Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows from Operating Activities:
Net income	$ 166.5	$ 141.7
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization of intangibles	100.8	100.3
Amortization of deferred financing costs	0.7	0.6
Share-based compensation expense	11.6	10.1
Deferred income tax provision	12.0	13.5
Loss on asset disposals	3.7	2.3
Pension and post-retirement benefits expense, net of contributions	(0.2)	1.0
Other, net	3.7	3.2
Increase in assets —
Accounts receivable	(76.2)	(34.0)
Inventories	(11.7)	(15.7)
Prepaid expenses and other current assets	(19.0)	(23.0)
Increase (decrease) in liabilities —
Accounts payable	(12.3)	28.5
Accrued liabilities	(15.8)	(22.0)
Federal and state income taxes payable / receivable	27.8	30.2
Net cash provided by operating activities	191.6	236.7
Cash Flows from Investing Activities:
Additions to property, plant, and equipment	(85.1)	(70.5)
Additions to other long term assets	(1.3)	(2.7)
Proceeds from asset disposals	0.7	0.1
Purchases of marketable debt securities	(31.4)	(20.5)
Proceeds from sales of marketable debt securities	11.4	6.3
Proceeds from maturities of marketable debt securities	18.2	10.3
Net cash used for investing activities	(87.5)	(77.0)
Cash Flows from Financing Activities:
Repayments of debt and finance lease obligations	(0.4)	(0.4)
Common stock dividends paid	(94.8)	(74.8)
Shares withheld to cover employee restricted stock taxes	(0.1)
Net cash used for financing activities	(95.3)	(75.2)
Net increase in cash and cash equivalents	8.8	84.5
Cash and cash equivalents, beginning of period	974.6	679.5
Cash and cash equivalents, end of period	$ 983.4	$ 764.0