Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Net sales	$ 511.1	$ 496.1
Operating costs and expenses:
Cost of sales (exclusive of items shown separately below)	425.5	418.0
Selling, general and administrative expense	8.2	9.0
Depreciation and amortization	14.4	15.2
Other expense, net
Legal matters	16.1	0.0
Other	4.2	8.1
Total operating costs and expenses	468.4	450.3
Operating income	42.7	45.8
Non-operating:
Retirement benefits expense	0.3	8.5
Loss on debt	0.0	9.1
Interest income and other	0.2	(0.6)
Interest expense	3.9	5.1
Total non-operating expense, net	4.4	22.1
Income before income taxes	38.3	23.7
Income tax provision	10.5	5.6
Net income	$ 27.8	$ 18.1
Earnings per share of common stock
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.23
Diluted earnings per share (in dollars per share)	$ 0.33	$ 0.22
Weighted average shares of common stock outstanding, basic (in shares)	80.2	77.6
Weighted average shares of common stock outstanding, diluted (in shares)	85.8	80.7
Cash dividends paid per share (in USD per share)	$ 0	$ 5.00