| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities | | | | | | | | |
| Net loss | -147.6 | -148.4 | -99.3 | -122.4 | -85.3 | -60.1 | -30.3 | |
| |
| Adjustments to reconcile net loss to net cash used in operating activities | | | | | | | | |
| Stock-based compensation | 20.6 | 22.3 | 18.8 | 16.4 | 10.2 | 3.4 | 1.4 | 0.4 |
| Accretion of discount on available for sale securities | -0.5 | | | | | | | |
| Depreciation and amortization | 0.5 | 0.5 | 0.6 | 0.4 | 0.2 | 0.1 | 0.1 | 0.0 |
| Amortization of debt issuance costs | 2.2 | 1.1 | 0.6 | | | | | |
| Non-cash interest expense | 0.9 | 0.6 | 0.2 | | | | | |
| Non-cash equity interest, net | 0.5 | 0.4 | -0.9 | | | | | |
| |
| Change in operating assets and liabilities | | | | | | | | |
| Accounts receivable | -5.4 | -5.5 | -0.2 | | | | | |
| Inventories | -12.7 | -3.5 | | | | | | |
| Prepaid expenses and other assets | 7.2 | -3.4 | -5.5 | -0.2 | 0.1 | -0.3 | 0.2 | -0.8 |
| Accounts payable | 4.4 | -0.7 | -0.2 | 0.2 | -1.0 | 1.6 | 1.5 | |
| Accrued expenses and other liabilities | 1.2 | 3.3 | 1.7 | 6.0 | 1.4 | 4.7 | 1.9 | |
| Deferred revenue | 0.0 | 0.8 | 0.2 | | | | | |
| Net cash used in operating activities | -128.6 | -132.1 | -83.7 | -99.6 | -74.3 | -50.5 | -25.1 | |
| |
| Cash flows from investing activities | | | | | | | | |
| Purchases of marketable securities | -65.0 | | | | | | | |
| Maturities of marketable securities | 15.0 | | | | | | | |
| Purchases of property and equipment | -0.5 | | | -2.7 | -0.7 | -0.3 | -0.3 | -0.1 |
| Net cash provided by/(used in) investing activities | -50.5 | | 0.2 | -2.7 | -0.7 | -0.3 | -0.3 | |
| |
| Cash flows from financing activities | | | | | | | | |
| Proceeds from stock options exercised | 0.2 | 5.8 | 2.3 | 2.7 | 1.8 | 0.2 | 0.0 | 0.1 |
| Payment of public offering costs | 0.0 | -0.1 | | | -0.9 | -1.4 | -0.2 | -0.1 |
| Net cash (used in)/provided by financing activities | 52.5 | 145.9 | 21.7 | 2.7 | 340.5 | 107.3 | 49.8 | |
| Net change in cash, cash equivalents and restricted cash | -126.7 | 13.8 | -61.9 | -99.6 | 265.5 | | | |
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| Cash, cash equivalents and restricted cash | | | | | | | | |
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| Supplemental disclosure of cash flow information | | | | | | | | |
| Cash paid for interest | 7.9 | 2.9 | 1.0 | | | | | |
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| Non-cash operating, investing and financing activities | | | | | | | | |
| Upfront project costs and other current assets in accounts payable and accrued expenses | 0.0 | | 0.1 | 0.0 | 0.1 | | | |