Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 15,037	$ 12,805
Other comprehensive income (loss) before reclassifications	19	(6)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	16	(8)
Ending balance	16,950	14,382
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(589)	(624)
Other comprehensive income (loss) before reclassifications	(8)	13
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	0	(2)
Ending balance	(597)	(613)
Unrealized gain (loss) on available-for- sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(5)	(3)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	3	1
Ending balance	(2)	(2)
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(28)	8
Other comprehensive income (loss) before reclassifications	27	(19)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	13	(7)
Ending balance	12	(18)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(622)	(619)
Ending balance	$ (587)	$ (633)