Restructuring and Asset Impairment Charges - Narrative (Details) $ in Millions	3 Months Ended			6 Months Ended
	Dec. 31, 2020 USD ($) facility	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and asset impairment charges	$ 0.0		$ 2.3	$ 10.0	$ 2.3
Non-cash asset impairment charges		$ 8.7
Restructuring charges		$ 1.3		$ 1.3
Fixed Cost Reduction
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated, period percent	20.00%
Facility Closing
Restructuring Cost and Reserve [Line Items]
Number of small domestic power metals production facilities closed | facility	2