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Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Mar. 25, 2019	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018
Powersem
Related Party Transaction [Line Items]
Revenue from related parties		$ 0.1	$ 0.3	$ 0.2	$ 0.4
Purchase from related party		0.9	1.0	1.7	2.1
Receivable from related parties		0.1		0.1		$ 0.1
Payables to related parties		0.1		0.1		0.2
EB Tech
Related Party Transaction [Line Items]
Payables to related parties						0.1
Amount of transaction		0.1		0.2
ATEC
Related Party Transaction [Line Items]
Payables to related parties						$ 0.5
Amount of transaction		$ 2.3	$ 2.8	$ 3.8	$ 5.2
MWT
Related Party Transaction [Line Items]
Loss on disposal	$ 2.6
Powersem
Related Party Transaction [Line Items]
Ownership percentage		45.00%		45.00%
EB Tech
Related Party Transaction [Line Items]
Ownership percentage		19.00%		19.00%
ATEC
Related Party Transaction [Line Items]
Ownership percentage		24.00%		24.00%