Debt (Details 1) (Convertible Senior Notes Due Twenty-Fifteen [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
Apr. 04, 2015	Mar. 29, 2014
Convertible Senior Notes Due Twenty-Fifteen [Member]
Effective interest rate and components of interest expense of 2015 notes
Effective interest rate	8.10%	8.10%
Contractual interest expense	$ 1,809	$ 2,289
Amortization of debt discount	$ 5,030	$ 4,232

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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