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Debt - Credit Facility (Details) - USD ($)
Mar. 31, 2016
Dec. 31, 2015
Nov. 27, 2013
Jun. 04, 2013
Line of Credit Facility [Line Items]        
Fair value of debt instrument $ 184,063,000 $ 169,220,000    
U.S. revolving credit facility [Member] | Long-term Debt [Member]        
Line of Credit Facility [Line Items]        
Credit facility face amount 150,000,000      
Credit facility maximum amount 150,000,000      
Borrowing availability 85,844,000      
Borrowing availability, net of outstanding letters of credit and borrowings 41,085,000      
U.S. letter of credit [Member] | Long-term Debt [Member]        
Line of Credit Facility [Line Items]        
Letter of credit sub-facility amount 110,000,000      
Borrowing availability, net of outstanding letters of credit and borrowings 44,759,000      
Outstanding borrowings 0      
Iceland revolving line of credit [Member] | Long-term Debt [Member]        
Line of Credit Facility [Line Items]        
Credit facility face amount     $ 50,000,000  
Credit facility maximum amount 50,000,000      
Borrowing availability 45,397,000      
Outstanding borrowings 0      
Borrowing availability, net of outstanding letters of credit and borrowings $ 45,397,000      
Senior secured notes due June 01, 2021 [Member] | Long-term Debt [Member]        
Line of Credit Facility [Line Items]        
Face amount       $ 250,000,000
Stated interest rate, percentage 7.50% 7.50%   7.50%