| In millions, except per share items | Sep-30-19 | Jun-30-19 | Mar-31-19 | Dec-31-18 | Sep-30-18 | Jun-30-18 | Mar-31-18 | Dec-31-17 |
| | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q | 10-Q |
| Revenue | | | | | | | | |
| Total revenue | 772.0 | 803.2 | 705.2 | 767.8 | 749.9 | 731.3 | 653.4 | 649.3 |
| Total revenue growth | 2.9% | 9.8% | 7.9% | 18.3% | 2.6% | 0.3% | 3.9% | -10.0% |
| Cost of revenue | | | | | | | | |
| Total cost of revenue | 596.7 | 635.2 | 548.5 | 613.2 | 590.9 | 580.9 | 513.8 | 511.7 |
| Gross margin | 175.3 | 168.0 | 156.7 | 154.6 | 159.0 | 150.4 | 139.6 | 137.6 |
| Gross margin | 22.7% | 20.9% | 22.2% | 20.1% | 21.2% | 20.6% | 21.4% | 21.2% |
| |
| Operating expenses | | | | | | | | |
| Selling expenses | 74.8 | 80.5 | 79.8 | 75.2 | 70.8 | 72.2 | 70.5 | 65.2 |
| General and administrative expenses | 30.7 | 35.8 | 30.3 | 27.4 | 29.7 | 24.0 | 26.1 | 26.0 |
| Transaction costs | 3.5 | 1.8 | 4.7 | 9.0 | 5.5 | 4.5 | 4.2 | 1.7 |
| Depreciation and amortization | 21.8 | 21.7 | 21.7 | 21.5 | 21.5 | 21.4 | 20.6 | 21.1 |
| Total operating expenses | 130.8 | 139.8 | 136.5 | 133.1 | 127.5 | 122.1 | 121.4 | 114.0 |
| Operating income | 44.5 | 28.2 | 20.2 | 21.5 | 31.5 | 28.3 | 18.2 | 23.6 |
| Operating margin | 5.8% | 3.5% | 2.9% | 2.8% | 4.2% | 3.9% | 2.8% | 3.6% |
| |
| Interest and other (income) expense | | | | | | | | |
| Interest expense | -11.6 | -12.5 | -13.1 | -13.1 | -11.2 | -10.7 | -10.1 | -12.7 |
| Loss on extinguishment of debt | 0.2 | 0.6 | 0.5 | 0.5 | 0.5 | | 13.3 | 0.7 |
| Other (income) expense, net | -0.2 | -0.3 | -0.3 | -0.2 | -0.1 | | -0.1 | -0.1 |
| Total interest and other (income) expense | 11.6 | 12.8 | 13.3 | 13.4 | 11.6 | 10.7 | 23.3 | 13.3 |
| Income before income taxes | 32.9 | 15.4 | 6.9 | 8.1 | 19.9 | 17.6 | -5.1 | 10.3 |
| Income tax expense | 8.9 | 5.6 | 1.9 | 2.5 | 5.2 | 3.4 | -5.6 | -89.1 |
| Net income | 24.0 | 9.8 | 5.0 | 5.6 | 14.7 | 14.2 | 0.5 | 99.4 |
| |
| Earnings per share: | | | | | | | | |
| Basic (in dollars per share) | $0.29 | $0.12 | $0.06 | $0.07 | $0.16 | $0.15 | $0.01 | $1.08 |
| Diluted (in dollars per share) | $0.28 | $0.12 | $0.06 | $0.07 | $0.15 | $0.15 | $0.01 | $1.03 |
| |
| Weighted-average common shares outstanding: | | | | | | | | |
| Basic (in shares) | 83.1 | 84.6 | 82.6 | 82.3 | 90.8 | 91.9 | 92.0 | 91.7 |
| Diluted (in shares) | 86.7 | 88.4 | 86.5 | 85.8 | 95.0 | 96.2 | 96.9 | 96.7 |
| |
| Common stock, dividends declared (in dollars per share) | $0.04 | $0.04 | $0.04 | $0.04 | $0.00 | | | |