Document and Entity Information [Abstract] Statement [Table] Statement [Line Items] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Current Reporting Status Entity Filer Category Trading Symbol Entity Small Business Entity Emerging Growth Company Entity Ex Transition Period Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Condensed Combined Balance Sheets Assets [Abstract] ASSETS Assets, Current [Abstract] Current assets: Prepaid Expense, Current Prepaid expenses Other Assets, Current Other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property and equipment, net Property and equipment, net Other Assets, Noncurrent Other assets Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND NET PARENT INVESTMENT Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Carrying value as of the balance sheet date of obligations incurred through that date and payable for research and development. Used to reflect the current portion of liabilities. Accrued Research And Development Current Accrued research and development costs Other Liabilities, Current Accrued expenses and other current liabilities Total Liabilities, Current Total current liabilities Other Liabilities, Noncurrent Other liabilities Equity [Abstract] Net parent investment: Stockholders' Equity Attributable to Parent Parent company net investment, end of period Parent company net investment, beginning of period Net parent investment Liabilities and Equity Total liabilities and net parent investment Condensed Combined Statements of Operations Operating Expenses [Abstract] Cost and expenses: Research and Development Expense Research and development General and Administrative Expense General and administrative Operating Expenses Total cost and expenses Operating Income (Loss) Loss from operations Net Income (Loss) Attributable to Parent Net loss Condensed Combined Statements of Net Parent Investment Increase (Decrease) in Stockholders' Equity [Roll Forward] Change in Net Parent Investment he amount of capital contributed by the parent through transfers. Contributed Capital Net transfers from Parent Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Parent allocation - Share-based compensation Condensed Combined Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities [Abstract] Cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Share-based Compensation Share-based compensation expense Increase (Decrease) in Operating Capital [Abstract] Changes in assets and liabilities: Increase (Decrease) in Prepaid Expense Prepaid expenses Increase (Decrease) in Other Current Assets Other current assets Increase (Decrease) in Other Noncurrent Assets Other assets Increase (Decrease) in Accounts Payable Accounts payable The increase (decrease) during the reporting period in accrued research and development expense. Increase Decrease in Accrued Research and Development Accrued research and development costs Increase (Decrease) in Other Current Liabilities Accrued expenses and other current liabilities Increase (Decrease) in Other Noncurrent Liabilities Other liabilities Net Cash Provided by (Used in) Operating Activities Net cash used in operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Cash flows from investing activities: Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Cash flows from financing activities: Proceeds from Contributed Capital Transfer from Parent Company Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash and cash equivalents, end of period Cash and cash equivalents, beginning of period Cash amount reflected in the condensed combined financial statements Supplemental Cash Flow Information [Abstract] Supplemental cash flow disclosure: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Non-cash investing activities Capital Expenditures Incurred but Not yet Paid Fixed asset purchases in accounts payable and accrued expenses Nature of Business Business Description and Basis of Presentation [Text Block] Nature of Business Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Property and Equipment Accrued Expenses and Other Current Liabilities Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Accrued Expenses and Other Current Liabilities Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Share-based Compensation Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Share-based Compensation Plans Defined Contribution Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Defined Contribution Plan Related Party Transactions Related Party Transactions Disclosure [Text Block] Related Party Transactions Workforce Reduction Restructuring and Related Activities Disclosure [Text Block] Workforce Reduction Subsequent Events Subsequent Events [Text Block] Subsequent Events Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Consolidation, Policy [Policy Text Block] Principles of Combination Segment Reporting, Policy [Policy Text Block] Segment Information Use of Estimates, Policy [Policy Text Block] Use of Estimates Cash and Cash Equivalents, Policy [Policy Text Block] Cash and Cash Equivalents Property, Plant and Equipment, Policy [Policy Text Block] Property and Equipment Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment of Long-Lived Assets Research and Development Expense, Policy [Policy Text Block] Research and Development Costs Selling, General and Administrative Expenses, Policy [Policy Text Block] General and Administrative Expenses Disclosure of accounting policy for patent costs. Patent Costs [Policy Text Block] Patent Costs Subsequent Events, Policy [Policy Text Block] Subsequent Events New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements Tabular disclosure of the useful life of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Schedule of Property, Plant and Equipment, Useful Life [Table Text Block] Schedule of estimated useful lives of property and equipment Property, Plant and Equipment [Table Text Block] Schedule of property and equipment, net Other Current Liabilities [Table Text Block] Schedule of accrued expenses and other current liabilities Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of allocation of share-based compensation expense Restructuring and Related Costs [Table Text Block] Schedule of accrued liabilities activity allocated in connection with reduction in workforce activities Subsequent Event [Table] Subsequent Event [Line Items] Nature of Business Subsequent Events Ratio applied to the distribution of shares for the spin-off of the reporting entity from its Parent, as of the declared record date of the distribution. Spin Off Exchange Ratio Distribution exchange ratio (shares of Cyclerion per share of Ironwood) Common stock dividend ratio applied to the distribution of shares for the spin-off of the reporting entity from its Parent, as of the separation date. Dividends, Common Stock, Stock Ratio Common stock dividend issued (shares of Cyclerion per share of Ironwood) Stock Issued During Period, Shares, New Issues Shares issued to accredited investors