Revenue Recognition and Related Costs - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Net revenue	$ 20,106,000	$ 18,964,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	9,774,000	4,132,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	4,198,000	10,136,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	5,443,000	3,931,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	584,000	745,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 107,000	$ 20,000