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Nature of Operations and Summary of Significant Accounting Policies - Disaggregation of Company's Net Revenue by Major Source (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net revenue	$ 81,329,000	$ 98,614,000	[1]
Equipment Sales [Member] | Transferred over Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	43,489,000	70,836,000
Equipment Sales [Member] | Transferred at Point in Time [Member]
Disaggregation of Revenue [Line Items]
Net revenue	19,987,000	11,521,000
Parts and Component Sales [Member]
Disaggregation of Revenue [Line Items]
Net revenue	13,356,000	11,580,000
Freight Revenue [Member]
Disaggregation of Revenue [Line Items]
Net revenue	4,130,000	4,474,000
Other [Member]
Disaggregation of Revenue [Line Items]
Net revenue	$ 367,000	$ 203,000
[1] The amounts for the year ended September 30, 2018 have been adjusted to reflect the change in inventory accounting method, as described in Notes 1 and 2 to the Consolidated Financial Statements.

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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
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-Section 50
-Paragraph 4
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-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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