Leases - Summary of right-of-use assets and lease liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2021	Jun. 30, 2021
Operating lease assets:
Other assets	$ 46.7	$ 34.3
Operating lease liabilities:
Accrued liabilities	9.7	9.0
Other liabilities	46.9	35.5
Total operating lease liabilities	$ 56.6	$ 44.5