Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Accrual on interest and penalties related to income taxes	$ 0	$ 0
Tax years subject to examination by taxing authorities	Beginning 2007 to date
Net operating loss carryforwards	13,200,000
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	1,600,000
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	33,200,000
Expiry date of carry forwards	Dec. 31, 2027
Tax credit carry forwards	1,100,000
California [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	32,500,000
Expiry date of carry forwards	Dec. 31, 2017
Tax credit carry forwards	$ 737,000