Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2012

Fair Value Measurements [Abstract]

Summary Of Assets And Liabilities Accounted At Fair Value On A Recurring Basis

	March 31, 2012
	Level 1		Level 2			Total
Derivative instruments
Risk management assets	$	1,442	$	5,729		$	7,171
Risk management liabilities		—		(939	)		(939	)
Firm commitments
Hedged portion of firm commitment		—		(5,729	)		(5,729	)
Marketable securities
Available-for-sale equity securities		58,547		—			58,547

	December 31, 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

Summary Of Carrying And Fair Values Of Long-Term Debt

	March 31, 2012				December 31, 2011
	Carrying Value		Fair Value		Carrying Value		Fair Value
65/8% senior notes due 2016	$	249,694	$	255,000	$	249,674	$	254,890
6   1/2% senior notes due 2029		100,000		112,316		100,000		108,834
6   3/4% senior notes due 2032		250,000		274,348		250,000		263,988
2035 GO Zone 6  1/2% Notes		89,000		96,091		89,000		93,090
2035 IKE Zone 6  1/2% Notes		65,000		70,179		65,000		67,987
Loan related to tax-exempt waste disposal revenue bonds due 2027		10,889		10,889		10,889		10,889