| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K/A | 10-K/A | 10-K/A | 10-K | 10-K/A |
| Cash flows from operating activities: | | | | | | | | |
| Net loss | -24.0 | -66.1 | -32.9 | -33.0 | -10.9 | -1.1 | -1.1 | -0.7 |
| Adjustments to reconcile net loss to net cash provided by operating activities: | | | | | | | | |
| Depreciation and amortization | 2.5 | 0.7 | 3.1 | 2.9 | 0.3 | 0.2 | 0.2 | 0.2 |
| Stock-based compensation | 7.8 | 1.1 | 1.6 | 4.7 | 1.8 | 0.5 | 0.2 | 0.2 |
| Impairment of cryptocurrencies | 0.4 | 0.0 | | | | | | |
| Realized losses on sale of marketable securities | -21.2 | -0.1 | 0.1 | 0.2 | | | | |
| Unrealized gains on equity securities | | | | | | | | |
| Income from cash held in trust | | | | | | | | |
| Loss from investment in unconsolidated entity | | | | | | | | |
| Loss on remeasurement of investment in unconsolidated entity | | | | | | | | |
| Provision for loan losses | | | | | | | | |
| Change in the fair value of warrant liability | | | | | | | | |
| Changes in operating assets and liabilities: | | | | | | | | |
| Marketable equity securities | | | | | | | | |
| Accounts receivable | -1.4 | -0.6 | -0.5 | 2.8 | 0.3 | -0.3 | 0.3 | 0.6 |
| Inventories | -2.0 | 0.2 | 0.8 | 0.0 | 0.1 | 0.2 | 0.1 | 0.0 |
| Prepaid expenses and other current assets | -5.5 | -1.6 | -1.0 | 1.2 | -0.8 | -0.1 | 0.0 | 0.0 |
| Other assets | -1.5 | -0.1 | -0.2 | -0.2 | -0.1 | 0.0 | | |
| Net cash provided by operating activities | -61.7 | -11.2 | -10.2 | -10.4 | -4.1 | -0.4 | -0.5 | 0.7 |
| |
| Cash flows from investing activities: | | | | | | | | |
| Purchase of property and equipment | -152.0 | -0.6 | -0.2 | -8.9 | -0.4 | -0.1 | -0.3 | -0.1 |
| Purchase of marketable equity securities | -2.8 | -1.4 | | -0.9 | -1.5 | | | |
| Sales of marketable equity securities | 4.1 | 0.4 | 0.6 | 2.2 | 0.1 | | | |
| Investments in equity securities | -17.6 | -0.2 | | | | | | |
| Proceeds from the sale of fixed assets | | | | | 0.0 | | | |
| Net cash used in investing activities | -333.5 | -7.8 | -2.9 | -20.6 | -8.7 | -1.0 | -0.3 | -0.1 |
| |
| Cash flows from financing activities: | | | | | | | | |
| Proceeds from sales of preferred stock | | | 0.1 | 0.0 | | | | |
| Financing cost in connection with sales of preferred stock | -5.9 | -1.7 | -1.4 | -2.1 | -0.4 | | | |
| Payments on notes payable | -2.5 | -8.8 | -2.1 | -12.1 | -0.2 | | | |
| Payments of preferred dividends | 0.0 | 0.0 | 0.0 | | 0.0 | | | |
| Purchase of treasury stock | -13.2 | | | -0.1 | | | | -0.1 |
| Net cash provided by financing activities | 397.9 | 37.3 | 12.9 | 30.5 | 13.2 | 1.3 | | -0.1 |
| |
| Supplemental disclosures of cash flow information: | | | | | | | | |
| Cash paid during the period for interest | 0.3 | 0.7 | 1.9 | 0.8 | 0.3 | | | |
| Non-cash investing and financing activities: | | | | | | | | |