Derivatives and Fair Value of Financial Instruments (Details 5) (USD $)	3 Months Ended
	Mar. 31, 2012 counterparty	Dec. 31, 2011
Commodities
Fair value of each type of derivative and its location in the Consolidated Balance Sheets
Asset Derivatives	$ 2,398,000	$ 5,144,000
Liability Derivatives	3,360,000	5,529,000
Margin account	6,188,000	8,619,000
Derivative assets and liabilities, net basis	5,226,000	8,234,000
Foreign currencies
Fair value of each type of derivative and its location in the Consolidated Balance Sheets
Asset Derivatives	88,000	2,247,000
Liability Derivatives	500,000	3,380,000
Loss due to credit risk associated with derivative contracts	88,000
Number of counterparties	4
Interest rate
Fair value of each type of derivative and its location in the Consolidated Balance Sheets
Liability Derivatives	$ 9,900,000	$ 11,268,000