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Schedule of Estimated Fair Value Assumption of 2017 Notes (Detail) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Jun. 30, 2016
Debt Instrument [Line Items]      
Stock price     $ 9.00
Convertible 2017 Notes      
Debt Instrument [Line Items]      
Stock price $ 3.40 $ 12.40  
Conversion Rate per $1,000 2.90 2.90  
Conversion Price $ 344.83 $ 344.83  
Maturity date Mar. 15, 2017 Mar. 15, 2017  
Risk-free interest rate 0.49% 0.74%  
Estimated stock volatility 80.00% 140.00%  
Estimated credit spread 20.00% 30.00%