Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Income Taxes [Line Items]
Net deferred tax asset	$ 19,279,000	$ 13,894,000
Federal tax, net operating loss carryforwards	19,900,000
Operating loss carryforward expiration year	2031
Research and development tax credit carryforward	1,983,000	1,303,000
Federal research and development tax credit carryforward expiration year	2029
Limitation of company's ability to utilize certain tax credit carryforwards and net operating loss carryforwards, minimum percentage of ownership change	50.00%
Unrecognized tax benefits that, if recognized, would not impact income tax benefit or effective tax rate	600,000
California
Schedule Of Income Taxes [Line Items]
California tax, net operating loss carryforwards	30,100,000
Research and development tax credit carryforward	1,400,000
Federal
Schedule Of Income Taxes [Line Items]
Research and development tax credit carryforward	$ 1,500,000