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Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Income Taxes [Line Items]
Effective tax rate (ETR) from continuing operations	40.90%	23.60%	27.60%	23.70%
Statutory federal tax rate			21.00%
State net operating loss carryforwards					$ 2.7
Domestic Tax Authority [Member] | 2027-2037 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					478.2
State and Local Jurisdiction [Member] | 2020-2039 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards					$ 228.0
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					2020
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					2039

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