CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
CONDENSED CONSOLIDATED BALANCE SHEETS
Marketable securities-amortized cost	$ 292,350	$ 291,871
Marketable securities-allowance for credit losses	$ 0	$ 0
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	221,875,396	221,084,433
Common stock, shares outstanding	221,875,396	221,084,433