Derivatives (Details 1)	Mar. 31, 2012 lb	Dec. 31, 2011 lb
Copper [Member]
Outstanding commodity futures contracts designated as cash flow hedges
Notional amounts	21,200,000	23,300,000
Outstanding commodity futures contracts not designated as cash flow hedges
Notional amounts	2,600,000	2,800,000
Aluminum [Member]
Outstanding commodity futures contracts not designated as cash flow hedges
Notional amounts	2,800,000	3,000,000