Income Taxes - Deferred Taxes Table (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Deferred Tax Assets:
Real estate	$ 10.5	$ 10.2
Employee benefits	1.5	1.5
Net operating loss carryforwards	1.7	15.1
AMT credits	0.0	0.6
Accruals not deductible until paid	0.2	0.2
Gross deferred tax assets	13.9	27.6
Valuation allowance	(1.5)	(3.3)
Deferred tax asset net of valuation allowance	12.4	24.3
Deferred Tax Liabilities, Tax Deferred Income	(18.1)	(6.4)
Convertible debt	0.0	(0.5)
Deferred Tax Liabilities:
Total deferred tax liabilities	(18.1)	(6.9)
Deferred Tax Liabilities, Net	$ (5.7)
Deferred tax asset, net		$ 17.4