Goodwill and Identified Intangible Assets - Estimated Future Amortization Expense of Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 27, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
2019 (remaining three months)	$ 2,075
2020	3,948
2021	495
Total future amortization expense	6,518	$ 12,817
Cost of Revenue [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2019 (remaining three months)	1,295
2020	951
2021	0
Total future amortization expense	2,246
Operating Expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2019 (remaining three months)	780
2020	2,997
2021	495
Total future amortization expense	$ 4,272