Annual report pursuant to Section 13 and 15(d)

Financial Instruments - Fair Value (Details)

v3.10.0.1
Financial Instruments - Fair Value (Details) - Derivatives designated as cash flow hedges: - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Derivative assets:    
Total derivative assets $ 20,768 $ 1,043
Cash Flow Hedging    
Derivative assets:    
Total derivative assets 1,925 1,043
Liability derivatives:    
Total derivative liabilities 2,026 448
Cash Flow Hedging | Natural gas swaps | Prepaid and other current assets    
Derivative assets:    
Total derivative assets 21 0
Cash Flow Hedging | Natural gas swaps | Accrued liabilities    
Liability derivatives:    
Total derivative liabilities 36 318
Cash Flow Hedging | Natural gas swaps | Other long-term liabilities    
Liability derivatives:    
Total derivative liabilities 148 130
Cash Flow Hedging | Interest rate caps | Prepaid and other current assets    
Derivative assets:    
Total derivative assets 1,358 44
Cash Flow Hedging | Interest rate caps | Other long-term assets    
Derivative assets:    
Total derivative assets 546 999
Cash Flow Hedging | Interest rate caps | Other long-term liabilities    
Liability derivatives:    
Total derivative liabilities 1,842 0
Net Investment Hedging    
Derivative assets:    
Total derivative assets 18,843 0
Net Investment Hedging | Cross currency swap | Prepaid and other current assets    
Derivative assets:    
Total derivative assets 5,499 0
Net Investment Hedging | Cross currency swap | Other long-term assets    
Derivative assets:    
Total derivative assets $ 13,344 $ 0