Discontinued Operations and Disposal Groups [Abstract] Total Assets and Liabilities of Discontinued Operations Disposal Groups, Including Discontinued Operations [Table Text Block] Leases [Abstract] 2019 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two 2021 Lessee, Operating Lease, Liability, Payments, Due Year Three 2022 Lessee, Operating Lease, Liability, Payments, Due Year Four 2023 Lessee, Operating Lease, Liability, Payments, Due Year Five 2024 Lessee, Operating Lease, Liability, Payments Due Year Six Lessee, Operating Lease, Liability, Payments Due Year Six Thereafter Lessee, Operating Lease, Liability, Payments Due After Year Six Lessee, Operating Lease, Liability, Payments Due After Year Six Total lease payments Lessee, Operating Lease, Liability, Payments, Due Less: imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Present value of lease liabilities Operating Lease, Liability DISCONTINUED OPERATIONS Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years 2024 and Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total Operating Leases, Future Minimum Payments Due Organization, Consolidation and Presentation of Financial Statements [Abstract] Use of Estimates Use of Estimates, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Aetna Part D Membership Reinsurance Reinsurance Accounting Policy [Policy Text Block] Premium Receivable and Unearned Premiums Revenue from Contract with Customer [Policy Text Block] Medicare Part D Settlements Funds Receivable/Payable for the Benefit of Members [Policy Text Block] [Table Text Block] for Disclosure of accounting policy for Funds Receivable or Payable for the Benefit of Members [Table] ACA Industry Fee ACA Industry Fee [Policy Text Block] ACA Industry Fee [Policy Text Block] Accounting Standards Recently Adopted and Pending Adoption New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Stockholders' Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Preferred stock, par value (in USD per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, issued (in shares) Preferred Stock, Shares Issued Preferred stock, outstanding (in shares) Preferred Stock, Shares Outstanding Common stock, par value (in USD per share) Common Stock, Par or Stated Value Per Share Common stock, authorized (in shares) Common Stock, Shares Authorized Common stock, issued (in shares) Common Stock, Shares, Issued Common stock, outstanding (in shares) Common Stock, Shares, Outstanding Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Statement, Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Paid in Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (in shares) Beginning balance Stockholders' Equity Attributable to Parent Common stock issued for vested equity-compensation awards (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Common stock issued for vested equity-compensation awards Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Repurchase and retirement of shares to satisfy tax withholding requirements (in shares) Stock Repurchased During Period, Shares Repurchase and retirement of shares to satisfy tax withholding requirements Stock Repurchased During Period, Value Stock-based compensation expense, net of forfeitures APIC, Share-based Payment Arrangement, Increase for Cost Recognition Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Ending balance (in shares) Ending balance Assets Assets [Abstract] Current Assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Short-term investments Short-term Investments Premiums receivable, net Premiums Receivable, Net Pharmacy rebates receivable, net Other Receivables, Net, Current Funds receivable for the benefit of members Funds Receivable For The Benefit Of Members Funds held or receivable for the benefit of members represent government payments received or to be received to subsidize the member portion of medical payments for certain of our stand-alone prescription drug program members. We do not bear underwriting risk since such funds represent pass-through payments from our government partners to fund deductibles, co-payments and other participant benefits. Prepaid expenses and other current assets, net Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property, equipment and capitalized software, net Property, Plant and Equipment, Net Goodwill Goodwill Other intangible assets, net Intangible Assets, Net (Excluding Goodwill) Long-term investments Long-term Investments Restricted cash, cash equivalents and investments Restricted Cash and Investments, Noncurrent Other assets Other Assets, Noncurrent Assets of discontinued operations Disposal Group, Including Discontinued Operation, Assets, Noncurrent Total Assets Assets Current Liabilities: Liabilities, Current [Abstract] Medical benefits payable Liability for Claims and Claims Adjustment Expense Unearned premiums Unearned Premiums Accounts payable and accrued expenses Accounts Payable and Other Accrued Liabilities, Current Funds payable for the benefit of members Funds Payable For The Benefit of Members Funds held (payable) or receivable for the benefit of members represent government payments received or to be received to subsidize the member portion of medical payments for certain of our stand-alone prescription drug program members. We do not bear underwriting risk since such funds represent pass-through payments from our government partners to fund deductibles, co-payments and other participant benefits. Other