Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Income Tax Disclosure [Line Items]
Income tax provision	$ (268,000)	$ (309,000)	$ (40,000)
Increase in valuation allowance	$ 55,500,000
Period over which certain cumulative changes in the ownership interest of significant shareholders will be considered, subject to an annual limitation of net operating loss and tax credit carryforwards	3 years
Operating Loss And Tax Credit Carryforwards Limitations Threshold Percentage Of Cumulative Changes In Ownership Interest Of Significant Shareholders Considered	50
Interest or penalties related to uncertain tax positions recognized in statements of operations and comprehensive loss	$ 0	0	0
Deferred Tax Assets, Valuation Allowance	330,902,000	275,389,000
Fair market value of the rights upfront payment	75,000,000.0
Deferred income tax provision		0	0
Maximum [Member]
Income Tax Disclosure [Line Items]
Income tax provision			100,000
Internal Revenue Service (IRS) [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	735,200,000	698,800,000	576,500,000
Net operating loss carryforwards indefinite life	442,300,000
Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	80,600,000	69,800,000	58,500,000
State and Local Jurisdiction [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	590,300,000	575,200,000	502,300,000
Net operating loss carryforwards indefinite life	735,200,000
Net operating loss carryforwards indefinite life remaining	292,900,000
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	0	0	0
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforwards	9,400,000	6,800,000	4,900,000
Foreign Tax Authority [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Assets, Valuation Allowance	$ 17,200,000
Income tax provision in federal tax expense		200,000
Income tax expense		$ (100,000)	$ 100,000