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, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Net revenue	$ 77,420,000	$ 81,329,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	35,579,000	43,489,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	23,642,000	19,987,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	13,896,000	13,356,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	3,983,000	4,130,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 320,000	$ 367,000