For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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Summary of Significant Accounting Policies - Concentration (Details) - contract	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
U.S. Department of Defense
Risk Associated with Certain Concentrations
Number of contracts	2	2	2
U.S. Department of Defense \| Revenue \| Surplus Contract
Risk Associated with Certain Concentrations
Concentration risk (as a percent)		0.00%	12.40%
U.S. Department of Defense \| Revenue \| Scrap Contract
Risk Associated with Certain Concentrations
Concentration risk (as a percent)		7.40%	10.20%
Supplier Concentration Risk \| Cost of Goods Sold \| Contract with commercial client
Risk Associated with Certain Concentrations
Concentration risk (as a percent)	55.10%	43.60%	33.70%
Maximum
Risk Associated with Certain Concentrations
Term for release of funds to the seller	30 days