payables to government partners Other Payables To Government Partners Other payables due to government partners represent amounts due to government agencies under various contractual and plan arrangements. We estimate the amounts due to CMS for risk protection under the risk corridor provisions of our contract with CMS each period based on pharmacy claims experience. Also this line item includes reserves for the return of premium on minimum loss ratio guarantees for certain state Medicaid contracts. Total current liabilities Liabilities, Current Deferred income tax liability, net Deferred Income Tax Liabilities, Net Long-term debt, net Long-term Debt, Excluding Current Maturities Other liabilities Other Liabilities, Noncurrent Liabilities of discontinued operations Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent Total Liabilities Liabilities Commitments and contingencies (see Note 14) Commitments and Contingencies Preferred stock, $0.01 par value (20,000,000 authorized, no shares issued or outstanding) Preferred Stock, Value, Issued Common stock, $0.01 par value (100,000,000 authorized, 50,311,933 and 49,993,219 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively) Common Stock, Value, Issued Paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Total Stockholders' Equity Total Liabilities and Stockholders' Equity Liabilities and Equity Fair Value Disclosures [Abstract] Assets and Liabilities Measured at Fair Value on a Recurring Basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Assets and Liabilities Measured at Fair Value on a Recurring Basis Fair Value, by Balance Sheet Grouping [Table Text Block] Carrying Value and Fair Value of Long-term Debt Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block] Income Tax Disclosure [Abstract] INCOME TAXES Income Tax Disclosure [Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Fair Value, Recurring and Nonrecurring [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Debt Securities Debt Securities [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Fair value, measurements, recurring Fair Value, Recurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Schedule of Available-for-sale Securities, Major Types of Debt and Equity Securities [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Asset-backed securities Asset-backed Securities [Member] Corporate debt securities Corporate Debt Securities [Member] Municipal securities Municipal Bonds [Member] Residential mortgage-backed securities Residential Mortgage Backed Securities [Member] Short-term time deposits Bank Time Deposits [Member] Government and agency obligations US Government Agencies Debt Securities [Member] Other securities Other Security Investments [Member] Cash Cash [Member] Money market funds Money Market Funds [Member] U.S. government securities and other US Treasury Securities [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Investments Investments, Fair Value Disclosure Equity securities Equity Securities, FV-NI Restricted cash, cash equivalents and investments Restricted Investment, Fair Value Disclosure This element represents restricted investments reported on the balance sheet at period end measured at fair value by the entity. This element in intended to be used in connection with fair value disclosures required in the footnote disclosures to the financial statements. Commitments and Contingencies Disclosure [Abstract] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Traditional Insurance Business Traditional Insurance Business [Member] Traditional Insurance Business [Member] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Discontinued operations, held-for-sale Discontinued Operations, Held-for-sale [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Number Of Subsidiaries Sold Number Of Subsidiaries Sold Number Of Subsidiaries Sold Assets Disposal Group, Including Discontinued Operation, Assets [Abstract] Cash and cash equivalents Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents Investments Disposal Group, Including Discontinued Operation, Investments Disposal Group, Including Discontinued Operation, Investments Reinsurance recoverables Disposal Group, Including Discontinued Operation, Reinsurance Recoverables Disposal Group, Including Discontinued Operation, Reinsurance Recoverables Other assets Disposal Group, Including Discontinued Operation, Other Assets Total Assets Disposal Group, Including Discontinued Operation, Assets Liabilities Disposal Group, Including Discontinued Operation, Liabilities [Abstract] Reserves and other policy liabilities Disposal Group, Including Discontinued Operation, Accrued Liabilities Other liabilities Disposal Group, Including Discontinued Operation, Other Liabilities Total liabilities Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Medicaid Health Plan Medicaid [Member] A reportable segment and business line which includes plans for beneficiaries of various Medicaid programs and state-based programs that are not a part of the Medicaid program. Medicare Health Plan Medicare Health Plans [Member] Medicare Health Plans Segment [Member] Medicare PDP Prescription Drug Plans [Member] A reportable segment within the Medicare business line through which the entity offers Medicare Part D coverage to Medicare-eligible beneficiaries. Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Corporate, Non-Segment Corporate, Non-Segment [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Premium Premiums Earned, Net Products and services Revenues From Products And Services Revenues From Products And Services Total premium and products and services revenues Revenue From Premiums, Products And Services Revenue From Premiums, Products And Services Medical benefits Policyholder Benefits and Claims Incurred, Net, Health Costs of products and services Cost of Goods and Services Sold ACA industry fee ACA Industry Fee Expense ACA Industry Fee Expense Medicaid premium taxes Medicaid Premium Taxes Medicaid Premium Taxes Total gross margin expenses Operating Costs and Expenses Gross margin Gross Profit Investment and other income Investment And Other Income Investment income represents income derived from bank deposits and investments in securities consisting of interest income from cash instruments and securities, dividend income, and income or expense derived from the amortization of investment related discounts or premiums, respectively. Other expenses Other Expenses Income from operations Operating Income (Loss) Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Derivative Lawsuits Derivative Lawsuits [Member] A lawsuit brought by a corporation shareholder against the directors, management and/or other shareholders of the corporation, for a failure by management. Litigation Case [Axis] Litigation Case [Axis] Litigation Case [Domain] Litigation Case [Domain] Mr. Farha Case Mr. Farha Case [Member] Mr. Farha Case [Member] Mr. Behrens Case Mr. Behrens Case [Member] Mr. Behrens Case [Member] Mr. Bereday Case Mr. Bereday Case [Member] Mr. Bereday Case Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Securities and Exchange Commission (SEC) United States Securities And Exchange Commission [Member] United States Securities And Exchange Commission [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Number of former officers receiving notices of cross appeal Number Of Former Employees Receiving Notices of Cross Appeal Number Of Former Employees Receiving Notices of Cross Appeal Number of former associates being pursued in action filed by entity Number Of Former Associates Being Pursued In Action Filed By Entity Number Of Former Associates Being Pursued In Action Filed By Entity Number of former employees found guilty and appealing Number Of Former Employees Found Guilty and Appealing Number Of Former Employees Found Guilty and Appealing Number of former employees being pursued in action filed by entity Number Of Former Employees Being Pursued In Action Filed By Entity Number Of Former Employees Being Pursued In Action Filed By Entity Number of actions filed in the federal and state courts between October 2007 and January 2008 Number of actions filed in the Federal Court The number of actions filed in Federal Court related to government investigations in a derivative action filed against the entity. Number of former executives being pursued in action filed by entity Number Of Former Officers Being Pursued In Action Filed By Entity The number of former officers being pursued in an action filed by the entity pursuant to a report filed by the Special Litigation Committee to the Federal Court determining, among other things, that the entity should pursue such an action. Settlement agreement, amount awarded Litigation Settlement, Amount Awarded from Other Party Maximum legal fee obligation Litigation Settlement, Legal Fee Advances, Maximum Litigation Settlement, Legal Fee Advances, Maximum Number of putative class action lawsuits Loss Contingency, Number Of Putative Class Action Lawsuits Loss Contingency, Number Of Putative Class Action Lawsuits Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 5.375% Senior Notes, due August 15, 2026 Senior Notes Due 2026 Issued 2018 - 5.375 percent [Member] Senior Notes Due 2026 Issued 2018 - 5.375 percent [Member] 5.25% Senior Notes, due April 1, 2025 Senior Notes Due 2025 Issued 2017 - 5.25 percent [Member] Senior Notes Due 2025 Issued 2017 - 5.25 percent [Member] 5.75% Senior Notes, due November 15, 2020 Senior Notes Due 2020 Issued 2013 - 5.75 percent [Member] Senior Notes Due 2020 Issued 2013 - 5.75 percent [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Interest rate Debt Instrument, Interest Rate, Stated Percentage Aggregate principal amount Debt Instrument, Face Amount Debt repurchase amount Debt Instrument, Repurchase Amount Credit facility, maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Credit facility increase subject to certain conditions Line of Credit Facility, Accordian Loan Feature Line of Credit Facility, Accordion Loan Feature Commitment fee percentage on unused amount Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Net payments on revolving credit facility Proceeds from (Repayments of) Debt Borrowings outstanding Long-term Line of Credit, Noncurrent Earnings Per Share [Abstract] Calculation of the Weighted-Average Common Shares Outstanding - Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Investments, Debt and Equity Securities [Abstract] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract] Due in one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Due after ten years Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Asset-backed and mortgage-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Total Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost Fair Value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Due in one year or less Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Due after ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Asset-backed and mortgage-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Total Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value ORGANIZATION, BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Schedule of Outstanding Debt Obligations Schedule of Long-term Debt Instruments [Table Text Block] Funds Receivable/Payable for the Benefit of Members [Table] Funds Receivable/Payable for the Benefit of Members [Table] Disclosure of accounting policy for Funds Receivable or Payable for the Benefit of Members [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Aetna Part D Business Aetna Part D Business [Member] Aetna Part D Business [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Premiums receivable, net Premiums Receivable [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] State Partners State Partners [Member] State Partners [Member] Medicare Advantage and PDP Medicare Advantage and PDP [Member] Medicare Advantage and PDP [Member] Medicare Advantage Medicare Advantage [Member] A reportable segment within the Medicare business line which consists of Medicare Advantage coordinated care plans. Funds Receivable/Payable for the Benefit of Members [Line Items] Funds Receivable/Payable for the Benefit of Members [Line Items] [Line Items] for Disclosure of accounting policy for Funds Receivable or Payable for the Benefit of Members [Table] Membership Membership Represents the number of members enrolled in the health care plan as of the end of the reporting period. Reinsurance receivables related to premiums receivable Reinsurance Recoverables, Incurred but Not Reported Claims Reinsurance payable Reinsurance Payable Reinsurance recoverables Reinsurance Recoverables, Including Reinsurance Premium Paid Premiums revenue related to Aetna Part D Membership Medical benefits ceded related to Aetna Part D membership Medical Benefits Ceded Medical Benefits Ceded Medicaid retroactive rate change and risk score adjustments Medicaid Retroactive Rate Change and Risk Score Adjustments Medicaid Retroactive Rate Change and Risk Score Adjustments ACA industry fee Medicaid ACA industry fee reimbursement revenue Medicaid ACA Industry Fee Reimbursement Revenue Medicaid ACA Industry Fee Reimbursement Revenue Right of use assets Operating Lease, Right-of-Use Asset Elimination of straight-line lease liabilities Deferred Rent Credit EQUITY AND EARNINGS PER SHARE Earnings Per Share [Text Block] Balance sheet information related to operating leases Assets And Liabilities, Leases [Table Text Block] Assets And Liabilities, Leases [Table Text Block] Maturities of operating leases Lessee, Operating Lease, Liability, Maturity [Table Text Block] Supplemental cash flow information related to leases Lease, Cost [Table Text Block] Schedule of noncalcellable minimum lease payments under ASC Topic 840 Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Schedule of Revenues from External Customers and Long-Lived Assets [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Florida FLORIDA Illinois ILLINOIS Kentucky KENTUCKY Revenues from External Customers and Long-Lived Assets [Line Items] Revenues from External Customers and Long-Lived Assets [Line Items] Premium revenue as a percentage of total consolidated premium revenue Premium Revenue, Net Of Premium Tax Represents premium revenue net of premium tax of consolidated premium revenue. MEDICAL BENEFITS PAYABLE [Abstract] Reconciliation of the Beginning and Ending Balances of Medical Benefits Payable, by Segment Reconciliation of Medical Benefits Payable [Table Text Block] A reconciliation of the beginning and ending balances of medical benefits payable, including separate disclosure of medical benefits incurred and medical benefits paid during the reporting period. Debt Securities, Available-For-Sale, Percent Investment Grade Securities Debt Securities, Available-For-Sale, Percent Investment Grade Securities Debt Securities, Available-For-Sale, Percent Investment Grade Securities Proceeds from sale of available-for-sale investments Proceeds from Sale of Debt Securities, Available-for-sale Realized gains and losses on sales and redemptions of investments Debt Securities, Available-for-sale, Realized Gain (Loss) Other than temporary impairment losses Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale Long-term debt, fair value Long-term Debt, Fair Value Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Financial Instrument [Axis] Government and agency obligations Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Debt securities: Debt Securities, Unrealized Gain (Loss) [Abstract] Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Estimated Fair Value Debt Securities, Available-for-sale Equity securities Equity Securities, FV-NI, Unrealized Gain (Loss) [Abstract] Amortized Cost Equity Securities, FV-NI, Cost Gross Unrealized Gains Equity Securities, FV-NI, Unrealized Gain Gross Unrealized Losses Equity Securities, FV-NI, Unrealized Loss Estimated Fair Value Total Debt Securities, Trading, and Equity Securities, FV-NI [Abstract] Amortized Cost Debt Securities, Trading, and Equity Securities, FV-NI, Cost Gross Unrealized Gains Debt Securities, Trading, and Equity Securities, FV-NI, Unrealized Gain Debt Securities, Trading, and Equity Securities, FV-NI, Unrealized Gain Gross Unrealized Losses Debt Securities, Trading, and