| 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 | 38.1 | 43.5 | 29.4 | 25.7 | 24.9 | 18.5 | 19.6 | 17.7 |
| Depreciation and amortization [+] | 3.1 | 2.7 | 2.9 | 3.1 | 2.3 | 2.0 | 1.7 | 1.6 |
| Amortization of intangible assets | 0.4 | 0.5 | 0.6 | 0.7 | 0.9 | 1.0 | 1.2 | 1.2 |
| Stock-based compensation | 0.5 | 0.5 | 0.6 | 0.6 | 0.3 | 0.2 | 0.1 | 0.1 |
| Deferred taxes | 0.6 | 0.5 | -1.8 | 0.4 | -0.7 | 1.7 | -1.4 | -0.8 |
| Change in working capital | -2.7 | 1.3 | 11.7 | 2.6 | -1.2 | -2.5 | -3.0 | -1.1 |
| Other | -2.7 | 1.3 | 11.7 | 2.6 | -1.2 | -2.5 | -3.0 | -1.1 |
| Other operating activities | 2.8 | -7.7 | -5.6 | 4.7 | 7.0 | 8.8 | 11.2 | 11.7 |
| Cash from operations | 42.4 | 40.8 | 37.2 | 37.1 | 32.6 | 28.6 | 28.1 | 29.2 |
| |
| Capital expenditures [+] | -7.8 | -4.9 | -2.3 | -5.6 | -4.1 | -6.2 | -6.8 | -4.4 |
| Purchases of property and equipment | -7.8 | -4.9 | -2.3 | -5.6 | -4.1 | -6.2 | -6.8 | -4.4 |
| Sales of property and equipment | 0.2 | 0.1 | 0.4 | | 0.4 | | | 0.0 |
| Purchases of short-term investments, net | -65.9 | -231.3 | -22.1 | -66.3 | -0.7 | -16.4 | 20.1 | 52.4 |
| Purchases of short-term investments | -112.8 | -291.7 | -107.2 | -124.5 | -32.7 | -73.5 | -62.0 | -90.4 |
| Sales of short-term investments | 46.9 | 60.4 | 85.0 | 58.2 | 32.0 | 57.0 | 82.1 | 142.8 |
| Other cash from investing | -394.3 | -204.0 | -177.2 | -112.8 | -130.4 | -161.9 | -199.7 | -137.4 |
| Cash from investing | -467.8 | -440.1 | -201.2 | -184.7 | -134.8 | -184.6 | -186.4 | -89.4 |
| |
| Cash dividends paid | -11.3 | -10.8 | -10.5 | -10.1 | -9.7 | -9.3 | -9.2 | |
| Repurchase of common stock, net | -1.3 | -2.4 | -6.9 | -0.6 | | | -0.6 | -5.2 |
| Other cash from financing | 196.0 | 464.2 | 378.5 | 156.9 | 107.0 | 162.8 | 175.1 | 66.9 |
| Cash from financing | 183.4 | 451.1 | 361.1 | 146.2 | 97.3 | 153.5 | 165.3 | 61.7 |
| |
| Free cash flow | 34.5 | 35.9 | 34.9 | 31.5 | 28.6 | 22.3 | 21.3 | 24.8 |
| Per share (diluted) | $4.79 | $4.96 | $4.75 | $4.25 | $3.86 | $3.02 | $2.88 | $3.29 |
| |
| Cash paid for interest | 15.1 | 9.8 | 14.9 | 17.8 | 12.6 | 8.7 | 7.3 | 6.8 |
| Cash paid for income taxes | 10.0 | 6.7 | 6.3 | 4.6 | 2.7 | 5.9 | 5.9 | 4.2 |