Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balances as of January 1	$ (2,784)
Net unrealized pension and other postretirement benefit, net of tax	62	$ 19	$ (32)
Balances as of December 31	(2,428)	(2,784)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Investment securities	1	5	(20)
Foreign currency translation adjustments	(172)	(15)	(124)
Net investment hedges	(215)	139	340
Pension and other postretirement benefit losses	7	37	0
Total tax impact	(384)	134	196
Accumulated Other Comprehensive (Loss) Income [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balances as of January 1	(2,784)	(2,534)	(1,919)
Net unrealized gains (losses)	(7)	(45)	(37)
Reclassification for realized (gains) losses into earnings	(7)	(2)	(2)
Net translation of investments in foreign operations	678	(503)	(1,122)
Net gains (losses) related to hedges of investment in foreign operations	(370)	281	578
Net unrealized pension and other postretirement benefit, net of tax	62	19	(32)
Net change in accumulated other comprehensive (loss) income	356	(250)	(615)
Balances as of December 31	(2,428)	(2,784)	(2,534)
Net Unrealized Investment Gains (Losses) on Investment Securities [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balances as of January 1	7	58	96
Net unrealized gains (losses)	(7)	(45)	(37)
Reclassification for realized (gains) losses into earnings	0	(6)	(1)
Net translation of investments in foreign operations	0	0	0
Net gains (losses) related to hedges of investment in foreign operations	0	0	0
Net unrealized pension and other postretirement benefit, net of tax	0	0	0
Net change in accumulated other comprehensive (loss) income	(7)	(51)	(38)
Balances as of December 31	0	7	58
Foreign Currency Translation Adjustments [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balances as of January 1	(2,262)	(2,044)	(1,499)
Net unrealized gains (losses)	0	0	0
Reclassification for realized (gains) losses into earnings	(7)	4	(1)
Net translation of investments in foreign operations	678	(503)	(1,122)
Net gains (losses) related to hedges of investment in foreign operations	(370)	281	578
Net unrealized pension and other postretirement benefit, net of tax	0	0	0
Net change in accumulated other comprehensive (loss) income	301	(218)	(545)
Balances as of December 31	(1,961)	(2,262)	(2,044)
Net Unrealized Pension and Other Postretirement Benefit Losses [Member]
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Balances as of January 1	(529)	(548)	(516)
Net unrealized gains (losses)	0	0	0
Reclassification for realized (gains) losses into earnings	0	0	0
Net translation of investments in foreign operations	0	0	0
Net gains (losses) related to hedges of investment in foreign operations	0	0	0
Net unrealized pension and other postretirement benefit, net of tax	62	19	(32)
Net change in accumulated other comprehensive (loss) income	62	19	(32)
Balances as of December 31	$ (467)	$ (529)	$ (548)