Summary of Option Activity (Detail) - 2002 Stock Incentive Plan - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Shares
Beginning Balance		6,612,000
Granted at fair market value		611,000
Forfeited, cancelled, or expired		(206,000)
Ending Balance		7,017,000	6,612,000
Options exercisable at March 31, 2017		3,582,000
Vested options expired during the quarter ended March 31, 2017		63,000
Weighted Average Exercise Price
Beginning Balance		$ 2.06
Granted at fair market value		1.55
Forfeited, cancelled, or expired		2.14
Ending Balance		2.02	$ 2.06
Options exercisable at March 31, 2017		2.42
Vested options expired during the quarter ended March 31, 2017		$ 2.91
Weighted Average Remaining Contractual Term (Years)
Options outstanding		7 years 8 months 19 days	7 years 8 months 12 days
Options exercisable		6 years 3 months 15 days
Aggregate Intrinsic Value
Options outstanding	[1]	$ 160	$ 178
Options exercisable	[1]	$ 71

[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 the grant.