Debt (Details 1) (Convertible Senior Notes Due Twenty-Fifteen [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
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%	8.10%	8.10%
Contractual interest expense	$ 2,289	$ 2,289	$ 6,867	$ 6,867
Amortization of debt discount	$ 4,379	$ 4,045	$ 12,886	$ 11,906

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

-Publisher FASB

-Name Accounting Standards Codification

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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-Publisher SEC

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