Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Segment Claim	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment	1
Impairment charge	$ 0
Guarantees and Indemnifications [Member]
Summary Of Significant Accounting Policies [Line Items]
Indemnification obligations, claims outstanding | Claim	0
Indemnification obligations claims, reserves established	$ 0
Cost-Sharing Collaborations [Member]
Summary Of Significant Accounting Policies [Line Items]
External costs related to cost-sharing collaborations	2,000,000	$ 4,700,000	$ 3,000,000
Cost-sharing collaborations recorded as a reduction to research and development expense	$ 1,000,000	$ 2,400,000	$ 1,400,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	three years
Percentage of income tax contingency realized	50.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	five years