Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (14,969)	$ (16,162)	$ (15,083)	$ (16,373)
OCI before reclassifications	[1]	(31)	(173)	(10)	(149)
Amounts reclassified from AOCI	[1]	92	196	185	383
Net current period Other comprehensive income/(loss)	[1]	61	23	175	234
Ending Balance	[1]	(14,908)	(16,139)	(14,908)	(16,139)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		115	219	233	438
Amortization of actuarial losses included in net periodic pension cost, tax		(33)	(62)	(65)	(122)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(100)	12	(101)	(15)
OCI before reclassifications		(3)	(84)	(2)	(57)
Net current period Other comprehensive income/(loss)		(3)	(84)	(2)	(57)
Ending Balance		(103)	(72)	(103)	(72)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		1			(2)
OCI before reclassifications			1	1	3
Net current period Other comprehensive income/(loss)			1	1	3
Ending Balance		1	1	1	1
Unrealized Gains and Losses on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(53)	56	(62)	54
OCI before reclassifications		(28)	(91)	(17)	(93)
Amounts reclassified from AOCI		(1)	6	(3)	10
Net current period Other comprehensive income/(loss)		(29)	(85)	(20)	(83)
Ending Balance		(82)	(29)	(82)	(29)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(14,817)	(16,230)	(14,920)	(16,410)
OCI before reclassifications			1	8	(2)
Amounts reclassified from AOCI	[2]	93	190	188	373
Net current period Other comprehensive income/(loss)		93	191	196	371
Ending Balance		$ (14,724)	$ (16,039)	$ (14,724)	$ (16,039)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the six and three months ended June 30, 2018 totaling $438 and $219 (net of tax of ($122) and ($62)) and for the six and three months ended June 30, 2019 totaling $233 and $115 (net of tax of ($65) and ($33)). These are included in the net periodic pension cost.