| 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 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 190.3 | 63.6 | 83.8 | 80.2 | 52.4 | 39.4 | 33.0 | 22.4 |
| Depreciation and amortization [+] | 8.4 | 7.5 | 5.2 | 4.3 | 6.3 | 4.0 | 3.3 | 3.1 |
| Amortization of intangible assets | 5.5 | 5.3 | 4.3 | 3.2 | 2.0 | 2.1 | 1.7 | 1.6 |
| Stock-based compensation | 10.3 | 10.2 | 7.1 | 7.2 | 6.8 | 4.7 | | |
| Deferred taxes | 30.8 | -25.5 | -1.9 | 6.4 | 6.5 | 9.3 | 1.6 | 0.8 |
| Change in working capital [+] | -100.1 | 43.5 | 13.0 | -16.1 | 47.6 | 15.3 | 4.5 | 16.6 |
| Accrued expenses | -100.1 | 43.5 | 13.0 | -16.1 | 47.6 | 15.3 | 12.8 | 10.1 |
| Other | | | | | | | -8.4 | 6.4 |
| Other operating activities | -84.8 | -369.4 | -43.3 | 130.2 | -81.9 | -317.9 | -88.2 | -148.5 |
| Cash from operations | 54.9 | -270.0 | 63.9 | 212.2 | 37.6 | -245.2 | -45.8 | -105.6 |
| |
| Capital expenditures [+] | -6.1 | -5.9 | -6.8 | -10.1 | -4.5 | -4.8 | -5.9 | -5.4 |
| Purchases of property and equipment | -6.1 | -5.9 | -6.8 | -10.1 | -4.5 | -4.8 | -5.9 | -5.4 |
| Sales of property and equipment | | | 1.3 | 0.4 | 0.0 | 0.0 | 0.0 | 0.6 |
| Purchases of short-term investments, net | -533.2 | 88.6 | 10.6 | -128.0 | 96.7 | 59.1 | 133.0 | 43.6 |
| Purchases of short-term investments | -847.2 | -425.0 | -151.4 | -203.8 | -81.4 | -316.4 | -164.9 | -109.7 |
| Sales of short-term investments | 314.0 | 513.5 | 162.0 | 75.8 | 178.1 | 375.5 | 297.8 | 153.3 |
| Other cash from investing | -310.2 | 227.5 | -188.0 | -448.7 | -359.4 | -87.1 | -178.9 | -68.4 |
| Cash from investing | -849.6 | 310.1 | -182.9 | -586.5 | -267.2 | -32.7 | -51.8 | -29.6 |
| |
| Cash dividends paid | -21.6 | -14.3 | -10.0 | -6.1 | | -69.3 | -25.4 | -14.9 |
| Issuance of common stock, net | -6.1 | 1.0 | 0.8 | 1.2 | -88.0 | 116.1 | | |
| Other cash from financing | 1,302.2 | 1,058.4 | 235.6 | 384.8 | 301.0 | 269.8 | 170.7 | 132.4 |
| Cash from financing | 1,274.5 | 1,045.1 | 226.3 | 379.9 | 213.0 | 316.5 | 145.4 | 117.6 |
| |
| Free cash flow | 48.8 | -275.9 | 57.1 | 202.1 | 33.1 | -250.0 | -51.7 | -111.0 |
| Per share (diluted) | $1.02 | ($7.24) | $1.82 | $6.45 | $1.17 | ($12.94) | ($3.01) | ($6.46) |
| |
| Cash paid for interest | 41.2 | 48.7 | 55.1 | 32.0 | 15.5 | 9.5 | 9.0 | 9.7 |