Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (13,623)	$ (12,748)
OCI before reclassifications	[1]	88	(241)
Amounts reclassified from AOCI	[1]	120	151
Net current period Other comprehensive income/(loss)	[1]	208	(90)
Ending Balance	[1]	(13,415)	(12,838)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), Net of Tax		132	131
Amortization of actuarial losses included in net periodic pension cost, tax		(72)	(72)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(143)	(39)
OCI before reclassifications		34	23
Amounts reclassified from AOCI
Net current period Other comprehensive income/(loss)		34	23
Ending Balance		(109)	(16)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(2)
OCI before reclassifications		1	(2)
Amounts reclassified from AOCI
Net current period Other comprehensive income/(loss)		1	(2)
Ending Balance		(1)	(2)
Unrealized Gains and Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(127)	(197)
OCI before reclassifications		52	58
Amounts reclassified from AOCI		16	23
Net current period Other comprehensive income/(loss)		68	81
Ending Balance		(59)	(116)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(13,351)	(12,512)
OCI before reclassifications		1	(320)
Amounts reclassified from AOCI	[2]	104	128
Net current period Other comprehensive income/(loss)		105	(192)
Ending Balance		$ (13,246)	$ (12,704)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the three months ended March 31, 2017 and 2016 totaling $132 and $131 (net of tax of $(72) and ($72)). These are included in the net periodic pension cost of which a portion is allocated to production as inventoried costs. See Note 17.