| 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 | 28.3 | 25.9 | 16.1 | 15.3 | 11.2 | 7.2 | 7.3 | 6.3 |
| Depreciation and amortization [+] | | 2.0 | 2.2 | 2.3 | 2.5 | 1.6 | 1.5 | 1.4 |
| Depreciation | 1.6 | 1.5 | 1.6 | 1.6 | 1.7 | 1.6 | 1.5 | 1.4 |
| Amortization of intangible assets | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 | | | |
| Stock-based compensation | 0.3 | 0.8 | 0.4 | 0.3 | 0.5 | 0.5 | 0.5 | 0.3 |
| Deferred taxes | 0.0 | 1.2 | -2.8 | -0.7 | -0.3 | 1.9 | -0.6 | -0.8 |
| Change in working capital | | 0.1 | -3.1 | 0.6 | 1.3 | -0.2 | 0.7 | 1.6 |
| Other | | 0.1 | -3.1 | 0.6 | 1.3 | -0.2 | 0.7 | 1.6 |
| Other operating activities | -22.1 | 3.3 | 15.2 | -2.1 | 4.2 | -0.9 | 3.5 | 3.6 |
| Cash from operations | 6.5 | 33.2 | 28.1 | 15.7 | 19.4 | 10.1 | 12.9 | 12.5 |
| |
| Capital expenditures | 0.0 | -2.6 | -0.3 | -0.8 | -1.8 | -0.8 | -4.0 | -3.5 |
| Purchases of property and equipment | | -2.6 | -0.3 | -0.8 | -1.8 | -0.8 | -4.0 | -3.5 |
| Purchases of short-term investments, net | -23.4 | -261.2 | -32.8 | 24.4 | -5.3 | 7.6 | 5.2 | 24.8 |
| Purchases of short-term investments | -78.4 | -327.7 | -149.4 | -50.0 | -66.1 | -26.3 | -31.3 | -2.1 |
| Sales of short-term investments | 55.1 | 66.5 | 116.7 | 74.3 | 60.8 | 33.8 | 36.5 | 26.8 |
| Other cash from investing | 23.4 | 7.8 | -159.7 | -120.0 | -29.1 | -76.3 | -196.3 | -95.9 |
| Cash from investing | 0.0 | -256.0 | -192.7 | -96.5 | -36.2 | -69.6 | -195.1 | -74.6 |
| |
| Cash dividends paid | -3.8 | -3.2 | -2.8 | -2.7 | -2.2 | -1.8 | -1.8 | -1.9 |
| Repurchase of common stock, net | -3.6 | -7.0 | -0.3 | 10.6 | -0.1 | | -0.9 | -1.8 |
| Option exercises | | | | | | 0.2 | | |
| Other cash from financing | 0.1 | 295.6 | 212.4 | 72.3 | 36.6 | 65.6 | 185.0 | 55.6 |
| Cash from financing | -7.2 | 285.4 | 209.2 | 80.2 | 34.4 | 63.6 | 182.3 | 51.9 |
| |
| Free cash flow | 6.5 | 30.6 | 27.8 | 14.9 | 17.6 | 9.3 | 8.9 | 9.0 |
| Per share (diluted) | | $5.27 | $4.72 | $2.68 | $3.18 | $2.01 | $1.94 | $1.93 |
| |
| Cash paid for interest | 8.9 | 4.4 | 9.1 | 18.9 | 14.2 | 10.0 | 8.0 | 6.8 |
| Cash paid for income taxes | 9.2 | 8.1 | 7.1 | 6.5 | 3.5 | 7.5 | | |