Insurance [Abstract] Schedule of Activity in Benefits Payable Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Schedule of Benefits Payable Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block] Debt Disclosure [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Senior notes Senior Notes [Member] Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Commercial paper Commercial Paper [Member] Term note Notes Payable to Banks [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] $400 million, 2.50% due December 15, 2020 2.50 Percent Senior Notes Due December 2020 [Member] 2.50 Percent Senior Notes Due December 2020 [Member] $600 million, 3.15% due December 1, 2022 3.15 Percent Senior Notes Due December 2022 [Member] 3.15 Percent Senior Notes Due December 2022 [Member] $400 million, 2.90% due December 15, 2022 2.90 Percent Senior Notes Due December 2022 [Member] 2.90 Percent Senior Notes Due December 2022 [Member] $600 million, 3.85% due October 1, 2024 3.85 Percent Senior Notes Due October 2024 [Member] 3.85 Percent Senior Notes Due October 2024 [Member] $600 million, 4.50% due April 1, 2025 A 4.500 Percent Senior Notes Due April 2025 [Member] A 4.500 Percent Senior Notes Due April 2025 [Member] $600 million, 3.95% due March 15, 2027 3.95 Percent Senior Notes Due March 2027 [Member] 3.95 Percent Senior Notes Due March 2027 [Member] $500 million, 3.125% due August 15, 2029 A 3.125 Percent Senior Notes Due August 2029 [Member] A 3.125 Percent Senior Notes Due August 2029 [Member] $500 million, 4.875% due April 1, 2030 A 4.875 Percent Senior Notes Due April 2030 [Member] A 4.875 Percent Senior Notes Due April 2030 [Member] $250 million, 8.15% due June 15, 2038 8.15 Percent Senior Notes Due June 2038 [Member] 8.15 Percent Senior Notes Due June 2038 [Member] $400 million, 4.625% due December 1, 2042 4.625 Percent Senior Notes Due December 2042 [Member] 4.625 Percent Senior Notes Due December 2042 [Member] $750 million, 4.95% due October 1, 2044 4.95 Percent Senior Notes Due October 2044 [Member] 4.95 Percent Senior Notes Due October 2044 [Member] $400 million, 4.80% due March 15, 2047 4.80 Percent Senior Notes Due March 2047 [Member] 4.80 Percent Senior Notes Due March 2047 [Member] $500 million, 3.95% due August 15, 2049 A 3.95 Percent Senior Notes Due August 2049 [Member] A 3.95 Percent Senior Notes Due August 2049 [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Face amount Debt Instrument, Face Amount Stated interest rate (percent) Debt Instrument, Interest Rate, Stated Percentage Short-term debt Short-term Debt Long-term debt, current maturities Long-term Debt, Current Maturities Total short-term debt Debt, Current Long-term debt Long-term Debt, Excluding Current Maturities Schedule of Balance Sheet Amounts Associated With Medicare Part D Balance Sheet Account Associated With Medicare Part D Table [Table Text Block] Balance Sheet Account Associated With Medicare Part D Earnings Per Share [Abstract] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Employee stock options Share-based Payment Arrangement, Option [Member] Restricted stock Restricted Stock [Member] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Net income available for common stockholders Net Income (Loss) Attributable to Parent Weighted average outstanding shares of common stock used to compute basic earnings per common share (in shares) Weighted Average Number of Shares Outstanding, Basic Dilutive effect of employee stock options and restricted stock (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Shares used to compute diluted earnings per common share (in shares) Weighted Average Number of Shares Outstanding, Diluted Basic earnings per common share (in dollars per share) Earnings Per Share, Basic Diluted earnings per common share (in dollars per share) Earnings Per Share, Diluted Number of antidilutive stock options and restricted stock excluded from computation (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Equity [Abstract] Schedule of Details of Dividend Payments Dividends Declared [Table Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] Line of Credit Line of Credit [Member] Unsecured Revolving Credit Agreement Unsecured Revolving Credit Agreement Expires May 2022 [Member] Unsecured Revolving Credit Agreement Expires May 2022 [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving Credit Facility Revolving Credit Facility [Member] Letter of Credit Letter of Credit [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Debt instrument term (in years) Debt Instrument, Term Maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Basis spread on variable rate (percent) Debt Instrument, Basis Spread on Variable Rate Facility fee (percent) Line of Credit Facility, Commitment Fee Percentage Debt to capitalization percentage, maximum Debt Instrument, Covenant, Debt To Capitalization Percentage, Maximum Debt Instrument, Covenant, Debt To Capitalization Percentage, Maximum Actual debt to capitalization percentage (percent) Debt Instrument, Covenant, Debt To Capitalization Percentage Debt Instrument, Covenant, Debt To Capitalization Percentage Maximum borrowing capacity including uncommitted incremental loan facility Line Of Credit Facility, Maximum Borrowing Capacity Including Uncommitted Incremental Capacity Maximum borrowing capacity under the credit facility including uncommitted incremental capacity and without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. Uncommitted incremental loan facility Line Of