Inventories - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Jun. 30, 2021 USD ($) $ / shares	Jun. 30, 2020 USD ($) facility $ / shares	Jun. 30, 2019 USD ($) $ / shares
Inventory [Line Items]
Inventory LIFO reserve	$ 238.8	$ 134.5
Current cost of LIFO inventory	557.0	722.5
Cost of sales	52.2	1.8	$ 0.0
LIFO decrement	$ 37.3	$ 1.4	$ 0.0
Earnings per share, diluted (in dollars per share) | $ / shares	$ 0.77	$ 0.03	$ 0
Inventory adjustment	$ 4.2	$ 29.3	$ 0.0
Facility Closing
Inventory [Line Items]
Number of power production facilities closed | facility		2