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Restructuring Charges - Restructuring Reserves (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 27, 2020	Mar. 29, 2019	Mar. 27, 2020	Mar. 29, 2019	Sep. 30, 2018
Restructuring Reserve [Roll Forward]
Beginning balance			$ 537	$ 551
Charges			2,865		$ 3,804
Utilization			(1,642)		(3,818)
Exchange rate effects			5
Ending balance	$ 1,765		1,765		551
Facility Closing
Restructuring Reserve [Roll Forward]
Charges	1,075	$ 759	1,283	1,834
Reduction in Workforce, COVID-19
Restructuring Reserve [Roll Forward]
Charges	1,570		1,570
Operating Segments \| Electrical Raceway \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			392	212
Charges			1,116		1,047
Utilization			(228)		(867)
Exchange rate effects			5
Ending balance	1,285		1,285		212
Operating Segments \| Electrical Raceway \| Other
Restructuring Reserve [Roll Forward]
Beginning balance			0	310
Charges			1,283		2,544
Utilization			(1,283)		(2,854)
Exchange rate effects			0
Ending balance	0		0		310
Operating Segments \| MP&S \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			145	0
Charges			398		213
Utilization			(131)		(68)
Exchange rate effects			0
Ending balance	412		412		0
Operating Segments \| MP&S \| Other
Restructuring Reserve [Roll Forward]
Beginning balance			0	29
Charges			0		0
Utilization			0		(29)
Exchange rate effects			0
Ending balance	0		0		29
Other/Corporate \| Severance
Restructuring Reserve [Roll Forward]
Beginning balance			0	$ 0
Charges			68		0
Utilization			0		0
Exchange rate effects			0
Ending balance	$ 68		$ 68		$ 0