Derivatives And Risk Management (Commodity Contract Commitments) (Details)	May 31, 2012 Mg
Aluminum [Member] | Long [Member]
Commodity Contract Commitments [Abstract]
Commodity contract commitments	6,325
Aluminum [Member] | Short [Member]
Commodity Contract Commitments [Abstract]
Commodity contract commitments	3,400
Copper [Member] | Long [Member]
Commodity Contract Commitments [Abstract]
Commodity contract commitments	1,122
Copper [Member] | Short [Member]
Commodity Contract Commitments [Abstract]
Commodity contract commitments	5,103
Zinc [Member] | Long [Member]
Commodity Contract Commitments [Abstract]
Commodity contract commitments	15
Natural gas [Member] | Long [Member]
Commodity Contract Commitments [Abstract]
Energy contract commitment	50,000