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Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 22, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Asset impairment charges $ 0 $ 0 $ 0  
Transfers between fair value measurement levels 0 0    
Non-recurring fair value measurements 0 0    
Recurring Basis [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Liabilities measured at fair value 0 $ 0    
Senior Convertible Notes [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Aggregate principal amount of loan 125,000,000      
Carrying value of debt 88,500,000      
Senior Convertible Notes [Member] | Level 2 [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair value of debt 184,600,000      
2022 Notes [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Aggregate principal amount of loan       $ 175,000,000
Fair value of debt 175,000,000      
Carrying value of debt 169,200,000      
Private placement $ 175,000,000      
Interest rate (as a percent)       11.50%
2022 Notes [Member] | Private Placement [Member]        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Interest rate (as a percent) 11.50%