Derivative Financial Instruments (Derivatives And Hedging-Overall-Subsequent Measurement) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Derivative, Gain (Loss) on Derivative, Net | $ 69,065 | $ (27,770) | $ (32,586) |
| Sales [Member] | Commodity Contract [Member] | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Derivative, Gain (Loss) on Derivative, Net | 85,012 | (56,338) | (38,584) |
| Cost of Sales [Member] | Commodity Contract [Member] | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Derivative, Gain (Loss) on Derivative, Net | (15,947) | 25,566 | 10,998 |
| Operating Expenses [Member] | Commodity Contract [Member] | |||
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Derivative, Gain (Loss) on Derivative, Net | $ 0 | $ 3,002 | $ (5,000) |