Credit Facility, Uncommitted Incremental Capacity Line Of Credit Facility, Uncommitted Incremental Capacity Line of credit, outstanding borrowings Line of Credit, Current Remaining borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Risk Corridor Settlement Risk Corridor Settlements Medicare Part D [Member] Risk Corridor Settlements - Medicare Part D [Member] CMS Subsidies/ Discounts Cms Subsidies Or Discounts [Member] CMS Subsidies Or Discounts [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Other current assets Other Assets, Current Trade accounts payable and accrued expenses Accounts Payable and Accrued Liabilities, Current Net current (liability) asset Net Current (Liability) Asset Net current (liability) asset Other long-term assets Other Assets, Noncurrent Other long-term liabilities Other Liabilities, Noncurrent Net long-term asset (liability) Net Noncurrent Asset (Liability) Net Noncurrent Asset (Liability) Total net (liability) asset Net Asset (Liability) Net Asset (Liability) Investments, Debt and Equity Securities [Abstract] Gross realized gains Debt Securities, Available-for-sale, Realized Gain Gross realized losses Debt Securities, Available-for-sale, Realized Loss Net realized capital gains (losses) Debt Securities, Available-for-sale, Realized Gain (Loss) Net proceeds from issuance of notes Proceeds from Debt, Net of Issuance Costs Redemption price, percentage Debt Instrument, Redemption Price, Percentage Statement of Financial Position [Abstract] ASSETS Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Investment securities Debt Securities, Available-for-sale, Current Receivables, less allowance for doubtful accounts of $73 in 2020 and $69 in 2019 Receivables, Net, Current Total current assets Assets, Current Property and equipment, net Property, Plant and Equipment, Net Long-term investment securities Debt Securities, Available-for-sale, Noncurrent Equity method investments Equity Method Investments Goodwill Goodwill Total assets Assets LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Benefits payable Liability for Claims and Claims Adjustment Expense Trade accounts payable and accrued expenses Book overdraft Book Overdraft Liability Book Overdraft Liability Unearned revenues Contract with Customer, Liability, Current Short-term debt Total current liabilities Liabilities, Current Long-term debt Future policy benefits payable Liability for Future Policy Benefit, before Reinsurance Other long-term liabilities Total liabilities Liabilities Commitments and contingencies (Note 13) Commitments and Contingencies Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $1 par; 10,000,000 shares authorized; none issued Preferred Stock, Value, Issued Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,629,992 shares issued at March 31, 2020 and December 31, 2019 Common Stock, Value, Issued Capital in excess of par value Additional Paid in Capital, Common Stock Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Treasury stock, at cost, 66,423,923 shares at March 31, 2020 and 66,524,771 shares at December 31, 2019 Treasury Stock, Value Total stockholders’ equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders’ equity Liabilities and Equity Fair Value Disclosures [Abstract] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Recurring Basis Fair Value, Recurring [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Quoted Prices in Active Markets (Level 1) Fair Value, Inputs, Level 1 [Member] Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] U.S. Treasury and agency obligations US Treasury and Government [Member] Mortgage-backed securities Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Tax-exempt municipal securities Nontaxable Municipal Notes [Member] Commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Asset-backed securities Asset-backed Securities [Member] Corporate debt securities Corporate Debt 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] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Debt securities Debt Securities, Available-for-sale Common stock Equity Securities, FV-NI Total invested assets Assets, Fair Value Disclosure Goodwill and Intangible Assets Disclosure [Abstract] Schedule of Changes in Carrying Amount of Goodwill By Reportable Segments Schedule of Goodwill [Table Text Block] Schedule of Intangible Assets Included in Other Long-Term Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Schedule of Estimated Amortization Expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] 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 net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Net realized capital (gains) losses Equity in net earnings Income (Loss) from Equity Method Investments Stock-based compensation Share-based Payment Arrangement, Noncash Expense Depreciation Depreciation Amortization Amortization of Intangible Assets Benefit for deferred income taxes Increase (Decrease) in Deferred Income Taxes Changes in operating assets and liabilities, net of effect of businesses acquired and dispositions: Increase (Decrease) in Operating Capital [Abstract] Receivables Increase (Decrease) in Receivables Other assets Increase (Decrease) in Other Operating Assets Benefits payable Increase (Decrease) in Health Care Insurance Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Unearned revenues Increase (Decrease) in Contract with Customer, Liability Other Other Operating Activities, Cash Flow Statement 