Stockholders' Equity (Stock Option and RSU Activity) (Detail) shares in Thousands	3 Months Ended
	Mar. 31, 2020 $ / shares shares
Number of options
Number of options, ending outstanding number (in shares)	6,116
Stock options and performance stock options
Number of options
Number of options, beginning outstanding number (in shares)	3,098
Number of options, Granted (in shares)	3,073
Number of options, Exercised (in shares)	(1)
Number of options, Canceled/forfeited/expired (in shares)	(54)
Number of options, ending outstanding number (in shares)	6,116
Weighted average exercise price
Weighted average exercise price, beginning balance (in dollars per share) | $ / shares	$ 1.17
Weighted average exercise price, Granted (in dollars per share) | $ / shares	1.31
Weighted average exercise price, Exercised (in dollars per share) | $ / shares	0.95
Weighted average exercise price, Canceled/forfeited/expired (in dollars per share) | $ / shares	1.78
Weighted average exercise price, ending balance (in dollars per share) | $ / shares	$ 1.24
Restricted Stock Units (RSUs)
Number of RSUs
Shares outstanding (in shares)	129
Shares granted (in shares)	0
Shares vested in period (in shares)	(21)
Shares canceled in period (in shares)	(19)
Shares outstanding (in shares)	89
Weighted average grant date fair value
Beginning balance (usd per share) | $ / shares	$ 1.50
Granted (usd per share) | $ / shares	0.00
Exercised (usd per share) | $ / shares	1.50
Canceled/forfeited/expired (usd per share) | $ / shares	1.50
Ending balance (usd per share) | $ / shares	$ 1.50