Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (16,153)	$ (15,083)
OCI before reclassifications	[1]	(352)	21
Amounts reclassified from AOCI	[1]	172	93
Net current period Other comprehensive income/(loss)	[1]	(180)	114
Ending Balance	[1]	(16,333)	(14,969)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		193	118
Amortization of actuarial losses included in net periodic pension cost, tax		(53)	(32)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(128)	(101)
OCI before reclassifications		(77)	1
Net current period Other comprehensive income/(loss)		(77)	1
Ending Balance		(205)	(100)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		1
OCI before reclassifications			1
Net current period Other comprehensive income/(loss)			1
Ending Balance		1	1
Unrealized Gains and Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(84)	(62)
OCI before reclassifications		(275)	11
Amounts reclassified from AOCI		2	(2)
Net current period Other comprehensive income/(loss)		(273)	9
Ending Balance		(357)	(53)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(15,942)	(14,920)
OCI before reclassifications			8
Amounts reclassified from AOCI	[2]	170	95
Net current period Other comprehensive income/(loss)		170	103
Ending Balance		$ (15,772)	$ (14,817)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the three months ended March 31, 2020 and 2019 totaling $193 and $118 (net of tax of ($53) and ($32)). These are included in the net periodic pension cost.