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		9 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2016
Net Sales:
Net Sales:	$ 473.6	$ 456.3	$ 1,289.9	$ 1,355.7
Operating Income (Loss):
Operating Income (Loss):	35.8	(24.3)	52.6	22.4
Depreciation and Amortization:
Depreciation and Amortization:	30.0	29.6	88.8	90.0
Capital Expenditures:
Capital Expenditures:	18.0	16.6	63.1	66.1
Total Assets:
Total Assets:	2,822.4		2,822.4		$ 2,794.3
Corporate
Operating Income (Loss):
Operating Income (Loss):	(15.8)	(64.5)	(45.6)	(89.3)
Depreciation and Amortization:
Depreciation and Amortization:	1.3	0.9	3.0	2.8
Capital Expenditures:
Capital Expenditures:	6.6	1.9	21.8	3.5
Total Assets:
Total Assets:	123.2		123.2		151.3
Segment Reconciling Items
Operating Income (Loss):
Pension earnings, interest and deferrals	(5.6)	(4.8)	(18.2)	(14.4)
Intersegment
Net Sales:
Net Sales:	(8.4)	(5.6)	(17.5)	(19.3)
Operating Income (Loss):
Operating Income (Loss):	0.6	0.3	1.1	2.0
Depreciation and Amortization:
Depreciation and Amortization:	(0.2)	(0.2)	(0.5)	(0.7)
Capital Expenditures:
Capital Expenditures:	(0.1)	(0.1)	(0.2)	(0.2)
Total Assets:
Total Assets:	(14.9)		(14.9)		(29.3)
Specialty Alloys Operations | Operating
Net Sales:
Net Sales:	383.3	370.5	1,047.0	1,106.7
Operating Income (Loss):
Operating Income (Loss):	51.9	45.6	112.6	128.3
Depreciation and Amortization:
Depreciation and Amortization:	23.7	23.4	70.8	70.9
Capital Expenditures:
Capital Expenditures:	8.6	11.2	31.6	47.9
Total Assets:
Total Assets:	2,261.1		2,261.1		2,256.5
Performance Engineered Products | Operating
Net Sales:
Net Sales:	98.7	91.4	260.4	268.3
Operating Income (Loss):
Operating Income (Loss):	4.7	(0.9)	2.7	(4.2)
Depreciation and Amortization:
Depreciation and Amortization:	5.2	5.5	15.5	17.0
Capital Expenditures:
Capital Expenditures:	2.9	$ 3.6	9.9	$ 14.9
Total Assets:
Total Assets:	$ 453.0		$ 453.0		$ 415.8