Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivative not designated as hedging instrument:
Total	$ 0	$ 311
Derivative not designated as hedging instrument:
Net amount recognized in earnings	(3,384)	(987)
Commodity Contract [Member] | Other Current Assets [Member]
Derivative not designated as hedging instrument:
Total	0	(470)
Commodity Contract [Member] | Sales [Member]
Derivative not designated as hedging instrument:
Net amount recognized in earnings	(1,498)	(532)
Commodity Contract [Member] | Cost Of Sales [Member]
Derivative not designated as hedging instrument:
Net amount recognized in earnings	(1,886)	(455)
Cash Collateral [Member] | Other Current Assets [Member]
Derivative not designated as hedging instrument:
Total	$ 0	$ 781