Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail)

v3.7.0.1
Stock Based Compensation - Weighted-Average Fair Value Valuation Assumptions (Detail) - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Employee Stock Options        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Risk-free interest rate 0.00% 1.08% 0.00% 1.60%
Expected term (in years) 0 years 5 years 3 months 8 days 0 years 5 years 11 months 19 days
Dividend yield 0.00% 0.00% 0.00% 0.00%
Volatility 0.00% 109.00% 0.00% 108.00%
Weighted-average fair value of stock options granted $ 0 $ 0.30 $ 0 $ 0.44
Employee Stock Purchase Plan (ESPP)        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Risk-free interest rate 0.56% 0.56% 0.56% 0.56%
Expected term (in years) 1 year 2 months 27 days 1 year 2 months 27 days 1 year 2 months 27 days 1 year 2 months 27 days
Dividend yield 0.00% 0.00% 0.00% 0.00%
Volatility 161.00% 161.00% 161.00% 161.00%
Weighted-average fair value of ESPP purchase rights $ 0.22 $ 0.22 $ 0.22 $ 0.22