Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 22,984	$ 23,071
Net change in accumulated other comprehensive income (loss)	(3)	(259)
Ending Balance	24,449	21,006
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Total tax impact	16	290
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2,895)	(2,737)
Ending Balance	(2,898)	(2,996)
Net Unrealized Gains (Losses) on Debt Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	65	33
Net change in accumulated other comprehensive income (loss)	(12)	57
Ending Balance	53	90
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Total tax impact	(3)	18
Foreign Currency Translation Adjustment Gains (Losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2,229)	(2,189)
Net change in accumulated other comprehensive income (loss)	(17)	(322)
Ending Balance	(2,246)	(2,511)
Net Translation On Investments In Foreign Operations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net change in accumulated other comprehensive income (loss)	(23)	(1,054)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Total tax impact	8	30
Net Hedges Of Investments In Foreign Operations
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Net change in accumulated other comprehensive income (loss)	6	732
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Total tax impact	0	230
Net Unrealized Pension and Other Postretirement Benefit Gains (Losses)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(731)	(581)
Net change in accumulated other comprehensive income (loss)	26	6
Ending Balance	(705)	(575)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Total tax impact	$ 11	$ 12