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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Mar. 31, 2021 | Mar. 31, 2020 | Sep. 30, 2020
Income Taxes [Line Items] |  |  |  |  |
Effective tax rate (ETR) from continuing operations | 24.90% | 40.90% | 25.30% | 27.60% |
Statutory federal tax rate |  |  |  | 21.00% |
State net operating loss carryforwards |  |  |  |  | $ 0.7
Domestic Tax Authority [Member] | 2027-2038 [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss carryforwards |  |  |  |  | 512.4
State and Local Jurisdiction [Member] | 2021-2040 [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss carryforwards |  |  |  |  | $ 223.9
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 |  |  |  |  | 2040

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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32632-109319 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319 + Details
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