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, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Purchases of investment securities Payments to Acquire Debt Securities, Available-for-sale Maturities of investment securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Proceeds from sales of investment securities Proceeds from Sale of Debt Securities, Available-for-sale 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] Receipts from contract deposits, net Increase (Decrease) in Other Deposits Proceeds from issuance of senior notes, net Proceeds from Issuance of Senior Long-term Debt Proceeds from issuance of commercial paper, net Proceeds from Issuance of Commercial Paper Proceeds from term loan Proceeds from Notes Payable Change in book overdraft Increase (Decrease) in Book Overdrafts Common stock repurchases Payments for Repurchase of Common Stock Dividends paid Payments of Dividends Proceeds from stock option exercises and other, net Proceeds From Stock Options Exercised And Other Proceeds From Stock Options Exercised And Other Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Increase in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash and cash equivalents at beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash and cash equivalents at end of period Supplemental cash flow disclosures: Supplemental Cash Flow Information [Abstract] Interest payments Interest Paid, Excluding Capitalized Interest, Operating Activities Income tax refunds, net Proceeds from Income Tax Refunds Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] Services Accounts Receivable Trade Accounts Receivable [Member] Scenario [Axis] Scenario [Axis] Scenario [Domain] Scenario [Domain] Forecast Forecast [Member] Regulatory Matters [Axis] Regulatory Matters [Axis] Regulatory Matters [Axis] Regulatory Matters [Domain] Regulatory Matters [Domain] Regulatory Matters [Domain] Health Care Reform Health Care Reform [Member] Health Care Reform [Member] Receivables and Other [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Contributions to Humana Foundation to promote COVID-19 relief efforts Contributions To Foundation For COVID-19 Relief Efforts Contributions To Foundation For COVID-19 Relief Efforts Accounts receivable Payment of annual health insurance industry fee Payment Of Annual Health Insurance Industry Fee Payment Of Annual Health Insurance Industry Fee Amortization of deferred costs Amortization of Deferred Charges New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Revenue Recognition Revenue [Policy Text Block] Recently Issued Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Liability for Claims and Claims Adjustment Expense [Table] Liability for Claims and Claims Adjustment Expense [Table] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Retail Retail [Member] Group and Specialty Group And Specialty [Member] Group And Specialty [Member] Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Claims and Claims Adjustment Expense [Line Items] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Balances, beginning of period Less: Reinsurance recoverables Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Balances, beginning of period, net Liability for Unpaid Claims and Claims Adjustment Expense, Net 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 incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims 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 paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Reinsurance recoverable Balances, end of period Total IBNR included in benefits payable Liability for Unpaid Claims and Claims Adjustment Expense, Incurred but Not Reported (IBNR) Claims, Amount RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS New Accounting Pronouncements and Changes in Accounting Principles [Text Block] Segment Reporting [Abstract] Revenue from External Customers by Products and Services [Table] Revenue from External Customers by Products and Services [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Eliminations/ Corporate Corporate And Eliminations [Member] Corporate And Eliminations [Member] Healthcare Services Healthcare Services [Member] Healthcare Services [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Services Service [Member] Products Product [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Individual Medicare Advantage Medicare Advantage [Member] Medicare Advantage [Member] Group Medicare Advantage Group Medicare Advantage [Member] Group Medicare Advantage Medicare stand-alone PDP Medicare Stand Alone Prescription Drug Plan [Member] Medicare Stand Alone Prescription Drug Plan [Member] Total Medicare Medicare [Member] Medicare [Member] Fully-insured Fully Insured [Member] Fully Insured [Member] Specialty Specialty [Member] Specialty [Member] Medicaid and other Medicaid And Other [Member] Medicaid and Other [Member] Provider Provider [Member] Provider ASO and other A S O And Other [Member] ASO and Other [Member] Pharmacy Pharmacy [Member] Pharmacy Premiums Premiums Earned, Net Services revenue Revenue from Contract with Customer, Including Assessed Tax Total external revenues Revenues, Premiums And Service, External Revenues, Premiums And Service, External Intersegment revenues Revenues, Intersegment Revenues, Intersegment Investment income Investment Income, Interest and Dividend Total revenues Revenues Benefits Policyholder Benefits and Claims Incurred, Net, Health Operating costs Selling, General and Administrative Expense Depreciation and amortization Depreciation And Amortization