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Schedule of Estimated Fair Value Assumption of 2017 Notes (Detail) - Convertible 2017 Notes - $ / shares
3 Months Ended 12 Months Ended
Mar. 31, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Stock price $ 1.14 $ 3.40
Conversion Rate per $1,000 2.90 2.90
Conversion Price $ 344.83 $ 344.83
Maturity date Jun. 23, 2017 Mar. 15, 2017
Risk-free interest rate 0.76% 0.49%
Estimated stock volatility 100.00% 80.00%
Estimated credit spread 20.00% 20.00%