Segment and Geographic Information - Summary of Reconciliation of Segment Financial Information to Loss from Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Stock-based compensation expense	$ 1,270,702	$ 241,970	$ 248,503
Loss from operations	(1,173,679)	(576,444)	(623,440)
Reconciling items
Segment Reporting Information [Line Items]
Research and development expenses	203,597	237,630	213,412
General and administrative expenses	293,637	254,025	242,910
Stock-based compensation expense	1,270,702	241,970	248,503
Operating Segments
Segment Reporting Information [Line Items]
Contribution	$ 594,257	$ 157,181	$ 81,385

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