STATEMENTS OF CONSOLIDATED CASH FLOWS (UNAUDITED) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net income	$ 4.5	$ 29.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment	12.8	12.5
Amortization of definite-lived intangible assets	0.7	0.7
Amortization of debt premium and debt issuance costs	0.7	0.3
Deferred income taxes	(0.9)	14.8
Non-cash equity compensation	3.1	1.7
Gain on disposition of short-term investments		(0.5)
Loss on disposition of property, plant and equipment		0.2
Changes in operating assets and liabilities, net of effects of acquisition:
Trade and other receivables	(31.7)	(12.6)
Contract assets	(8.3)	7.5
Inventories	(24.3)	(17.0)
Prepaid expenses and other current assets	(0.4)	(2.6)
Accounts payable	33.0	21.7
Accrued liabilities	4.2	(2.4)
Annual variable cash contributions to Salaried VEBA	(1.7)	(2.9)
Long-term assets and liabilities, net	(3.1)	1.9
Net cash (used in) provided by operating activities	(11.4)	52.4
Cash flows from investing activities:
Capital expenditures	(9.1)	(21.1)
Cash payment for acquisition of Warrick Rolling Mill	(617.5)
Purchase of short-term investments		(39.1)
Proceeds from disposition of short-term investments		78.8
Net cash (used in) provided by investing activities	(626.6)	18.6
Cash flows from financing activities:
Repayment of finance lease	(0.4)	(0.4)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares	(2.4)	(4.3)
Repurchase of common stock		(12.5)
Cash dividends and dividend equivalents paid	(11.7)	(11.3)
Net cash used in financing activities	(14.5)	(28.5)
Net (decrease) increase in cash, cash equivalents and restricted cash during the period	(652.5)	42.5
Cash, cash equivalents and restricted cash at beginning of period	794.3	278.6
Cash, cash equivalents and restricted cash at end of period	$ 141.8	$ 321.1