Leases - Summary of right-of-use assets and lease liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2021	Jun. 30, 2020
Operating lease assets:
Other assets	$ 35.9	$ 52.0
Operating lease liabilities:
Other accrued liabilities	9.3	11.5
Other liabilities	37.2	50.3
Total operating lease liabilities	$ 46.5	$ 61.8