Segment Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 04, 2020 USD ($)	Mar. 30, 2019 USD ($)	Apr. 04, 2020 USD ($) segment	Mar. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			2
Net sales	$ 255,412	$ 211,642	$ 408,629	$ 366,568
Gross profit	24,169	25,954	45,469	45,064
United States
Segment Reporting Information [Line Items]
Net sales	232,477	191,684	368,743	343,169
Canada
Segment Reporting Information [Line Items]
Net sales	22,746	18,784	35,902	21,860
Rest of world
Segment Reporting Information [Line Items]
Net sales	189	1,174	3,984	1,539
Operating Segments
Segment Reporting Information [Line Items]
Gross profit	24,169	25,954	45,469	45,064
Operating Segments | Bus
Segment Reporting Information [Line Items]
Net sales	238,697	195,065	373,469	334,275
Gross profit	17,938	20,142	32,805	33,657
Operating Segments | Parts
Segment Reporting Information [Line Items]
Net sales	16,715	16,577	35,160	32,293
Gross profit	6,231	5,812	12,664	11,407
Intersegment Eliminations | Parts
Segment Reporting Information [Line Items]
Net sales	$ 1,200	$ 900	$ 2,400	$ 1,500