Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2017	Dec. 30, 2016	[1]	Sep. 30, 2017
Goodwill [Line Items]
Intangible asset amortization	$ 8,687	$ 5,589
Electrical Raceway
Goodwill [Line Items]
Accumulated impairment loss				$ 3,924
MP&S
Goodwill [Line Items]
Accumulated impairment loss	$ 43,000

[1] * Adjusted due to the adoption of ASU 2017-07 Compensation - Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1, ''Basis of Presentation and Summary of Significant Accounting Policies'' for additional information.