Business, Product, and Geographical Area Information - Schedule of Significant Segment Expenses Provided to CODM (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Net sales		$ 777.4	$ 737.5	[1]
Hedged cost of alloyed metal		414.2	370.6
Manufacturing costs		181.7	202.5
Plant overhead		44.2	42.1
Freight costs		20.7	22.2
Other cost of products sold		12.6	13.9
Depreciation and amortization		30.0	28.8	[1]
Selling, general, administrative, research and development		30.8	32.6	[1]
Research and development costs		0.3	0.6
Employee costs		22.5	22.3
Other selling, general and administrative costs		8.0	9.7
Restructuring costs		1.8	0.1
Other operating charges, net		0.0	0.4	[1]
Interest expense		11.2	11.5	[1]
Other expense (income), net - Note 9		1.4	(10.9)	[1]
Income tax provision		7.2	5.5	[1]
Net income	[2]	$ 21.6	$ 18.2	[1]

[1] Adjusted to reflect the retrospective change in inventory valuation methodology from LIFO to WAC. See Note 14 for further discussion.

[2] See Note 12 for supplemental cash flow information.