Goodwill and Purchased Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Aug. 03, 2018	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Finite-Lived Intangible Assets [Line Items]
Amortization of finite-lived intangibles		$ 2,400	$ 1,200	$ 4,607	$ 3,693
Consideration received in connection with sale of subsidiary				$ 291
UAMC [Member]
Finite-Lived Intangible Assets [Line Items]
Date of disposal	Aug. 03, 2018
Carry value of assets sold	$ 1,100
Loss on sale of business	1,100
Sale of subsidiary, description				On August 3, 2018, the Company sold its subsidiary, UAMC, for $0.3 million, in the form of note receivable from the purchaser. UAMC was launched in November 2004 to develop additive, 3D printing manufacturing capabilities. At closing, the carry value of the UAMC assets sold were $1.1 million. The Company also included free rent, labor and utilities for a period of six months are part of the agreement. The Company believes that the assets related to UAMC that were sold include all key inputs and processes necessary to generate output, and, accordingly, the Company has determined that UAMC qualified as a business. As a result of the sale, the Company recognized a loss on sale of a business of $1.1 million in the accompanying Condensed Consolidated Statements of Operations as Interest and other income (expense), net.
UAMC [Member] | Note Receivable [Member]
Finite-Lived Intangible Assets [Line Items]
Consideration received in connection with sale of subsidiary	$ 300