CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 780.3	$ 264.3
Short-term investments		78.7
Receivables:
Trade receivables, net	112.8	167.1
Other	11.6	18.1
Contract assets	36.1	54.6
Inventories	152.0	177.6
Prepaid expenses and other current assets	28.6	19.4
Total current assets	1,121.4	779.8
Property, plant and equipment, net	627.2	622.0
Operating lease assets	26.5	25.8
Deferred tax assets, net		11.8
Intangible assets, net	26.7	29.6
Goodwill	18.8	18.8
Other assets	44.1	38.4
Total	1,864.7	1,526.2
Current liabilities:
Accounts payable	86.1	92.0
Accrued salaries, wages and related expenses	30.8	34.4
Other accrued liabilities	41.4	44.0
Total current liabilities	158.3	170.4
Long-term portion of operating lease liabilities	25.6	25.2
Net liabilities of Salaried VEBA	17.8	32.6
Deferred tax liabilities	13.9	4.5
Long-term liabilities	78.6	67.0
Long-term debt	838.1	492.6
Total liabilities	1,132.3	792.3
Commitments and contingencies
Stockholders' equity:
Preferred stock, 5,000,000 shares authorized at both December 31, 2020 and December 31, 2019; no shares were issued and outstanding at December 31, 2020 and December 31, 2019
Common stock, par value $0.01, 90,000,000 shares authorized at both December 31, 2020 and December 31, 2019; 22,647,455 shares issued and 15,812,169 shares outstanding at December 31, 2020; 22,550,827 shares issued and 15,868,304 shares outstanding at December 31, 2019	0.2	0.2
Additional paid in capital	1,068.6	1,062.9
Retained earnings	158.2	172.8
Treasury stock, at cost, 6,835,286 shares at December 31, 2020 and 6,682,523 shares at December 31, 2019	(475.9)	(463.4)
Accumulated other comprehensive loss	(18.7)	(38.6)
Total stockholders' equity	732.4	733.9
Total	$ 1,864.7	$ 1,526.2