Derivative Instruments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Derivative [Line Items]
Foreign currency contracts maximum maturity term (in months)	18
Forward contracts maturity period	18
Amount of loss relating to accumulated OCI expected to be recognized in earnings over the next 12 months	$ 0.9
Maximum percentage of the forecasted intercompany sales to be hedged by using foreign currency risk derivatives	75.00%
Minimum percentage of the forecasted natural gas requirements to be hedged by using derivatives	0.00%
Maximum percentage of the forecasted natural gas requirements to be hedged by using derivatives	75.00%
Natural Gas Forward Contracts [Member] | Minimum [Member]
Derivative [Line Items]
Forward contracts maturity period	1
Natural Gas Forward Contracts [Member] | Maximum [Member]
Derivative [Line Items]
Forward contracts maturity period	18