Stock-Based Compensation Plans - Summary of Transactions Involving Stock Options Awarded (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	4,820,750	4,340,750	4,150,410
Number of Shares, Granted	1,785,000	495,000	505,000
Number of Shares, Expired	(58,500)	(2,000)	(88,000)
Number of Shares, Forfeited		(13,000)	(226,660)
Number of Shares Outstanding, Ending Balance	6,547,250	4,820,750	4,340,750	4,150,410
Weighted Average Exercise Price, Beginning Balance	$ 0.84	$ 0.90	$ 1.07
Stock options vested and exercisable	4,197,244
Weighted Average Exercise Price, Granted	$ 0.57	0.31	0.20
Number of stock options vested and expected to vest	6,211,254
Weighted Average Exercise price, Expired	$ 4.81	5.20	3.03
Weighted Average Exercise Price, Forfeited		0.67	1.61
Weighted Average Exercise Price, Ending Balance	0.73	$ 0.84	$ 0.90	$ 1.07
Stock options vested and exercisable, Weighted Average Exercise Price	0.79
Stock options vested and expected to vest, Weighted Average Exercise Price	$ 0.74
Weighted Average Remaining Contractual Term in Years	7 years	7 years 1 month 6 days	7 years 9 months 18 days	8 years 4 months 24 days
Stock options vested and exercisable, Weighted Average Remaining Contractual Term in Years	6 years 2 months 12 days
Stock options vested and expected to vest, Weighted Average Remaining Contractual Term in Years	7 years
Options Outstanding, Aggregate Intrinsic Value	$ 969	$ 223	$ 56	$ 1,076
Stock options vested and exercisable, Aggregate Intrinsic Value	874
Stock options vested and expected to vest, Aggregate Intrinsic Value	$ 959
Non-Plan Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance			5,000
Number of Shares, Expired			(5,000)
Number of Shares Outstanding, Ending Balance				5,000
Director Stock Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares Outstanding, Beginning Balance	21,000	21,000	42,000
Number of Shares, Expired			(21,000)
Number of Shares Outstanding, Ending Balance	21,000	21,000	21,000	42,000
Weighted Average Exercise Price, Beginning Balance	$ 8.97	$ 8.97	$ 5.93
Stock options vested and exercisable	21,000
Weighted Average Exercise price, Expired			2.89
Weighted Average Exercise Price, Ending Balance	$ 8.97	$ 8.97	$ 8.97	$ 5.93
Stock options vested and exercisable, Weighted Average Exercise Price	$ 8.97
Weighted Average Remaining Contractual Term in Years	4 months 24 days	1 year 4 months 24 days	2 years 8 months 12 days	1 year 10 months 24 days
Stock options vested and exercisable, Weighted Average Remaining Contractual Term in Years	4 months 24 days
Non-Plan Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Beginning Balance			$ 3.15
Weighted Average Exercise price, Expired			$ 3.15
Weighted Average Exercise Price, Ending Balance				$ 3.15
Weighted Average Remaining Contractual Term in Years				6 months