Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified		3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 Not designated	Mar. 31, 2011 Not designated	Dec. 31, 2011 Not designated Commodity futures net	Mar. 31, 2012 Aluminum Long Commodity futures net MT	Mar. 31, 2012 Aluminum Short Commodity futures net MT	Mar. 31, 2012 Copper Long Commodity futures net MT	Mar. 31, 2012 Copper Short Commodity futures net MT	Mar. 31, 2012 Nickel Commodity options MT	Mar. 31, 2012 Nickel Long Commodity futures net MT	Mar. 31, 2012 Nickel Short Commodity futures net MT	Mar. 31, 2012 Silver Short Commodity futures net lbs
Commodity contract commitments
Commodity contract (in MT/Lbs)					8,400	5,225	4,559	11,215	60	132	192	686
Fair values of derivative instruments, balance sheet
Commodity contract, net asset (liability) (in dollars)	$ 784			$ (1,219)
Gain (loss) on commodity futures contracts (in dollars)		$ (3,618)	$ 2,923