Segment Information, Geographic and Product Data - Schedule of Results of Operation, Depreciation and Amortization, Capital Expenditures and Total Assets by Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Net sales	$ 457.7	$ 456.3	$ 443.8	$ 455.6	$ 558.0	$ 570.6	$ 548.4	$ 549.8	$ 1,813.4	$ 2,226.7	$ 2,173.0
Operating income	29.2	$ (24.3)	$ 21.8	$ 24.8	39.5	$ 4.8	$ 45.0	$ 22.1	51.6	111.5	212.0
Depreciation and Amortization									119.3	122.3	111.9
Capital Expenditures									95.2	170.5	349.2
Assets	2,794.3				2,902.6				2,794.3	2,902.6
Operating
Segment Reporting Information [Line Items]
Pension EID									(19.3)	(9.4)	(21.8)
Corporate costs (including restructuring and impairment charges)
Segment Reporting Information [Line Items]
Operating income									(103.0)	(72.0)	(43.8)
Depreciation and Amortization									3.8	4.6	5.5
Capital Expenditures									8.6	4.3	5.4
Assets	151.3				121.7				151.3	121.7
Intersegment
Segment Reporting Information [Line Items]
Net sales									(26.3)	(67.6)	(67.2)
Operating income									2.5	(1.4)	(0.6)
Depreciation and Amortization									(0.8)	(0.6)	(0.8)
Capital Expenditures									(0.2)	(0.9)	(0.8)
Assets	(29.3)				(41.3)				(29.3)	(41.3)
Specialty Alloys Operations | Operating
Segment Reporting Information [Line Items]
Net sales									1,481.0	1,796.6	1,741.6
Operating income									176.9	155.2	232.7
Depreciation and Amortization									94.4	95.0	83.4
Capital Expenditures									67.0	129.0	319.9
Assets	2,256.5				2,323.0				2,256.5	2,323.0
Performance Engineered Products | Operating
Segment Reporting Information [Line Items]
Net sales									358.7	497.7	498.6
Operating income									(5.5)	39.1	45.5
Depreciation and Amortization									21.9	23.3	23.8
Capital Expenditures									19.8	38.1	$ 24.7
Assets	$ 415.8				$ 499.2				$ 415.8	$ 499.2