Stockholders' Equity - Additional Information (Detail) (Stockholders' Equity [Member], USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Stockholders' Equity [Member]
Changes In Equity [Line Items]
Shares of common stock issued under employee stock purchase plan, and warrant and stock option exercises during the period	3,780,945	3,006
Proceeds from common stock issued under employee stock purchase plan, and warrant and stock option exercises during the period	$ 1,864,000	$ 3,000