Financial Instruments (Narrative) (Details) (USD $)			3 Months Ended		9 Months Ended
	Sep. 27, 2013 derivatives	Dec. 31, 2012 derivatives	Sep. 27, 2013 Not Designated as Hedging Instrument [Member]	Sep. 28, 2012 Not Designated as Hedging Instrument [Member]	Sep. 27, 2013 Not Designated as Hedging Instrument [Member]	Sep. 28, 2012 Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative contracts held that require collateral securities		$ 0
Number of derivative require collateral security	0	0
Gain (loss) on derivative instruments not designated as cash flow hedges			2,900,000	8,100,000	(17,500,000)	7,800,000
Forward pricing agreements	15,700,000	37,700,000
Fair value forward pricing agreements	15,800,000	38,000,000
Unrealized gain (loss) related to forward pricing agreements	$ (100,000)	$ 300,000