Derivatives (Details 1)	Dec. 31, 2011 lb	Dec. 31, 2010 lb
Copper [Member]
Outstanding commodity futures contracts designated as cash flow hedges
Notional amounts	23,300,000	18,500,000
Outstanding commodity futures contracts not designated as cash flow hedges
Notional amounts	2,800,000	1,400,000
Aluminum [Member]
Outstanding commodity futures contracts not designated as cash flow hedges
Notional amounts	3,000,000	1,400,000