| In millions, except per share items | Jun-30-21 | Mar-31-21 | Dec-31-20 | Sep-30-20 | Jun-30-20 | Mar-31-20 | Dec-31-19 | Sep-30-19 |
| | 10-Q | 10-Q | 10-K | 10-Q | 10-Q | 10-Q | 10-K | 10-Q |
| Cash flows from operating activities: | | | | | | | | |
| Net loss | -40.2 | -44.2 | -45.1 | -42.1 | -52.7 | -43.7 | -49.5 | 43.6 |
| Adjustments to reconcile net loss income to net cash used in operating activities: | | | | | | | | |
| Stock-based compensation | 8.2 | 7.9 | 7.4 | 7.1 | 7.2 | 8.0 | 8.6 | 9.1 |
| Amortization of intangible asset | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | 5.4 |
| Change in fair value of warrant liability | -5.9 | 2.2 | 0.8 | -1.5 | 2.3 | -13.8 | -11.4 | -10.0 |
| Amortization of debt discounts and debt issuance costs | 1.3 | 1.0 | 0.7 | 0.4 | | | | |
| Accretion of discounts on marketable securities | | | | | -0.4 | -0.4 | -0.4 | |
| Depreciation | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 | 0.1 |
| Changes in operating assets and liabilities: | | | | | | | | |
| Accounts receivable | -0.7 | -0.2 | -0.5 | 0.5 | 3.5 | 1.2 | -0.7 | -0.8 |
| Inventory | 0.2 | 0.1 | 1.1 | 0.9 | 1.5 | 2.4 | 1.6 | 3.5 |
| Prepaid expenses and other current assets | 0.2 | -0.8 | 0.2 | 0.7 | 0.5 | 1.6 | 3.1 | 0.3 |
| Other assets | -0.1 | -0.1 | 0.1 | 0.4 | 0.7 | 0.7 | -0.8 | -1.0 |
| Accounts payable | -1.3 | 0.5 | -1.8 | -0.4 | 0.5 | 3.6 | 2.2 | -1.3 |
| Accrued and other liabilities | -0.8 | -7.7 | -6.0 | -5.7 | -3.9 | -6.4 | -2.6 | -12.3 |
| Net cash used in operating activities | -34.0 | -36.3 | -38.1 | -34.7 | -35.7 | -41.7 | -44.8 | -75.9 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Sales and maturities of marketable securities | | | | | 21.1 | 14.8 | | |
| Purchases of property and equipment | | 0.0 | | 0.0 | | | -0.1 | -0.1 |
| Net cash (used in) provided by investing activities | | 6.3 | | 40.8 | 28.3 | -5.9 | -20.8 | 118.9 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Payments related to tax withholding for net-share settled equity awards | -0.8 | -0.7 | | -0.4 | -0.4 | -0.1 | | -0.1 |
| Proceeds from long-term debt, net | | | 19.3 | 9.3 | 9.5 | | | |
| Proceeds from exercise of stock options | | 0.1 | | | | | | 0.2 |
| Net cash (used in) provided by financing activities | 37.9 | 47.4 | 47.5 | 36.8 | 9.1 | -0.1 | | -71.4 |
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| Supplemental disclosures of cash flow information: Cash paid during the year for: | | | | | | | | |
| Interest | 1.5 | 1.1 | 0.6 | 0.4 | 0.1 | | | |
| Income taxes other, net of refunds | | 2.0 | 0.7 | 0.7 | 0.5 | | | |