Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Not designated	Sep. 30, 2011 Not designated	Sep. 30, 2012 Not designated	Sep. 30, 2011 Not designated	Sep. 30, 2012 Not designated Commodity futures net	Dec. 31, 2011 Not designated Commodity futures net	Sep. 30, 2012 Aluminum Long Commodity futures net MT	Sep. 30, 2012 Aluminum Short Commodity futures net MT	Sep. 30, 2012 Copper Long Commodity futures net MT	Sep. 30, 2012 Copper Short Commodity futures net MT	Sep. 30, 2012 Nickel Commodity options MT	Sep. 30, 2012 Nickel Short Commodity futures net MT	Sep. 30, 2012 Silver Short Commodity futures net lbs
Commodity contract commitments
Commodity contract (in MT/Lbs)							5,575	5,600	10,444	28,406	60	90	343
Fair values of derivative instruments, balance sheet
Commodity contract, net liability (in dollars)					$ 7,487	$ 1,219
Gain on commodity futures & options contracts (in dollars)	$ (9,085)	$ 7,112	$ (6,810)	$ 11,457