Stockholders' Equity - Narrative (Details)	9 Months Ended	12 Months Ended
Jun. 30, 2020 item shares	Sep. 30, 2019 item
Stockholders' Equity
Retirement age for participants	60 years
Notice period	1 year
Long term equity incentive program, service period (in years)	10 years
RSUs
Stockholders' Equity
Number of shares of common stock that each award holder has the contingent right to receive	1
Time-based RSUs
Stockholders' Equity
Number of equal installments for vesting of stock awards \| item	3	4
Expected awards vested (in shares)	511,508
Performance-based RSUs
Stockholders' Equity
Vesting period	3 years
Expected awards vested (in shares)	106,772
Performance and market-based RSUs
Stockholders' Equity
Number of shares of common stock that each award holder has the contingent right to receive	1.25
Vesting period	3 years
Maximum TSR multiplier rate	100.00%
Expected awards vested (in shares)	194,237
Performance and market-based RSUs \| Maximum
Stockholders' Equity
Increase (decrease) in multiplier based on performance	25.00%
Performance and market-based RSUs \| Minimum
Stockholders' Equity
Decrease in multiplier based on performance	25.00%

The percentage in decrease in multiplier based on performance.

No definition available.

Name:	cub_DecreaseInMultiplierBasedOnPerformancePercentage
Namespace Prefix:	cub_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage in increase in multiplier based on performance.

+ References

No definition available.

+ Details

Name:	cub_IncreaseInMultiplierBasedOnPerformancePercentage
Namespace Prefix:	cub_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Notice period by the Participants who have reached the retirement age criteria provide notice of retirement to the Company, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	cub_LongTermEquityIncentiveProgramAcceleratedVestingNoticePeriod
Namespace Prefix:	cub_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The age of participant in the long-term equity incentive program to provide accelerated vesting for retirement age participants in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	cub_LongTermEquityIncentiveProgramAcceleratedVestingRetirementAgeForParticipants
Namespace Prefix:	cub_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated period over which an employee is required to provide service to get accelerated vesting under long-term equity incentive program, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	cub_LongTermEquityIncentiveProgramAcceleratedVestingYearsOfService
Namespace Prefix:	cub_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The rate of TSR multiplier.

+ References

No definition available.

+ Details

Name:	cub_MaximumTsrMultiplierRate
Namespace Prefix:	cub_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of shares of common stock that each award holder has the contingent right to receive.

+ References

No definition available.

+ Details

Name:	cub_ShareBasedCompensationArrangementByShareBasedPaymentAwardContingentRightToReceiveNumberOfSharesOfCommonStock
Namespace Prefix:	cub_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that are expected to vest during the reporting period.

+ References

No definition available.

+ Details

Name:	cub_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedToVestedInPeriod
Namespace Prefix:	cub_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of equal installments for vesting of share-based compensation awards.

+ References

No definition available.

+ Details

Name:	cub_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfEqualInstallmentsForVestingOfStockAwards
Namespace Prefix:	cub_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=cub_TimeBasedRestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=cub_PerformanceBasedRestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=cub_PerformanceAndMarketBasedRestrictedStockUnitsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: