Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ 23.4	$ 22.7	$ 41.6	$ 15.8
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustment	0.0	(1.6)	0.3	(3.8)
Other comprehensive (loss) income	0.0	(1.6)	0.3	(3.8)
Comprehensive income	$ 23.4	$ 21.1	$ 41.9	$ 12.0