| In millions, except per share items | Sep-30-20 | Jun-30-20 | Mar-31-20 | Dec-31-19 | Sep-30-19 | Jun-30-19 | Mar-31-19 | Dec-31-18 |
| | 10-Q | 10-Q | 10-Q | 8-K | 10-Q | 10-Q | 10-Q | 10-K |
| Net sales | 473.4 | 504.5 | 534.2 | 521.9 | 498.5 | 493.1 | 504.9 | 538.2 |
| Net sales growth | -5.0% | 2.3% | 5.8% | -3.0% | -9.1% | -9.0% | -6.3% | 3.6% |
| Cost of sales | 240.8 | 255.9 | 271.1 | | 324.2 | 320.9 | 332.8 | 352.4 |
| Gross profit | 110.2 | 126.2 | 140.6 | 183.4 | 174.4 | 172.2 | 172.1 | 185.9 |
| Gross margin | 23.3% | 25.0% | 26.3% | 35.1% | 35.0% | 34.9% | 34.1% | 34.5% |
| |
| Operating expenses: | | | | | | | | |
| Advertising and marketing | 16.0 | 16.9 | 19.0 | 19.2 | 16.9 | 15.9 | 14.0 | 12.0 |
| Selling, general, and administrative | 131.1 | 142.1 | 155.0 | 154.1 | 146.9 | 139.2 | 129.9 | 120.6 |
| Transaction costs | 1.2 | 1.7 | 2.0 | 1.9 | 2.2 | 2.3 | 1.9 | 1.7 |
| Impairment of goodwill | | | 18.6 | | | | | |
| Loss on disposal of intangible assets and equipment | | | 3.8 | | 0.1 | 0.0 | 0.0 | |
| Amortization of intangible assets | 14.3 | 14.8 | 16.1 | 17.0 | 16.5 | 15.4 | 13.6 | 11.9 |
| Total operating expenses | 168.9 | 181.1 | 195.5 | 173.2 | 165.7 | 156.9 | 145.4 | 134.2 |
| Income (loss) from operations | -58.7 | -54.9 | -54.9 | 10.2 | 8.7 | 15.3 | 26.7 | 51.7 |
| Operating margin | -12.4% | -10.9% | -10.3% | 2.0% | 1.7% | 3.1% | 5.3% | 9.6% |
| |
| Other income (expense): | | | | | | | | |
| Interest expense | -5.0 | -5.3 | -5.4 | -4.9 | -3.9 | -3.0 | -2.2 | -1.7 |
| Other income (expense) | 0.7 | -0.6 | 0.4 | -0.1 | 0.1 | 0.4 | -1.5 | -0.5 |
| Total other expense | -1.8 | -4.3 | -2.3 | -2.3 | -2.6 | -1.4 | -3.7 | -1.7 |
| Income (loss) before provision for income taxes | -82.8 | -80.7 | -79.9 | | 4.9 | 12.7 | 23.0 | 49.5 |
| Income tax (provision) benefit | 14.5 | 14.9 | 12.1 | 8.1 | -1.7 | -3.5 | -5.3 | -10.3 |
| Net income (loss) | -47.7 | -45.2 | -47.2 | 13.9 | 3.2 | 9.2 | 17.7 | 39.2 |
| |
| Earnings (loss) per share attributable to stockholders: | | | | | | | | |
| Basic earnings (loss) per share (in usd per share) | ($1.58) | ($1.49) | ($1.56) | $0.48 | $0.14 | $0.36 | $0.65 | $1.40 |
| Diluted earnings (loss) per share (in usd per share) | ($1.59) | ($1.50) | ($1.57) | $0.47 | $0.13 | $0.34 | $0.63 | $1.37 |