Derivative Instruments - General Information (Details) - Maximum	12 Months Ended
	Dec. 31, 2015
Managing foreign currency and natural gas exposure
Percentage of the value of the forecasted exposure to be hedged by using foreign currency risk derivatives	75.00%
Percentage of the forecasted natural gas requirements to be hedged by using derivatives	75.00%
Foreign currency forward exchange contracts
Managing foreign currency and natural gas exposure
Maturity period of derivatives	18 months
Foreign exchange option contracts
Managing foreign currency and natural gas exposure
Maturity period of derivatives	18 months
Natural gas contracts | Forward contracts
Managing foreign currency and natural gas exposure
Maturity period of derivatives	24 months