Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Valuation allowance, deferred tax asset, increase (decrease)	$ 17,312,000	$ 6,313,000
Operating loss carryforwards, federal	105,336,000
Operating loss carryforwards, state	62,653,000
Unrecognized tax benefits	488,000	333,000	$ 284,000
Federal [Member]
Income Taxes [Line Items]
Provision for income taxes	$ 0	0
Operating loss carryforwards, expiration year	2036
Tax credit carryforwards, research and development	$ 4,654,000
State [Member]
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0
Operating loss carryforwards, expiration year	2036
Tax credit carryforwards, research and development	$ 717,000