Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (13,234)	$ (12,795)	$ (13,623)	$ (12,748)
OCI before reclassifications	[1]	84	6	233	(332)
Amounts reclassified from AOCI	[1]	114	131	354	422
Net current period Other comprehensive income/(loss)	[1]	198	137	587	90
Ending Balance	[1]	(13,036)	(12,658)	(13,036)	(12,658)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		131	131	394	392
Amortization of actuarial losses included in net periodic pension cost, tax		(72)	(72)	(217)	(217)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(66)	(32)	(143)	(39)
OCI before reclassifications		44	(10)	121	(3)
Amounts reclassified from AOCI
Net current period Other comprehensive income/(loss)		44	(10)	121	(3)
Ending Balance		(22)	(42)	(22)	(42)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(2)	(1)	(2)
OCI before reclassifications			2		1
Amounts reclassified from AOCI
Net current period Other comprehensive income/(loss)			2		1
Ending Balance		(2)	1	(2)	1
Unrealized Gains and Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(22)	(113)	(127)	(197)
OCI before reclassifications		40	13	111	54
Amounts reclassified from AOCI		10	15	44	58
Net current period Other comprehensive income/(loss)		50	28	155	112
Ending Balance		28	(85)	28	(85)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(13,144)	(12,649)	(13,351)	(12,512)
OCI before reclassifications			1	1	(384)
Amounts reclassified from AOCI	[2]	104	116	310	364
Net current period Other comprehensive income/(loss)		104	117	311	(20)
Ending Balance		$ (13,040)	$ (12,532)	$ (13,040)	$ (12,532)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the nine and three months ended September 30, 2016 totaling $392 and $131 (net of tax of ($217) and ($72)) and for the nine and three months ended September 30, 2017 totaling $394 and $131 (net of tax of ($217) and ($72)). These are included in the net periodic pension cost of which a portion is allocated to production as inventoried costs.