Changes in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance			$ (2,428)
Net unrealized Pension and other postretirement benefits, net of tax	$ 9	$ 7	38	$ 8
Balance as of end of period	(2,504)		(2,504)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Investment securities	(4)	(1)	(9)	2
Foreign currency translation adjustments	8	(25)	(60)	(204)
Net investment hedges	(7)	(99)	46	(306)
Pension and other postretirement benefits	3	(2)	12	(10)
Total tax impact	0	(127)	(11)	(518)
Accumulated Other Comprehensive Loss [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(2,483)	(2,428)	(2,428)	(2,784)
Net unrealized gains	(11)	(2)	(31)	4
Increase (decrease) due to amounts reclassified into earnings		(1)		(1)
Net translation of investments in foreign operations	3	292	(221)	972
Net gains (losses) related to hedges of investment in foreign operations	(22)	(184)	136	(515)
Net unrealized Pension and other postretirement benefits, net of tax	9	7	38	8
Other - Net Unrealized Gains (Losses) on Equity Securities			2
Net change in accumulated other comprehensive (loss) income	(21)	112	(76)	468
Balance as of end of period	(2,504)	(2,316)	(2,504)	(2,316)
Net Unrealized Gains (Losses) on Investment Securities [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(18)	13	0	7
Net unrealized gains	(11)	(2)	(31)	4
Increase (decrease) due to amounts reclassified into earnings		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	0	0	0	0
Other - Net Unrealized Gains (Losses) on Equity Securities			2
Net change in accumulated other comprehensive (loss) income	(11)	(2)	(29)	4
Balance as of end of period	(29)	11	(29)	11
Foreign Currency Translation Adjustments [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(2,027)	(1,913)	(1,961)	(2,262)
Net unrealized gains	0	0	0	0
Increase (decrease) due to amounts reclassified into earnings		(1)		(1)
Net translation of investments in foreign operations	3	292	(221)	972
Net gains (losses) related to hedges of investment in foreign operations	(22)	(184)	136	(515)
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	(19)	107	(85)	456
Balance as of end of period	(2,046)	(1,806)	(2,046)	(1,806)
Net Unrealized Pension and Other Postretirement Gains (Losses) [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Beginning balance	(438)	(528)	(467)	(529)
Net unrealized gains	0	0	0	0
Increase (decrease) due to amounts reclassified into earnings		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	9	7	38	8
Other - Net Unrealized Gains (Losses) on Equity Securities			0
Net change in accumulated other comprehensive (loss) income	9	7	38	8
Balance as of end of period	$ (429)	$ (521)	$ (429)	$ (521)