Shareholders' Equity (Accumulated other comprehensive income) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	[1]	$ (14,908)	$ (16,139)	$ (15,083)	$ (16,373)
OCI before reclassifications	[1]	(139)	(3)	(149)	(152)
Amounts reclassified from AOCI	[1]	120	193	305	576
Net current period Other comprehensive income/(loss)	[1]	(19)	190	156	424
Ending Balance	[1]	(14,927)	(15,949)	(14,927)	(15,949)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		117	219	350	657
Amortization of actuarial losses included in net periodic pension cost, tax		(32)	(60)	(97)	(182)
Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(103)	(72)	(101)	(15)
OCI before reclassifications		(59)	2	(61)	(55)
Net current period Other comprehensive income/(loss)		(59)	2	(61)	(55)
Ending Balance		(162)	(70)	(162)	(70)
Unrealized Gains and Losses on Certain Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		1	1		(2)
OCI before reclassifications				1	3
Net current period Other comprehensive income/(loss)				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		(82)	(29)	(62)	54
OCI before reclassifications		(89)	(4)	(106)	(97)
Amounts reclassified from AOCI		25	9	22	19
Net current period Other comprehensive income/(loss)		(64)	5	(84)	(78)
Ending Balance		(146)	(24)	(146)	(24)
Defined Benefit Pension Plans and Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		(14,724)	(16,039)	(14,920)	(16,410)
OCI before reclassifications		9	(1)	17	(3)
Amounts reclassified from AOCI	[2]	95	184	283	557
Net current period Other comprehensive income/(loss)		104	183	300	554
Ending Balance		$ (14,620)	$ (15,856)	$ (14,620)	$ (15,856)

[1] Net of tax.

[2] Primarily relates to amortization of actuarial losses for the nine and three months ended September 30, 2018 totaling $657 and $219 (net of tax of ($182) and ($60)) and for the nine and three months ended September 30, 2019 totaling $350 and $117 (net of tax of ($97) and ($32)). These are included in the net periodic pension cost.