Derivative Financial Instruments and Related Hedging Programs (Details)	Jun. 30, 2011 mm
Euros [Member] | Derivative Swap Type Fixed Price Purchase [Member] | Foreign Currency [Member]
Summary of material derivative positions
Notional Amount of Contracts	0.2
Call Options Purchased [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	24.5
Call Options Purchased [Member] | Natural Gas [Member]
Summary of material derivative positions
Notional Amount of Contracts	5,430,000
Call Options Written [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	24.5
Call Options Written [Member] | Natural Gas [Member]
Summary of material derivative positions
Notional Amount of Contracts	1,380,000
Put Options Purchased [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	50.8
Put Options Purchased [Member] | Natural Gas [Member]
Summary of material derivative positions
Notional Amount of Contracts	1,380,000
Put Options Written [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	24.5
Put Options Written [Member] | Natural Gas [Member]
Summary of material derivative positions
Notional Amount of Contracts	5,430,000
Derivative Swap Type Fixed Price Purchase [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	93.1
Derivative Swap Type Fixed Price Purchase [Member] | Natural Gas [Member]
Summary of material derivative positions
Notional Amount of Contracts	2,110,000
Derivative Swap Type Fixed Price Purchase [Member] | Electricity [Member]
Summary of material derivative positions
Notional Amount of Contracts	175,680
Derivative Swap Type Fixed Price Sales [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	11.2
Midwest premium swap contracts [Member] | Aluminum Commodity [Member]
Summary of material derivative positions
Notional Amount of Contracts	49.6
Bifurcated Conversion Feature [Member] | Hedges Relating to Notes [Member]
Summary of material derivative positions
Notional Amount of Contracts (Common Shares)	3,621,608
Call Option [Member] | Hedges Relating to Notes [Member]
Summary of material derivative positions
Notional Amount of Contracts (Common Shares)	3,621,608