Basis of presentation.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, for redemption of redeemable noncontrolling interests.

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Amount of asset related to consideration paid in advance for income and other taxes that provide economic benefits.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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The cumulative amount of the reporting entity's undistributed earnings or deficit.

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Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

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Basis of Presentation - Additional information (Details) - USD ($) $ in Thousands				3 Months Ended	9 Months Ended
	Sep. 27, 2018	Jan. 10, 2017	Jan. 09, 2017	Sep. 29, 2017	Sep. 29, 2017	Sep. 28, 2018	Mar. 30, 2018	Dec. 31, 2017
Basis Of Presentation [Line Items]
Accumulated deficit						$ 90,736		$ 127,740
ASU 2017-07
Basis Of Presentation [Line Items]
Reclassification of net periodic benefit cost				$ 100	$ 400
ASU 2016-16
Basis Of Presentation [Line Items]
Reclassification of prepaid income taxes and income taxes receivable							$ 2,500
Accumulated deficit							2,200
Deferred tax assets, net							$ 300
Laser Quantum
Basis Of Presentation [Line Items]
Equity method investment ownership percentage on Laser Quantum		76.00%	41.00%
Percentage of outstanding shares acquired	24.00%	35.00%
Consideration transferred in cash and restricted stock for percentage of shares acquired	$ 45,100