Goodwill and Intangible Assets - Change in Carrying Amount (Details) $ in Thousands	6 Months Ended
	Mar. 30, 2018 USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 147,716
Goodwill divested during year	(2,626)
Goodwill acquired during year	827
Purchase price adjustments	21,750
Exchange rate effects	1,440
Balance at end of period	169,107
Electrical Raceway
Goodwill [Roll Forward]
Balance at beginning of period	108,528
Goodwill divested during year	0
Goodwill acquired during year	827
Purchase price adjustments	21,750
Exchange rate effects	1,440
Balance at end of period	132,545
MP&S
Goodwill [Roll Forward]
Balance at beginning of period	39,188
Goodwill divested during year	(2,626)
Purchase price adjustments	0
Exchange rate effects	0
Balance at end of period	$ 36,562