Derivatives (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Derivative [Line Items]
Income / (Loss) activity recognized in other comprehensive loss	$ 2,500,000	$ (2,700,000)	$ 2,400,000	$ (5,800,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(1,000,000)	(1,000,000)	(900,000)	(2,200,000)
Net income/ (loss)	15,954,000	27,651,000	(477,000)	86,474,000
Cash Flow Hedging [Member]
Derivative [Line Items]
Cash flow hedge gain (loss) to be reclassified within 12 months			(1,800,000)
Net income/ (loss)			0
Forward Contracts [Member] | Commodity Contract [Member]
Derivative [Line Items]
Forward purchase amount	$ 4,400,000		$ 4,400,000