| In millions, except per share items | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 | Dec-31-12 | Dec-31-11 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 227.0 | 335.0 | 274.0 | 976.0 | 38.0 | 94.0 | -307.0 | -786.0 |
| Depreciation and amortization | 150.0 | 132.0 | 134.0 | 131.0 | 142.0 | 155.0 | 156.0 | 164.0 |
| Stock-based compensation | 21.0 | 18.0 | 18.0 | 14.0 | 20.0 | 19.0 | 17.0 | 21.0 |
| Deferred taxes | 28.0 | 255.0 | 57.0 | -742.0 | 4.0 | 2.0 | 4.0 | -8.0 |
| Change in working capital [+] | -108.0 | -146.0 | -168.0 | -936.0 | -115.0 | -181.0 | 101.0 | 110.0 |
| Accounts receivable | -5.0 | -32.0 | 6.0 | 21.0 | -35.0 | -44.0 | 6.0 | -15.0 |
| Inventories | -42.0 | -13.0 | -20.0 | -16.0 | -11.0 | -28.0 | -12.0 | -17.0 |
| Other current assets | 1.0 | -3.0 | 9.0 | 1.0 | | -4.0 | 5.0 | -3.0 |
| Accounts payable | 7.0 | 20.0 | 21.0 | -16.0 | 9.0 | -4.0 | 27.0 | 17.0 |
| Accrued expenses | -2.0 | -36.0 | -39.0 | -61.0 | -9.0 | -23.0 | 14.0 | -10.0 |
| Other | -67.0 | -82.0 | -145.0 | -865.0 | -69.0 | -78.0 | 61.0 | 138.0 |
| Other operating activities | -37.0 | -212.0 | -1.0 | 836.0 | | | | |
| Cash from operations | 281.0 | 382.0 | 314.0 | 279.0 | 160.0 | 80.0 | 10.0 | 11.0 |
| |
| Capital expenditures [+] | -219.0 | -168.0 | -83.0 | -87.0 | -125.0 | -124.0 | -70.0 | -54.0 |
| Purchases of property and equipment | -219.0 | -168.0 | -83.0 | -87.0 | -125.0 | -124.0 | -70.0 | -54.0 |
| Sales of property and equipment | 14.0 | 2.0 | 12.0 | 58.0 | 13.0 | 2.0 | 14.0 | 9.0 |
| Acquisitions | 2.0 | -52.0 | | | | | | |
| Sales of short-term investments, net [+] | 1.0 | -8.0 | 139.0 | -76.0 | -14.0 | -11.0 | 154.0 | -10.0 |
| Purchases of short-term investments | -102.0 | -105.0 | -274.0 | -246.0 | -204.0 | -205.0 | -137.0 | -355.0 |
| Sales of short-term investments | 103.0 | 97.0 | 413.0 | 170.0 | 190.0 | 194.0 | 291.0 | 345.0 |
| Other cash from investing | 7.0 | 7.0 | 669.0 | 42.0 | -557.0 | -24.0 | 40.0 | |
| Cash from investing | -195.0 | -219.0 | 737.0 | -63.0 | -683.0 | -157.0 | 138.0 | -55.0 |
| |
| Cash dividends paid | -70.0 | | | | | | | |
| Repurchase of common stock, net | -65.0 | -169.0 | 4.0 | 6.0 | -3.0 | -5.0 | -2.0 | -3.0 |
| Financing costs | | -8.0 | | -6.0 | -3.0 | -6.0 | -5.0 | |
| Other cash from financing | -15.0 | -41.0 | -1,133.0 | -56.0 | -66.0 | 349.0 | -41.0 | -6.0 |
| Cash from financing | -150.0 | -202.0 | -1,129.0 | -44.0 | -66.0 | 350.0 | -38.0 | -9.0 |
| |
| Free cash flow | 62.0 | 214.0 | 231.0 | 192.0 | 35.0 | -44.0 | -60.0 | -43.0 |
| Per share (diluted) | $0.43 | $1.46 | $1.56 | $1.30 | $0.24 | ($0.39) | ($0.56) | ($0.41) |
| |
| Cash paid for interest | 53.0 | 82.0 | 153.0 | 158.0 | 172.0 | 192.0 | 200.0 | 196.0 |
| Cash paid for income taxes | 9.0 | 10.0 | 4.0 | | 7.0 | 10.0 | 1.0 | 6.0 |