Annual report pursuant to Section 13 and 15(d)

Equity Incentive Plans and Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail)

v2.4.0.8
Equity Incentive Plans and Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Employee Stock Purchase Plan (ESPP) [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 0.19% 0.21% 0.15%
Expected life (in years) 1 year 3 months 1 year 3 months 1 year 3 months
Dividend yield         
Volatility 77.00% 111.00% 80.00%
Weighted-average fair value of ESPP purchase rights $ 2.27 $ 3.46 $ 0.66
Employee Stock Options [Member]
     
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Risk-free interest rate 1.14% 1.12% 1.88%
Expected life (in years) 5 years 11 months 19 days 5 years 11 months 27 days 5 years 11 months 23 days
Dividend yield         
Volatility 101.00% 105.00% 92.00%
Weighted-average fair value of stock options granted $ 4.04 $ 5.09 $ 1.23