Equity Securities, FV-NI, Unrealized Loss Debt, Trading, and Equity Securities, FV-NI, Unrealized Loss Estimated Fair Value Debt Securities, Trading, and Equity Securities, FV-NI LEASES Lessee, Operating Leases [Text Block] Business Combinations [Abstract] Fair Values of Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] Final Fair Values and Weighted Average Useful Lives for Identifiable Intangible Assets Acquired Schedule of Goodwill [Table Text Block] Unaudited Pro Forma Results Business Acquisition, Pro Forma Information [Table Text Block] Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] Segments [Domain] Corporate and Other Corporate and Other [Member] Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Claims and Claims Adjustment Expense [Line Items] Reconciliation of the beginning and ending balance of medical benefits payable [Roll Forward] Reconciliation of the beginning and ending balance of medical benefits payable [Roll Forward] A roll forward is a reconciliation of the beginning and ending balance of medical benefits payable. Beginning balance Acquisitions Liability for Unpaid Claims and Claims Adjustment Expense, Business Acquisitions Medical benefits incurred related to Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Current year Current Year Claims and Claims Adjustment Expense Prior years Prior Year Claims and Claims Adjustment Expense Total Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Medical benefits paid related to Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Total Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Ending balance Premium deficiency reserve Deferred Tax Assets, Premium Deficiency Reserve Deferred Tax Assets, Premium Deficiency Reserve Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Long-term debt, net Long-term Debt, Excluding Current Maturities [Abstract] Senior notes Senior Notes, Noncurrent Revolving Credit Facility Debt issuance costs Debt Issuance Costs, Noncurrent, Net Total long-term debt, net Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Meridian Meridian [Member] Meridian [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Sale of stock, number of shares issued in transaction Sale of Stock, Number of Shares Issued in Transaction Offering price per share Shares Issued, Price Per Share Issuance of common stock, net of issuance costs Proceeds from Issuance of Common Stock Investment banking, advisory, brokerage, and underwriting fees and commissions Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions Weighted-average common shares outstanding — basic (in shares) Weighted Average Number of Shares Outstanding, Basic Dilutive effect of outstanding stock-based compensation awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted-average common shares outstanding — diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Anti-dilutive stock-based compensation awards excluded from computation (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Scenario [Axis] Scenario [Axis] Scenario [Domain] Scenario [Domain] Forecast Forecast [Member] Centene Centene [Member] Centene [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Cash received per share Business Acquisition, Share Price Shares received for each common share (in shares) Business Acquisition, Shares Issued Per Common Share Outstanding Business Acquisition, Shares Issued Per Common Share Outstanding Aggregate Amount Of Capital Expenses Budgeted, Percentage Business Acquisition, Aggregate Amount Of Capital Expenses Budgeted, Percentage Business Acquisition, Aggregate Amount Of Capital Expenses Budgeted, Percentage Acquisition consideration transferred Business Combination, Consideration Transferred Estimated weighted average useful live of identifiable intangible assets Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Net deferred tax liabilities acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Income Statement [Abstract] Revenues: Revenues [Abstract] Investment and other income Total revenues Revenues Expenses: Cost of Revenue [Abstract] Medical benefits Selling, general and administrative Selling, General and Administrative Expense Medicaid premium taxes Premium Tax Expense An assessment levied by a state government agency on premium revenue. Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Interest Interest Expense Total expenses Operating Expenses Income before income taxes and equity in losses of unconsolidated subsidiaries Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Equity in earnings (losses) of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax expense Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Change in net unrealized gains and losses on available-for-sale securities, before tax Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax Income tax expense (benefit) related to other comprehensive income Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Earnings per common share: Basic (in USD per share) Earnings Per Share, Basic Diluted (in USD per share) Earnings Per Share, Diluted Weighted average common shares outstanding: Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract] Basic (in shares) Diluted (in shares) Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Cash, cash equivalents and restricted cash Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Investments, including restricted investments Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments Premiums