Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Benefit for income taxes	$ 0	$ 0	$ 110,333,000
Statutory federal rate	21.00%	21.00%	21.00%
Increase in valuation allowance	$ 173,100,000
NOL carryforwards	$ 1,047,200,000
Operating loss carryforwards, percentage of limitation	80.00%
Unrecognized tax benefits, that would impact the effective tax rate	$ 12,800,000
Accrued interest or penalties	0	$ 0
Recognize interest and/or penalties expense	$ 0	$ 0	$ 0
Tax credit carryforwards beginning year	2003
Minimum
Income Tax Disclosure [Line Items]
NOL carryforwards expiration date, year	2028
California
Income Tax Disclosure [Line Items]
NOL carryforwards	$ 951,200,000
California | Minimum
Income Tax Disclosure [Line Items]
NOL carryforwards expiration date, year	2028
California | Research and Development Tax Credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards amount	$ 29,500,000
Federal
Income Tax Disclosure [Line Items]
NOL carryforwards	$ 1,437,600,000
Federal | Minimum
Income Tax Disclosure [Line Items]
Tax credit carryforwards expiration year	2026
Federal | Research and Development Tax Credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards amount	$ 58,900,000
Federal | Orphan Drug Credit
Income Tax Disclosure [Line Items]
Tax credit carryforwards amount	$ 15,000,000