Entity Central Index Key Accrued of final payment fee. Document and entity information. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity Shell Company Entity Shell Company Entity Well-known Seasoned Issuer Entity Well Known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Accounts receivable, net Accounts Receivable Net Current Inventory Inventory Net Prepaid expenses and other current assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Other assets Other Assets Noncurrent Total Assets Assets Liabilities, Convertible Preferred Stock and Stockholders’ Equity (Deficit) Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued expenses Accrued Liabilities Current Deferred revenue Deferred Revenue Current Total current liabilities Liabilities Current Long-term debt, net Long Term Debt Noncurrent Deferred revenue Deferred Revenue Noncurrent Deferred rent Deferred Rent Credit Noncurrent Convertible preferred stock warrant liability Warrants And Rights Outstanding Total Liabilities Liabilities Commitments and contingencies (Note 15) Commitments And Contingencies Convertible preferred stock, $0.01 par value: 308,593 shares previously authorized prior to initial public offering, issuable in series; no and 304,958 shares issued and outstanding at December 31, 2018 and 2017, respectively; no liquidation value at December 31, 2018 Temporary Equity Carrying Amount Attributable To Parent Stockholders’ Equity (Deficit): Stockholders Equity [Abstract] Preferred stock, $0.01 par value: 10,000 shares authorized; no shares issued or outstanding at December 31, 2018 and 2017, respectively Preferred Stock Value Common stock, $0.01 par value: 200,000 shares authorized; 17,744 and 231 shares issued and outstanding at December 31, 2018 and 2017, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Total Stockholders' Equity (Deficit) Stockholders Equity Total Liabilities, Convertible Preferred Stock and Stockholders’ Equity (Deficit) Liabilities And Stockholders Equity Convertible preferred stock, par value Temporary Equity Par Or Stated Value Per Share Convertible preferred stock, authorized Temporary Equity Shares Authorized Convertible preferred stock, issued Temporary Equity Shares Issued Convertible preferred stock, outstanding Temporary Equity Shares Outstanding Liquidation preference Temporary Equity Liquidation Preference Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Income Statement [Abstract] Revenues Revenues Cost of revenues Cost Of Revenue Gross Profit Gross Profit Operating expenses: Operating Expenses [Abstract] Sales and marketing Selling And Marketing Expense General and administrative General And Administrative Expense Research and development Research And Development Expense Total operating expenses Operating Expenses Loss from Operations Operating Income Loss Other (income) expense: Other Nonoperating Income Expense [Abstract] Interest expense Interest Expense Other (income) expense, net Other Nonoperating Income Expense Net Loss Net Income Loss Net loss per share of common stock outstanding, basic and diluted Earnings Per Share Basic And Diluted Weighted-average common shares outstanding, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Issuance of series G convertible preferred stock issuance cost,Shares Issuance of series G convertible preferred stock issuance cost Adjustments to additional paid in capital, conversion of convertible preferred stock warrants into common stock warrants. Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid In Capital [Member] Accumulated Deficit Retained Earnings [Member] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Convertible Preferred Stock Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Beginning balance Beginning balance, shares Shares Outstanding Beginning balance, shares Beginning balance Conversion of convertible preferred stock into common stock Stock Issued During Period Value Conversion Of Convertible Securities Conversion of convertible preferred stock into common stock, shares Stock Issued During Period Shares Conversion Of Convertible Securities Conversion of convertible preferred stock warrants into common stock warrants Adjustments To Additional Paid In Capital Conversion Of Convertible Preferred Stock Warrants Into Common Stock Warrants Issuance of common stock initial public offering, net of issuance costs of $3,463 Stock Issued During Period Value New Issues Issuance of common stock initial public offering, net of issuance costs of $3,463, shares Stock Issued During Period Shares New Issues Issuance of Series G convertible preferred stock, net of issuance costs Issuance Of Series G Convertible Preferred Stock Issuance Cost Issuance of Series G convertible stock, net of issuance costs of $175, shares Issuance Of Series G Convertible Preferred Stock Issuance Cost Shares Issuance of restricted stock awards Stock Issued During Period Value Restricted Stock Award Gross Issuance of restricted stock awards, shares Stock Issued During Period Shares Restricted Stock Award Gross Exercises of stock options Stock Issued During Period Value Stock Options Exercised Exercises of stock options, shares Stock Issued During Period Shares Stock Options Exercised Share-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Net loss Ending balance Ending balance, shares Ending balance, shares Ending balance Stock issuance costs on issuance of series G convertible preferred stock. Issuance of series G convertible preferred stock issuance cost Stock Issuance Costs On Issuance Of Series G Convertible Preferred Stock Issuance costs on issuance of common stock. Issuance of common stock in initial public offering, issuance costs Issuance Costs On Issuance Of Common Stock Cost of rental units purchased by customers. Transfer of inventory to property and equipment. Value of convertible preferred stock warrant liability converted to additional paid in capital related to conversion of convertible preferred stock warrants into common stock warrants. Deferred public offering costs included in accounts payable and accrued expenses. Statement Of Cash Flows [Abstract] Cash Flows from Operating Activities: Net Cash Provided By Used In Operating Activities [Abstract] Net loss Profit Loss Adjustments to reconcile net loss to net cash used in operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Depreciation and amortization Depreciation Depletion And Amortization Share-based compensation Share Based Compensation Non-cash interest expense Amortization Of Financing Costs And Discounts Change in fair value of convertible preferred stock warrant liability Fair Value Adjustment Of Warrants Cost of rental units purchased by customers Cost Of Rental Units Purchased By Customers Changes in certain assets and liabilities: Increase Decrease In Operating Capital [Abstract] Accounts receivable, net Increase Decrease In Accounts Receivable Inventory Increase Decrease In Inventories Prepaid expenses and other assets Increase Decrease In Prepaid Expenses Other Accounts payable Increase Decrease In Accounts Payable Accrued expenses Increase Decrease In Accrued Liabilities Deferred revenue Increase Decrease In Deferred Revenue Deferred rent Increase Decrease In Deferred Leasing Fees Net Cash Used in Operating Activities Net Cash Provided By Used In Operating Activities Cash Flows from Investing Activities: Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment and capitalized software Payments To Acquire Productive Assets Net Cash Used in Investing Activities Net Cash Provided By Used In Investing Activities Cash Flows from Financing Activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from issuance of common stock in initial public offering Proceeds From Issuance Initial Public Offering Payments of public offering costs Payments Of Stock Issuance Costs Proceeds from exercises of stock options Proceeds From Stock Options Exercised Proceeds from issuance of Series G convertible preferred stock, net Proceeds From Issuance Of Convertible Preferred Stock Borrowings under credit facilities Proceeds From Lines Of Credit Payments of debt issuance costs Payments Of Debt Issuance Costs Net Cash Provided by Financing Activities Net Cash Provided By Used In Financing Activities Net Increase (Decrease) in Cash and Cash Equivalents Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect Cash and Cash Equivalents, Beginning of Year Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash and Cash Equivalents, End of Year Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid Net Transfer of inventory to property and equipment Transfer Of Inventory To Property And Equipment Supplemental disclosure of non-cash investing and financing activities: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Purchases of property and equipment and capitalized software in accounts payable and accrued expenses Capital Expenditures Incurred But Not Yet Paid Conversion of convertible preferred stock into common stock Conversion Of Stock Amount Converted1 Conversion of convertible preferred stock warrants into common stock warrants Conversion Of Convertible Preferred Stock Warrants Into Common Stock Warrant Deferred public offering costs included in accounts payable and accrued expenses Deferred Public Offering Costs Included In Accounts Payable And Accrued Expenses Allocation of proceeds from debt financing to convertible preferred stock warrant liability Debt Issuance Costs Incurred During Noncash Or Partial Noncash Transaction Organization Consolidation And Presentation Of Financial Statements [Abstract] Description of Business Nature Of Operations Accounting Policies [Abstract] Basis of Presentation Basis Of Accounting Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] New Accounting Pronouncements And Changes In Accounting Principles [Abstract] Recent Accounting Pronouncements New Accounting Pronouncements And Changes In Accounting Principles [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurement and Financial Instruments Fair Value Disclosures [Text Block] Receivables [Abstract] Accounts Receivable Loans Notes Trade And Other Receivables Disclosure [Text Block] Property Plant And Equipment [Abstract] Property and Equipment and Capitalized Software Property Plant And Equipment Disclosure [Text Block] Payables And Accruals [Abstract] Accrued expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Debt Disclosure [Abstract] Debt Debt Disclosure [Text Block] Equity [Abstract] Convertible Preferred Stock and Stockholders' Deficit Stockholders Equity Note Disclosure [Text Block] Earnings Per Share [Abstract] Loss Per Share Earnings Per Share [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Share-based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Compensation And Retirement Disclosure [Abstract] Employee Benefit Plans Compensation And Employee Benefit Plans Other Than Share Based Compensation [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Distribution Agreement with Teijin Pharma Limited Collaborative Arrangement Disclosure [Text Block] Segments Geographical Areas [Abstract] Geographical Segment Information Segment Reporting Disclosure [Text Block] Quarterly Financial Information Disclosure [Abstract] Supplementary Financial Information (Unaudited) Quarterly Financial Information [Text Block] Use of Estimates Use Of Estimates Recapitalization Comparability Of Prior Year Financial Data Cash and Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Concentration of Credit Risk Concentration Risk Credit Risk Allowance for Doubtful Accounts Receivables Trade And Other Accounts Receivable Allowance For Doubtful Accounts Policy Inventory Inventory Policy [Text Block] Property and Equipment and Capitalized Software Property Plant And Equipment Policy [Text Block] Impairment of Long-Lived Assets Impairment Or Disposal Of Long Lived Assets Policy [Text Block] Warrant liability policy. Warrant Liability Warrant Liability Policy Policy [Text Block] Deferred Debt Issuance Costs Deferred Charges Policy [Text Block] Revenue Recognition Revenue From Contract With Customer Policy [Text Block] Research and Development Expenses Research And Development Expense Policy Share-based Compensation Compensation Related Costs Policy [Text Block] Income Taxes Income Tax Policy [Text Block]