Derivative Financial Instruments (Fair Value Hedging Disclosures) (Details) - Commodity Contract [Member] - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Derivative Instruments, Gain (Loss) [Line Items] | |||
| Increase (Decrease) in Fair Value of Price Risk Fair Value Hedging Instruments | $ 543 | $ 4,806 | $ (8,988) |
| Increase (Decrease) in Fair Value of Hedged Item in Price Risk Fair Value Hedge | $ (543) | $ (4,806) | $ 8,988 |