receivable, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Premiums Receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Premiums Receivable Other current assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Pharmacy Rebates Receivable And Other Current Assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Pharmacy Rebates Receivable and Other Current Assets Property, equipment and capitalized software, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment Other intangible assets, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill Fair value of total assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract] Medical benefits payable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable ACA Fee liability Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Other liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other Fair value of liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Fair value of net assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Net income Adjustments to reconcile net income to cash flows from operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Stock-based compensation expense Share-based Payment Arrangement, Noncash Expense Deferred taxes, net Deferred Income Tax Expense (Benefit) Other, net Other Operating Activities, Cash Flow Statement Changes in operating accounts, net of effects from acquisitions and divestitures: Increase (Decrease) in Operating Capital [Abstract] Premiums receivable, net Increase (Decrease) in Premiums Receivable Pharmacy rebates receivable, net Increase (Decrease) in Other Receivables Medical benefits payable Increase (Decrease) in Health Care Insurance Liabilities Unearned premiums Increase (Decrease) in Unearned Premiums Other receivables/payables to government partners Increase Decrease In Other Payables To Government Partners The net change during the reporting period in amounts due to government agencies under various contractual and plan arrangements. We estimate the amounts due from CMS for risk protection under the risk corridor provisions of our contract with CMS each period based on pharmacy claims experience. Prepaid and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Accrued liabilities and other, net Increase (Decrease) in Accrued Liabilities and Other Operating Liabilities Net cash provided by 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 investments Payments to Acquire Investments Proceeds from sales and maturities of investments Proceeds from Sale, Maturity and Collection of Investments Acquisitions and acquisition-related settlements Payments to Acquire Businesses, Net of Cash Acquired Additions to property, equipment and capitalized software, net 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] Repurchase and retirement of shares to satisfy employee tax withholding requirements Payment, Tax Withholding, Share-based Payment Arrangement Payments on Revolving Credit Facility, net Funds received for the benefit of members, net Proceeds from (Payments for) the Benefit of Members Proceeds from (Payments for) the Benefit of Members Other, net Proceeds from (Payments for) Other Financing Activities Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities (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 Balance at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Balance at end of period SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION: Supplemental Cash Flow Information [Abstract] Cash paid for taxes, net of refunds Income Taxes Paid, Net Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activities SUPPLEMENTAL DISCLOSURES OF NON-CASH TRANSACTIONS: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Non-cash additions to property, equipment, and capitalized software Capital Expenditures Incurred but Not yet Paid Short-term and Long-term Investments by Security Type Debt Securities, Available-for-sale [Table Text Block] Contractual Maturities of Available-for-sale Securities Investments Classified by Contractual Maturity Date [Table Text Block] Favorable development of medical benefits payable Net Favorable (Unfavorable) Development of Medical Benefits Payable Net Favorable (Unfavorable) Development of Medical Benefits Payable Favorable development of medical benefits payable excluding the release of the provision for moderately adverse conditions Net Favorable (Unfavorable) Development of Medical Benefits Payable, Excluding Release of the Provision for Moderately Adverse Conditions Net Favorable (Unfavorable) Development of Medical Benefits Payable, Excluding Release of the Provision for Moderately Adverse Conditions Restricted Investments Note [Abstract] RESTRICTED CASH, CASH EQUIVALENTS AND INVESTMENTS Restricted Assets Disclosure [Text Block] Assets [Abstract] Liabilities [Abstract] Liabilities [Abstract] Current Operating Lease, Liability, Current Noncurrent Operating Lease, Liability, Noncurrent Total liabilities Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Membership Membership [Member] Tradenames Trade Names [Member] Provider network Provider Network [Member] Provider networks are lists of physicians and hospitals that provide services to a health insurance plan. Technology and other Other Intangible Assets [Member] Gross Fair Value (in millions) Finite-lived Intangible Assets Acquired Weighted Average Useful Life (in years) Cover page. Document Type Document Type Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Total