Fair Value Measurement (Tables)

3 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Financial assets and financial liabilities at fair value on a recurring basis

The following table presents our financial assets and financial liabilities that are measured at fair value on a recurring basis for each of the fair value hierarchy levels, including both current and noncurrent portions, as of December 31, 2012, September 30, 2012 and December 31, 2011:

	Asset (Liability)
	Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1)		Significant Other Observable Inputs (Level 2)			Unobservable Inputs (Level 3)		Total
December 31, 2012:
Assets:
Derivative financial instruments:
Commodity contracts	$	—	$	3,108		$	—	$	3,108
Liabilities:
Derivative financial instruments:
Commodity contracts	$	—	$	(28,290	)	$	—	$	(28,290	)
September 30, 2012:
Assets:
Derivative financial instruments:
Commodity contracts	$	—	$	2,089		$	—	$	2,089
Liabilities:
Derivative financial instruments:
Commodity contracts	$	—	$	(42,598	)	$	—	$	(42,598	)
December 31, 2011:
Assets:
Derivative financial instruments:
Commodity contracts	$	—	$	27		$	—	$	27
Liabilities:
Derivative financial instruments:
Commodity contracts	$	—	$	(16,538	)	$	—	$	(16,538	)