Significant Accounting Policies Significant Accounting Policies [Text Block] Interest coverage ratio Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Debt Instrument, Covenant, Interest Coverage Ratio, Minimum Statistical Measurement [Domain] Statistical Measurement [Domain] Prior years Prior period claims, favorable development Prior Year Claims and Claims Adjustment Expense Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Additional Paid-in Capital Additional Paid-in Capital [Member] Stock purchases (in shares) Weighted Average Number of Shares, Common Stock Subject to Repurchase or Cancellation Tabular List, Table Tabular List [Table Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Covenant Period Four Covenant Period Four [Member] Covenant Period Four Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Other operating expenses Other Expenses Measurement Basis [Axis] Measurement Basis [Axis] Risk adjustment receivable Affordable Care Act, Premium Stabilization Program, Risk Adjustment, Receivable Affordable Care Act, Premium Stabilization Program, Risk Adjustment, Receivable Net income per share - Basic (in dollars per share) Earnings Per Share, Basic Adjustment to Compensation: Adjustment to Compensation [Axis] Amounts due government agencies Medical Premium Liability Due To Agency Medical Premium Liability Due to Agency Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Accounts payable, accrued liabilities and other Increase (Decrease) in Accounts Payable and Accrued Liabilities Schedule of Operating Segment Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Investments Schedule of Available-for-Sale Securities Reconciliation [Table Text Block] Adjustment to Compensation, Amount Adjustment to Compensation Amount Share-based compensation Share-Based Payment Arrangement, Noncash Expense Employee Stock Option Share-Based Payment Arrangement, Option [Member] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Stock purchase excise tax Share Repurchase Program, Excise Tax Total stockholders’ equity Beginning balance Ending balance Equity, Attributable to Parent Impairment Impairment Asset Impairment Charges Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Insider Trading Policies and Procedures [Line Items] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Current assets: Assets, Current [Abstract] Total liabilities and stockholders’ equity Liabilities and Equity Concentrations of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Cover [Abstract] Cover [Abstract] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Maximum Maximum [Member] Structured Securities Structured Securities [Member] Structured Securities [Member] Contract Rights and Licensing Agreements Contract Rights and Licenses [Member] Contract Rights and Licenses Cash consideration amount Debt Instrument, Debt To Capitalization Ratio, Cash Consideration Amount Debt Instrument, Debt To Capitalization Ratio, Cash Consideration Amount Accounting Policies [Abstract] Accounting Policies [Abstract] Due after ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Pay vs Performance Disclosure [Line Items] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Income before income tax expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Other long-term liabilities Other Liabilities, Noncurrent Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating segments Operating Segments [Member] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Comprehensive (loss) income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Segment expenses Segment Expenses Segment Expenses Amortized cost, due in one year or less Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, Year One Name Measure Name Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Document Fiscal Period Focus Document Fiscal Period Focus Receivables Receivable [Policy Text Block] Goodwill, and intangible assets, net Intangible Assets, Net (Including Goodwill) Premium Deficiency Reserve on Loss Contracts Premium Deficiency Reserves on Loss Contracts [Policy Text Block] Premium Deficiency Reserves on Loss Contracts Award Timing Method Award Timing Method [Text Block] Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss Award Type Award Type [Axis] Total assets Assets Consolidation and Interim Financial Information Consolidation And Interim Financial Information, Policy [Policy Text Block] Consolidation And Interim Financial Information, Policy [Policy Text Block] Trading Symbol Trading Symbol Number of states with programs Number Of States With Government-Sponsored Healthcare Programs Number Of States With Government-Sponsored Healthcare Programs Income Taxes Income Tax, Policy [Policy Text Block] Share-based compensation (in shares) Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture Entity Address, City or Town Entity Address, City or Town Operating activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Receivable Type [Axis] Receivable Type [Axis] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Fair value of assets measured on recurring basis Assets, Fair Value Disclosure [Abstract] Entity Emerging Growth Company Entity Emerging Growth Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] (Level 2) Fair Value, Inputs, Level 2 [Member] Restricted cash and cash equivalents Restricted Cash and Cash Equivalent Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Number of members eligible for the health care programs, approximately Number Of Members Eligible For Government-Sponsored Healthcare Programs Number of members eligible for the health care programs. Common stock, shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Insurance [Abstract] Average maturity period (less than) Investments, Average Maturity Period Investments, Average Maturity Period PEO PEO [Member] Percent due to medicare, medical loss ratio of marketplace Percent Due To Government Agencies, Medicare, Medical Loss Ratio