Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash Flows from Operating Activities:
Net income	$ 624.6	$ 337.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization of intangibles	311.1	309.0
Amortization of deferred financing costs	2.0	1.9
Share-based compensation expense	26.9	23.8
Deferred income tax provision	41.7	21.1
Loss on asset disposals	7.3	4.1
Goodwill impairment	0.0	55.2
Pension and post-retirement benefits expense, net of contributions	(50.4)	(68.1)
Other, net	8.9	18.8
(Increase) decrease in assets -
Accounts receivable	(234.3)	(19.0)
Inventories	(92.3)	16.5
Prepaid expenses and other current assets	(11.8)	(5.6)
Increase (decrease) in liabilities -
Accounts payable	22.3	(6.2)
Accrued liabilities	53.5	29.0
Federal and state income taxes payable / receivable	(6.1)	43.8
Net cash provided by operating activities	703.4	761.7
Cash Flows from Investing Activities:
Additions to property, plant, and equipment	(366.2)	(253.5)
Additions to other long term assets	(1.8)	(6.2)
Proceeds from asset disposals	2.6	4.4
Purchases of marketable debt securities	(100.3)	(71.5)
Proceeds from sales of marketable debt securities	17.7	17.2
Proceeds from maturities of marketable debt securities	83.0	53.7
Net cash used for investing activities	(365.0)	(255.9)
Cash Flows from Financing Activities:
Repayments of debt and finance lease obligations	(1.2)	(1.1)
Proceeds from issuance of debt	696.3	0.0
Financing costs paid	(8.5)	0.0
Common stock dividends paid	(284.8)	(224.6)
Shares withheld to cover employee restricted stock taxes	(11.9)	(10.5)
Net cash provided by (used for) financing activities	389.9	(236.2)
Net increase in cash and cash equivalents	728.3	269.6
Cash and cash equivalents, beginning of period	974.6	679.5
Cash and cash equivalents, end of period	$ 1,702.9	$ 949.1