| In millions, except per share items | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-05-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 | Dec-31-13 |
| | 10-K | 10-K | 10-K | 8-K | 10-K | 10-K | 10-K | 10-K |
| Net sales | 521.9 | 538.2 | 519.5 | | 401.9 | 269.3 | 261.6 | 219.4 |
| Net sales growth | -3.0% | 3.6% | 29.3% | | 49.2% | 3.0% | 19.3% | -17.0% |
| Cost of sales | 338.6 | 352.4 | 350.5 | | 274.3 | | | |
| Gross profit | 183.4 | 185.9 | 169.0 | | 127.6 | 101.7 | 83.3 | 87.1 |
| Gross margin | 35.1% | 34.5% | 32.5% | | 31.8% | 37.8% | 31.9% | 39.7% |
| |
| Operating expenses: | | | | | | | | |
| Advertising and marketing | 19.2 | 12.0 | 11.1 | 11.1 | 12.4 | 10.4 | 7.5 | 9.0 |
| Selling, general, and administrative | 154.2 | 120.6 | 116.5 | 116.5 | 108.7 | 67.2 | 56.7 | 55.3 |
| Transaction costs | 1.9 | 1.7 | 0.7 | 0.7 | 2.6 | 0.2 | | |
| Amortization of intangible assets | 17.0 | 11.9 | 12.0 | | 13.4 | 8.5 | 9.7 | 9.6 |
| Total operating expenses | 173.2 | 134.2 | 255.5 | 119.2 | 149.0 | 75.8 | 66.4 | 76.2 |
| Income (loss) from operations | 10.2 | 51.7 | 44.7 | | -21.4 | 25.9 | 17.0 | 10.9 |
| Operating margin | 2.0% | 9.6% | 8.6% | | -5.3% | 9.6% | 6.5% | 5.0% |
| |
| Other income (expense): | | | | | | | | |
| Interest expense | -4.9 | -1.7 | -2.1 | -2.1 | -1.9 | -0.1 | -0.2 | -0.6 |
| Other income (expense) | 0.6 | -0.5 | 0.7 | -0.7 | -0.3 | -0.1 | 0.1 | 0.1 |
| Total other expense | -4.3 | -2.2 | -1.4 | -0.7 | -2.2 | -0.2 | 0.1 | -2.5 |
| Income (loss) before provision for income taxes | 5.9 | 49.5 | 43.4 | | -23.6 | 25.7 | 16.9 | 8.5 |
| Income tax (provision) benefit | 8.1 | -10.3 | -28.3 | | 8.0 | -10.1 | -6.5 | -3.7 |
| Net income (loss) | 13.9 | 39.2 | | | | | 10.5 | 4.8 |
| |
| Earnings (loss) per share attributable to stockholders: | | | | | | | | |
| Basic earnings (loss) per share (in usd per share) | $0.48 | $1.40 | $0.54 | $0.54 | ($0.56) | $0.54 | $0.35 | $0.16 |
| Diluted earnings (loss) per share (in usd per share) | $0.48 | $1.38 | $0.53 | $0.53 | ($0.56) | $0.54 | $0.34 | $0.15 |