Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)
Income Taxes [Line Items]
Benefits related to stock options	$ 707,000
Deferred tax asset valuation allowance percentage in each of the last two years	100.00%
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Net operating loss carryforwards	$ 135,945,000
Operating loss carryforwards, expiration year	2035
Research and development credits	$ 998,000
Research and development credits, expiration year	2034
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating loss carryforwards	$ 97,530,000
Operating loss carryforwards, expiration year	2035
Research and development credits	$ 196,000
Research and development credits, expiration year	2034