Summary of Option Activity (Detail) - USD ($)		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Number of Shares
Beginning Balance		3,391,000
Granted		3,096,000
Exercised		(38,000)
Forfeited, cancelled, or expired		(329,000)
Ending Balance		6,120,000	3,391,000
Options exercisable, June 30, 2015		2,862,000
ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod		113,000
Weighted Average Exercise Price
Beginning Balance		$ 3.11
Granted		2.35
Exercised		1.15
Forfeited, cancelled, or expired		3.16
Ending Balance		2.74	$ 3.11
Options exercisable, June 30, 2015		3.05
ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice		$ 3.09
Weighted Average Remaining Contractual Term (In Years)
Options outstanding		5 years 11 months 12 days	2 years 11 months 19 days
Options exercisable		2 years 7 months 21 days
Aggregate Intrinsic Value
Options outstanding	[1]	$ 1,063,000
Options outstanding	[1]	113,000	$ 1,063,000
Options exercisable	[1]	$ 94,000

[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.