Revenue Recognition and Related Costs - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Net revenue	$ 22,940,000	$ 18,848,000	$ 66,963,000	$ 66,845,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	10,350,000	7,844,000	32,269,000	36,203,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	8,995,000	6,747,000	20,946,000	17,190,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	2,671,000	2,870,000	10,492,000	10,387,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	822,000	1,312,000	2,926,000	2,744,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 102,000	$ 75,000	$ 330,000	$ 321,000