Stockholders' Equity (Stock Option and RSU Activity) (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Number of options
Ending outstanding number (in shares)	12,846
Stock options
Number of options
Beginning outstanding number (in shares)	8,661
Granted (in shares)	4,357
Canceled/forfeited/expired (in shares)	(172)
Ending outstanding number (in shares)	12,846
Weighted average exercise price
Beginning balance (in usd per share) | $ / shares	$ 1.17
Granted (in usd per share) | $ / shares	0.26
Canceled/forfeited/expired (in usd per share) | $ / shares	0.90
Ending balance (in usd per share) | $ / shares	$ 0.87
Restricted Stock Units (RSUs)
Number of RSUs
Beginning balance (in shares)	401
Shares granted (in shares)	848
Canceled/forfeited/expired (in shares)	(23)
Ending balance (in shares)	1,226
Weighted average grant date fair value
Beginning balance (in usd per share) | $ / shares	$ 0.95
Granted (in usd per share) | $ / shares	0.26
Canceled/forfeited/expired (in usd per share) | $ / shares	0.95
Ending balance (in usd per share) | $ / shares	$ 0.47