Of Marketplace Percent Due To Government Agencies, Medicare, Medical Loss Ratio Of Marketplace Schedule of Contractual Maturities of Investments Investments Classified by Contractual Maturity Date [Table Text Block] Term Loans Term Loan [Member] Term Loan [Member] Changes in operating assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Contract term Health Plan, Contract Term Health Plan, Contract Term Retained Earnings Retained Earnings [Member] Total paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Medical margin Medical [Member] Medical Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Cash, cash equivalents, and restricted cash and cash equivalents at beginning of period Cash, cash equivalents, and restricted cash and cash equivalents at end of period Total cash, cash equivalents, and restricted cash and cash equivalents presented in the consolidated statements of cash flows Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Income tax expense Income Tax Expense (Benefit) In a Continuous Loss Position for 12 Months or More, Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Percent due to medicare, medical loss ratio Percent Due To Government Agencies, Medicare, Medical Loss Ratio And Profit Sharing, Threshold Percent Due To Government Agencies, Marketplace, Medical Loss Ratio And Profit Sharing, Threshold Purchases of investments Payments to Acquire Marketable Securities Medicare Medicare [Member] Medicare Government Receivables Government Receivables [Member] Government Receivables [Member] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Product and Service [Domain] Product and Service [Domain] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Investment income Net Investment Income Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Health Plans Health Plans [Member] Health plans. City Area Code City Area Code Net cash paid in business combinations Payments to Acquire Businesses, Net of Cash Acquired Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Debt Instrument Covenant Period [Domain] Debt Instrument Covenant Period [Domain] Debt Instrument Covenant Period [Domain] Proceeds from borrowings under credit facility and term loans Proceeds from Long-Term Lines of Credit Investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] General and administrative expenses General and Administrative Expense Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Debt term Debt Instrument, Term Debt securities, sale Proceeds from Sale of Debt Securities, Available-for-Sale 3.875% Notes due 2030 3.875% Senior Notes Due 2030 [Member] 3.875% Senior Notes Due 2030 4.375% Notes due 2028 4.375% Senior Notes Due 2028 [Member] 4.375% Senior Notes Due 2028 Debt securities, available-for-sale Estimated Fair Value Debt Securities, Available-for-Sale, Excluding Accrued Interest Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year PEO Total Compensation Amount PEO Total Compensation Amount Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Weighted-average number of shares issued: Weighted Average Number of Shares Outstanding, Basic [Abstract] Equity Components [Axis] Equity Components [Axis] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Total Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value Number of reportable segments Number of Reportable Segments Other Performance Measure, Amount Other Performance Measure, Amount Schedule of Restricted Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Entity Address, State or Province Term Loans Delayed Draw Term Loan (DDTL) [Member] Total current liabilities Liabilities, Current Medical claims and benefits payable Increase (Decrease) in Health Care Insurance Liabilities Revenue from external customers Premiums Earned And Service Revenue Premiums Earned And Service Revenue Individual: Individual [Axis] Covenant Period One Covenant Period One [Member] Covenant Period One Additional paid-in capital Additional Paid in Capital, Common Stock Net cash provided by (used in) investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Document Fiscal Year Focus Document Fiscal Year Focus Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Entity Interactive Data Current Entity Interactive Data Current Carrying Amount Reported Value Measurement [Member] New Credit Agreement New Credit Agreement [Member] New Credit Agreement Premium Revenue Recognition and Amounts Due Government Agencies, Minimum MLR, Medical Cost Corridors and Profit Sharing and Risk Adjustment Revenue from Contract with Customer [Policy Text Block] Covenant Period Two Covenant Period Two [Member] Covenant Period Two Segments Segment Reporting Disclosure [Text Block] U.S. Treasury notes US Treasury Notes 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] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Medical Claims and Benefits Payable Medical Claims And Benefits Payable [Text Block] Medical claims and benefits payable. Deferred income taxes, net Deferred Income Tax Assets, Net Depreciation and amortization Depreciation, Depletion and Amortization Other assets Other Assets, Noncurrent Entity Central Index Key Entity Central Index Key PEO Name PEO Name Total revenue Revenues Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Components of medical care costs related to: Components Of Medical Care Costs [Abstract] Components of medical care costs. Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Minimum MLR, medical cost corridors and profit sharing liability Medical Premiums Liability, Medical Care Costs Threshold Medical Premiums Liability, Medical Care Costs Threshold Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Total medical care costs Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Credit Facility Revolving Credit Facility [Member] Arrangement Duration Trading Arrangement Duration Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Deferred revenue Contract with Customer, Liability, Current Segments [Axis] Segments [Axis] Prepaid expenses and other current assets Increase (Decrease) in Prepaid Expense and Other Assets Exercise Price Award Exercise Price Medicaid Medicaid [Member] Medicaid Entity Filer Category Entity Filer Category Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Other, net Payment for (Proceeds from) Other Investing Activity Other, net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Common stock purchases (in shares) Stock Repurchased and Retired During Period, Shares ASSETS Assets [Abstract] Long-term debt Total Long-Term Debt, Excluding Current Maturities Credit Facility [Axis] Credit Facility [Axis] Underlying Security Market Price Change Underlying Security Market Price Change, Percent Debt Instrument [Axis] Debt Instrument [Axis] Net income per share: Earnings Per Share, Basic and Diluted EPS [Abstract] Earnings Per Share, Basic and Diluted EPS Fair Value Measurements Fair Value Disclosures [Text Block] Credit Facility [Domain] Credit Facility [Domain] Stockholders’ equity: Equity, Attributable to Parent [Abstract] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Debt instrument, interest rate, stated percentage Percentage of contractual interest rate Debt Instrument, Interest Rate, Stated Percentage Amortized cost, due after five years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year 5 through 10 Fair Value as of Grant Date Award Grant Date Fair Value Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Schedule of Long Term Debt Schedule of Long-Term Debt Instruments [Table Text Block] Stock-based compensation (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Total operating expenses Costs and Expenses Document Quarterly Report Document Quarterly Report In a Continuous Loss Position for Less than 12 Months, Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Total assets Assets, Fair Value Disclosure Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Service margin Service [Member] Restatement Determination Date: Restatement Determination Date [Axis] Debt instrument, covenant, debt to capitalization ratio Debt Instrument, Debt To Capitalization Ratio Debt Instrument, Debt To Capitalization Ratio Share-based compensation Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Non-PEO NEO Non-PEO NEO [Member] Other, net Proceeds from (Payment for) Other Financing Activity Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Name Trading Arrangement, Individual Name All Award Types Award Type [Domain] Cost of service revenue Cost Of Service Revenue Cost Of Service Revenue Incurred but not paid Reinsurance Recoverables, Incurred but Not Reported Claims Equity Awards Adjustments Equity Awards Adjustments [Member] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Other revenue Other Income Compensation Amount Outstanding Recovery Compensation Amount Aggregate principal amount Debt Instrument, Face Amount Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Fair Value Estimate of Fair Value Measurement [Member] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Due after one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Name Awards Close in Time to MNPI Disclosures, Individual Name Amortized cost, due one year through five years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five Denominator: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] 6.500% Notes due February 15, 2031 6.500% Senior Notes Due 2031 [Member] 6.500% Senior Notes Due 2031 Maturity period (less than) Investments, Maturity Period Investments, Maturity Period Provider Networks Provider Networks [Member] Provider Networks Revenue: Revenues [Abstract] Due after five years through ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 In a Continuous Loss Position for 12 Months or More, Total Number of Positions Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Less: effect of income taxes OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Financial Instruments [Domain] Financial Instruments [Domain] Segments [Domain] Segments [Domain] Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Basis Of Presentation [Table] Basis Of Presentation [Table] Basis Of Presentation [Table] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Payments for medical care costs related to: Payments For Medical Care Costs [Abstract] Payments for medical care costs. Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Minimum Minimum [Member] Company Selected Measure Name Company Selected Measure Name Fair Value Measurement [Domain] Fair Value Measurement [Domain] Senior Notes Senior Notes [Member] Preferred stock, $0.001 par value; 20 million shares authorized, no shares issued and outstanding Preferred Stock, Value, Issued Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] All Executive Categories All Executive Categories [Member] Current year Current Year Claims and Claims Adjustment Expense Other operating revenues Other Operating Income Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] Premium revenue Premiums Earned, Net Shares outstanding at the beginning of the period (in shares) Shares, Outstanding, Excluding Restricted Stock Awards Shares, Outstanding, Excluding Restricted Stock Awards Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Denominator for diluted net income per share (in shares) Weighted Average Number of Shares Outstanding, Diluted Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Entity Small Business Entity Small Business Non-current portion of long-term debt Long-Term Debt, Noncurrent, Net Of Unamortized Debt Discount Long-Term Debt, Noncurrent, Net Of Unamortized Debt Discount Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Debt Long-Term Debt [Text Block] Document Transition Report Document Transition Report Risk adjustments liability Amounts Due to Government Agencies, Risk Adjustment and Part D risk sharing Amounts Due to Government Agencies, Risk Adjustment and Part D risk