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