v3.19.3
Derivative Financial Instruments (Derivatives and Hedging - Designated) (Details) - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset   $ 774
Derivative Liability, Fair Value, Gross Liability   8,438
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset   462
Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability   0
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset   312
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability   8,438
Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset $ 16,978  
Derivative Liability, Fair Value, Gross Liability 29,894  
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 16,978 61,704
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability 12,139 $ 7,155
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other Current Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 0  
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other Current Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability 8,957  
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other Noncurrent Assets [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Asset, Fair Value, Gross Asset 0  
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other Noncurrent Liabilities [Member]    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Gross Liability $ 8,798