Potential Common Shares Excluded in Calculating Basic and Diluted Net Loss Per Common Share (Detail) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities to purchase common stock	10,361	11,256	9,973
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities to purchase common stock	7,245	6,868	5,414
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities to purchase common stock	3,116	4,388	4,559