Leases - Summary of lease cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2021
Leases [Abstract]
Operating lease cost	$ 2.5	$ 3.2	$ 5.0	$ 6.8
Short-term lease cost	0.8	0.7	1.7	1.6
Variable lease cost	0.1	0.1	0.3	0.2
Sublease income	(0.2)	(0.2)	(0.5)	(0.3)
Total lease cost	3.2	3.8	6.5	8.3
Operating cash flow payments from operating leases	2.8	3.3	5.6	6.9
Non-cash ROU assets obtained in exchange for lease obligations	$ 15.1	$ 0.0	$ 15.5	$ 1.4
Weighted-average remaining lease term - operating leases	8 years 9 months 18 days		8 years 9 months 18 days		8 years 4 months 24 days
Weighted-average discount rate - operating leases	3.50%		3.50%		4.00%