Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash Flows from Operating Activities:
Net income	$ 345.9	$ 392.8
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization of intangibles	256.9	257.4
Amortization of deferred financing costs	1.2	1.1
Share-based compensation expense	29.2	24.8
Deferred income tax benefit	(5.9)	(5.4)
Net loss on asset disposals	7.4	3.2
Pension and post-retirement benefits expense, net of contributions	3.1	9.8
Other, net	22.2	12.7
(Increase) decrease in assets -
Accounts receivable	(112.0)	7.8
Inventories	(16.4)	(14.9)
Prepaid expenses and other current assets	(142.3)	(17.5)
Increase (decrease) in liabilities -
Accounts payable	53.1	(32.2)
Accrued liabilities	92.3	(43.0)
Federal and state income taxes payable/receivable	4.0	43.7
Net cash provided by operating activities	538.7	640.3
Cash Flows from Investing Activities:
Additions to property, plant, and equipment	(321.7)	(238.8)
Additions to other long-term assets	(1.7)	(2.2)
Proceeds from asset disposals	0.6	0.4
Purchases of available-for-sale debt securities	(62.6)	(55.7)
Proceeds from sales of available-for-sale debt securities	1.5	1.2
Proceeds from maturities of available-for-sale debt securities	60.1	52.9
Net cash used for investing activities	(323.8)	(242.2)
Cash Flows from Financing Activities:
Repayments of debt and finance lease obligations	(1.0)	(0.9)
Common stock dividends paid	(224.2)	(224.5)
Shares withheld to cover employee restricted stock taxes	(24.1)	(15.6)
Net cash used for financing activities	(249.3)	(241.0)
Net (decrease) increase in cash and cash equivalents	(34.4)	157.1
Cash and cash equivalents, beginning of period	648.0	320.0
Cash and cash equivalents, end of period	$ 613.6	$ 477.1