Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 15,037	$ 12,805
Other comprehensive income (loss) before reclassifications	11	(1)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	18	(14)
Ending balance	16,286	13,682
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(589)	(624)
Other comprehensive income (loss) before reclassifications	5	(9)
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	0	(2)
Ending balance	(584)	(635)
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	(5)	5
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	2	0
Ending balance	(8)	2
Unrealized gain (loss) on forward contracts
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(28)	8
Other comprehensive income (loss) before reclassifications	11	3
Amounts reclassified from accumulated other comprehensive income (loss) into earnings	16	(12)
Ending balance	(1)	(1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(622)	(619)
Ending balance	$ (593)	$ (634)