Income Taxes - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Accrual on interest and penalties related to income taxes	$ 0
Unrecognized tax benefits	1,961,595
Net operating loss carryforwards	$ 20,500,000
Cumulative change in ownership for limitation of use of net operating loss and research and development credit carryforwards	50.00%
Period of cumulative change of ownership	3 years
Research and development credit	$ 2,500,000
Unrecognized tax benefits that would affect company's effective tax rate, if recognized	0
Unrecognized tax benefits, period increase (decrease)	0
Unrecognized tax benefits, interest and penalties expense	0
California [Member]
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits	1,900,000
Net operating loss carry forwards	$ 42,900,000
Expiry date of carry forwards	Dec. 31, 2017
Tax credit carry forwards	$ 1,100,000
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	$ 53,000,000
Expiry date of carry forwards	Dec. 31, 2027
Tax credit carry forwards	$ 1,800,000
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax years subject to examination by taxing authorities	2007