Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Sep. 30, 2020
Deferred tax assets:
Share-based compensation	$ 1.7	$ 3.1
Deferred compensation	4.7	4.1
Net operating loss carryforwards	17.7	16.2
Intangible assets	6.5	9.9
Bad debt reserve	7.3	4.4
Tax credit carryforwards	0.0	0.2
Foreign tax credit carryforwards	2.0	2.4
Other compensation	7.0	5.8
Property and equipment	6.3	7.3
Pension	1.2	0.0
Other	3.1	1.9
Total gross deferred tax assets	57.5	55.3
Less valuation allowance	(15.0)	(12.4)
Deferred tax assets	42.5	42.9
Deferred income tax liabilities:
Unrealized gain on securities	2.8	2.4
Prepaid expenses	4.2	3.4
Pension liability	0.0	0.2
Other deferred liabilities	0.4	0.0
Deferred income tax liabilities	7.4	6.0
Deferred income taxes, net	$ 35.1	$ 36.9