Revenue Recognition and Related Costs - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Net revenue	$ 24,919,000	$ 22,940,000	$ 65,235,000	$ 66,963,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	6,507,000	10,350,000	14,509,000	32,269,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	12,258,000	8,995,000	31,959,000	20,946,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	5,240,000	2,671,000	16,001,000	10,492,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	996,000	822,000	2,888,000	2,926,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ (82,000)	$ 102,000	$ (122,000)	$ 330,000