Fair Value Measurements (Reconciliations Of Level 3 Fair Value Measurements) (Details) - Level 3 [Member] - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period			$ 948	$ 0	$ 1,204
Included in earnings	[1]	$ 0	714	0	1,277
Settlements		0	(819)	0	(1,638)
End of period		0	843	0	843
Total losses for the period included in earnings attributable to the change in unrealized gain (loss) relating to assets still held at end of period		$ 0	$ (105)	$ 0	$ (361)

[1] Commodity derivative activity is reported in the unaudited condensed consolidated statements of operations in gain (loss) on derivatives.