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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019
Income Taxes [Line Items] |  |  |
Operating loss carryforwards, valuation allowance | $ 2.9 | $ 3.1 |
Unrecognized tax benefits if unrecognized, the balance of uncertain tax benefits would impact the effective tax rate | 4.9 | $ 4.9 | $ 4.7
Domestic Tax Authority [Member] |  |  |
Income Taxes [Line Items] |  |  |
Net operating loss carryforwards not subject to expiration | $ 130.7 |  |
Effective income tax rate reconciliation, at federal statutory income tax rate, percent | 80.00% |  |
Domestic Tax Authority [Member] | 2027-2038 [Member] |  |  |
Income Taxes [Line Items] |  |  |
Net operating loss carryforwards | $ 541.3 |  |
State and Local Jurisdiction [Member] | 2021-2041 [Member] |  |  |
Income Taxes [Line Items] |  |  |
Net operating loss carryforwards | $ 235.7 |  |
Minimum [Member] | Domestic Tax Authority [Member] |  |  |
Income Taxes [Line Items] |  |  |
Operating loss carryforwards, expiration year | 2027 |  |
Minimum [Member] | State and Local Jurisdiction [Member] |  |  |
Income Taxes [Line Items] |  |  |
Operating loss carryforwards, expiration year | 2021 |  |
Maximum [Member] | Domestic Tax Authority [Member] |  |  |
Income Taxes [Line Items] |  |  |
Operating loss carryforwards, expiration year | 2038 |  |
Maximum [Member] | State and Local Jurisdiction [Member] |  |  |
Income Taxes [Line Items] |  |  |
Operating loss carryforwards, expiration year | 2041 |  |

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are not subject to expiration dates. + References No definition available. + Details
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates. + References No definition available. + Details
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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 6.I.Fact.4) -URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)(2)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 + Details
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- Definition The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32537-109319 + Details
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