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Revenue Recognition and Related Costs - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Net revenue	$ 25,993,000	$ 26,670,000	$ 44,023,000	$ 47,997,000
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	9,829,000	12,006,000	21,919,000	28,359,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	10,044,000	8,929,000	11,951,000	10,443,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	4,675,000	4,466,000	7,821,000	7,517,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	1,201,000	1,030,000	2,104,000	1,432,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 244,000	$ 239,000	$ 228,000	$ 246,000

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+ References

No definition available.

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+ References

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

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