XML 65 R50.htm IDEA: XBRL DOCUMENT v3.10.0.1
Derivative Financial Instruments (Narrative) (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Derivative Financial Instruments [Abstract]          
Accumulated other comprehensive loss $ (4,208,000)   $ (4,208,000)   $ (13,110,000)
Gain or loss from discontinuing cash flow hedge treatment 0 $ 0 0 $ 0  
Energy trading contracts, gain (loss) $ 4,100,000 $ 6,800,000 $ 10,800,000 $ 15,100,000