Convertible Senior Notes - Interest Expense Recognized Related to Notes Prior to Capitalization of Interest (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 27, 2014	Sep. 28, 2013	Sep. 27, 2014	Sep. 28, 2013
Debt Disclosure [Abstract]
Contractual interest expense	$ 656	$ 656	$ 1,969	$ 875
Amortization of debt issuance costs	169	152	493	202
Amortization of debt discount	1,956	1,770	5,724	2,350
Total interest expense recognized related to notes prior to capitalization of interest	$ 2,781	$ 2,578	$ 8,186	$ 3,427

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

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

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

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