Forecasted revenue from contract agreement.

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The amount of incremental forecasted revenue from amended contract agreement.

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Number of long term debt facilities.

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The cash outflow for accrued interest on line of credit initially having maturity due after one year or beyond the normal operating cycle, if longer.

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Amount of amortization expense attributable to debt issuance costs.

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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.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Face (par) amount of debt instrument at time of issuance.

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Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

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Nominal or face amount used to calculate payment on derivative.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The cash outflow for the settlement of obligation drawn from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Period in which remaining performance obligation is expected to be recognized as revenue, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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Variable Interest Entities - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2018 USD ($)	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) item	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Revenue recognition
Termination costs				$ (16,090)	$ 0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue recognition
Contract term		12 months		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue recognition
Contract term		24 months		24 months
Revolving Credit Agreement
Revenue recognition
Maximum borrowing capacity under credit agreement						$ 800,000
Borrowings outstanding						226,500
Design and Build Phase \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility \| LIBOR \| Minimum
Revenue recognition
Variable interest rate (as a percent)		1.75%
Design and Build Phase \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility \| LIBOR \| Maximum
Revenue recognition
Variable interest rate (as a percent)		2.00%
Operate and Maintain Phase \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility \| LIBOR \| Minimum
Revenue recognition
Variable interest rate (as a percent)		2.00%
Operate and Maintain Phase \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility \| LIBOR \| Maximum
Revenue recognition
Variable interest rate (as a percent)		2.50%
Amended MBTA Agreement \| Design and Build Phase \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility
Revenue recognition
Maximum borrowing capacity under credit agreement		$ 421,600		$ 421,600
MBTA \| Original MBTA Contract \| Operate and Maintain Phase \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue recognition
Contract term		10 years		10 years
MBTA \| Amended MBTA Agreement \| Design and Build Phase \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue recognition
Contract term		4 years		4 years
MBTA \| Amended MBTA Agreement \| Operate and Maintain Phase \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01
Revenue recognition
Contract term		12 years		12 years
Cubic Corporation Excluding VIE
Revenue recognition
Restricted cash		$ 22,279		$ 22,279		19,507
VIE
Revenue recognition
Restricted cash		1,669		1,669		$ 9,967
P3 Joint Venture
Revenue recognition
Maximum exposure to loss		$ 2,700		$ 2,700
OpCo.
Revenue recognition
Ownership percentage		10.00%		10.00%
OpCo. \| Interest Rate Swaps \| Not Designated as Hedging Instrument
Revenue recognition
Notional principal outstanding derivative instruments		$ 172,800		$ 172,800
Unrealized losses		(6,900)	$ (7,000)	(18,400)	$ (16,900)
OpCo. \| Interest Rate Swaps \| Not Designated as Hedging Instrument \| Other noncurrent liabilities
Revenue recognition
Fair value interest rate swaps		$ 5,600		$ 5,600
OpCo. \| Boston OpCo Credit Agreement \| Maximum
Revenue recognition
Borrowings outstanding	$ 212,400
OpCo. \| Boston OpCo Credit Agreement \| Long-term Debt Facility \| LIBOR
Revenue recognition
Variable interest rate (as a percent)	1.30%
OpCo. \| Boston OpCo Amended Credit Agreement
Revenue recognition
Number of long-term debt facilities \| item		2		2
Repayment of outstanding balance		$ 92,600
Repayment of accrued interest		7,400
Debt issuance and modification costs		8,600
OpCo. \| Boston OpCo Amended Credit Agreement \| Interest Rate Swaps
Revenue recognition
Termination costs		34,400
OpCo. \| Boston OpCo Amended Credit Agreement \| Long-term Debt Facility
Revenue recognition
Carrying value		172,800		$ 172,800
Unamortized deferred financing costs		17,300		17,300
OpCo. \| Amended MBTA Agreement
Revenue recognition
Expected contract revenue		175,800		175,800
OpCo. \| Amended MBTA Agreement \| Design and Build Phase
Revenue recognition
Expected contract revenue		43,500		43,500
OpCo. \| Amended MBTA Agreement \| Operate and Maintain Phase
Revenue recognition
Expected contract revenue		618,000		618,000
OpCo. \| Amended MBTA Agreement \| Operate and Maintain Phase \| Boston OpCo Amended Credit Agreement \| Revolving Credit Agreement
Revenue recognition
Maximum borrowing capacity under credit agreement		15,800		15,800
OpCo. \| MBTA \| Original MBTA Contract
Revenue recognition
Expected contract revenue		558,500		$ 558,500
OpCo. \| MBTA \| Amended MBTA Agreement
Revenue recognition
Incremental forecasted revenue		$ 278,900
Cubic Transportation Systems \| HoldCo.
Revenue recognition
Ownership percentage		10.00%		10.00%
Cubic Transportation Systems \| HoldCo. \| Letter of credit agreement
Revenue recognition
Maximum borrowing capacity under credit agreement	$ 2,900
Borrowings outstanding		$ 0		$ 0
Cubic Transportation Systems \| OpCo. \| Original MBTA Contract
Revenue recognition
Expected contract revenue		427,600		427,600
Cubic Transportation Systems \| OpCo. \| Amended MBTA Agreement
Revenue recognition
Expected contract revenue		$ 596,400		$ 596,400
John Laing \| HoldCo.
Revenue recognition
Ownership percentage		90.00%		90.00%
John Laing \| HoldCo. \| Equity Bridge Loan
Revenue recognition
Loan amount	$ 24,300
John Laing \| HoldCo. \| Amended MBTA Agreement \| Equity Bridge Loan
Revenue recognition
Loan amount		$ 1,900		$ 1,900