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
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Business Segments - Narrative (Details) - segment	3 Months Ended		12 Months Ended
Business Segments - Narrative (Details) - segment	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Concentration Risk [Line Items]
Number of reportable segments	2
Customer Concentration Risk \| Revenue \| Howmet Aerospace Inc.
Concentration Risk [Line Items]
Concentration risk	10.00%	10.00%
Customer Concentration Risk \| Accounts Receivable \| Howmet Aerospace Inc.
Concentration Risk [Line Items]
Concentration risk	10.00%		12.00%