Revenue Recognition and Related Costs - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Net revenue	$ 18,030,000	$ 21,327,000
Equipment Sales [Member] \| Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	12,090,000	16,353,000
Equipment Sales [Member] \| Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	1,907,000	1,514,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	3,146,000	3,051,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	903,000	402,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ (16,000)	$ 7,000

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Name:	us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration