| In millions, except per share items | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Net income | 56.4 | 64.1 | 48.9 | 32.2 | 62.4 | 68.6 | 57.8 | 37.3 |
| Depreciation and amortization [+] | 65.6 | 68.8 | 73.4 | 77.6 | 69.0 | 58.7 | 60.7 | 58.0 |
| Depreciation | 51.6 | 52.1 | 57.8 | 56.5 | 49.6 | 44.5 | 46.3 | 43.1 |
| Amortization of intangible assets | 14.0 | 16.6 | 15.5 | 21.1 | 19.4 | 14.2 | 14.4 | 14.9 |
| Asset impairment charges | 41.6 | 1.7 | 9.4 | 5.4 | | | | |
| Stock-based compensation | 10.7 | 7.4 | 7.5 | 7.6 | 10.8 | 8.7 | 6.4 | 4.9 |
| Deferred taxes | -5.6 | 0.3 | -1.5 | 7.9 | 2.3 | 2.5 | 4.9 | -0.4 |
| Change in working capital [+] | 10.5 | -33.1 | -24.4 | 13.8 | -11.1 | -13.0 | -27.4 | -18.4 |
| Accounts receivable | -9.3 | -40.2 | -8.2 | -10.2 | -32.9 | 2.5 | -40.3 | -22.1 |
| Accounts payable | -3.6 | 2.1 | -1.6 | 7.3 | -2.9 | -0.1 | 2.0 | -1.3 |
| Deferred revenues | | | | | | -2.6 | 2.1 | 2.8 |
| Income taxes | -2.1 | 0.8 | 1.5 | -1.7 | 6.0 | -6.3 | 2.6 | 0.8 |
| Other | 25.5 | 4.3 | -16.2 | 18.4 | 18.8 | -6.5 | 6.1 | 1.4 |
| Other operating activities | -3.5 | -7.9 | -4.2 | -9.8 | -0.6 | -4.6 | | |
| Cash from operations | 175.7 | 101.3 | 109.1 | 134.8 | 132.8 | 120.9 | 94.3 | 86.2 |
| |
| Capital expenditures [+] | -52.7 | -38.7 | -46.9 | -63.3 | -78.3 | -49.7 | -44.7 | -59.2 |
| Purchases of property and equipment | -52.7 | -38.7 | -46.9 | -63.3 | -78.3 | -49.7 | -44.7 | -59.2 |
| Sales of property and equipment | | | | | | | 3.6 | 0.4 |
| Purchases of intangible assets | | -0.3 | -8.2 | -4.8 | 0.0 | | | |
| Acquisitions | -88.5 | -3.1 | -78.4 | -9.1 | -205.3 | -9.4 | | |
| Other cash from investing | 1.8 | 1.5 | -3.5 | -10.0 | 10.9 | 2.1 | | |
| Cash from investing | -139.4 | -40.6 | -136.9 | -87.3 | -272.8 | -57.0 | -40.9 | -59.4 |
| |
| Repurchase of common stock, net | -52.2 | -30.3 | | | -11.1 | -20.9 | -12.6 | -5.4 |
| Financing costs | | -1.1 | | | | -1.0 | | |
| Other cash from financing | -11.8 | -34.4 | -176.7 | -1.5 | 190.9 | -9.9 | -23.2 | 7.0 |
| Cash from financing | -64.0 | -63.6 | -176.7 | -1.5 | 179.7 | -29.8 | -35.8 | 1.6 |
| |
| Free cash flow | 123.1 | 62.6 | 62.2 | 71.4 | 54.5 | 71.2 | 49.6 | 27.0 |
| Per share (diluted) | $3.04 | $1.50 | $1.47 | $1.70 | $1.29 | $1.68 | $1.16 | $0.63 |
| |
| Cash paid for interest | 1.4 | 3.5 | 3.9 | 6.7 | 4.0 | 1.5 | 1.7 | 2.1 |