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Leases and Commitments - Additional Information (Detail) $ in Thousands | 12 Months Ended |
--- | --- | ---
Sep. 30, 2020 USD ($) Air-craft | Sep. 30, 2019 USD ($) | Oct. 01, 2019 USD ($)
Operating Leased Assets [Line Items] |  |  |
Operating lease, right-of-use assets | $ 123,251 |  |
Number of leased aircraft | Air-craft | 18 |  |
Aggregate rental expense under all operating aircraft, equipment and facility leases | $ 64,700 | $ 72,800 |
Operating lease current liabilities | 43,932 |  |
Operating lease noncurrent liabilities | 62,531 |  |
Operating lease payments in operating cash flows | $ 44,173 |  |
Accounting Standards Update 2016-02 [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Operating lease, right-of-use assets |  |  | $ 154,600
Operating lease, liability |  |  | 141,900
Accounting Standards Update 2016-02 [Member] | Prepaid Aircraft Rent [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Operating lease, right-of-use assets |  |  | 35,800
Accounting Standards Update 2016-02 [Member] | Deferred Rent Credits [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Operating lease, right-of-use assets |  |  | 21,300
Accounting Standards Update 2016-02 [Member] | Accrued Aircraft Rents [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Operating lease, right-of-use assets |  |  | $ 1,800

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- Definition Present value of lessee's discounted obligation for lease payments from operating lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977 + Details
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- Definition Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977 + Details
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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121573735&loc=d3e41499-112717 + Details
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