Fair Value (Tables)

3 Months Ended

Mar. 31, 2012

Fair Value [Abstract]

Schedule Of Carrying Amounts And Fair Values Of Financial Instruments

	December 31, 2011						March 31, 2012
Assets (Liabilities)	Carrying Amount			Fair Value			Carrying Amount			Fair Value
Cash and cash equivalents	$	209,620		$	209,620		$	151,642		$	151,642
Energy commodity derivatives deposits	$	26,917		$	26,917		$	41,667		$	41,667
Long-term receivables	$	2,534		$	2,510		$	2,852		$	2,816
Energy commodity derivatives contracts (current)	$	4,914		$	4,914		$	(4,654	)	$	(4,654	)
Energy commodity derivatives contracts (noncurrent)	$	(6,457	)	$	(6,457	)	$	(11,744	)	$	(11,744	)
Debt	$	(2,151,775	)	$	(2,389,700	)	$	(2,150,107	)	$	(2,387,630	)

Schedule Of Recurring Fair Value Measurements Of Commodity Contracts

				Fair Value Measurements as of December 31, 2011 using:
					Quoted Prices in			Significant
					Active Markets			Other		Significant
					for Identical			Observable		Unobservable
					Assets			Inputs		Inputs
Assets (Liabilities)		Total			(Level 1)			(Level 2)		(Level 3)
Long-term receivables	$	2,510		$	—		$	—	$	2,510
Energy commodity derivatives contracts (current)	$	4,914		$	4,914		$	—	$	—
Energy commodity derivatives contracts (noncurrent)	$	(6,457	)	$	(6,457	)	$	—	$	—
Debt	$	(2,389,700	)	$	(2,389,700	)	$	—	$	—

				Fair Value Measurements as of March 31, 2012 using:
					Quoted Prices in			Significant
					Active Markets			Other		Significant
					for Identical			Observable		Unobservable
					Assets			Inputs		Inputs
Assets (Liabilities)		Total			(Level 1)			(Level 2)		(Level 3)
Long-term receivables	$	2,816		$	—		$	—	$	2,816
Energy commodity derivatives contracts (current)	$	(4,654	)	$	(4,654	)	$	—	$	—
Energy commodity derivatives contracts (noncurrent)	$	(11,744	)	$	(11,744	)	$	—	$	—
Debt	$	(2,387,630	)	$	(2,387,630	)	$	—	$	—