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		6 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016
Net Sales:
Net Sales:	$ 427.4	$ 443.8	$ 816.3	$ 899.4
Operating Income:
Operating Income:	15.4	21.8	16.8	46.7
Depreciation and Amortization:
Depreciation and Amortization:	29.9	30.3	58.7	60.3
Capital Expenditures:
Capital Expenditures:	18.5	19.6	45.1	49.5
Total Assets:
Total Assets:	2,777.4		2,777.4		$ 2,794.3
Corporate
Operating Income:
Operating Income:	(16.0)	(12.7)	(29.8)	(24.8)
Depreciation and Amortization:
Depreciation and Amortization:	0.9	0.9	1.7	1.9
Capital Expenditures:
Capital Expenditures:	7.7	0.5	15.2	1.6
Total Assets:
Total Assets:	119.8		119.8		151.3
Intersegment
Net Sales:
Net Sales:	(4.4)	(5.2)	(9.1)	(13.8)
Operating Income:
Operating Income:	0.6	0.7	0.7	1.7
Pension earnings, interest and deferrals	(5.6)	(4.8)	(12.7)	(9.6)
Depreciation and Amortization:
Depreciation and Amortization:	0.1	(0.2)	(0.5)	(0.4)
Capital Expenditures:
Capital Expenditures:	0.0	(0.1)	(0.1)	(0.1)
Total Assets:
Total Assets:	(18.2)		(18.2)		(29.3)
Specialty Alloys Operations | Operating
Net Sales:
Net Sales:	348.6	363.6	663.7	736.2
Operating Income:
Operating Income:	35.6	41.5	60.6	82.7
Depreciation and Amortization:
Depreciation and Amortization:	23.7	23.9	47.2	47.4
Capital Expenditures:
Capital Expenditures:	8.3	17.0	23.0	36.7
Total Assets:
Total Assets:	2,267.6		2,267.6		2,256.5
Performance Engineered Products | Operating
Net Sales:
Net Sales:	83.2	85.4	161.7	177.0
Operating Income:
Operating Income:	0.8	(2.9)	(2.0)	(3.3)
Depreciation and Amortization:
Depreciation and Amortization:	5.2	5.7	10.3	11.4
Capital Expenditures:
Capital Expenditures:	2.5	$ 2.2	7.0	$ 11.3
Total Assets:
Total Assets:	$ 408.2		$ 408.2		$ 415.8