Changes in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			$ (2,428)
Net unrealized Pension and other postretirement benefits, net of tax	$ 1	$ 9	29	$ 1
Balances as of June 30	(2,483)		(2,483)		$ (2,428)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Investment securities	(2)	0	(5)	3	1
Foreign currency translation adjustments	(70)	12	(68)	(179)
Net investment hedges	107	(67)	53	(207)
Pension and other postretirement benefits	6	1	9	(8)
Total tax impact	41	(54)	(11)	(391)
Accumulated Other Comprehensive Loss [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(2,381)	(2,470)	(2,428)	(2,784)	(2,784)
Net unrealized gains	(7)		(20)	6
Net translation of investments in foreign operations	(416)	135	(224)	680
Net gains (losses) related to hedges of investment in foreign operations	320	(102)	158	(331)
Net unrealized Pension and other postretirement benefits, net of tax	1	9	29	1
Other - Net Unrealized Gains (Losses) on Equity Securities			2
Net change in accumulated other comprehensive (loss) income	(102)	42	(55)	356
Balances as of June 30	(2,483)	(2,428)	(2,483)	(2,428)	(2,428)
Net Unrealized Gains (Losses) on Investment Securities [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(11)	13	0	7	7
Net unrealized gains	(7)		(20)	6
Net translation of investments in foreign operations	0	0	0	0
Net gains (losses) related to hedges of investment in foreign operations	0	0	0	0
Net unrealized Pension and other postretirement benefits, net of tax	0	0	0	0
Other - Net Unrealized Gains (Losses) on Equity Securities			2
Net change in accumulated other comprehensive (loss) income	(7)	0	(18)	6
Balances as of June 30	(18)	13	(18)	13	0
Foreign Currency Translation Adjustments [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(1,931)	(1,946)	(1,961)	(2,262)	(2,262)
Net unrealized gains	0		0	0
Net translation of investments in foreign operations	(416)	135	(224)	680
Net gains (losses) related to hedges of investment in foreign operations	320	(102)	158	(331)
Net unrealized Pension and other postretirement benefits, net of tax	0	0	0	0
Other - Net Unrealized Gains (Losses) on Equity Securities			0
Net change in accumulated other comprehensive (loss) income	(96)	33	(66)	349
Balances as of June 30	(2,027)	(1,913)	(2,027)	(1,913)	(1,961)
Net Unrealized Pension and Other Postretirement Gains (Losses) [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(439)	(537)	(467)	(529)	(529)
Net unrealized gains	0		0	0
Net translation of investments in foreign operations	0	0	0	0
Net gains (losses) related to hedges of investment in foreign operations	0	0	0	0
Net unrealized Pension and other postretirement benefits, net of tax	1	9	29	1
Other - Net Unrealized Gains (Losses) on Equity Securities			0
Net change in accumulated other comprehensive (loss) income	1	9	29	1
Balances as of June 30	$ (438)	$ (528)	$ (438)	$ (528)	$ (467)