Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 79.8	$ 117.8
Marketable securities, current	4.5	7.1
Accounts receivable—trade, less allowance for doubtful accounts of $0.6 and $1.3 at 2024 and 2023, respectively	386.5	336.7
Inventories, at lower of cost or market	315.9	341.2
Prepaid expenses and other current assets	33.4	23.7
Total current assets	820.1	826.5
Marketable securities, non-current	3.0	4.4
Property, plant and equipment, at cost less accumulated depreciation and amortization of $1,824.9 and $1,739.2 at 2024 and 2023, respectively	2,655.4	2,571.8
Operating lease right of use assets, net	463.5	452.1
Intangible assets, net of amortization	139.6	139.8
Goodwill	328.0	328.0
Other assets	20.3	17.5
Total assets	4,429.9	4,340.1
Current liabilities
Current maturities of long-term debt	15.6	15.0
Trade accounts payable and accrued liabilities	924.0	834.7
Income taxes payable	31.1	23.1
Total current liabilities	970.7	872.8
Long-term debt, including capitalized lease obligations	1,781.4	1,784.7
Deferred income taxes	323.0	329.5
Asset retirement obligations	46.3	46.1
Non-current operating lease liabilities	464.6	450.3
Deferred credits and other liabilities	32.6	27.8
Total liabilities	3,618.6	3,511.2
Stockholders' Equity
Preferred Stock, par $0.01 (authorized 20,000,000 shares, none outstanding)	0.0	0.0
Common Stock, par $0.01 (authorized 200,000,000 shares, 46,767,164 shares issued at 2024 and 2023, respectively)	0.5	0.5
Treasury stock (26,274,959 and 25,929,836 shares held at 2024 and 2023, respectively)	(3,139.4)	(2,957.8)
Additional paid in capital (APIC)	479.3	508.1
Retained earnings	3,470.9	3,278.1
Total stockholders' equity	811.3	828.9
Total liabilities and stockholders' equity	$ 4,429.9	$ 4,340.1

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1