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Related Party Transactions (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Mar. 25, 2019	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018	Dec. 29, 2018
Related Party Transaction [Line Items]
Cost method investments		$ 1.2		$ 1.2
Powersem
Related Party Transaction [Line Items]
Revenue from related parties		0.2	$ 0.2	0.4	$ 0.6
Purchase from related party		0.8	1.3	2.4	3.4
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		0.1		0.1
Amount of transaction		0.1	0.1	0.3	0.3
ATEC
Related Party Transaction [Line Items]
Payables to related parties		0.2		0.2		$ 0.5
Amount of transaction		$ 1.7	$ 2.5	$ 5.5	$ 7.7
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%