Revenue - Additional Information (Detail)	9 Months Ended
	Sep. 29, 2018 USD ($) Installment	Dec. 30, 2017 USD ($)
Revenue From Contract With Customers [Line Items]
Revenue remaining performance obligation	$ 72,200,000
Revenue performance obligation, description of timing	We expect to recognize approximately 44% of our remaining performance obligations as revenue in 2018, 52% in 2019 and 4% in 2020.
TFE
Revenue From Contract With Customers [Line Items]
Contract liabilities	$ 17,266,000	$ 15,394,000
Revenue remaining performance obligation	$ 63,600,000
TFE | Accounts Receivable, Unbilled
Revenue From Contract With Customers [Line Items]
Number of installments | Installment	3
Change in contract assets	$ (851,000)
TFE | Customer Advances
Revenue From Contract With Customers [Line Items]
Contract with customer liability revenue recognized	6,600,000
Contract liabilities	11,066,000	10,204,000
TFE | Deferred Revenue
Revenue From Contract With Customers [Line Items]
Contract with customer liability revenue recognized	69,000
Contract liabilities	6,200,000	5,190,000
Photonics
Revenue From Contract With Customers [Line Items]
Change in contract assets	(6,000)
Contract liabilities	1,867,000	919,000
Revenue remaining performance obligation	8,600,000
Photonics | Accounts Receivable, Unbilled
Revenue From Contract With Customers [Line Items]
Change in contract assets	130,000
Photonics | Customer Advances
Revenue From Contract With Customers [Line Items]
Contract with customer liability revenue recognized	536,000
Contract liabilities	550,000	822,000
Photonics | Deferred Revenue
Revenue From Contract With Customers [Line Items]
Contract with customer liability revenue recognized	324,000
Contract liabilities	$ 1,317,000	$ 97,000