Fair Value Measurements (Reconciliations Of Level 3 Fair Value Measurements) (Details) - Level 3 [Member] - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period		$ (4,761)	$ 207	$ 9,094	$ 3,355
Included in earnings	[1]	3,077	4,436	(3,257)	5,324
Settlements		(443)	(2,161)	(7,964)	(6,197)
End of period		(2,127)	2,482	(2,127)	2,482
Total gains (losses) for the period included in earnings attributable to the change in unrealized gain (loss) relating to assets still held at end of period		$ 2,634	$ 2,275	$ (11,221)	$ (873)

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