Derivatives (Effect Of Derivative Instruments Recognized In Statement Of Operations, Not Designated As Hedging Instruments) (Details) - USD ($) $ in Thousands	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2020	Aug. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (985)	$ (10,704)	$ 4,225
Derivative Instruments Not Designated Amount Paid (Received) During Period	(1,133)	(4,244)	16,196
Commodity Contract | Gain (loss) on derivatives not designated as hedges and hedge ineffectiveness [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivatives	$ (985)	$ (10,704)	$ 4,225