Income Taxes - Additional Information (Detail) - USD ($)			12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Percentage of annual research and development credit for cash			65.00%
Valuation allowance on the deferred tax asset	100.00%	100.00%
Change in valuation allowance			$ 10,317,000	$ 7,156,000
Tax benefit on exercise of non-qualified stock options and disqualified disposition of incentive stock options			839,000
Unrecognized tax benefits	$ 0	$ 0	$ 0	$ 0
Unrecognized tax benefits, related interest and penalties	0	$ 0
Tax examinations, description			Tax years 2007 through 2015 remain open to U.S. federal and state tax examinations.
Earliest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2007
Latest Tax Year [Member]
Income Taxes [Line Items]
Open tax years			2015
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	95,900,000		$ 95,900,000
Federal [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2026
Federal [Member] | Research and Development Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	3,642,000		$ 3,642,000
Federal [Member] | Research and Development Tax Credit Carryforward [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax credit expiration year			2025
State and Local [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	89,899,000		$ 89,899,000
State and Local [Member] | Earliest Tax Year [Member]
Income Taxes [Line Items]
Tax loss carryforwards expiration year			2027
State and Local [Member] | Research and Development Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Tax credit carryforwards	$ 707,000		$ 707,000