Convertible Notes, Other Debts And Finance Leases - Interest (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 27, 2019	Sep. 28, 2018	Sep. 27, 2019	Sep. 28, 2018
Debt Disclosure [Abstract]
Contractual interest expense	$ 1,235	$ 1,283	$ 3,800	$ 3,848
Amortization of debt discount	1,513	1,364	4,425	4,001
Amortization of debt issuance costs	185	164	535	481
Total interest expense recognized	$ 2,933	$ 2,811	$ 8,760	$ 8,330

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.

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Amount of amortization expense attributable to debt issuance costs.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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