Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Consolidated Statement of Other Comprehensive Income (Loss) [Abstract]
Net income	$ 24.0	$ 12.7	$ 39.8	$ 30.0
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment	(4.9)	(1.9)	(8.7)	(2.1)
Other comprehensive income (loss)	(4.9)	(1.9)	(8.7)	(2.1)
Comprehensive income	$ 19.1	$ 10.8	$ 31.1	$ 27.9