Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Schedule Of Assets And Liabilities On A Recurring Basis

	2011
	Level 1		Level 2			Total
Derivative instruments
Risk management assets	$	1,090	$	1,347		$	2,437
Risk management liabilities		—		(4,235	)		(4,235	)
Firm commitments
Hedged portion of firm commitment		—		3,262			3,262
Marketable securities
Available-for-sale equity securities		30,113		—			30,113

	2010
	Level 1			Level 2		Total
Derivative instruments
Risk management assets	$	47		$	—	$	47
Risk management liabilities		(46	)		—		(46	)

Schedule Of Carrying And Fair Values Of Long-Term Debt

	2011				2010
	Carrying Value		Fair Value		Carrying Value		Fair Value
6 5/8% senior notes due 2016	$	249,674	$	254,890	$	249,593	$	258,438
6 1/2% senior notes due 2029		100,000		108,834		100,000		99,875
6 3/4% senior notes due 2032		250,000		263,988		250,000		251,925
2035 GO Zone 6 1/2% Notes		89,000		93,090		89,000		88,653
2035 IKE Zone 6 1/2% Notes		65,000		67,987		65,000		64,905
Variable rate tax-exempt waste disposal revenue bonds due 2027		10,889		10,889		10,889		10,889