Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Jan. 01, 2022	Jan. 02, 2021
Disaggregation of Revenue [Line Items]
Net sales	$ 129,223	$ 130,434
Diesel buses
Disaggregation of Revenue [Line Items]
Net sales	46,033	59,710
Alternative fuel buses
Disaggregation of Revenue [Line Items]
Net sales	57,637	52,301
Other
Disaggregation of Revenue [Line Items]
Net sales	9,297	6,160
Parts
Disaggregation of Revenue [Line Items]
Net sales	$ 16,256	$ 12,263