Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Income Taxes [Line Items]
Deferred tax asset valuation allowance percentage in each of the last two years	100.00%
Benefits related to stock options	$ 707,000
Income tax benefit related to federal research and development credit	61,000
Unrecognized tax benefits	1,082,000
Unrecognized tax benefits which affects effective tax rate	923,000
Internal Revenue Service (IRS)
Income Taxes [Line Items]
Net operating loss carryforwards	60,886,000
Operating loss carryforwards, expiration year	2032
Research and development credits	223,000
Research and development credits, expiration year	2032
State and Local Jurisdiction
Income Taxes [Line Items]
Net operating loss carryforwards	25,160,000
Operating loss carryforwards, expiration year	2032
Research and development credits	$ 143,000
Research and development credits, expiration year	2032