Condensed Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Statement [Abstract]
Net sales	$ 566.3	$ 511.1
Operating costs and expenses:
Cost of sales (exclusive of items shown separately below)	488.2	425.5
Selling, general and administrative expense	10.3	8.2
Depreciation and amortization	13.3	14.4
Other expense, net
Merger costs	20.0	0.0
Legal matters	0.0	16.1
Other	1.2	4.2
Total operating costs and expenses	533.0	468.4
Operating income	33.3	42.7
Non-operating:
Retirement benefits (income) expense	(2.4)	0.3
Interest income and other	(3.8)	0.2
Interest expense	5.7	3.9
Total non-operating (income) expense, net	(0.5)	4.4
Income before income taxes	33.8	38.3
Income tax provision	6.0	10.5
Net income	$ 27.8	$ 27.8
Earnings per share of common stock
Basic earnings per share (in dollars per share)	$ 0.34	$ 0.34
Diluted earnings per share (in dollars per share)	$ 0.34	$ 0.33
Weighted average shares of common stock outstanding, basic (in shares)	80.6	80.2
Weighted average shares of common stock outstanding, diluted (in shares)	80.7	85.8