Income Taxes - Deferred Taxes Table (Detail) - USD ($) $ in Millions	Sep. 30, 2019	Sep. 30, 2018
Deferred Tax Assets:
Real estate	$ 10.2	$ 11.0
Employee benefits	1.5	1.5
Net operating loss carryforwards	15.1	17.7
AMT credits	0.6	1.2
Accruals not deductible until paid	0.2	0.4
Gross deferred tax assets	27.6	31.8
Valuation allowance	(3.3)	(3.4)
Deferred tax asset net of valuation allowance	24.3	28.4
Deferred Tax Liabilities, Tax Deferred Income	(6.4)	0.0
Deferred Tax Liabilities:
Convertible debt	(0.5)	(1.5)
Gross deferred tax liabilities	(6.9)	(1.5)
Deferred tax asset, net	$ 17.4	$ 26.9