Summary of Significant Accounting Policies and Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2023 USD ($) Segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment	1
Cash and cash equivalents	$ 389,477,000	$ 211,885,000	$ 923,031,000
Letters of credit secured by cash held in restricted depository account	0	540,000	0
Marketable securities	197,800,000	159,300,000
Accounts receivable	200,000,000	0
Contract liabilities	12,300,000	12,300,000
Significant uncertain tax positions	$ 0	0	$ 0
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Marketable securities maturity period	1 year
Vertex and Casebia [Member] | Collaborative Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Milestone payment receivable	$ 200,000,000
Other receivables	6,500,000	11,200,000
Marketable Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Marketable securities	1,306,200,000	1,656,600,000
Letter of Credit [Member]
Summary Of Significant Accounting Policies [Line Items]
Letters of credit secured by cash held in restricted depository account	11,600,000	12,200,000
Letter of Credit [Member] | Prepaid Expenses and Other Current Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Letters of credit secured by cash held in restricted depository account	0	500,000
Letter of Credit [Member] | Restricted Cash Noncurrent [Member]
Summary Of Significant Accounting Policies [Line Items]
Letters of credit secured by cash held in restricted depository account	$ 11,600,000	$ 11,600,000