Fair Value Measurements Fair Value Measurements, Schedule of Quantitative Information for Level 3 Derivative Contracts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Midwest Premium Swap Asset Beginning Curve Value	$ 0.084
Midwest Premium Swap Asset Ending Curve Value	0.086
Midwest Premium Swap Liability Beginning Curve Value	0.08
Midwest Premium Swap Liability Ending Curve Value	0.086
Derivative Asset	1,600,000	$ 85,700,000
Derivative Liability	16,200,000	96,800,000
Fair Value, Measurements, Recurring | Midwest premium swap contracts | Aluminum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Asset	900,000	1,000,000
Fair Value, Measurements, Recurring | Midwest premium swap contracts | Aluminum | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Asset		$ 1,000,000
Fair Value, Measurements, Recurring | Midwest premium swap contracts | Aluminum | Income Approach Valuation Technique
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Liability	300,000
Fair Value, Measurements, Recurring | Midwest premium swap contracts | Aluminum | Income Approach Valuation Technique | Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Asset	900,000
Derivative Liability	$ 300,000