Fair Value Measurements (Reconciliations Of Level 3 Fair Value Measurements) (Details) (Collar [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Collar [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period	$ (6,081)		$ 1,446		$ (2,595)		$ (595)
Included in earnings	5,785	[1]	(3,949)	[1]	(2,043)	[1]	(2,544)	[1]
Included in other comprehensive income (loss)	0		(119)		0		(119)
Settlements	887		0		5,229		636
End of period	591		(2,622)		591		(2,622)
Total gains (losses) for the period included in earnings attributable to the change in unrealized loss relating to assets still held at end of period	$ 6,672		$ (3,949)		$ 3,186		$ (1,908)

[1] Commodity collars are reported in the Unaudited Condensed Consolidated Statements of Income in oil and natural gas revenues (for cash flow hedges) and gain (loss) on derivatives not designated as hedges and hedge ineffectiveness, net, respectively.