Schedule I — Condensed Financial Information of Registrant - Condensed Statements of Operations and Comprehensive Loss (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Expenses:
Research and development	$ (265,868,000)	$ (286,408,000)	$ (573,306,000)
Loss from operations	(366,573,000)	(404,357,000)	(700,064,000)
Interest income	39,797,000	14,582,000	2,190,000
Other income (expense), net	7,006,000	3,113,000	(10,201,000)
Loss before income tax and share of loss from equity method investment	(334,620,000)	(443,065,000)	(703,414,000)
Income tax expense	0	0	0
Net loss	(334,620,000)	(443,286,000)	(704,471,000)
Other comprehensive income (loss) , net of tax of nil:
Other comprehensive (loss) income, tax	0	0	0
Foreign currency translation adjustments	11,941,000	49,330,000	(9,121,000)
Comprehensive loss	(322,679,000)	(393,956,000)	(713,592,000)
Parent Company
Operating Expenses:
Research and development	(82,000)	(178,000)	(6,000)
General and administrative	(16,958,000)	(19,773,000)	(12,074,000)
Loss from operations	(17,040,000)	(19,951,000)	(12,080,000)
Interest income	30,840,000	12,857,000	1,881,000
Other income (expense), net	4,029,000	(8,678,000)	(18,173,000)
Loss before income tax and share of loss from equity method investment	17,829,000	(15,772,000)	(28,372,000)
Equity in loss of subsidiaries	(352,449,000)	(427,514,000)	(676,099,000)
Income tax expense	0	0	0
Net loss	(334,620,000)	(443,286,000)	(704,471,000)
Other comprehensive income (loss) , net of tax of nil:
Other comprehensive (loss) income, tax	0	0	0
Foreign currency translation adjustments	11,941,000	49,330,000	(9,121,000)
Comprehensive loss	$ (322,679,000)	$ (393,956,000)	$ (713,592,000)