Segment Information - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenue	$ 23,601	$ 32,917	$ 32,815
United States
Segment Reporting Information [Line Items]
Revenue	$ 4,500	$ 9,300	$ 10,100