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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period		$ 9,983	$ 857	$ 9,094	$ 3,355
Included in earnings	[1]	(12,322)	111	(6,334)	888
Settlements		(2,422)	(761)	(7,521)	(4,036)
End of period		(4,761)	207	(4,761)	207
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		$ (14,744)	$ (650)	$ (13,855)	$ (3,148)

[1] Commodity derivatives are reported in the Unaudited Condensed Consolidated Statements of Operations in gain (loss) on derivatives