Goodwill and Purchased Intangible Assets - Goodwill (Details) $ in Thousands	12 Months Ended
Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)
Changes in the carrying amount of goodwill
Net balances at the beginning of the period	$ 321,562	$ 312,596
Acquisitions	13,750	5,885
Foreign currency exchange rate changes	(1,686)	3,081
Net balance at the end of the period	$ 333,626	321,562
Number of reporting segments \| item	3
Impairment of goodwill	$ 0
Transportation Systems
Changes in the carrying amount of goodwill
Net balances at the beginning of the period	50,870	49,630
Foreign currency exchange rate changes	(1,084)	1,240
Net balance at the end of the period	$ 49,786	50,870
Transportation Systems \| Minimum
Changes in the carrying amount of goodwill
Estimated percentage of excess of fair value over carrying value	100.00%
Cubic Global Defense
Changes in the carrying amount of goodwill
Net balances at the beginning of the period	$ 270,692	262,966
Reassignment on October 1, 2017	(125,321)
Acquisitions	665	5,885
Foreign currency exchange rate changes	(323)	1,841
Net balance at the end of the period	$ 145,713	$ 270,692
Cubic Global Defense \| Minimum
Changes in the carrying amount of goodwill
Estimated percentage of excess of fair value over carrying value	40.00%
Cubic Mission Solutions
Changes in the carrying amount of goodwill
Reassignment on October 1, 2017	$ 125,321
Acquisitions	13,085
Foreign currency exchange rate changes	(279)
Net balance at the end of the period	$ 138,127
Cubic Mission Solutions \| Minimum
Changes in the carrying amount of goodwill
Estimated percentage of excess of fair value over carrying value	40.00%

Represents the percentage by which fair value exceeds carrying value in determination of goodwill impairment.

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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Amount of transfers into (out of) an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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No definition available.

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