Accumulated Other Comprehensive Income/(Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Abstract]
Total AOCI ending balance at September 30	$ (7,429)		$ (7,429)		$ (6,959)
Derivative instruments [Abstract]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	95
Parent Company [Member]
Accumulated Other Comprehensive Income (Loss) [Abstract]
Total AOCI ending balance at September 30	(7,429)	$ (6,759)	(7,429)	$ (6,759)
Foreign currency transaction [Abstract]
Beginning balance	(4,577)	(4,266)	(4,277)	(4,593)
Gains/(Losses) on foreign currency translation	(136)	25	(419)	175
Less: Tax/(Tax benefit)	(2)	(94)	17	(271)
Net gains/(losses) on foreign currency translation	(134)	119	(436)	446
(Gains)/Losses reclassified from AOCI to income	1	(17)	3	(17)
Other comprehensive income/(loss), net of tax	(133)	102	(433)	429
Ending balance	(4,710)	(4,164)	(4,710)	(4,164)
Marketable securities [Abstract]
Beginning balance	(103)	(11)	(48)	(14)
Gains/(Losses) on available for sale securities	(7)	(3)	(91)	0
Less: Tax/(Tax benefit)	(1)	(3)	(22)	2
Net gains/(losses) on available for sale securities	(6)	0	(69)	(2)
(Gains)/Losses reclassified from AOCI to net income	4	0	14	5
Less: Tax/(Tax benefit)	0	1	2	1
Net (gains)/losses reclassified from AOCI to net income	4	(1)	12	4
Other comprehensive income/(loss), net of tax	(2)	(1)	(57)	2
Ending balance	(105)	(12)	(105)	(12)
Derivative instruments [Abstract]
Beginning balance	103	253	18	283
Gains/(Losses) on available for sale securities	(91)	(116)	30	90
Less: Tax/(Tax benefit)	(21)	(36)	8	15
Net gains/(losses) on available for sale securities	(70)	(80)	22	75
(Gains)/Losses reclassified from AOCI to net income	(45)	(115)	(50)	(357)
Less: Tax/(Tax benefit)	(12)	(24)	(10)	(81)
Net (gains)/losses reclassified from AOCI to net income	(33)	(91)	(40)	(276)
Other comprehensive income/(loss), net of tax	(103)	(171)	(18)	(201)
Ending balance	0	82	0	82
Pension and other postretirement benefits
Beginning balance	(2,627)	(2,692)	(2,652)	(2,689)
Amortization of prior service costs/(credits)	15	15	44	45
Less: Tax/(Tax benefit)	2	(13)	8	15
Net prior service costs/(credits) reclassified from AOCI to net income	13	28	36	30
Translation impact on non-U.S. plans	0	(1)	2	(6)
Other comprehensive income/(loss), net of tax	13	27	38	24
Ending balance	$ (2,614)	$ (2,665)	$ (2,614)	$ (2,665)