v3.10.0.1
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