Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net earnings including redeemable noncontrolling interest	$ 100.1	$ 123.1	$ 96.1
Hedging adjustments:
Net gain (loss) on derivatives, before tax	(10.4)	0.0	0.0
Reclassification adjustment from AOCI on derivatives, before tax	1.0	0.0	0.0
Foreign currency translation adjustments:
Unrealized foreign currency translation adjustments	1.4	(1.2)	(0.4)
Tax benefit (expense) on other comprehensive income (loss)
Net gain (loss) on derivatives, tax	0.8	0.0	0.0
Reclassification adjustment from AOCI on derivatives, tax	(0.2)	0.0	0.0
Total other comprehensive income (loss)	(7.4)	(1.2)	(0.4)
Less: Comprehensive income attributable to redeemable noncontrolling interest	70.6	121.9	95.7
Total comprehensive income available to Class A common stockholders	$ 22.1	$ 0.0	$ 0.0