Accounting Policies [Abstract] Net Receivables and Payables from Government Partners [Table] Net Receivables and Payables from Government Partners [Table] Net Receivables and Payables from Government Partners [Table] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Current Assets Current Assets [Member] Current Assets [Member] Current Liabilities Current Liabilities [Member] Current Liabilities [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2016 Part D Plan 2016 Part D Plan [Member] 2016 Part D Plan [Member] Net Receivables and Payables from Government Partners [Line Items] Net Receivables and Payables from Government Partners [Line Items] [Line Items] for Net Receivables and Payables from Government Partners [Table] Allowance for uncollectible premiums receivable Premiums Receivable, Allowance for Doubtful Accounts Supplemental Medicaid premium revenue Premium revenue related to newborn and obstetric deliveries Premium revenue recognized during the period related to supplemental payments for newborns and/or obstetric deliveries under Medicaid contracts with state governments. Medicaid Retroactive Rate Change and Risk Score Adjustments Medicaid Retroactive Rate Change and Risk Score Adjustments Medicaid Retroactive Rate Change and Risk Score Adjustments Risk adjusted premiums receivable Risk Adjusted Premiums Risk Adjusted Premiums Variance above target amount before additional premiums are received Minimum variance above target amount before CMS makes additional payments to plan sponsors The minimum percentage variance above the target amount before Centers for Medicare and Medicaid Services makes additional payments to plan sponsors as part of the CMS corridor calculation. Minimum medical loss ratio Minimum Medical Loss Ratio Minimum Medical Loss Ratio "MLR" as determined under the Affordable Care Act "ACA." Insurance settlement period subsequent to plan year Insurance Settlements, Subsequent Payment Period Insurance Settlements, Subsequent Payment Period Drug costs reimbursed Drug Costs Reimbursed The percentage of drug costs reimbursed by CMS after a member reaches his or her out of pocket catastrophic threshold through a catastrophic reinsurance subsidy. Net payable for the benefit of members Funds (Payable) Receivable For The Benefit Of Members Funds (Payable) Receivable For The Benefit Of Members Net payable for the benefit of members, settlement period Funds (Payable) Receivable For The Benefit Of Members, Settlement Period Funds (Payable) Receivable For The Benefit Of Members, Settlement Period Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Segment Reconciling Items Segment Reconciling Items [Member] 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. Corporate & Other 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) Adjustment to other expense to exclude medicaid premium tax Other Expense, Adjustment to Exclude Medicaid Premium Tax Other Expense, Adjustment to Exclude Medicaid Premium Tax Condensed Financial Information Disclosure [Abstract] Schedule of Condensed Financial Statements [Table] Condensed Financial Statements [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Parent Company Parent Company [Member] Condensed Financial Statements, Captions [Line Items] Condensed Financial Statements, Captions [Line Items] Revenues: Revenues [Abstract] Total revenues Revenues Expenses: Cost of Revenue [Abstract] Selling, general and administrative Selling, General and Administrative Expense Interest expense Interest Expense Total expenses, net Operating Expenses Loss on extinguishment of debt Gain (Loss) on Extinguishment of Debt Loss before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income tax benefit Income Tax Expense (Benefit) Loss before equity in subsidiaries Net Income (Loss) before Net Income (Loss) from Subsidiaries Net Income (Loss) before Net Income (Loss) from Subsidiaries Equity in earnings of subsidiaries Income (Loss) from Subsidiaries, Net of Tax Net income Net Income (Loss) Attributable to Parent Other comprehensive (loss) income, before tax: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Change in net unrealized gains and losses on available-for-sale securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax Income tax (benefit) expense related to other comprehensive income Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Other comprehensive (loss) income, 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 Share [Abstract] 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 Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value Measurements, Recurring Fair Value, Measurements, Recurring [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Auction Rate Securities Auction Rate Securities [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [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] Realized gains (losses) in earnings Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Auction rate securities, par value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Revolving Credit Facility Long-term Line of Credit, Noncurrent Commitments and Contingencies Disclosure [Abstract] Future Minimum Lease Payments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Property, Plant and Equipment [Abstract] PROPERTY, EQUIPMENT AND CAPITALIZED SOFTWARE Property, Plant and Equipment Disclosure [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] GOODWILL AND OTHER INTANGIBLE ASSETS, NET Goodwill and Intangible Assets Disclosure [Text Block] Restrictions on Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Other Net Payables to Government Partners Schedule of other payables to government partners [Table Text Block] Tabular disclosure of the amounts due to government agencies under various contractual and plan arrangements. Funds (Payable) Receivable for the Benefit of Members, Net Funds Receivable Held