Acquisitions and Divestitures - CGD Services - Income (loss) from discontinued operations (Details) - Cubic Global Defense Services - Disposed of by sale - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2018	May 31, 2018
Divestitures
Consideration from sale			$ 135.0
Cash received in connection with the sale	$ 2.7	$ 133.8

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585

Name:	us-gaap_ProceedsFromDivestitureOfBusinesses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration