Revenue - Changes in Contract Assets and Contract Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 29, 2018	Dec. 30, 2017
TFE
Revenue From Contract With Customers [Line Items]
Contract liabilities	$ 17,266	$ 15,394
Contract liabilities:
Change in contract liabilities	1,872
TFE \| Accounts Receivable, Unbilled
Revenue From Contract With Customers [Line Items]
Contract assets	517	1,368
Contract liabilities:
Change in contract assets	(851)
TFE \| Deferred Revenue
Revenue From Contract With Customers [Line Items]
Contract liabilities	6,200	5,190
Contract liabilities:
Change in contract liabilities	1,010
TFE \| Customer Advances
Revenue From Contract With Customers [Line Items]
Contract liabilities	11,066	10,204
Contract liabilities:
Change in contract liabilities	862
Photonics
Revenue From Contract With Customers [Line Items]
Contract assets	1,621	1,627
Contract liabilities	1,867	919
Contract liabilities:
Change in contract assets	(6)
Change in contract liabilities	948
Photonics \| Accounts Receivable, Unbilled
Revenue From Contract With Customers [Line Items]
Contract assets	1,476	1,346
Contract liabilities:
Change in contract assets	130
Photonics \| Deferred Revenue
Revenue From Contract With Customers [Line Items]
Contract liabilities	1,317	97
Contract liabilities:
Change in contract liabilities	1,220
Photonics \| Retainage
Revenue From Contract With Customers [Line Items]
Contract assets	145	281
Contract liabilities:
Change in contract assets	(136)
Photonics \| Customer Advances
Revenue From Contract With Customers [Line Items]
Contract liabilities	550	$ 822
Contract liabilities:
Change in contract liabilities	$ (272)

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Amount of increase (decrease) in revenue recognized for cumulative catch-up adjustment from change in measure of progress which increases (decreases) right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

+ References

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

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