For The Benefit Of Members [Table Text Block] Tabular disclosure of funds receivable or held for the benefit of members that includes catastrophic reinsurance, low-income cost sharing and coverage gap discount subsidies from the Center for Medicare and Medicaid Services in connection with the Medicare Part D program. Quarterly Financial Information Disclosure [Abstract] Adjustments to gross profit to include medicaid premium taxes Adjustments To Gross Profit Adjustments to Gross Profit Total revenues Gross margin Income (loss) from operations Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Net (loss) income Net income per share - basic (in dollars per share) Earnings Per Share, Basic Net income per share - diluted (in dollars per share) Earnings Per Share, Diluted Period end membership Membership Represents the number of members enrolled in the health care plan as of the end of the reporting period. Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] 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 networks 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] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Universal American Universal American [Member] Universal American [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Preferred Stock Preferred Stock [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Gross fair value Finite-lived Intangible Assets Acquired Weighted average useful life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Purchase price Business Combination, Consideration Transferred Cash purchase price (in dollars per share) Business Acquisition, Share Price Assumption of convertible debt Business Combination, Consideration Transferred, Liabilities Incurred Cash settlement of preferred shares Business Combination, Consideration Transferred, Payments to Repurchase Redeemable Preferred Stock Business Combination, Consideration Transferred, Payments to Repurchase Redeemable Preferred Stock Deferred tax liabilities, net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Goodwill Goodwill Interest rate Debt Instrument, Interest Rate, Stated Percentage Consideration transferred, preferred shares redemption amount Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Revenues Transaction and integration-related costs Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] DHHS DHHS [Member] DHHS [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Number of Beneficiaries Number of Beneficiaries Number of Beneficiaries Restricted Investments Note [Abstract] 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] Cash Cash [Member] Money market funds Money Market Funds [Member] 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] Restricted Investments Restricted Cash and Investments [Abstract] 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 Realized gains (losses) Restricted Investments, Realized Gains (Losses) Restricted Investments, Realized Gains (Losses) Income Tax Disclosure [Abstract] Components of Income Tax Expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Reconciliation of Income Tax Statutory Rate to Effective Rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Significant Components of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Reconciliation of Beginning and Ending Unrecognized Tax Benefits Summary of Income Tax Contingencies [Table Text Block] Equity and Earnings Per Common Share Earnings Per Share [Text Block] Investments, Debt and Equity Securities [Abstract] INVESTMENTS Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Medicaid premium taxes incurred Medicaid premium taxes incurred Premium taxes related to Medicaid that are assessed by certain state agencies and that are included in the premium rates established in the Medicaid contracts with each state agency and recorded as a component of revenue, as well as administrative expense, when incurred. 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 dollars 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 dollars 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 FAIR VALUE MEASUREMENTS Fair Value Disclosures [Text Block] Senior Notes Senior Notes [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] 4.00% Convertible Senior Notes 4.00% Convertible Senior Notes [Member] 4.00% Convertible Senior Notes [Member] Award Type [Axis] Award Type [Axis] Equity Award Equity Award [Domain] Stock Compensation Plan Stock Compensation Plan [Member] Business Combination, Consideration Transferred [Abstract] Business Combination, Consideration Transferred [Abstract] Cash consideration transferred Payments to Acquire Businesses, Gross Assumed debt Equity interests issued Total consideration transferred Common stock, outstanding (in shares) Payments for repurchase of preferred shares (in shares) Payments for Repurchase of Redeemable Preferred Stock Payments for repurchase of preferred shares and accrued dividends Payments for Repurchase of Redeemable Preferred Stock, Including Ordinary Dividends Payments for Repurchase of Redeemable Preferred Stock, Including Ordinary Dividends Payments of accrued dividends Payments of Ordinary Dividends, Preferred Stock and Preference Stock Unrecognized stock compensation cost Acquisition Related Compensation Cost Acquisition Related Compensation Cost Debt Disclosure [Abstract] Debt Instrument Redemption [Table] Debt Instrument Redemption [Table] Senior Notes Due 2026 Issued 2018 - 5.375 percent Senior Notes Due 2026 Issued 2018 - 5.375 percent [Member] Senior Notes Due 2026 Issued 2018 - 5.375 percent [Member] Senior Notes Due 2025 Issued 2017 - 5.25 percent Senior Notes Due 2025 Issued 2017 - 5.25 percent [Member] Senior Notes Due 2025 Issued 2017 - 5.25 percent [Member] Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Axis] Debt Instrument, Redemption, Period [Domain] Debt Instrument, Redemption, Period [Domain] 2020 Debt Instrument, Redemption, Period Two [Member] 2021 Debt Instrument, Redemption, Period Three [Member] 2022 Debt Instrument, Redemption, Period Four [Member] 2023 and thereafter Debt Instrument, Redemption, Period Five [Member] Debt Instrument, Redemption [Line Items] Debt Instrument, Redemption [Line Items] Redemption price Debt Instrument, Redemption Price, Percentage Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Scenario, Forecast Scenario, Forecast [Member] 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] Meridian Meridian [Member] Meridian [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Operating Lease, Liability Operating Lease, Liability Shares of common stock issued Sale of Stock, Number of Shares Issued in Transaction Price per share (in USD per share) Shares Issued, Price Per Share Proceeds from issuance of common stock, net of issuance fees paid Proceeds from Issuance of Common Stock Underwriting discounts and offering costs Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions SEGMENT REPORTING Segment Reporting Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] STOCK-BASED COMPENSATION Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Loss Contingencies [Table] Loss Contingencies [Table] Loss Contingencies by Nature of Contingency [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. United States Securities And Exchange Commission United States Securities And Exchange Commission [Member] United States Securities And Exchange Commission [Member] 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 Loss Contingencies [Line Items] Loss Contingencies [Line Items] Number of former officers being pursued in an action filed by the 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. 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 Number Of Former Employees Found Guilty and Appealing Number Of Former Employees Found Guilty and Appealing Number of former employees 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 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. Settlement payment received Litigation Settlement, Amount Awarded from Other Party Maximum legal fee obligation Litigation Settlement, Legal Fee Advances, Maximum Litigation Settlement, Legal Fee Advances, Maximum Legal fees Legal Fees Premium Revenue by Geographic Location Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block] Financial Information by Reportable Operating Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Significant Accounting Policies [Text Block] Outstanding Debt Obligations Schedule of Debt [Table Text Block] Redemption Prices as Percentage of Principal Amount Schedule of Redemption Prices as Percentage of Principal Amount [Table Text Block] Schedule of Redemption Prices as Percentage of Principal Amount [Table Text Block] Deferred tax assets Deferred Tax Assets, Gross [Abstract] Net operating losses Deferred Tax Assets, Operating Loss Carryforwards Foreign tax credits Deferred Tax Assets, Tax Credit Carryforwards, Foreign Medical and other benefits discounting Deferred Tax Assets, Medical and other benefits discounting The tax effect as of the balance sheet date of the amount of the estimated future tax deductions arising from unrealized losses on medical and other benefits discounting which can only be deducted for tax purposes when the losses are realized, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken. Allowance for doubtful accounts Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Stock-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Unearned premium discounting Deferred Tax Assets, Unearned Premium Discounting Deferred Tax Assets, Unearned Premium Discounting Capital losses Deferred Tax Assets, Capital Loss Carryforwards Premium deficiency reserve Deferred Tax Assets, Premium Deficiency Reserve Deferred Tax Assets, Premium Deficiency Reserve Accrued expenses and other Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other Total deferred tax assets Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Deferred tax liabilities Deferred Tax Liabilities, Gross [Abstract] Goodwill and other intangible assets Deferred Tax Liabilities, Goodwill and Intangible Assets Software development costs and property and equipment Deferred Tax Liabilities, Deferred Expense, Capitalized Software Prepaid assets Deferred Tax Liabilities, Prepaid assets The amount as of the balance sheet date of the estimated future tax effects attributable to the difference between the methods used to account for prepaid assets for tax purposes and under generally accepted accounting principles. Total deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax liability Deferred Tax Liabilities, Net RESTRICTED CASH, CASH EQUIVALENTS AND INVESTMENTS Restricted Assets Disclosure [Text Block] Liability to states under Medicaid risk sharing provisions Liability to states under minimum medical expense provision Liability to states under minimum medical expense provision. Liability to CMS under risk corridor and other provisions Receivable (Liability) To CMS Under Risk Corridor Provision Receivable (Liability) To CMS Under Risk Corridor Provision Liability to CMS under MA/PDP minimum MLR provisions of the ACA Liability to CMS under minimum MLR provisions of the ACA Liability to CMS under minimum MLR provisions of the ACA Net payables to government partners Net Receivables/Payables To Government Partners Net Receivables/Payables To Government Partners Receivables from government partners Receivables from government partners Receivables from government partners 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. Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Other Comprehensive Income (Loss) Other Comprehensive Income (Loss) [Member] Funds drawn on revolving line of credit facility Proceeds from Long-term Lines of Credit Proceeds from issuance of senior notes Proceeds from Debt, Net of Issuance Costs Aggregate principal amount Debt Instrument, Face Amount Common stock issuance fees paid Assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract] Assets 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 [Abstract] 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 Finite-lived Intangible Assets Acquired Measurement period adjustment, goodwill Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Goodwill Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Goodwill Measurement period adjustment, intangible assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles Measurement period adjustment, net assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Tangible Net Assets Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Tangible Net Assets Total pre-tax net losses Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Transaction and integration costs Business Combination, Integration Related Costs Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] 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] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Total Debt Securities, Available-for-sale Within 1 Year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value 1 Through 5 Years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value 5 Through 10 Years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Thereafter Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value 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 Depreciation, Depletion and Amortization, Nonproduction Stock-based compensation expense Share-based Compensation 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. 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] Acquisitions and acquisition-related settlements, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Purchases of investments Payments to Acquire Investments Proceeds from sales and maturities of investments Proceeds from Sale, Maturity and Collection of Investments Additions to property, equipment and capitalized software, net Payments to Acquire Productive Assets Net cash (used in) provided by 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 debt, net of financing costs paid Proceeds from Issuance of Long-term Debt Borrowings on Revolving Credit Facility, net of financing costs paid Proceeds from Lines of Credit Payments on debt Repayments of Short-term Debt Repurchase and retirement of shares to satisfy tax withholding requirements Payments Related to Tax Withholding for Share-based Compensation Funds (paid) 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 provided by (used in) 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 Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Membership and state contracts Contractual Rights [Member] Trademarks and tradenames Trademarks [Member] Licenses and permits Licensing Agreements [Member] Technology and other Technology And Other Intangible Assets [Member] Technology And Other Intangible Assets [Member] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Weighted Average Amortization Period (In Years) Finite-Lived Intangible Assets Finite-Lived Intangible Assets, Net [Abstract] Gross Carrying Amount Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Other Intangibles, Net Intangible Assets, Net (Excluding Goodwill) Other than temporary impairment losses, investments Other than Temporary Impairment Losses, Investments Meridian and Universal American Meridian and Universal American [Member] Meridian and Universal American [Member] Total revenues Business Acquisition, Pro Forma Revenue Net income Business Acquisition, Pro Forma Net Income (Loss) Earnings per common share 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 Amortization expense Amortization of Intangible Assets Expected Amortization Expense Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] 2019 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Five 2024 and thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Total Finite-Lived Intangible Assets, Net Rental expense Operating Leases, Rent Expense Minimum Lease Payments Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 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 Premium deficiency reserve Provision for Loss on Contracts Insurance [Abstract] Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] 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 Liability for Claims and Claims Adjustment Expense 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 Schedule of Goodwill [Table] Schedule of Goodwill [Table] Medicare Health Plans Goodwill [Line Items] Goodwill [Line Items] Estimated useful life Finite-Lived Intangible Asset, Useful Life Impairment of intangible assets Impairment of Intangible Assets (Excluding Goodwill) Calculated Weighted-Average Common Shares Outstanding Schedule of Weighted Average Number of Shares [Table Text Block] Document and Entity Information [Abstract] Document and Entity Information [Abstract] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date 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 Filer Category Entity Filer Category Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Document Type Document Type Amendment Flag Amendment Flag Entity Small Business Entity Small Business Entity Emerging Growth Entity Emerging Growth Company Entity Shell Company Entity Shell Company Document Period End Date Document Period End Date Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted Cash and Cash Equivalents Restricted Cash and Cash Equivalents Total cash, cash equivalents, and restricted cash and cash equivalents Leases [Abstract] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Operating lease, right-of-use assets Operating Lease, Right-of-Use Asset DEBT Debt Disclosure [Text Block] INCOME TAXES Income Tax Disclosure [Text Block] Changes in Goodwill by Reportable Segment Schedule of Goodwill [Table Text Block] Other Intangible Assets Schedule of Acquired Finite-Lived Intangible Assets by Major Class [Table Text Block] Expected Amortization Expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Kentucky KENTUCKY Florida FLORIDA Georgia GEORGIA Premium revenue as a percentage of consolidated premium revenue Premium Revenue, Net Of Premium Tax Represents premium revenue net of premium tax of consolidated premium revenue. 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] Managed Medical Assistance Program (MMA) Managed Medical Assistance Program [Member] Managed Medical Assistance Program Number of reportable segments Number of Reportable Segments Term of Agreement Term of Agreement Term of Agreement Number of regions executed contracts Number Of Regions Executed Contracts Number of Regions executed contracts during the period Total number of regions Total Number Of Regions Total number of regions Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] 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] 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, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Long-term debt outstanding Long-term Debt, Fair Value Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type Restricted Stock Units Restricted Stock Units (RSUs) [Member] Performance Stock Units Performance Shares [Member] Market Stock Units Market Stock Units [Member] Market stock units (MSUs) as awarded by a company to their employees as a form of incentive compensation. Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Equity Instruments Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding at 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 and expired (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) Weighted Average Grant-Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding as of beginning of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars 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 Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited and expired (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding at end of period (in dollars per share) Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Recently Adopted and Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Premium Revenue Recognition and Premiums Receivable Revenue Recognition, Policy [Policy Text Block] Minimum Medical Expense and Risk Corridor Provisions Other payables to government partners [Policy Text Block] Disclosure of accounting policy for the amounts due to government agencies under various contractual and plan arrangements. Medicare Part D Settlements Funds receivable held for benefit of members [Policy Text Block] Disclosure of accounting policy for government payments received or to be received to subsidize the member portion of medical payments for certain of the company's stand-alone prescription drug program members. Medical Benefits Expense and Medical Benefits Payable Medical benefits payable and expense [Policy Text Block] Disclosure of accounting policy for medical benefits payable and expense. ACA Industry Fee ACA Industry Fee [Policy Text Block] ACA Industry Fee [Policy Text Block] Equity-Based Employee Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Medicaid Premium Taxes Medicaid premium taxes [Policy Text Block] Disclosure of accounting policy for Medicaid premium taxes. Income Tax Expense Income Tax, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Investments Investment, Policy [Policy Text Block] Restricted Investments Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets, net [Policy Text Block] Disclosure of accounting policy for the total of the amounts paid in advance for capitalized costs that will be expensed with the passage of time or the occurrence of a triggering event, and will be charged against earnings within one year or the normal operating cycle, if longer, and the aggregate carrying amount of current assets, as of the balance sheet date, not separately presented elsewhere in the balance sheet. Property, Equipment and Capitalized Software, net Property, Plant and Equipment, Policy [Policy Text Block] Goodwill and Other Intangible Assets Goodwill and Intangible Assets, Policy [Policy Text Block] Accounts Payable and Accrued Expenses Accounts Payable and Accrued Expenses [Policy Text Block] Accounts Payable and Accrued Expenses [Policy Text Block] Reconciliation of income tax at the effective rate to income tax at the statutory federal rate Effective Income Tax Rate Reconciliation, Amount [Abstract] Income tax expense at statutory federal rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Adjustments resulting from: Increase (reduction) resulting from [Abstract] State income tax, net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Unrecognized tax benefits Effective Income Tax Rate Reconciliation, Nondeductible Expense, Executive Compensation The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to non-deductible executive compensation. Tax rate change Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount Non-deductible ACA industry fees Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount Other, net Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Total income tax expense Stock-based compensation expense Common stock price (in dollars per share) Share Price Unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted average period of forfeitures Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Weighted-average grant-date fair value of shares granted (in dollars per share) Total fair value of shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Organization, Consolidation and Presentation of Financial Statements [Abstract] Number of members served Number Of Members Represents the number of members under the government-sponsored health care programs. Discontinued Operations and Disposal Groups [Abstract] DISCONTINUED OPERATIONS Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Statement of Comprehensive Income [Abstract] Premium Products and services Expenses and other: Medical benefits Costs of products and services Medicaid premium taxes Premium Tax Expense An assessment levied by a state government agency on premium revenue. Interest Equity in (losses) earnings of unconsolidated subsidiaries Income (Loss) from Equity Method Investments Income before income taxes Income tax expense Other comprehensive income, before tax: Income tax (benefit) expense related to other comprehensive (loss) income Earnings per common share (see Note 5): Basic (in dollars per share) Diluted (in dollars per share) Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Diluted (in shares) Corporate and Other Corporate and Other [Member] Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net Reinsurance Recoverable Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments Total gross liability for unpaid claims and claim adjustment expense Reconciliation of the beginning and ending amount of unrecognized tax benefits Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Unrecognized tax benefits, beginning of period Unrecognized Tax Benefits Increases: Gross increases [Abstract] Prior year tax positions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Current year tax positions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Decreases: Gross decreases [Abstract] Prior year tax positions Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Unrecognized tax benefits, end of period Performance Stock Units Performance Share Awards [Member] Performance share awards to a former executive of the company as a form of incentive compensation. Summary of Activity for RSU Awards Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Summary of Activity for Nonvested Awards Schedule of Nonvested Performance-based Units Activity [Table Text Block] Current Assets: Assets, Current [Abstract] Short-term investments Short-term Investments Taxes receivable Income Taxes Receivable Affiliate receivables and other current assets Affiliate receivables and other current assets The aggregate amount of receivables to be collected from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth, at the financial statement date. which are usually due within one year (or one business cycle), along with other current assets. Total current assets Assets, Current Other assets Other Assets, Noncurrent Investment in subsidiaries Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Total Assets Assets Liabilities and Stockholders' Equity Current Liabilities: Liabilities, Current [Abstract] Accrued expenses and other current liabilities Accrued Liabilities and Other Liabilities Total current liabilities Liabilities, Current Long-term debt Long-term Debt, Excluding Current Maturities Other liabilities Other Liabilities, Noncurrent Total Liabilities Liabilities Commitments and contingencies (see Note 13) 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, 49,993,219 and 44,522,988 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively) Common Stock, Value, Issued Paid-in capital Additional Paid in Capital Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total Stockholders' Equity Stockholders' Equity Attributable to Parent Total Liabilities and Stockholders' Equity Liabilities and Equity Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] 2021 2022 2023 2024 and thereafter Senior Notes Due 2020 Issued 2013 - 5.75 percent Senior Notes Due 2020 Issued 2013 - 5.75 percent [Member] Senior Notes Due 2020 Issued 2013 - 5.75 percent [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Long-term debt, net Long-term Debt, Excluding Current Maturities [Abstract] Senior notes, noncurrent Senior Notes, Noncurrent Debt issuance costs Debt Issuance Costs, Noncurrent, Net Total long-term debt, net Selected Unaudited Quarterly Financial Data Quarterly Financial Information [Table Text Block] Short-duration Insurance Contracts, Claims Development [Table] Short-duration Insurance Contracts, Claims Development [Table] Short-duration Insurance Contracts, Accident Year [Axis] Short-duration Insurance Contracts, Accident Year [Axis] Short-duration Insurance Contracts, Accident Year [Domain] Short-duration Insurance Contracts, Accident Year [Domain] 2017 Short-duration Insurance Contracts, Accident Year 2015 [Member] 2018 Short-duration Insurance Contracts, Accident Year 2016 [Member] Claims Development [Line Items] Claims Development [Line Items] Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net Total of IBNR Liabilities Plus Expected Development on Reported Claims Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net Cumulative Number of Reported Claims Short-duration Insurance Contract, Cumulative Number of Reported Claims Acquired reinsurance receivable Acquired medical benefits payable liabilities Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance Short-duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net All outstanding liabilities before 2017, net of reinsurance Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net, Not Separately Presented Statutory federal income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent One-time, non-cash decrease to income tax expense Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit) Previously unrecognized tax benefits recognized SUBSEQUENT EVENTS Subsequent Events [Text Block] 2016 Debt Instrument, Redemption, Period One [Member] Debt Instrument Redemption Period Six Debt Instrument Redemption Period Six [Member] Debt Instrument, Redemption, Period Six Debt Instrument, Redemption Price, Allowed Percentage of Principle Amount Redeemable Debt Instrument, Redemption Price, Allowed Percentage of Principle Amount Redeemable Debt Instrument, Redemption Price, Allowed Percentage of Principle Amount Redeemable Aggregate net proceeds from the issuance of debt Proceeds from Issuance of Debt Borrowings outstanding Debt repurchase amount Debt Instrument, Repurchase Amount Minimum additional indebtedness pursuant to the fixed charge coverage ratio Debt Instrument, Covenant, Restructuring Restrictions, Minimum Additional Borrowing Capacity Pursuant To Fixed Charge Coverage Ratio Debt Instrument, Covenant, Restructuring Restrictions, Minimum Additional Borrowing Capacity Pursuant To Fixed Charge Coverage Ratio Percentage of principal amount redeemed Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed Percentage of principal amount outstanding Debt Instrument, Redemption Price, Required Percentage Of Principal Amount Outstanding Debt Instrument Redemption Period Debt Instrument Redemption Period Debt Instrument Redemption Period Days within closing of equity offering Debt Instrument, Early Redemption Condition, Maximum Days Within Closing Equity Offering Debt Instrument, Early Redemption Condition, Maximum Days Within Closing Equity Offering Redemption premium, percentage of principal amount redeemed Debt Instrument, Redemption Premium, Percentage of Principal Amount Redeemed Issue price Debt Instrument, Issue Price, Percentage Debt Instrument, Issue Price, Percentage Depreciation expense Depreciation Depreciation expense on capitalized software Capitalized Computer Software, Amortization Schedule I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT Condensed Financial Information of Parent Company Only Disclosure [Text Block] Summary of Restricted Cash and Investment Securities Restrictions On Cash, Cash Equivalents And Investments [Table Text Block] Restrictions On Cash, Cash Equivalents And Investments [Table Text Block] Schedule of Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment by Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Leasehold improvements Leasehold Improvements [Member] Computer equipment Computer Equipment [Member] Capitalized software Software and Software Development Costs [Member] Furniture and equipment Furniture and Equipment [Member] Long lived, depreciable assets, commonly used in offices and stores and tangible personal property, nonconsumable in nature, with finite lives used to produce goods and services. Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, equipment and capitalized software, gross Property, Plant and Equipment, Gross Less accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Total property and equipment, net Property, Plant and Equipment, Net ABR Loans ABR Loans [Member] ABR Loans [Member] Eurodollar Eurodollar [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] London Interbank Offered Rate (LIBOR) London Interbank Offered Rate (LIBOR) [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Lender Concentration Risk Lender Concentration Risk [Member] Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Revolving credit facility accordion loan amount Line of Credit Facility, Accordian Loan Feature Line of Credit Facility, Accordion Loan Feature Unutilized commitment fee percentage Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Minimum lender holding for accelerated maturity rights Debt Instrument, Covenant Terms, Default Provisions, Qualifying Lender, Minimum Percentage of Loans Held under Debt Agreement Debt Instrument, Covenant Terms, Default Provisions, Qualifying Lender, Minimum Percentage of Loans Held under Debt Agreement Funds repaid on revolving credit facility Repayments of Long-term Lines of Credit 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 Loss AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholder's Equity (in shares) Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract] Balance, beginning of period (in shares) Issuance of common stock (in shares) Stock Issued During Period, Shares, New Issues Common stock issued for vested stock-based compensation awards (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures Repurchase and retirement of shares to satisfy tax withholding requirements (in shares) Stock Repurchased During Period, Shares Balance, end of period (in shares) Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance, beginning of period Issuance of common stock, net of issuance costs Stock Issued During Period, Value, New Issues Common stock issued for vested stock-based compensation awards Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures Repurchase and retirement of shares to satisfy tax withholding requirements Stock Repurchased During Period, Value Stock-based compensation expense, net of forfeitures Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Balance, end of period REGULATORY CAPITAL AND DIVIDEND RESTRICTIONS [Abstract] Subsidiaries Subsidiaries [Member] Minimum capital and surplus requirement Statutory Accounting Practices, Statutory Capital and Surplus Required Combined statutory capital and surplus Statutory Accounting Practices, Statutory Capital and Surplus, Balance Dividends received from regulated subsidiaries Dividends received from regulated subsidiaries Dividends received from regulated subsidiaries during the current period. Dividends paid without regulatory approval Statutory Accounting Practices, Dividends Paid without Approval of Regulatory Agency Statutory Accounting Practices, Dividends Paid without Approval of Regulatory Agency Dividends paid with regulatory approval Statutory Accounting Practices, Dividends Paid with Approval of Regulatory Agency Amount of dividends that may be paid through the end of 2019 without prior approval by regulatory authorities Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval 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] Life insurance subsidiaries disposed by sale