Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Shares
Beginning Balance		1,287,000	1,623,000	1,347,000
Granted at fair market value		1,258,000	90,000	611,000
Exercised			(2,000)	(1,000)
Forfeited, cancelled, or expired		(147,000)	(424,000)	(334,000)
Ending Balance		2,398,000	1,287,000	1,623,000
Options exercisable at December 31, 2020		1,074,000
Vested options expired during the twelve months ended December 31, 2020		17
Weighted-Average Exercise Price Per Share
Beginning Balance		$ 5.77	$ 6.54	$ 8.99
Granted at fair market value		0.38	1.74	1.98
Exercised			2.10	2.10
Forfeited, cancelled, or expired		6.87	9.43	10.68
Ending Balance		2.96	$ 5.77	$ 6.54
Options exercisable at December 31, 2020		6.05
Vested options expired during the twelve months ended December 31, 2020		$ 13.20
Options outstanding		7 years 2 months 12 days
Options exercisable		4 years 6 months
Aggregate Intrinsic Value
Options outstanding	[1]	$ 53

[1] The intrinsic value calculation does not include negative values. This can occur when the fair market value on the reporting date is less than the exercise price of a grant.