Stock-based compensation - Summary of Restricted Stock Units (Detail) - Restricted stock units (in shares) shares in Thousands	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Shares (in thousands)
Unvested balance at beginning of period (in shares) | shares	1,495
Granted (in shares) | shares	1,128
Vested (in shares) | shares	(421)
Forfeited (in shares) | shares	(337)
Unvested balance at end of period (in shares) | shares	1,865
Weighted- average grant date fair value
Unvested balance at beginning of period (in dollars per share) | $ / shares	$ 102.34
Granted (in dollars per share) | $ / shares	21.38
Vested (in dollars per share) | $ / shares	59.35
Forfeited (in dollars per share) | $ / shares	77.19
Unvested balance at end of period (in dollars per share) | $ / shares	$ 59.02