Debt (Details 1) (Convertible Senior Notes Due Twenty-Fifteen [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 28, 2014	Jun. 29, 2013	Jun. 28, 2014	Jun. 29, 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	$ 4,578	$ 4,578
Amortization of debt discount	$ 4,275	$ 3,951	$ 8,507	$ 7,861

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

-Topic 835

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-Section 45

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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

-Publisher FASB

-Name Accounting Standards Codification

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-Publisher SEC

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