Derivatives Derivates Impact on Income (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative Instruments, Gain (Loss) [Line Items]
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	$ 93,298,000
Commodity Contract [Member] | Sales [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain Recognized in Income	1,034,000	31,000
Derivative Instruments, Loss Recognized in Income			(962,000)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	95,006,000	166,276,000	239,956,000
Commodity Contract [Member] | Other Comprehensive Income (Loss) [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain Recognized in Other Comprehensive Income (Loss), Effective Portion	$ 200,699,000	$ 140,985,000	$ 186,824,000