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Restructuring Charges - Restructuring Reserves (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 26, 2020	Jun. 28, 2019	Jun. 26, 2020	Jun. 28, 2019	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Beginning balance			$ 537	$ 551	$ 551
Charges			3,339		3,804
Utilization			(2,911)		(3,818)
Exchange rate effects			9
Ending balance	$ 974		974		537
Reduction in Workforce, COVID-19
Restructuring Reserve [Roll Forward]
Charges	91		1,673
Facility Closing
Restructuring Reserve [Roll Forward]
Charges	383	$ 638	1,666	2,473
Operating Segments \| Electrical Raceway \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			392	212	212
Charges			1,207		1,047
Utilization			(821)		(867)
Exchange rate effects			9
Ending balance	787		787		392
Operating Segments \| Electrical Raceway \| Other
Restructuring Reserve [Roll Forward]
Beginning balance			0	310	310
Charges			1,666		2,544
Utilization			(1,666)		(2,854)
Exchange rate effects			0
Ending balance	0		0		0
Operating Segments \| MP&S \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			145	0	0
Charges			398		213
Utilization			(388)		(68)
Exchange rate effects
Ending balance	155		155		145
Operating Segments \| MP&S \| Other
Restructuring Reserve [Roll Forward]
Beginning balance			0	29	29
Charges			0		0
Utilization			0		(29)
Exchange rate effects			0
Ending balance	0		0		0
Other/Corporate \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			0	$ 0	0
Charges			68		0
Utilization			(36)		0
Exchange rate effects			0
Ending balance	$ 32		$ 32		$ 0