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Contract Revenue and Pass-through and Other Revenue - Additional Information (Detail) $ in Millions | 12 Months Ended
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Sep. 30, 2021 USD ($) Air-craft | Sep. 30, 2020 USD ($) | Sep. 30, 2019 USD ($)
Disaggregation Of Revenue [Line Items] |  |  |
Deferred revenue | $ 10.7 | $ 23.8 |
Lease revenue | 170.2 | 208.9 | $ 219.0
Lease incentive assets | 12.4 |  |
Lease incentive obligations | 9.7 |  |
Amounts deferred for supplemental rent payments | 0.8 |  |
GoJet Agreements [Member] |  |  |
Disaggregation Of Revenue [Line Items] |  |  |
Lease revenue recognized | $ 9.5 |  |
CRJ 700 [Member] |  |  |
Disaggregation Of Revenue [Line Items] |  |  |
Number of aircraft to be leased | Air-craft | 14 |  |
Operating lease, term of contract | 9 years |  |
Contract Revenue [Member] |  |  |
Disaggregation Of Revenue [Line Items] |  |  |
Lease revenue | $ 170.2 | $ 208.9 | $ 219.0

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- Definition Lease incentive assets. + References No definition available. + Details
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- Definition Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918673-209980 + Details
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- Definition Amount of operating lease income from lease payments and variable lease payments paid and payable to lessor. Includes, but is not limited to, variable lease payments not included in measurement of lease receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=124258985&loc=SL77919372-209981 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=123420820&loc=SL77919311-209978 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 6A -URI http://asc.fasb.org/extlink&oid=124502072&loc=SL77927221-108306 + Details
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