Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2014

Fair Value Disclosures [Abstract]

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

The following tables summarize, by level within the fair value hierarchy, the Company's assets and liabilities that were accounted for at fair value on a recurring basis:

	September 30, 2014
	Level 1			Level 2			Total
Derivative instruments
Risk management assets - Commodity forward contracts	$	428		$	23		$	451
Risk management liabilities - Commodity forward contracts	(119		)	(6,358		)	(6,477		)
Available-for-sale marketable securities	21,066			—			21,066
	December 31, 2013
	Level 1			Level 2			Total
Derivative instruments
Risk management assets - Commodity forward contracts	$	48		$	248		$	296
Risk management liabilities - Commodity forward contracts	—			(176		)	(176		)
Available-for-sale marketable securities	91,595			147,793			239,388

Summary Of Carrying And Fair Values Of Long-Term Debt

The carrying and fair values of the Company's long-term debt are summarized in the table below. The Company's long-term debt instruments are publicly-traded. A market approach, based upon quotes from financial reporting services, is used to measure the fair value of the Company's long-term debt. Because the Company's long-term debt instruments may not be actively traded, the inputs used to measure the fair value of the Company's long-term debt are classified as Level 2 inputs within the fair value hierarchy.

	September 30, 2014				December 31, 2013
	Carrying Value		Fair Value		Carrying Value		Fair Value
3.60% senior notes due 2022	$	249,079	$	247,633	$	248,990	$	236,905
6 ½% senior notes due 2029	100,000		114,624		100,000		109,490
6 ¾% senior notes due 2032	250,000		275,313		250,000		265,148
6 ½% GO Zone Senior Notes Due 2035	89,000		101,855		89,000		94,606
6 ½% IKE Zone Senior Notes Due 2035	65,000		74,389		65,000		69,094
Loan related to tax-exempt waste disposal revenue    bonds due 2027	10,889		10,889		10,889		10,889