Net Loss Per Share Attributable to Common Stockholders - Schedule of Anti-Dilutive Common Equivalent Shares (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Options (convertible to Series A common stock)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive outstanding potential common stock	923,750	1,137,026	923,750	1,137,026
Warrants (convertible to Series A common stock)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive outstanding potential common stock		1,973,763		1,973,763
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive outstanding potential common stock		39,223,194		39,223,194
Restricted stock and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive outstanding potential common stock	64,360,347	84,486,332	64,360,347	84,486,332
Performance stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive outstanding potential common stock	1,500,000		1,500,000