Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net earnings including redeemable noncontrolling interest	$ 114.4	$ 100.1	$ 123.1
Hedging adjustments:
Net loss on derivatives	0.0	(10.4)	0.0
Reclassifications to net earnings	2.3	1.0	0.0
Foreign currency translation adjustments:
Unrealized foreign currency translation adjustments	(0.2)	1.4	(1.2)
Tax (expense) benefit on other comprehensive income (loss):
Net loss on derivatives	0.0	0.8	0.0
Reclassifications to net earnings	(0.2)	(0.2)	0.0
Total Other Comprehensive Income (Loss) Including Redeemable Noncontrolling Interest	1.9	(7.4)	(1.2)
Comprehensive income attributable to redeemable noncontrolling interest	88.2	70.6	121.9
Total comprehensive income available to Class A common stockholders	$ 28.1	$ 22.1	$ 0.0