Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
NOL DTA related to excess benefits from stock option exercises	$ 400,000
Increase in valuation allowance	7,800,000	11,600,000	10,300,000
Accrued interest or penalties	0	0
Federal [Member]
Federal and State net operating loss carryforwards	113,000,000
Year net operating loss carryforwards begin to expire	2021
Research and development credits	1,700,000
Year research and development credits begin to expire	2022
State [Member]
Federal and State net operating loss carryforwards	110,000,000
Year net operating loss carryforwards begin to expire	2013
Research and development credits	$ 3,700,000