Discontinued Operations, Subsidiaries Disposed by Sale Discontinued Operations, Subsidiaries Disposed by Sale 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 Disposal Group, Including Discontinued Operation, Liabilities Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Table] Corporate debt securities Municipal securities Cash Municipal securities U.S. government securities and other US Treasury Securities [Member] Investments Investments, Fair Value Disclosure Restricted investment 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. Assets and Liabilities Measured at Fair Value Fair Value, Assets Measured on Recurring Basis [Table Text Block] Changes in Fair Value of Level 3 Investments Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [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] ACQUISITIONS Business Combination Disclosure [Text Block] Net cash (used in) provided by operating activities Cash used in investing activities: Net proceeds (payments) from purchases and sales and maturities of investments Payments for (Proceeds from) Investments Payments to subsidiaries, net Capital contributions to subsidiaries The cash outflow associated with capital contributions to subsidiaries during the period. Cash provided by financing activities: Repurchase and retirement of shares to satisfy tax withholding requirements Other, net Cash and cash equivalents: Cash and Cash Equivalents, Period Increase (Decrease) [Abstract] (Decrease) increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Balance at beginning of period Balance at end of period QUARTERLY FINANCIAL INFORMATION Quarterly Financial Information [Text Block] REGULATORY CAPITAL AND DIVIDEND RESTRICTIONS Statutory Capital And Dividend Restrictions [Text Block] This element may be used to capture the complete disclosure for insurance companies for regulatory capital requirements imposed by state insurance regulatory agencies. In addition, it discloses how the entity's reporting under GAAP as of the balance sheet date differs from the results based on prescribed and permitted accounting practices of the state or country of domicile in which a relevant statutory filing is made, or differences in results based on the National Association of Insurance Commissioners (NAIC) prescribed practices. Favorable 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 Investments by Security Type Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Contractual Maturities of Long-term Available-for-sale Investments Investments Classified by Contractual Maturity Date [Table Text Block] Low-income cost sharing subsidy Funds Receivable For Benefit Of Members Low Income Cost Sharing Subsidy Amount of low-income cost sharing subsidy for qualifying low income status members that the Center for Medicare and Medicaid Services ("CMS") reimburses for all or a portion of the member's deductible, coinsurance and co-payment amounts above the out of pocket threshold for low income beneficiaries. Low-income cost sharing subsidies are paid by CMS prospectively as a fixed amount per member per month, and are determined based upon the plan year bid the entity submitted to CMS. Catastrophic reinsurance subsidy Funds Receivable For Benefit Of Members Catastrophic Reinsurance Subsidy Amount of catastrophic reinsurance subsidy paid by Center for Medicare and Medicaid Services ("CMS") prospectively as a fixed amount per member per month, and determined based upon the plan year bid we submitted to CMS. CMS reimburses for 80% of the drug costs after a member reaches his or her out of pocket catastrophic threshold through a catastrophic reinsurance subsidy. Coverage gap discount subsidy Funds Receivable For Benefit Of Members Coverage Gap Discount Subsidy Amount of coverage gap discount subsidy for monthly prospective payments by Center for Medicare and Medicaid Services ("CMS") for pharmaceutical manufacturer discounts made available to members. The prospective discount payments are determined based upon the plan year bid submitted by plan sponsors to CMS and current plan enrollment. Funds payable for the benefit of members 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. 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. Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value Measurements Using Significant Unobservable Inputs (Level 3) Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Balance at beginning of period Realized gains (losses) in earnings Changes in net unrealized gains and losses in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Purchases, sales and redemptions Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) Net transfers in or (out) of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net Balance at end of period Performance Shares Restricted stock units, conversion ratio Share-based Compensation Arrangement by Share-based Payment Award, Conversion Ratio Share-based Compensation Arrangement by Share-based Payment Award, Conversion Ratio Vesting period Share-Based Compensation Restricted Stock Units Vesting Period Share-Based Compensation Restricted Stock Units Vesting Period Cliff vesting number of shares earned, minimum (in shares) Cliff Vesting, Number Of Shares Earned, Range, Minimum Cliff Vesting, Number Of Shares Earned, Range, Minimum Cliff vesting target range percentage, maximum Cliff Vesting Target Range Percentage Cliff Vesting Target Range Percentage Vesting period of certain equity-based compensation Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Number of plan variations Share-based Compensation, Number of Plans Share-based Compensation, Number of Plans Number of calendar days preceding the vesting date to the comparable average common stock price in the year immediately preceding the grant date Number Of Calendar Days Preceding End Of Fiscal Year Prior To Vesting Date With Maximum Quotient