Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (2,737)
Pension and other postretirement benefits	6	$ (27)
Balance as of end of period	(2,996)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Net unrealized debt securities	18	4
Net translation on investments in foreign operations	30	14
Net hedges on investments in foreign operations	230	(50)
Pension and other postretirement benefits	12	(11)
Total tax impact	290	(43)
Net Unrealized Gains (Losses) on Investment Securities [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	33	(8)
Net unrealized gains	57	17
Net translation gains (losses) on investments in foreign operations	0	0
Net gains related to hedges of investments in foreign operations	0	0
Pension and other postretirement benefits	0	0
Net change in accumulated other comprehensive income (loss)	57	17
Balance as of end of period	90	9
Foreign Currency Translation Adjustments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,189)	(2,133)
Net unrealized gains	0	0
Net translation gains (losses) on investments in foreign operations	(1,054)	170
Net gains related to hedges of investments in foreign operations	732	(162)
Pension and other postretirement benefits	0	0
Net change in accumulated other comprehensive income (loss)	(322)	8
Balance as of end of period	(2,511)	(2,125)
Net Unrealized Pension and Other Postretirement Gains (Losses) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(581)	(456)
Net unrealized gains	0	0
Net translation gains (losses) on investments in foreign operations	0	0
Net gains related to hedges of investments in foreign operations	0	0
Pension and other postretirement benefits	6	(27)
Net change in accumulated other comprehensive income (loss)	6	(27)
Balance as of end of period	(575)	(483)
Accumulated Other Comprehensive (Loss) Income [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(2,737)	(2,597)
Net unrealized gains	57	17
Net translation gains (losses) on investments in foreign operations	(1,054)	170
Net gains related to hedges of investments in foreign operations	732	(162)
Pension and other postretirement benefits	6	(27)
Net change in accumulated other comprehensive income (loss)	(259)	(2)
Balance as of end of period	$ (2,996)	$ (2,599)