Goodwill and Identified Intangible Assets - Estimated Future Amortization Expense of Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 28, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining three months)	$ 2,089
2019	8,354
2020	3,993
2021	502
Total future amortization expense	14,938	$ 21,279
Cost of Revenue [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining three months)	1,295
2019	5,180
2020	951
2021	0
Total future amortization expense	7,426
Operating Expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining three months)	794
2019	3,174
2020	3,042
2021	502
Total future amortization expense	$ 7,512