Organization and Description of Business (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) program divestiture	Dec. 31, 2020 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Number of development programs underway with other research institutions | program	2
Total cash, cash equivalents and marketable securities at fair value	$ 301,715	$ 505,109
Number of discrete business divestitures | divestiture	2
Accumulated deficit	$ 1,552,253	$ 1,324,840
Cash, cash equivalents and marketable securities balances, anticipated operating requirements	12 months
Upon FDA approval
Business Acquisition, Contingent Consideration [Line Items]
Accrued for contingent consideration related to our acquisition	$ 100,000
Upon EMA Approval in Europe
Business Acquisition, Contingent Consideration [Line Items]
Accrued for contingent consideration related to our acquisition	$ 50,000