Financial Statements Schedule I - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from Operating activities:
Net loss	$ (443,286)	$ (704,471)	$ (268,905)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of deferred income	(2,602)	(521)	(312)
Share-based compensation	61,302	40,714	24,830
Loss from fair value changes of equity investment of readily determinable fair value	8,952	14,617	0
Changes in operating assets and liabilities:
Prepayments and other current assets	(19,258)	(7,086)	(4,199)
Other current liabilities	7,392	30,142	10,682
Net cash used in operating activities	(367,642)	(549,231)	(216,055)
Cash flows from investing activities
Purchases of short-term investments	(260,274)	(445,000)	(949,161)
Proceeds from maturity of short-term investments	705,274	743,902	405,000
Purchase of investment in equity investee	0	(30,000)	0
Net cash provided by (used in) investing activities	420,016	249,957	(554,830)
Cash flows from financing activities
Proceeds from exercises of stock options	5,870	7,417	6,664
Proceeds from issuance of ordinary shares upon public offerings	0	818,875	1,137,683
Payment of public offering costs	0	(1,837)	(5,380)
Employee taxes paid related to settlement of equity awards	(7,600)	(4,253)	0
Net cash (used in) provided by financing activities	(1,730)	820,202	1,132,440
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	(6,274)	1,116	4,862
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	44,370	522,044	366,417
Cash, cash equivalents and restricted cash — beginning of the year	964,903	442,859	76,442
Cash, cash equivalents and restricted cash — end of the year	1,009,273	964,903	442,859
Parent Company
Cash flows from Operating activities:
Net loss	(443,286)	(704,471)	(268,905)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of deferred income	(234)	(312)	(312)
Share-based compensation	3,724	3,435	3,025
Equity in loss of subsidiaries	427,514	676,099	266,334
Loss from fair value changes of equity investment of readily determinable fair value	8,952	14,617	0
Changes in operating assets and liabilities:
Prepayments and other current assets	(7,839)	(439)	2,253
Other current liabilities	1,648	(376)	738
Net cash used in operating activities	(9,521)	(11,447)	3,133
Cash flows from investing activities
Purchases of short-term investments	(260,274)	(445,000)	(949,161)
Proceeds from maturity of short-term investments	705,274	743,902	405,000
Purchase of investment in equity investee	0	(30,000)	0
Investment in subsidiaries	(80,942)	(884,342)	(256,097)
Net cash provided by (used in) investing activities	364,058	(615,440)	(800,258)
Cash flows from financing activities
Proceeds from exercises of stock options	5,870	7,418	6,664
Proceeds from issuance of ordinary shares upon public offerings	0	818,875	1,137,683
Payment of public offering costs	0	(1,692)	(4,541)
Employee taxes paid related to settlement of equity awards	(7,600)	(4,253)	0
Net cash (used in) provided by financing activities	(1,730)	820,348	1,139,806
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	0	773	(515)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	352,807	194,234	342,166
Cash, cash equivalents and restricted cash — beginning of the year	591,842	397,608	55,442
Cash, cash equivalents and restricted cash — end of the year	$ 944,649	$ 591,842	$ 397,608