| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 85.0 | 89.3 | 77.6 | 81.7 | 82.3 | 52.5 | 59.3 | 58.4 |
| Depreciation and amortization [+] | 11.6 | 11.6 | 11.7 | 11.7 | 11.3 | 10.2 | 8.9 | 8.5 |
| Amortization of intangible assets | 0.9 | 1.3 | 1.5 | 1.7 | 1.8 | 1.9 | 2.1 | 2.0 |
| Stock-based compensation | 4.3 | 5.1 | 4.7 | 4.2 | 3.5 | 3.0 | 2.3 | 1.9 |
| Tax benefit from stock-based compensation | | | | | 0.7 | 1.6 | 1.4 | 0.4 |
| Deferred taxes | | | -6.3 | 3.1 | 2.4 | 14.6 | 1.9 | 2.9 |
| Change in working capital | -1.7 | 8.6 | -13.5 | 1.7 | -0.4 | -4.3 | -2.3 | 0.2 |
| Other | -1.7 | 8.6 | -13.5 | 1.7 | -0.4 | -4.3 | -2.3 | 0.2 |
| Other operating activities | 4.2 | 6.6 | 27.2 | -0.8 | 7.6 | 8.5 | 19.4 | 10.5 |
| Cash from operations | 103.3 | 121.2 | 101.4 | 101.6 | 107.3 | 86.1 | 90.9 | 82.8 |
| |
| Capital expenditures [+] | -8.2 | -4.7 | -4.6 | -6.0 | -18.1 | -35.3 | -16.3 | -6.3 |
| Purchases of property and equipment | -8.2 | -4.7 | -4.6 | -6.0 | -18.1 | -35.3 | -16.3 | -6.3 |
| Sales of property and equipment | 0.2 | 0.1 | 0.0 | 0.4 | 3.3 | 0.2 | 0.1 | 0.1 |
| Acquisitions | | | | -0.4 | | | | |
| Purchases of short-term investments, net | 214.5 | -475.4 | -317.0 | 202.4 | 36.2 | 30.3 | -51.0 | 8.0 |
| Purchases of short-term investments | -154.8 | -1,071.8 | -904.9 | -333.2 | -185.5 | -208.5 | -404.5 | -391.1 |
| Sales of short-term investments | 369.3 | 596.4 | 588.0 | 535.6 | 221.7 | 238.8 | 353.5 | 399.1 |
| Other cash from investing | -215.0 | -103.3 | -322.2 | -62.4 | -165.1 | -422.1 | -506.3 | -454.7 |
| Cash from investing | -8.4 | -583.3 | -643.7 | 134.0 | -143.6 | -427.0 | -573.5 | -452.9 |
| |
| Cash dividends paid | -33.6 | -32.4 | -31.4 | -30.6 | -29.6 | -27.6 | -26.6 | -25.4 |
| Repurchase of common stock, net | -15.4 | -23.8 | -9.4 | -29.9 | -2.4 | | -1.2 | -3.5 |
| Option exercises | 2.4 | -0.8 | -0.3 | -1.0 | 2.5 | 1.7 | 1.1 | 3.0 |
| Other cash from financing | -28.8 | 192.1 | 833.3 | -118.5 | 67.0 | 390.5 | 517.2 | 404.1 |
| Cash from financing | -80.2 | 136.8 | 792.8 | -178.0 | 32.4 | 361.2 | 488.3 | 372.3 |
| |
| Free cash flow | 95.2 | 116.4 | 96.8 | 95.6 | 89.2 | 50.8 | 74.6 | 76.5 |
| Per share (diluted) | $6.61 | $7.95 | $6.57 | $6.38 | $5.89 | $3.37 | $4.99 | $5.14 |
| |
| Cash paid for interest | 21.0 | 16.9 | 30.3 | 51.5 | 40.7 | 26.4 | 23.5 | 21.8 |
| Cash paid for income taxes | 23.9 | 28.6 | 22.9 | 16.7 | 16.9 | 31.0 | 24.7 | 22.7 |