Condensed Balance Sheets (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Allowance for doubtful accounts receivable, current	$ 0	$ 0
Stockholders equity
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	25,000	25,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	210,000	210,000
Common stock, shares issued	157,952	152,926
Common stock, shares outstanding	157,952	152,926