Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 92.9	$ 60.5
Marketable securities, current	13.0	17.9
Accounts receivable—trade, less allowance for doubtful accounts of $0.8 and $0.3 at 2023 and 2022, respectively	270.7	281.7
Inventories, at lower of cost or market	349.9	319.1
Prepaid expenses and other current assets	36.7	47.6
Total current assets	763.2	726.8
Marketable securities, non-current	7.4	4.4
Property, plant and equipment, at cost less accumulated depreciation and amortization of $1,656.3 and $1,553.1 at 2023 and 2022, respectively	2,500.7	2,459.3
Operating lease right of use assets, net	448.2	449.6
Intangible assets, net of amortization	140.2	140.4
Goodwill	328.0	328.0
Other assets	17.1	14.7
Total assets	4,204.8	4,123.2
Current liabilities
Current maturities of long-term debt	14.9	15.0
Trade accounts payable and accrued liabilities	800.4	839.2
Total current liabilities	815.3	854.2
Long-term debt, including capitalized lease obligations	1,787.3	1,791.9
Deferred income taxes	337.0	327.4
Asset retirement obligations	43.6	43.3
Non-current operating lease liabilities	445.3	444.2
Deferred credits and other liabilities	25.5	21.5
Total liabilities	3,454.0	3,482.5
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 2023 and 2022, respectively)	0.5	0.5
Treasury stock (25,314,150 and 25,017,324 shares held at 2023 and 2022, respectively)	(2,733.1)	(2,633.3)
Additional paid in capital (APIC)	505.8	518.9
Retained earnings	2,977.7	2,755.1
Accumulated other comprehensive income (loss) (AOCI)	(0.1)	(0.5)
Total stockholders' equity	750.8	640.7
Total liabilities and stockholders' equity	$ 4,204.8	$ 4,123.2

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.

Name:	us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI https://asc.fasb.org/extlink&oid=124259787&loc=d3e4531-111522