| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 8-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 4,245.9 | 3,806.3 | 1,758.7 | 365.6 | 122.2 | 28.1 | 113.1 | 88.8 |
| Depreciation and amortization | | 138.1 | 134.2 | 138.1 | 148.7 | 142.9 | 131.8 | 149.9 |
| Deferred taxes | | -978.9 | -450.2 | -120.9 | 82.0 | 51.4 | 6.4 | 6.3 |
| Change in working capital [+] | | 124.7 | 10.6 | -45.6 | 7.8 | 30.1 | 28.6 | -9.9 |
| Accounts payable | | 124.7 | 10.6 | -45.6 | 7.8 | 30.1 | 28.6 | -9.9 |
| Other operating activities | | -2,514.8 | -995.4 | -51.7 | -256.6 | -36.1 | -93.7 | 38.2 |
| Cash from operations | | 575.3 | 457.9 | 285.5 | 104.1 | 216.4 | 186.2 | 273.3 |
| |
| Capital expenditures [+] | | -98.9 | -98.5 | -129.8 | -111.3 | -141.4 | -112.0 | -121.0 |
| Purchases of property and equipment | | -98.9 | -98.5 | -129.8 | -111.3 | -141.4 | -112.0 | -121.0 |
| Sales of property and equipment | | 0.1 | 0.1 | 4.3 | 3.9 | 0.4 | 0.1 | 0.2 |
| Purchases of intangible assets | | | | | | -0.1 | -1.4 | -15.5 |
| Sales of short-term investments | | 368.1 | 331.5 | 302.3 | 299.8 | 219.9 | 249.5 | 196.1 |
| Sales of short-term investments | | 368.1 | 331.5 | 302.3 | 299.8 | 219.9 | 249.5 | 196.1 |
| Other cash from investing | | -329.5 | -442.0 | -363.8 | -367.9 | -292.6 | -303.1 | -250.4 |
| Cash from investing | | -60.3 | -208.9 | -187.0 | -175.6 | -213.9 | -166.9 | -190.5 |
| |
| Repurchase of common stock, net | | -92.7 | -23.0 | -43.6 | 11.7 | 11.3 | 8.2 | 15.1 |
| Option exercises | | 20.2 | 13.1 | 14.1 | | | | |
| Financing costs | | | -0.5 | | | | | -0.5 |
| Other cash from financing | -55.4 | -410.1 | 12.9 | 9.1 | -11.3 | | | |
| Cash from financing | -55.4 | -523.0 | -22.8 | -48.7 | 0.3 | 9.0 | 8.6 | 11.7 |
| |
| Free cash flow | | 476.4 | 359.4 | 155.7 | -7.2 | 75.0 | 74.2 | 152.3 |
| Per share (diluted) | | $15.80 | $11.91 | $5.15 | ($0.24) | $2.53 | $2.52 | $5.23 |
| |
| Cash paid for interest | -2.3 | -21.6 | -22.3 | -22.7 | -22.2 | -21.3 | -20.8 | -20.8 |
| Cash paid for income taxes | -134.7 | -65.2 | -45.1 | -62.4 | -52.1 | -38.4 | -31.7 | -28.9 |