Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Fair Value (Details)

v3.8.0.1
Financial Instruments - Fair Value (Details) - Derivatives designated as hedging instrument - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Derivative assets:    
Total derivative assets $ 10,223 $ 1,043
Derivative liabilities:    
Total derivative liabilities 16,026 448
Cash Flow Hedging    
Derivative assets:    
Total derivative assets 3,896 1,043
Derivative liabilities:    
Total derivative liabilities 423 448
Cash Flow Hedging | Prepaid and other current assets | Interest rate caps    
Derivative assets:    
Total derivative assets 1,039 44
Cash Flow Hedging | Other long-term assets | Interest rate caps    
Derivative assets:    
Total derivative assets 2,857 999
Cash Flow Hedging | Accrued liabilities | Natural gas swaps    
Derivative liabilities:    
Total derivative liabilities 246 318
Cash Flow Hedging | Other long-term liabilities | Natural gas swaps    
Derivative liabilities:    
Total derivative liabilities 177 130
Net Investment Hedging | Prepaid and other current assets | Cross currency swaps    
Derivative assets:    
Total derivative assets 6,327 0
Net Investment Hedging | Other long-term liabilities | Cross currency swaps    
Derivative liabilities:    
Total derivative liabilities $ 15,603 $ 0