| In millions, except per share items | Dec-31-18 | Sep-30-18 | Jun-30-18 | Mar-31-18 | Dec-31-17 | Sep-30-17 | Jun-30-17 | Mar-31-17 |
| | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q |
| Operating Activities | | | | | | | | |
| Net income | 196.0 | 85.0 | 92.0 | 70.0 | 88.0 | 464.0 | 601.0 | 565.0 |
| Less: Income (loss) from discontinued operations, net of tax | 3.0 | 3.0 | | -8.0 | -9.0 | | 275.0 | |
| Less: Gain on sale of discontinued operations, net of tax | | 12.0 | | 1.0 | 0.0 | | 255.0 | |
| Income from continuing operations | 193.0 | 82.0 | 90.0 | 78.0 | 97.0 | 195.0 | 312.0 | 266.0 |
| |
| Adjustments to reconcile income from continuing operations to net cash: | | | | | | | | |
| Depreciation, depletion, amortization, and accretion | 150.0 | 147.0 | 143.0 | 135.0 | 132.0 | 132.0 | 132.0 | 133.0 |
| Loss on extinguishment of debt | | | | | | | 55.0 | |
| Long-lived asset impairment charges | | | | | | | | |
| Recovery of receivable | | | | | | | | |
| Share-based compensation expense | 21.0 | 20.0 | 19.0 | 18.0 | 18.0 | 17.0 | 18.0 | 18.0 |
| Deferred income taxes | 28.0 | 213.0 | 227.0 | 233.0 | 255.0 | 47.0 | 47.0 | 61.0 |
| (Gain) loss on asset dispositions | -12.0 | | -12.0 | | | 1.0 | 0.0 | |
| Income from equity method investments | -42.0 | -50.0 | -53.0 | -55.0 | -59.0 | -54.0 | -53.0 | -55.0 |
| Dividends received from equity method investments | 30.0 | | 35.0 | | 42.0 | | 52.0 | |
| Pension settlement | | | | | | | | |
| (Increase) decrease in working capital | | | | | | | | |
| Receivables | -5.0 | | | | -32.0 | | | |
| Income taxes receivable, net | -4.0 | | | | -12.0 | | | |
| Inventories | -42.0 | | | | -13.0 | | | |
| Other current assets | | | | | -3.0 | | | |
| Accrued expenses | -2.0 | | | | -36.0 | | | |
| Decrease in pension and other postretirement benefits | -40.0 | | | | -57.0 | | | |
| Decrease in other liabilities | -23.0 | | | | -13.0 | | | |
| Other, net | 13.0 | 11.0 | 9.0 | 12.0 | 4.0 | -2.0 | 20.0 | 15.0 |
| Net cash provided by operating activities of continuing operations | 281.0 | 326.0 | 271.0 | 395.0 | 382.0 | 232.0 | 292.0 | 331.0 |
| |
| Net cash provided by operating activities of discontinued operations | 3.0 | 3.0 | | 2.0 | 0.0 | | | 42.0 |
| Net cash provided by operating activities | 284.0 | 329.0 | 273.0 | 397.0 | 382.0 | 278.0 | 337.0 | 373.0 |
| |
| Investing Activities | | | | | | | | |
| Purchases of marketable securities | -102.0 | -105.0 | -100.0 | -107.0 | -105.0 | -166.0 | -161.0 | -219.0 |
| Sales or maturities of marketable securities | 103.0 | 101.0 | 95.0 | 103.0 | 97.0 | 172.0 | 279.0 | 351.0 |
| Capital expenditures | -219.0 | -218.0 | -205.0 | -181.0 | -168.0 | -148.0 | -129.0 | -108.0 |
| Net proceeds from asset dispositions | | | 14.0 | | | | 2.0 | |
| Acquisition of business, including working capital adjustment | 2.0 | -54.0 | | -50.0 | -52.0 | | | |
| Insurance proceeds | | | | | | | 1.0 | |
| Net cash (used for) provided by investing activities of continuing operations | -195.0 | -253.0 | -243.0 | -232.0 | -225.0 | -147.0 | -16.0 | 29.0 |
| |
| Net cash provided by investing activities of discontinued operations | | | | | | | | 674.0 |
| Net cash (used for) provided by investing activities | -195.0 | -253.0 | -243.0 | -232.0 | -219.0 | 527.0 | 659.0 | 703.0 |
| |
| Financing Activities | | | | | | | | |
| Issuance of debt | | | | | | | 500.0 | |
| Repayment of debt | | | | | -521.0 | | -1,510.0 | |
| Payment of debt issuance fees | | | | | | | -8.0 | |
| Issuance of common stock | 11.0 | 22.0 | 18.0 | 16.0 | 15.0 | | | 7.0 |
| Repurchase of common stock | | | -163.0 | -221.0 | -184.0 | -153.0 | -97.0 | -25.0 |
| Repurchases of common stock to satisfy employee tax withholding obligations | -15.0 | | | -8.0 | | | -6.0 | |
| Net cash used for financing activities of continuing operations | -150.0 | -93.0 | -153.0 | -242.0 | -202.0 | -1,107.0 | -1,114.0 | -1,089.0 |
| |
| Net decrease in cash and cash equivalents from continuing operations | -69.0 | -6.0 | -219.0 | -129.0 | -39.0 | -1,290.0 | -930.0 | -722.0 |
| Net increase in cash and cash equivalents from discontinued operations | 3.0 | 3.0 | | 2.0 | 6.0 | | | 716.0 |
| |
| Supplemental Cash Flow Disclosures: | | | | | | | | |
| Interest paid, net of interest capitalized | 53.0 | 55.0 | 61.0 | 59.0 | 82.0 | 95.0 | 125.0 | 141.0 |
| Income taxes paid, net of refunds received | 9.0 | 2.0 | 5.0 | 10.0 | 10.0 | 11.0 | 8.0 | 3.0 |
| Noncash Investing and Financing Activities: | | | | | | | | |
| Amount in accounts payable for capital expenditures | 23.0 | 20.0 | | 22.0 | 18.0 | 19.0 | 18.0 | 21.0 |