Segment Information (Details) $ in Thousands	12 Months Ended
	Sep. 28, 2024 USD ($) segment	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	2
Net sales	$ 1,347,154	$ 1,132,793	$ 800,637
Net sales	1,347,154	1,132,793	800,637
Segment gross profit	256,156	138,850	36,546
United States
Segment Reporting Information [Line Items]
Net sales	1,199,527	1,048,279	726,227
Canada
Segment Reporting Information [Line Items]
Net sales	146,609	78,907	69,683
Rest of world
Segment Reporting Information [Line Items]
Net sales	1,018	5,607	4,727
Intersegment Eliminations | Parts
Segment Reporting Information [Line Items]
Net sales	9,300	5,600	3,900
Operating Segments
Segment Reporting Information [Line Items]
Net sales	1,347,154	1,132,793	800,637
Segment gross profit	256,156	138,850	36,546
Operating Segments | Bus
Segment Reporting Information [Line Items]
Net sales	1,242,885	1,034,625	723,505
Segment gross profit	203,791	91,003	5,065
Operating Segments | Parts
Segment Reporting Information [Line Items]
Net sales	104,269	98,168	77,132
Segment gross profit	$ 52,365	$ 47,847	$ 31,481