STATEMENTS OF CONSOLIDATED CASH FLOWS (UNAUDITED) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Cash flows from operating activities:
Net income	[1]	$ 21.6	$ 18.2	[2]
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment	[1]	28.9	27.7	[2]
Amortization of definite-lived intangible assets	[1]	1.1	1.1	[2]
Amortization of debt premium and debt issuance costs	[1]	0.5	0.6	[2]
Deferred income taxes	[1]	6.4	4.8	[2]
Non-cash equity compensation	[1]	4.2	4.0	[2]
Non-cash asset impairment charge	[1],[2],[3]		4.2
Loss on disposition of property, plant and equipment	[1],[2]		0.2
Bad debt expense	[1],[2]		0.1
Non-cash postretirement and postemployment defined benefit plan cost	[1]	2.3	1.5	[2]
Changes in operating assets and liabilities:
Trade and other receivables	[1]	(48.0)	(15.1)	[2]
Contract assets	[1]	5.5	(4.5)	[2]
Inventories	[1]	29.5	12.8	[2]
Prepaid expenses and other current assets	[1]	0.2	(1.7)	[2]
Accounts payable	[1]	20.3	18.6	[2]
Accrued liabilities	[1]	(14.3)	(5.2)	[2]
Annual variable cash contributions to Salaried VEBA	[1]	(0.7)	(1.1)	[2]
Long-term assets and liabilities, net	[1]	(0.5)	(2.9)	[2]
Net cash provided by operating activities	[1]	57.0	63.3	[2]
Cash flows from investing activities:
Capital expenditures	[1]	(38.2)	(30.0)	[2]
Proceeds from sale of equity securities	[1],[2]		0.1
Net cash used in investing activities	[1]	(38.2)	(29.9)	[2]
Cash flows from financing activities:
Borrowings under the Revolving Credit Facility	[1]	42.5
Repayment of borrowings under the Revolving Credit Facility	[1]	(42.5)
Repayment of finance lease	[1]	(0.7)	(0.4)	[2]
Cancellation of shares to cover tax withholdings upon common shares issued	[1]	(1.8)	(1.2)	[2]
Cash dividends and dividend equivalents paid	[1]	(12.9)	(12.6)	[2]
Net cash used in financing activities	[1]	(15.4)	(14.2)	[2]
Net increase in cash, cash equivalents and restricted cash during the period		3.4	19.2	[2]
Cash, cash equivalents and restricted cash at beginning of period		37.9	100.7	[2]
Cash, cash equivalents and restricted cash at end of period		$ 41.3	$ 119.9	[2]

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

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

[3] Non-cash asset impairment charge for the quarter ended March 31, 2024 is comprised of: (i) a $3.8 million inventory write-down related to certain alloying metals and (ii) a $0.4 million impairment charge on land held for sale.