Stock-based compensation - Summary of Restricted Stock Units (Detail) - Restricted stock units shares in Thousands	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Shares (in thousands)
Unvested balance at beginning of period (in shares) | shares	1,127
Granted (in shares) | shares	1,018
Vested (in shares) | shares	(433)
Forfeited (in shares) | shares	(217)
Unvested balance at end of period (in shares) | shares	1,495
Weighted-average grant date fair value
Unvested balance at beginning of period (in dollars per share) | $ / shares	$ 146.10
Granted (in dollars per share) | $ / shares	70.18
Vested (in dollars per share) | $ / shares	130.10
Forfeited (in dollars per share) | $ / shares	123.32
Unvested balance at end of period (in dollars per share) | $ / shares	$ 102.34