Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

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:

	March 31, 2015
	Level 1			Level 2			Total
Derivative instruments
Risk management assets—Commodity forward contracts	$	4,209		$	275		$	4,484
Risk management liabilities—Commodity forward contracts	(17		)	(6,844		)	(6,861		)
Marketable securities
Available-for-sale securities	17,033			—			17,033
	December 31, 2014
	Level 1			Level 2			Total
Derivative instruments
Risk management assets—Commodity forward contracts	$	3,143		$	2		$	3,145
Risk management liabilities—Commodity forward contracts	—			(10,108		)	(10,108		)
Marketable securities
Available-for-sale securities	15,414			—			15,414

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.

	March 31, 2015				December 31, 2014
	Carrying Value		Fair Value		Carrying Value		Fair Value
3.60% senior notes due 2022	$	249,138	$	253,240	$	249,108	$	248,630
6 ½% senior notes due 2029	100,000		118,493		100,000		116,384
6 ¾% senior notes due 2032	250,000		280,285		250,000		285,545
6 ½% GO Zone Senior Notes Due 2035	89,000		105,298		89,000		106,504
6 ½% IKE Zone Senior Notes Due 2035	65,000		76,903		65,000		77,784
Loan related to tax-exempt waste disposal revenue    bonds due 2027	10,889		10,889		10,889		10,889