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, 2019	Sep. 30, 2018	Jun. 30, 2019
Net Sales:
Consolidated net sales	$ 585.4	$ 572.4
Operating Income (Loss):
Consolidated operating income	59.8	45.0
Depreciation and Amortization:
Consolidated depreciation and amortization	30.6	29.7
Capital Expenditures:
Consolidated capital expenditures	47.5	41.6
Total Assets:
Consolidated total assets	3,341.5		$ 3,187.8
Corporate
Operating Income (Loss):
Consolidated operating income	(19.1)	(15.8)
Depreciation and Amortization:
Consolidated depreciation and amortization	1.3	1.2
Capital Expenditures:
Consolidated capital expenditures	16.2	7.7
Total Assets:
Consolidated total assets	216.6		192.5
Intersegment
Net Sales:
Consolidated net sales	(15.1)	(14.8)
Operating Income (Loss):
Consolidated operating income	(0.1)	0.7
Depreciation and Amortization:
Consolidated depreciation and amortization	(0.2)	(0.2)
Capital Expenditures:
Consolidated capital expenditures	(0.1)	(0.3)
Total Assets:
Consolidated total assets	(21.5)		(18.7)
Specialty Alloys Operations | Operating
Net Sales:
Consolidated net sales	491.1	475.5
Operating Income (Loss):
Consolidated operating income	81.0	52.8
Depreciation and Amortization:
Consolidated depreciation and amortization	23.6	23.7
Capital Expenditures:
Consolidated capital expenditures	25.2	20.6
Total Assets:
Consolidated total assets	2,442.1		2,349.2
Performance Engineered Products | Operating
Net Sales:
Consolidated net sales	109.4	111.7
Operating Income (Loss):
Consolidated operating income	(2.0)	7.3
Depreciation and Amortization:
Consolidated depreciation and amortization	5.9	5.0
Capital Expenditures:
Consolidated capital expenditures	6.2	$ 13.6
Total Assets:
Consolidated total assets	$ 704.3		$ 664.8