Income Statement Depreciation and amortization expense excluding depreciation and amortization primarily from the delivery of pharmacy services by our wholly-owned pharmacy business (included in our Healthcare Services segment) which has been reclassified to benefit expenses. Total operating expenses Benefits, Losses and Expenses Income from operations Operating Income (Loss) Interest expense Interest Expense Other expense, net Other Nonoperating Income (Expense) Income before income taxes and equity in net earnings Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Equity in net earnings Segment earnings (loss) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest GOODWILL AND OTHER INTANGIBLE ASSETS Goodwill and Intangible Assets Disclosure [Text Block] FAIR VALUE Fair Value Disclosures [Text Block] Equity securities Percentage of debt securities considered to be of investment-grade (percent) Percentage Of Total Debt Securities, Investment Grade Quality Percentage Of Total Debt Securities, Investment Grade Quality Maximum individual state general bond obligation as a percentage of total debt securities (percent) Maximum Individual State General Bond Obligation, As Percentage Of Total Debt Securities Maximum Individual State General Bond Obligation, As Percentage Of Total Debt Securities Securities in unrealized loss positions, number of positions Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions Securities, number of positions Debt, Securities, Available-For-Sale, Securities, Number of Positions Debt Securities, Available-for-sale, Securities, Number of Positions MEDICARE PART D Medicare Part D Disclosure [Text Block] Balance sheet amounts associated with Medicare Part D. Schedule of Acquired Finite-Lived Intangible Asset by Major Class [Table] Schedule of Acquired Finite-Lived Intangible Asset by Major Class [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] Customer contracts/ relationships Customer Contracts [Member] Trade names and technology Trade Names [Member] Provider contracts Contractual Rights [Member] Noncompetes and other Noncompetes And Other [Member] Noncompetes and Other [Member] Acquired Finite-Lived Intangible Assets [Line Items] Acquired Finite-Lived Intangible Assets [Line Items] Weighted Average Life Finite-Lived Intangible Asset, Useful Life Cost Finite-Lived Intangible Assets, Gross Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Intangible Assets, Net (Excluding Goodwill) Receivables, allowance for doubtful accounts Accounts Receivable, Allowance for Credit Loss, Current Preferred stock, par (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Common stock, par (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Treasury stock, shares (in shares) Treasury Stock, Shares Schedule of Segment Results Schedule of Segment Reporting Information, by Segment [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Loss Contingencies [Table] Loss Contingencies [Table] Medicare Military services Military Service [Member] Military Service [Member] Medicaid Medicaid [Member] Medicaid [Member] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Tricare East Region Contract Tricare East Region Contract [Member] Tricare East Region Contract [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Percentage of premiums and services revenue Percentage Of Total Premium And Services Revenues Percentage Of Total Premium And Services Revenues Percentage of risk score calculated from claims submitted through EDS Percentage Of Risk Score Calculated From Claims Submitted Through EDS Percentage Of Risk Score Calculated From Claims Submitted Through EDS Number of states comprising TRICARE beneficiaries Number Of States Comprising TRICARE Beneficiaries Number Of States Comprising TRICARE Beneficiaries Number of TRICARE beneficiaries Number Of TRICARE Beneficiaries Number Of TRICARE Beneficiaries Contract term years Contract Term Years Contract term, years. Litigation recoveries sought Gain Contingency, Recovery Sought Gain Contingency, Recovery Sought Subsequent Event [Table] Subsequent Event [Table] 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] Dividends Dividends, Common Stock [Abstract] Amount per Share (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Total Amount Dividends Cash dividend declared (in dollars per share) Common Stock, Dividends, Per Share, Declared Schedule of Short-term Debt [Table] Schedule of Short-term Debt [Table] Short-term Debt [Line Items] Short-term Debt [Line Items] Maximum amount outstanding during period Short-term Debt, Maximum Amount Outstanding During Period Short-term debt outstanding Weighted average annual interest rate (percent) Short-term Debt, Weighted Average Interest Rate, at Point in Time Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock Common Stock [Member] Capital In Excess of Par Value Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Balances Balances (in shares) Shares, Issued Cumulative Effect of New Accounting Principle in Period of Adoption Cumulative Effect of New Accounting Principle in Period of Adoption Other comprehensive income (loss) Other Comprehensive Income (Loss), Net Of Tax, Portion Attributable To Parent, Including Equity Method Investments Other Comprehensive Income (Loss), Net Of Tax, Portion Attributable To Parent, Including Equity Method Investments Common stock repurchases Treasury Stock, Value, Acquired, Cost Method Dividends and dividend equivalents Dividends, Common Stock, Cash Stock-based compensation