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Intangible Assets - Additional Information (Detail) - USD ($) | 12 Months Ended
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Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021
Finite-Lived Intangible Assets [Line Items] |  |  |
Impairment loss on intangible assets | $ 54,343,000 | $ 171,824,000 |
Amortization expense recognized | 100,000 | 1,000,000 | $ 1,200,000
Amortization expense next twelve months and year thereafter | 0 |  |
Customer Relationships [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Impairment loss on intangible assets | 3,700,000 | 1,900,000 | 0
Customer Relationships [Member] | American Capacity Purchase Agreement [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Impairment loss on intangible assets | 3,700,000 |  |
Customer Relationships [Member] | CRJ-900 Aircraft [Member] |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Impairment loss on intangible assets | $ 3,700,000 | $ 1,900,000 | $ 0

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- Definition Finite lived intangible assets amortization expense next twelve months and year thereafter. + References No definition available. + Details
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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482686/350-30-45-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-2 + Details
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- 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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 926 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147483154/926-20-50-5 + Details
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- Definition The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of an intangible asset (excluding goodwill) to fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -SubTopic 30 -Topic 350 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482665/350-30-50-3 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (b) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 + Details
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