| In millions, except per share items | Dec-31-21 | Jun-30-21 | Mar-31-21 | Dec-31-20 | Sep-30-20 | Jun-30-20 | Mar-31-20 | Dec-31-19 |
| | 8-K | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K |
| Net sales | 470.7 | 492.8 | 368.1 | 379.9 | 457.6 | 426.2 | 330.9 | 363.1 |
| Net sales growth | 23.9% | 15.6% | 11.3% | 4.6% | -1.5% | 3.9% | 13.4% | 7.1% |
| Cost of goods sold | | 373.2 | 285.9 | 293.8 | 331.3 | 320.6 | 272.1 | 296.6 |
| Gross profit | 102.0 | 119.6 | 82.3 | 86.1 | 126.3 | 105.6 | 58.7 | 66.6 |
| Gross margin | 21.7% | 24.3% | 22.3% | 22.7% | 27.6% | 24.8% | 17.8% | 18.3% |
| Selling, general & administrative expenses | 53.0 | 56.3 | 55.0 | 57.2 | 57.1 | 53.3 | 54.2 | 56.5 |
| Impairment and exit charges | -0.2 | -0.1 | -0.4 | 0.0 | -1.4 | -0.3 | -0.8 | -2.2 |
| Other operating income, net | -0.9 | 0.4 | 12.1 | 1.9 | 0.2 | -1.0 | 0.3 | 0.1 |
| Operating Expenses | 52.1 | 112.6 | 110.5 | 278.6 | 58.2 | 54.5 | 54.7 | -107.7 |
| Income from operations | 49.7 | 63.6 | 38.9 | 30.7 | 68.1 | 51.0 | 4.0 | 8.0 |
| Operating margin | 10.6% | 12.9% | 10.6% | 8.1% | 14.9% | 12.0% | 1.2% | 2.2% |
| |
| Other income (expenses) | | | | | | | | |
| Interest expense | -18.6 | -19.1 | -18.3 | -19.4 | -20.1 | -19.7 | -20.7 | -21.3 |
| Gain (loss) on extinguishment of debt | | | | -0.8 | -11.5 | 0.1 | -0.1 | 1.3 |
| Earnings from equity method investee | 3.1 | 3.6 | 2.6 | 3.1 | 2.3 | 3.1 | 2.8 | 1.5 |
| Income (loss) before income taxes | | 48.1 | 23.2 | 13.6 | 38.8 | 34.6 | -14.0 | -10.4 |
| Income tax (expense) benefit | -8.4 | -12.1 | -4.5 | 9.0 | -9.9 | -7.5 | -0.1 | 2.8 |
| Net income (loss) | 25.8 | 36.1 | 18.7 | 22.6 | 28.8 | 27.1 | -14.1 | -7.7 |
| |
| Earnings (loss) per share: | | | | | | | | |
| Basic (in usd per share) | | $0.54 | $0.28 | $0.35 | $0.44 | $0.42 | ($0.22) | ($0.12) |
| Diluted (in usd per share) | | $0.52 | $0.27 | $0.32 | $0.42 | $0.40 | ($0.22) | ($0.12) |
| |
| Weighted average shares of common stock outstanding: | | | | | | | | |
| Basic (in shares) | 69.7 | 66.7 | 66.2 | 65.3 | 65.3 | 65.1 | 64.8 | 64.2 |
| Diluted (in shares) | 69.7 | 69.5 | 69.4 | 68.2 | 68.7 | 67.2 | 64.8 | 64.2 |