Leases - Summary of lease cost (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021
Leases [Abstract]
Operating lease cost	$ 2.5	$ 3.6
Short-term lease cost	0.8	0.8
Variable lease cost	0.2	0.2
Sublease income	(0.2)	0.0
Total lease cost	3.3	4.6
Operating cash flow payments from operating leases	2.8	3.5
Non-cash ROU assets obtained in exchange for lease obligations	$ 0.2	$ 1.4
Weighted-average remaining lease term - operating leases	8 years 3 months 18 days		8 years 4 months 24 days
Weighted-average discount rate - operating leases	4.00%		4.00%