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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2019 | Mar. 31, 2018 | Sep. 30, 2018
Income Taxes [Line Items] |  |  |  |  |
Statutory federal tax rate | 21.00% |  | 21.00% |  | 24.50%
Effective tax rate (ETR) from continuing operations | 23.60% | 20.40% | 23.70% | (555.20%) |
State net operating loss carryforwards |  |  |  |  | $ 0.9
Domestic Tax Authority [Member] | 2027-2037 [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss carryforwards |  |  |  |  | $ 415.1
State and Local Jurisdiction [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Operating loss carryforwards, expiration year |  |  |  |  | 2019
State and Local Jurisdiction [Member] | 2019-2038 [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Net operating loss carryforwards |  |  |  |  | $ 199.6
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 |  |  |  |  | 2019
Maximum [Member] | Domestic Tax Authority [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Operating loss carryforwards, expiration year |  |  |  |  | 2037
Maximum [Member] | State and Local Jurisdiction [Member] |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |
Operating loss carryforwards, expiration year |  |  |  |  | 2038

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