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, 2015	Sep. 30, 2014	Jun. 30, 2015
Segment Data
Net sales	$ 455.6	$ 549.8
Operating income	24.8	22.1
Depreciation and amortization	29.9	30.3
Capital expenditures	29.9	59.0
Total assets	2,871.1		$ 2,905.9
Corporate
Segment Data
Operating income	(12.0)	(10.3)
Depreciation and amortization	0.9	1.1
Capital expenditures	1.1	1.0
Total assets	91.7		125.0
Intersegment
Segment Data
Net sales	(8.5)	(16.1)
Pension earnings, interest and deferrals	(4.8)	(2.4)
Operating income	0.9	0.5
Depreciation and amortization	(0.2)	(0.3)
Capital expenditures	0.0	(0.4)
Total assets	(40.0)		(41.3)
Specialty Alloys Operations | Operating
Segment Data
Net sales	372.6	436.0
Operating income	41.1	24.6
Depreciation and amortization	23.5	23.5
Capital expenditures	19.7	51.6
Total assets	2,324.9		2,323.0
Performance Engineered Products | Operating
Segment Data
Net sales	91.5	129.9
Operating income	(0.4)	9.7
Depreciation and amortization	5.7	6.0
Capital expenditures	9.1	$ 6.8
Total assets	$ 494.5		$ 499.2