Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (16,025)		$ (14,908)		$ (16,153)	$ (15,083)
OCI before reclassifications	[1]	87		(139)		(144)	(149)
Amounts reclassified from AOCI	[1]	159		120		518	305
Net current period Other comprehensive income/(loss)	[1]	246		(19)		374	156
Ending Balance	[1]	(15,779)		(14,927)		(15,779)	(14,927)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		172		117		562	350
Amortization of actuarial losses included in net periodic pension cost, tax		(76)		(32)		(179)	(97)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(161)		(103)		(128)	(101)
OCI before reclassifications		48		(59)		15	(61)
Net current period Other comprehensive income/(loss)		48		(59)		15	(61)
Ending Balance		(113)		(162)		(113)	(162)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		1		1		1
OCI before reclassifications							1
Net current period Other comprehensive income/(loss)							1
Ending Balance		1		1		1	1
Unrealized Gains and Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(258)		(82)		(84)	(62)
OCI before reclassifications		79		(89)		(107)	(106)
Amounts reclassified from AOCI		8		25		20	22
Net current period Other comprehensive income/(loss)		87		(64)		(87)	(84)
Ending Balance		(171)		(146)		(171)	(146)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(15,607)		(14,724)		(15,942)	(14,920)
OCI before reclassifications		(40)		9		(52)	17
Amounts reclassified from AOCI		151	[2]	95	[2]	498	283
Net current period Other comprehensive income/(loss)		111		104		446	300
Ending Balance		$ (15,496)		$ (14,620)		$ (15,496)	$ (14,620)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the nine and three months ended September 30, 2019 totaling $350 and $117 (net of tax of ($97) and ($32)) and for the nine and three months ended September 30, 2020 totaling $562 and $172 (net of tax of ($179) and ($76)). These are included in the net periodic pension cost.