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Arrangement Material Terms of Trading Arrangement [Text Block] Stock-based compensation (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements MICHIGAN MICHIGAN Accounts payable, accrued and other long-term liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Accounts Payable, Accrued And Other Noncurrent Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Accounts Payable, Accrued And Other Noncurrent Liabilities Adjustment to Compensation, Amount Adjustment to Compensation Amount Document Period End Date Document Period End Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Adoption Date Trading Arrangement Adoption Date Schedule of Fair Value Measurements of Senior Notes Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Finance lease liabilities Finance Lease, Liability, Noncurrent Entity Central Index Key Entity Central Index Key Amortized cost, due one year through five years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Income tax expense Income Tax Expense (Benefit) Fair Value Measurements Fair Value Disclosures [Text Block] Number of potential for renewals Health Plan, Number Of Extension Options Health Plan, Number Of Extension Options Name Trading Arrangement, Individual Name Other comprehensive (loss) gain, net of tax Other comprehensive income (loss), net Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent In a Continuous Loss Position for 12 Months or More, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Fair value of net assets acquired Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net Risk adjustment payable Affordable Care Act, Premium Stabilization Program, Risk Adjustment, (Payable) Affordable Care Act, Premium Stabilization Program, Risk Adjustment, (Payable) Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Amendment Flag Amendment Flag MISSISSIPPI MISSISSIPPI Deferred income taxes Increase (Decrease) in Deferred Income Taxes Other Other Program [Member] Other Program In a Continuous Loss Position for Less than 12 Months, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Net cash paid in business combinations Cash Payments to Acquire Businesses, Net of Cash Acquired Bright Health Medicare Brand New Day and Central Health Plan of California [Member] Brand New Day and Central Health Plan of California Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Credit Facility [Domain] Credit Facility [Domain] Insurance Claims Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Long-term debt Total Long-Term Debt, Excluding Current Maturities Denominator for diluted net income per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Restricted investments Restricted Investments, Noncurrent Other revenue Interest and Dividend Income, Operating Gross realized investment losses Debt Securities, Available-for-Sale, Realized Loss Purchases of property, equipment and capitalized software Payments to Acquire Property, Plant, and Equipment Company Selected Measure Amount Company Selected Measure Amount Additional paid-in capital Additional Paid in Capital, Common Stock Marketplace Marketplace [Member] Marketplace Additional Paid-in Capital Additional Paid-in Capital [Member] Total assets Assets Name Awards Close in Time to MNPI Disclosures, Individual Name Cover [Abstract] Cover [Abstract] Other operating Segment Reconciling Items [Member] Municipal securities Municipal Securities [Member] Municipal securities. Other long-term liabilities Other Liabilities, Noncurrent Non-NEOs Non-NEOs [Member] Segments Segment Reporting Disclosure [Text Block] Pharmacy rebate receivables Pharmacy Rebate Receivables [Member] Pharmacy Rebate Receivables [Member] Net (decrease) increase in cash, cash equivalents, and restricted cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Non-PEO NEO Non-PEO NEO [Member] Equity Component [Domain] Equity Component [Domain] Adjustment to Compensation: Adjustment to Compensation [Axis] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Debt Instrument [Line Items] Debt Instrument [Line Items] Denominator for basic net income per share (in shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status Operating income Operating Income (Loss) Revenue: Revenues [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Segments [Axis] Segments [Axis] Statement [Line Items] Statement [Line Items] Fair Value Estimate of Fair Value Measurement [Member] Acquired balances, net of post-acquisition adjustments Liability for Unpaid Claims and Claims Adjustment Expense, Business Acquisitions, Net Of Post-Closing Adjustments Liability for Unpaid Claims and Claims Adjustment Expense, Business Acquisitions, Net Of Post-Closing Adjustments Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Mortgage-backed securities Collateralized Mortgage-Backed Securities [Member] Common stock withheld to settle employee tax obligations Common Stock Withheld to Settle Employee Tax Obligations Common Stock Withheld to Settle Employee Tax Obligations Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Amount outstanding under letter of credit Long-Term Line of Credit Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Fiscal Year Maturity [Abstract]