Business Segments - Schedule of results of operation, depreciation and amortization, capital expenditures and total assets by reportable segments (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017
Net Sales:
Net Sales:	$ 479.8	$ 389.0
Operating Income:
Operating Income:	41.7	1.4
Depreciation and Amortization:
Depreciation and Amortization:	28.7	28.9
Capital Expenditures:
Capital Expenditures:	28.9	26.6
Total Assets:
Total Assets:	2,892.5		$ 2,878.1
Corporate
Operating Income:
Operating Income:	(12.9)	(13.8)
Depreciation and Amortization:
Depreciation and Amortization:	0.9	0.8
Capital Expenditures:
Capital Expenditures:	7.1	7.5
Total Assets:
Total Assets:	139.0		167.2
Segment Reconciling Items
Operating Income:
Pension earnings, interest and deferrals	(0.5)	(7.1)
Intersegment
Net Sales:
Net Sales:	(17.7)	(4.6)
Operating Income:
Operating Income:	(0.7)	0.1
Depreciation and Amortization:
Depreciation and Amortization:	(0.3)	(0.4)
Capital Expenditures:
Capital Expenditures:	(0.3)	(0.1)
Total Assets:
Total Assets:	(15.9)		(15.5)
Specialty Alloys Operations | Operating
Net Sales:
Net Sales:	396.8	315.1
Operating Income:
Operating Income:	50.5	25.0
Depreciation and Amortization:
Depreciation and Amortization:	23.1	23.4
Capital Expenditures:
Capital Expenditures:	17.2	14.7
Total Assets:
Total Assets:	2,310.2		2,292.1
Performance Engineered Products | Operating
Net Sales:
Net Sales:	100.7	78.5
Operating Income:
Operating Income:	5.3	(2.8)
Depreciation and Amortization:
Depreciation and Amortization:	5.0	5.1
Capital Expenditures:
Capital Expenditures:	4.9	$ 4.5
Total Assets:
Total Assets:	$ 459.2		$ 434.3