Proceeds from Issuance of Private Placement Gross proceeds from issuance of shares to accredited investors The cash inflow associated with the amount received from entity's raising of capital via private rather than public placement, net of related issuance costs. Proceeds from Issuance of Private Placement Net of Issuance Costs Net proceeds from issuance of shares to accredited investors Number of Reportable Segments Number of reportable business segment Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Property and Equipment Property, Plant and Equipment, Useful Life Estimated Useful Life (In Years) Operating expense incurred related to patents. Operating Expense Incurred Related to Patents Operating expense legal and other fees related to patents Property, Plant and Equipment, Gross Gross property and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: accumulated depreciation and amortization Accrued Bonuses, Current Accrued incentive compensation Accrued Salaries, Current Salaries Accrued Vacation, Current Accrued vacation Accrued Professional Fees, Current Professional fees Restructuring Reserve, Current Amounts accrued, end of period Amounts accrued, beginning of period Workforce reduction charges Other Sundry Liabilities, Current Other Commitments and Contingencies. No liabilities recorded Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Plans Number of share-based compensation plans pursuant to which awards were made to employees of the reporting entity. Share Based Compensation Arrangement Number Of Active Plans Number of share-based compensation plans pursuant to which awards were made to employees Number of share-based compensation plans with outstanding awards, but from which no further awards will be made. Share Based Compensation Arrangement Number Of Inactive Plans Number of share-based compensation plans with outstanding awards but from which no further awards will be made Allocated Share-based Compensation Expense Share-based compensation allocated to Cyclerion Portion of share-based compensation recognized in the period that is attributable to the reporting entity's direct employees Allocated Share Based Compensation Expense Direct Employees Share-based compensation directly attributable to Cyclerion employees Defined Contribution Plan [Table] Defined Contribution Plan Disclosure [Line Items] Defined Contribution Plan Defined Contribution Plan, Type [Extensible List] 401 (k) Savings Plan Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Percent of compensation eligible employees may elect to contribute Defined Contribution Plan, Employer Matching Contribution, Percent of Match Matching contribution (as a percent of employee's contributions) The maximum amount per employee of the employer's matching contributions. Defined Contribution Plan Employer Matching Contribution Maximum Maximum amount of employer matching contribution Portion of defined contribution plan cost recognized in the period that is attributable to the reporting entity's direct employees Defined Contribution Plan Employer Cost Recognized Direct Employees Defined contribution plan expense directly attributable to Cyclerion employees Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Line Items] Related Party Transactions Related Party Transaction, Expenses from Transactions with Related Party Related party expense Due to Related Parties Outstanding balance payable to related party Number of shares of Parent Company common stock donated to donor advised fund. Shares Donated Parent Company Number of shares of Ironwood common stock donated to American Endowment Foundation Number of shares of Ironwood common stock donated to American Endowment Foundation Amount received from related party for issuance of shares of common stock. Stock Issued During Period Value Related Party Investment in common stock by related party Schedule of Restructuring and Related Costs [Table] Restructuring Cost and Reserve [Line Items] Workforce Reduction Restructuring and Related Cost, Number of Positions Eliminated Reduction in workforce, number of employees Restructuring Reserve [Roll Forward] Summarizes the accrued liabilities activity allocated to Cyclerion in connection with the reduction in workforce Restructuring Charges Charges Payments for Restructuring Amount Paid The area of an operating lease. Operating Lease Rentable Space Lease rentable square feet Lessee, Operating Lease, Term of Contract Lease contract term Lessee, Operating Lease, Existence of Option to Extend [true false] Number of renewal terms of lessee's operating lease. Lessee Operating Lease Number of Renewal Terms Lease, number of renewal terms Lessee, Operating Lease, Renewal Term Lease renewal term Letters of Credit Outstanding, Amount Letter of credit posted as a security deposit for lease Noncontrolling Interest, Ownership Percentage by Parent Interest in subsidiary (as a percent) Legal Entity [Axis] Entity [Domain] Entity [Domain] Ironwood Pharmaceuticals, Inc., the parent of the reporting entity. The reporting entity was spun off from Ironwood. Ironwood Pharmaceuticals Inc [Member] Ironwood Sale of Stock [Axis] Sale Of Stock Name Of Transaction [Domain] Sale of Stock [Domain] Private Placement [Member] Private Placement Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event Property, Plant and Equipment, Type [Axis] Property Plant And Equipment Type [Domain] Property, Plant and Equipment, Type [Domain] Represents information pertaining to laboratory equipment. Laboratory Equipment [Member] Laboratory equipment Office Equipment [Member] Computer and office equipment Furniture And Fixtures [Member] Furniture and fixtures Software And Software Development Costs [Member] Software Construction In Progress [Member] Construction in progress Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research And Development Expense [Member] Research and development General And Administrative Expense [Member] General and administrative Range [Axis] Range [Member] Range [Domain] Minimum [Member] Minimum Maximum [Member] Maximum Related Party [Axis] Related Party [Domain] Related Party [Domain] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Represents services provided to the reporting entity for information systems, accounting, other financial services (such as treasury, audit and purchasing), human resources, legal and facilities. Corporate Costs [Member] Corporate costs Represents expenses for health insurance services from an insurance provider whose President and Chief Executive Officer is a member of the Board of Directors of the related party. Health Insurance Services [Member] Health insurance services Chief Executive Officer [Member] Peter Hecht A donor advised fund which received contributions from the chief executive officer. Donor Advised Fund Of Chief Executive Officer [Member] American Endowment Foundation President [Member] Mark Currie Restructuring Plan [Axis] Restructuring Plan [Domain] Restructuring Plan [Domain]