sharing Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Due after ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Fair value of debt Debt Instrument, Fair Value Disclosure Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Claims and Claims Adjustment Expense [Line Items] Document Type Document Type (Level 3) Fair Value, Inputs, Level 3 [Member] Net Income Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Government agencies liability Amounts Due To Government Agencies, Medicare, Medical Loss Ratio And Profit Sharing, Threshold Amounts Due To Government Agencies, Medicare, Medical Loss Ratio And Profit Sharing, Threshold Product and Service [Axis] Product and Service [Axis] Change in non-risk and other payables Medical Claims And Benefits Payable, Adjustments, Change In Provider Medical Claims and Benefits Payable, Adjustments, Change in Provider All Individuals All Individuals [Member] Long-term Debt, Type [Domain] Long-Term Debt, Type [Domain] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Receivables Increase (Decrease) in Receivables Purchases of property, equipment and capitalized software Payments to Acquire Property, Plant, and Equipment Name Forgone Recovery, Individual Name Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] 3.875% Notes due May 15, 2032 3.875% Senior Notes Due 2032 [Member] 3.875% Senior Notes Due 2032 Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Swingline sub facility Swingline Sub Facility [Member] Swingline Sub Facility Amounts due government agencies Increase (Decrease) In Medical Premium Liability Due To Agency Increase (Decrease) in Medical Premium Liability Due to Agency Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Investments Marketable Securities, Current Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Current liabilities: Liabilities, Current [Abstract] Other comprehensive (loss) gain, net of tax Other comprehensive income (loss), net Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Service revenue Service Revenue Service Revenue Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Schedule of Components of The Change in Medical Claims and Benefits Payable Components Of Change In Medical Claims And Benefits Payable [Table Text Block] Components Of Change In Medical Claims And Benefits Payable [Table Text Block] Amount outstanding under letter of credit Long-Term Line of Credit (Level 1) Fair Value, Inputs, Level 1 [Member] Risk adjustment, net receivable (payable) Affordable Care Act, Premium Stabilization Program, Risk Adjustment, Net Receivable Affordable Care Act, Premium Stabilization Program, Risk Adjustment, Receivable (Payable) Net income per share - Diluted (in dollars per share) Earnings Per Share, Diluted Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Title of 12(b) Security Title of 12(b) Security Basis Of Presentation [Line Items] Basis Of Presentation [Line Items] Basis Of Presentation [Line Items] Due after five years through ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Premium tax revenue Health Care Organization, Premium Tax Revenue Health Care Organization, Premium Tax Revenue Other comprehensive (loss) gain: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Premium tax expenses Premium Tax Expenses An assessment levied by a state government on the net premium income collected. Segment margin Gross Profit Stock-based compensation (in shares) Weighted Average Number of Shares, Share Based Compensation Weighted Average Number of Shares, Share Based Compensation Other Other Securities [Member] Other Securities Common stock purchases Stock Repurchased and Retired During Period, Value Deferred revenue Increase (Decrease) in Contract with Customer, Liability Award Timing Disclosures [Line Items] Property, equipment, and capitalized software, net Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization Trade name Trade Names [Member] Net income Net income Net Income (Loss) Attributable to Parent Schedule of Available-for-Sale Investments Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Expiration Date Trading Arrangement Expiration Date Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Common stock purchases Payments for Repurchase of Common Stock Adoption Date Trading Arrangement Adoption Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Entity Current Reporting Status Entity Current Reporting Status Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Operating income Operating Income (Loss) Credit Facility Line of Credit [Member] Due in one year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Retained earnings Retained Earnings (Accumulated Deficit) Financial Instrument [Axis] Financial Instrument [Axis] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Executive Category: Executive Category [Axis] In a Continuous Loss Position for 12 Months or More, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Other Other Operating Income (Expense), Net In a Continuous Loss Position for Less than 12 Months, Total Number of Positions Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Current Fiscal Year End Date Current Fiscal Year End Date In a Continuous Loss Position for Less than 12 Months, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Remaining intangible assets Impairment of Intangible Assets, Finite-Lived Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Risk adjustment receivable (payable) Affordable Care Act, Premium Stabilization Program, Risk Adjustment, (Payable) Affordable Care Act, Premium Stabilization Program, Risk Adjustment, Receivable (Payable) Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Debt Instrument Covenant Period [Axis] Debt Instrument Covenant Period [Axis] Debt Instrument Covenant Period Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Statement [Table] Statement [Table] Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in 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