| 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 | 356.9 | 171.5 | 73.6 | 107.2 | 201.7 | 135.2 | 74.8 | 70.9 |
| Depreciation and amortization | 46.0 | 37.5 | 31.2 | 28.5 | 83.9 | 62.2 | 44.7 | 37.0 |
| Stock-based compensation | | | | | 13.5 | 9.9 | 8.5 | 7.8 |
| Tax benefit from stock-based compensation | | | | | | | -0.7 | -0.1 |
| Deferred taxes | -4.4 | -4.0 | 7.5 | 1.8 | 39.5 | -41.4 | 13.8 | 16.4 |
| Change in working capital [+] | 14.8 | 0.9 | 0.7 | 0.0 | 23.4 | -37.8 | -38.8 | 39.7 |
| Accounts receivable | | | | | -31.5 | -84.8 | -87.6 | 36.4 |
| Other current assets | | | | | -1.8 | -7.5 | 1.1 | -3.4 |
| Accounts payable | | | | | 5.5 | 59.0 | 35.7 | -25.7 |
| Accrued expenses | | | | | 43.5 | -2.9 | 9.2 | 20.5 |
| Other | 14.8 | 0.9 | 0.7 | 0.0 | 7.6 | -1.6 | 2.8 | 11.9 |
| Other operating activities | 44.9 | 47.0 | 62.0 | 117.0 | -151.2 | -2.8 | 0.2 | -0.1 |
| Cash from operations | 458.2 | 252.8 | 175.0 | 254.5 | 210.8 | 125.2 | 102.5 | 171.7 |
| |
| Capital expenditures [+] | 219.1 | 133.0 | 115.3 | 94.8 | -199.8 | -74.5 | -107.4 | -83.0 |
| Purchases of property and equipment | 219.1 | 133.0 | 115.3 | 94.8 | -199.8 | -74.5 | -107.4 | -83.0 |
| Sales of property and equipment | 42.9 | 45.2 | 3.3 | 10.0 | 11.0 | 5.3 | 2.1 | 2.3 |
| Acquisitions | 102.7 | 122.4 | 84.8 | 0.7 | -248.7 | -165.9 | | |
| Other cash from investing | -643.6 | -510.6 | -400.3 | -171.7 | 228.0 | | | |
| Cash from investing | -278.9 | -210.1 | -196.9 | -66.1 | -209.5 | -235.1 | -105.3 | -80.7 |
| |
| Repurchase of common stock, net | 75.0 | | | -25.0 | | | -100.0 | -28.8 |
| Financing costs | | | | | | -1.4 | | |
| Other cash from financing | -127.5 | -7.4 | -22.3 | -56.1 | 31.6 | 9.7 | 22.6 | 36.0 |
| Cash from financing | -52.5 | -7.4 | -22.3 | -81.1 | 31.6 | 11.1 | -77.4 | 7.1 |
| |
| Free cash flow | 677.3 | 385.8 | 290.3 | 349.4 | 11.0 | 50.7 | -4.9 | 88.7 |
| Per share (diluted) | $20.18 | $11.38 | $8.65 | $10.43 | $0.33 | $1.52 | ($0.15) | $2.46 |
| |
| Cash paid for interest | 8.0 | 7.6 | 9.5 | 11.3 | 9.7 | 6.2 | 3.7 | 3.0 |