Stock-based compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 31,051	$ 48,529	$ 73,525	$ 84,822
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	17,324	26,073	37,983	50,513
Restricted stock units (in shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	8,534	14,143	23,267	25,996
ESPP shares and other (in shares)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 5,193	$ 8,313	$ 12,275	$ 8,313