Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024
Income Taxes [Line Items]
Effective tax rate (ETR) from continuing operations	6.20%	0.60%	3.10%	(2.10%)
State net operating loss carryforwards	$ 0.5		$ 0.5
Domestic Tax Authority [Member] | 2030-2038 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	276.2		276.2
State and Local Jurisdiction [Member] | 2024-2043 [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 146.6		$ 146.6
Minimum [Member] | Domestic Tax Authority [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year			2030
Minimum [Member] | State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Operating loss carryforwards, expiration year			2024
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			2043