Stock-Based Compensation - Summary of Stock-Based Compensation Expense by Grant Type Included within Condensed Consolidated Statements of Operations and Comprehensive Loss (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense		$ 43,500	$ 48,100	$ 134,600	$ 136,700
Total stock-based compensation expense included in expenses		43,450	48,061	134,624	136,688
Subtotal		48,996	48,061	149,855	136,688
Capitalized stock-based compensation costs	[1]	(5,546)	0	(15,231)	0
Research and Development Expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense included in expenses		18,034	22,325	54,113	60,315
Selling, General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense included in expenses		25,416	25,736	80,511	76,373
Employee Stock Option
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense included in expenses		15,158	17,471	46,954	62,436
Restricted stock units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense included in expenses		31,926	28,924	97,261	70,101
Employee Stock Purchase Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense included in expenses		$ 1,912	$ 1,666	$ 5,640	$ 4,151

[1] Prior to the nine months ended September 30, 2024, capitalized stock-based compensation costs were not material.