Interest Expense on Convertible Senior Notes (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Debt Instrument
Contractual interest expense on the coupon	$ 1,438	$ 1,438	$ 2,875	$ 2,875
Amortization of the discount component and debt issue fees recognized as interest expense	3,477	3,308	6,911	6,576
Total interest expense on the convertible debt	$ 4,915	$ 4,746	$ 9,786	$ 9,451

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://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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