Commitments (Schedule Of Purchases Under Long-Term Supply Contracts) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Recorded Unconditional Purchase Obligation [Line Items]
Total payments	$ 46,581	$ 46,983	$ 43,908
Raw And Other Materials [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Total payments	33,953	35,417	34,104
Transportation [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Total payments	8,782	7,663	6,853
Information Systems And Services [Member]
Recorded Unconditional Purchase Obligation [Line Items]
Total payments	$ 3,846	$ 3,903	$ 2,951