Fair Value Measurement

3 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Fair Value Measurements

Fair Value Measurements

Derivative Financial Instruments

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	)

The fair values of our non-exchange traded commodity derivative contracts are based upon indicative price quotations available through brokers, industry price publications or recent market transactions and related market indicators. For commodity option contracts not traded on an exchange, we use a Black Scholes option pricing model that considers time value and volatility of the underlying commodity.

Other Financial Instruments

The carrying amounts of other financial instruments included in current assets and current liabilities (except for current maturities of long-term debt) approximate their fair values because of their short-term nature. At December 31, 2012, the carrying amount and estimated fair value of our long-term debt (including current maturities) were $2,323,051 and $2,541,466, respectively. At December 31, 2011, the carrying amount and estimated fair value of our long-term debt (including current maturities) were $932,286 and $925,236, respectively. We estimate the fair value of long-term debt by using current market prices and by discounting future cash flows using rates available for similar type debt (Level 2).

We have financial instruments such as short-term investments and trade accounts receivable which could expose us to concentrations of credit risk. We limit our credit risk from short-term investments by investing only in investment-grade commercial paper and U.S. Government securities. The credit risk from trade accounts receivable is limited because we have a large customer base which extends across many different U.S. markets.