Nature of Operations and Summary of Significant Accounting Policies - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenue	$ 85,278,000	$ 77,420,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	24,093,000	35,579,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	36,671,000	23,642,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	21,017,000	13,896,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 3,497,000	3,983,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue		$ 320,000