Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 39.1	$ 60.1
Accounts receivable, net	287.2	248.7
Inventories, net	305.4	314.0
Contract assets	37.7
Prepaid expenses and other current assets	38.4	33.9
Total current assets	707.8	656.7
Property, plant and equipment	2,800.1	2,743.9
Less accumulated depreciation	(920.5)	(877.6)
Net property, plant and equipment	1,879.6	1,866.3
Goodwill and other intangible assets	145.3	148.7
Investments in affiliated companies	44.6	47.7
Other assets	58.8	61.5
Total assets	2,836.1	2,780.9
Current liabilities:
Current portion of debt	9.3	4.3
Accounts payable	147.1	144.1
Accrued compensation and benefits	68.8	73.0
Accrued liabilities	68.6	40.7
Total current liabilities	293.8	262.1
Commitments and contingencies (see Note 13)
Long-term debt	930.1	805.6
Retirement obligations	41.3	45.4
Other non-current liabilities	171.1	172.7
Total liabilities	1,436.3	1,285.8
Stockholders' equity:
Common stock, $0.01 par value, 200.0 shares authorized, 108.4 shares and 107.8 shares issued at June 30, 2018 and December 31, 2017, respectively	1.1	1.1
Additional paid-in capital	792.0	774.3
Retained earnings	1,606.2	1,496.1
Accumulated other comprehensive loss	(80.8)	(45.0)
Total stockholders' equity including treasury stock value	2,318.5	2,226.5
Less – Treasury stock, at cost, 20.9 shares at June 30, 2018, and 18.2 shares at December 31, 2017, respectively.	(918.7)	(731.4)
Total stockholders' equity	1,399.8	1,495.1
Total liabilities and stockholders' equity	$ 2,836.1	$ 2,780.9