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Derivative Financial Instruments - Significant Assumptions Utilized in Valuation Technique (Detail) (Monte Carlo Simulations [Member], Senior Convertible Notes [Member], USD $)
3 Months Ended 12 Months Ended
Mar. 31, 2014
Dec. 31, 2013
Derivative [Line Items]    
Quoted market price on valuation date $ 2.29 $ 2.02
Contractual conversion rate $ 3.17 $ 3.17
Range of effective contractual conversion rates      
Contractual term to maturity 1 month 1 day 3 months 29 days
Implied expected term to maturity 1 month 1 day 3 months 29 days
Market volatility:    
Range of equivalent volatilities 27.30%  
Contractual interest rate 9.00%  
Range of equivalent market risk adjusted interest rates 9.08%  
Range of equivalent credit risk adjusted yields 0.64% 0.67%
Minimum [Member]
   
Market volatility:    
Range of volatilities 18.20% 47.40%
Range of equivalent volatilities   59.90%
Contractual interest rate   8.00%
Range of equivalent market risk adjusted interest rates   8.08%
Risk-free rates 0.03% 0.01%
Maximum [Member]
   
Market volatility:    
Range of volatilities 38.40% 91.20%
Range of equivalent volatilities   69.90%
Contractual interest rate   9.00%
Range of equivalent market risk adjusted interest rates   9.08%
Risk-free rates 0.05% 0.07%