revenues Business Acquisition, Pro Forma Revenue Net income Business Acquisition, Pro Forma Net Income (Loss) Business Acquisition, Pro Forma Information [Abstract] Business Acquisition, Pro Forma Information [Abstract] Basic (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Basic Diluted (in dollars per share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Basic [Abstract] Basic (in shares) Business Combination, Pro Forma Information, Weighted Average Common Shares Outstanding, Basic Business Combination, Pro Forma Information, Weighted Average Common Shares Outstanding, Basic Diluted (in shares) Business Combination, Pro Forma Information, Weighted Average Common Shares Outstanding, Diluted Business Combination, Pro Forma Information, Weighted Average Common Shares Outstanding, Diluted MEDICAL BENEFITS PAYABLE Medical Benefits Payable [Text Block] Description and amounts of medical benefits payable at the end of the reporting period and other information and schedules needed to disclose the medical benefit payable account. Share-based Payment Arrangement [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] The 2019 Incentive Compensation Plan The 2019 Incentive Compensation Plan [Member] The 2019 Incentive Compensation Plan [Member] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Performance Stock Units Performance Shares [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of common shares available for issuance Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Compensation expense Unrecognized compensation cost Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Weighted-average period over which compensation costs are expected to be recognized Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Closing common stock price (in USD per share) Share Price Grants in period, weighted average grant date fair value (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Summary of Stock Unit Award Activity Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block] Award Type [Domain] RSUs Restricted Stock Units (RSUs) [Member] PSUs Equity Instruments Other than Options [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding as of beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding at end of period (in shares) Schedule of Restricted Investments Schedule of Restricted Investments [Table Text Block] [Table Text Block] for Schedule of Restricted Investments [Table] Cash paid for operating leases Operating Lease, Payments Leased assets obtained in exchange for new operating lease liabilities Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Restrictions on Cash and Cash Equivalents [Table] Restrictions on Cash and Cash Equivalents [Table] Restricted Cash and Cash Equivalents, Cash and Cash Equivalents [Axis] Restricted Cash and Cash Equivalents [Axis] Restricted Cash and Cash Equivalents, Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] U.S. government securities and other US Treasury and Government [Member] Restricted Cash and Cash Equivalents Items [Line Items] Restricted Cash and Cash Equivalents Items [Line Items] Amortized Cost Restricted Investments, Amortized Cost Basis Restricted Investments, Amortized Cost Basis Gross Unrealized Gains Restricted Investments, Gross Unrealized Gain, Before Tax Restricted Investments, Gross Unrealized Gain, Before Tax Gross Unrealized Losses Restricted Investments, Gross Unrealized Losses, Before Tax Restricted Investments, Gross Unrealized Losses, Before Tax Estimated Fair Value Restricted Cash and Cash Equivalents, Noncurrent INVESTMENTS Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] Remaining lease terms Lessee, Operating Leases, Remaining Lease Term Lessee, Operating Leases, Remaining Lease Term Operating lease expense Operating Lease, Expense Weighted-average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Weighted-average discount rate Operating Lease, Weighted Average Discount Rate, Percent SEGMENT REPORTING Segment Reporting Disclosure [Text Block] CENTENE PLAN OF MERGER AND ACQUISITIONS Business Combination Disclosure [Text Block] Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table] Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Changes in Goodwill Goodwill [Roll Forward] Beginning Balance Acquisition related adjustments Goodwill, Purchase Accounting Adjustments Ending Balance Realized gains (losses) on restricted investments Restricted Investments, Realized Gains (Losses) Restricted Investments, Realized Gains (Losses) STOCK-BASED COMPENSATION Share-based Payment Arrangement [Text Block] DEBT Debt Disclosure [Text Block] Revenue by Geographic Location Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Segment Results Schedule of Segment Reporting Information, by Segment [Table Text Block] Name of Healthcare Plan [Axis] Name of Healthcare Plan [Axis] Name of Healthcare Plan [Axis] Name of Healthcare Plan [Domain] Name of Healthcare Plan [Domain] [Domain] for Name of Healthcare Plan [Axis] Medical Services Managed Care Plan Medical Services Managed Care Plan [Member] Medical Services Managed Care Plan [Member] Serious Mental Illness Specialty Plan Serious Mental Illness Specialty Plan [Member] Serious Mental Illness Specialty Plan [Member] Number of Regions Number of Regions Number of Regions Number of reportable segments Number of Reportable Segments Term of agreement Term of Agreement Term of Agreement FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block]