Fair Value Measurements (Reconciliations Of Level 3 Fair Value Measurements) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Interest Rate Swaps [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period	$ (1,614)		$ (1,948)
Included in earnings (loss)	(1,734)	[1]	(1,218)	[1]
Included in other comprehensive income (loss)	1,614		334
Settlements	1,734		1,218
End of period	0		(1,614)
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (loss) relating to assets still held at end of period	0		0
Commodity Swap [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning of period	10,868		19,948
Included in earnings (loss)	20,086	[1]	64,470	[1]
Included in other comprehensive income (loss)	22,503		(10,116)
Settlements	(19,842)		(63,434)
End of period	33,615		10,868
Total gains (losses) for the period included in earnings attributable to the change in unrealized gains (loss) relating to assets still held at end of period	$ 244		$ 1,036

[1] Interest rate swaps and commodity sales swaps and collars are reported in the consolidated statements of operations in interest expense and revenues, respectively.