0
Other expense:
Net loss, other expense (income)	0	0	0
Other		0
Deferred income taxes	(6)	(7)	(7)
Amounts reclassified to net earnings as components of net periodic benefit cost	11	11	12
Other movements during the year:
Net loss, Other movements during the year	(11)	(9)	(5)
Prior service cost/credit, Other movements during the year	0	0	0
Deferred income taxes, Other movements during the year	4	3	1
Other movements	(7)	(6)	(4)
Total movements in other comprehensive earnings/losses	$ 4	$ 5	$ 8