Derivative Instruments (Impact of Derivative Instruments Designated as Fair Value Hedges and Related Hedges Item) (Details) (Designated As Fair Value Hedges, Cost of Sales, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Firm Commitment Derivative Items Designated As Hedged Item
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$ 515	$ 1,780	$ (13,546)	$ 1,780
Commodity Forward Contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on Derivative	$ (515)	$ (1,780)	$ 12,345	$ (1,780)