Goodwill and Intangible Assets - Intangible Assets (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 5,018		$ 5,018		$ 4,816
Accumulated Amortization	(4,274)		(4,274)		(3,922)
Net Carrying Amount	744		744		894
Amortization expense	123	$ 145	$ 352	$ 457
Acquired users
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Useful Lives (in years)			1 year
Gross Carrying Amount	2,056		$ 2,056		2,056
Accumulated Amortization	(1,767)		(1,767)		(1,550)
Net Carrying Amount	289		$ 289		506
Acquired technology
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Useful Lives (in years)			3 years
Gross Carrying Amount	1,293		$ 1,293		1,158
Accumulated Amortization	(1,060)		(1,060)		(986)
Net Carrying Amount	233		$ 233		172
Acquired patents
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Useful Lives (in years)			4 years 2 months 12 days
Gross Carrying Amount	805		$ 805		805
Accumulated Amortization	(665)		(665)		(625)
Net Carrying Amount	140		$ 140		180
Trade names
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Useful Lives (in years)			1 year 10 months 24 days
Gross Carrying Amount	641		$ 641		635
Accumulated Amortization	(618)		(618)		(604)
Net Carrying Amount	23		$ 23		31
Other
Finite-Lived Intangible Assets [Line Items]
Weighted-Average Remaining Useful Lives (in years)			3 years 4 months 24 days
Gross Carrying Amount	223		$ 223		162
Accumulated Amortization	(164)		(164)		(157)
Net Carrying Amount	$ 59		$ 59		$ 5