Stock-based compensation - Summary of Stock Option Activity Under Plan (Detail) shares in Thousands	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Shares (in thousands)
Outstanding at beginning of period (in shares) | shares	6,262
Granted (in shares) | shares	671
Exercised (in shares) | shares	(207)
Canceled, forfeited, or expired (in shares) | shares	(268)
Outstanding at end of period (in shares) | shares	6,458
Exercisable at end of period (in shares) | shares	3,829
Vested and expected to vest at end of period (in shares) | shares	6,458
Weighted- average exercise price per share
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 105.02
Granted (in dollars per share) | $ / shares	29.17
Exercised (in dollars per share) | $ / shares	5.88
Canceled, forfeited, or expired (in dollars per share) | $ / shares	110.62
Outstanding at end of period (in dollars per share) | $ / shares	100.08
Exercisable at end of period (in dollars per share) | $ / shares	111.17
Vested and expected to vest at end of period (in dollars per share) | $ / shares	$ 100.08