Schedule I - Condensed Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 122,863	$ 103,791		$ 299,968
Short-term investments	12,218	41,457
Investment securities, available-for sale	100,702	189,498
Investment securities, held-to-maturity	6,902	15
Other assets, current	1,404	4,043
Total current assets	427,970	624,997
Investment securities, available-for-sale	120,208	137,368
Total assets	570,671	808,620
Current liabilities
Accounts payable and accrued expenses	37,184	32,445
Accrued salaries and benefits	21,061	23,962
Total current liabilities	261,115	431,507		371,901
Total liabilities	284,277	451,733		410,764
Stockholders' equity
Additional paid-in capital	2,461,238	2,319,157
Accumulated other comprehensive loss	(2,370)	(9,374)
Accumulated deficit	(2,159,794)	(1,946,433)	$ 1,616,000	(1,616,015)
Less: Treasury stock, at cost; 7,912,750 and 2,072,752 shares held at December 31, 2023 and 2022, respectively	(12,729)	(6,509)
Total liabilities and stockholders' equity	570,671	808,620		$ 950,804
Common Class A
Stockholders' equity
Common stock, value	40	37
Common Class B
Stockholders' equity
Common stock, value	9	9
Parent Company
Current assets
Cash and cash equivalents	48,312	69,718
Short-term investments	454	31,725
Investment securities, available-for sale	23,564	117,834
Investment securities, held-to-maturity	146	0
Other assets, current	247	5,704
Total current assets	72,723	224,981
Intercompany interest receivable	4,958	4,958
Intercompany note receivable	40,000	40,000
Investment securities, available-for-sale	1,507	18,708
Investments in consolidated subsidiaries	197,012	115,571
Total assets	316,200	404,218
Current liabilities
Accounts payable and accrued expenses	683	865
Accrued salaries and benefits	6,598	6,576
Total current liabilities	7,281	7,441
Intercompany payable	22,165	39,530
Notes payable, net of discount and deferred issuance costs	360	360
Total liabilities	29,806	47,331
Stockholders' equity
Additional paid-in capital	2,461,238	2,319,157
Accumulated other comprehensive loss	(2,370)	(9,374)
Accumulated deficit	(2,159,794)	(1,946,433)
Less: Treasury stock, at cost; 7,912,750 and 2,072,752 shares held at December 31, 2023 and 2022, respectively	(12,729)	(6,509)
Total stockholders' equity	286,394	356,887
Total liabilities and stockholders' equity	316,200	404,218
Parent Company | Common Class A
Stockholders' equity
Common stock, value	40	37
Parent Company | Common Class B
Stockholders' equity
Common stock, value	$ 9	$ 9