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Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019	Mar. 27, 2020	Oct. 01, 2019	Sep. 30, 2019
Goodwill [Line Items]
Intangible asset amortization	$ 8,026	$ 7,868	$ 24,210	$ 24,278
Goodwill	186,609		186,609				$ 186,231
Electrical Raceway
Goodwill [Line Items]
Accumulated impairment loss	3,924		3,924			$ 3,924
Goodwill	150,046		150,046				149,668
MP&S
Goodwill [Line Items]
Accumulated impairment loss	43,000		43,000			$ 43,000
Goodwill	36,563		36,563				$ 36,563
EMEA
Goodwill [Line Items]
Percentage of fair value in excess of carrying amount (less than)					10.00%
Goodwill	$ 34,836		$ 34,836