APIC, Share-based Payment Arrangement, Increase for Cost Recognition Restricted stock unit vesting Stock Issued During Period, Value, Restricted Stock Award, Gross Restricted stock unit vesting (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Stock option exercises Stock Issued During Period, Value, Stock Options Exercised Stock option exercises (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Balances Balances (in shares) Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Enclara Enclara Healthcare [Member] Enclara Healthcare [Member] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] WCAS Welsh Carson Anderson And Stowe [Member] Welsh Carson Anderson And Stowe [Member] Business Acquisition [Line Items] Business Acquisition [Line Items] Cash consideration for acquisition Payments to Acquire Businesses, Gross Goodwill, acquired during period Goodwill, Acquired During Period Other intangible assets acquired Finite-lived Intangible Assets Acquired Net tangible liabilities assumed Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Other intangible assets, weighted average useful life Acquired Finite-lived Intangible Assets, Weighted Average Useful Life Expected number of payor-agnostic, senior-focused primary care centers to be opened by strategic partnership Strategic Partnership Agreement, Expected Number Of Payor-Agnostic Senior-Focused Primary Care Centers Strategic Partnership Agreement, Expected Number Of Payor-Agnostic Senior-Focused Primary Care Centers Expected time frame for opening primary care centers Strategic Partnership Agreement, Expected Timeframe For Opening Primary Care Centers Strategic Partnership Agreement, Expected Timeframe For Opening Primary Care Centers Value of partnership entity Strategic Partnership Agreement, Value Of Partnership Entity Strategic Partnership Agreement, Value Of Partnership Entity Time frame for put and call option activity per partnership agreement, minimum Strategic Partnership Agreement, Timeframe For Put And Call Option Activity, Minimum Strategic Partnership Agreement, Timeframe For Put And Call Option Activity, Minimum Time frame for put and call option activity per partnership agreement, maximum Strategic Partnership Agreement, Timeframe For Put And Call Option Activity, Maximum Strategic Partnership Agreement, Timeframe For Put And Call Option Activity, Maximum Available-for-sale Securities, Debt Maturities [Abstract] Available-for-sale Securities, Debt Maturities [Abstract] Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract] Due within one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Amortized Cost Due after ten years Debt Securities, Available-for-sale, Allocated and Single Maturity Date, Maturity, after 10 Years, Amortized Cost Mortgage and asset-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Fair Value Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract] Due within one year Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value Due after one year through five years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value Due after five years through ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after Five Through Ten Years, Fair Value Due after ten years Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after 10 Years, Fair Value Mortgage and asset-backed securities Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Fair Value Fair Value BENEFITS PAYABLE Insurance Disclosure [Text Block] INVESTMENT SECURITIES Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table] Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table] Asset-backed securities Corporate debt securities Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items] Fair Value Debt Securities, Available-for-sale, Sale [Abstract] Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months 12 months or more Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Total Debt Securities, Available-for-sale, Unrealized Loss Position Gross Unrealized Losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] Less than 12 months Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 months or more Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Statement of Comprehensive Income [Abstract] Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in gross unrealized investment gains/losses Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, before Tax Effect of income taxes Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax Total change in unrealized investment gains/losses, net of tax Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Reclassification adjustment for net realized gains Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Effect of income taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Total reclassification adjustment, net of tax Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax Other comprehensive (loss) income, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive loss attributable to equity method investments Comprehensive Income (Loss), Net of Tax, Attributable To Equity Method Investments Comprehensive Income (Loss), Net of Tax, Attributable To Equity Method Investments Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income Tax Disclosure [Abstract] Effective income tax rate (percent) Effective Income Tax Rate Reconciliation, Percent 2020 Term Loan Term Loan Agreement February 2020 [Member] Term Loan Agreement February 2020 [Member] Extension period term (in years) Debt Instrument, Extension Period Term Debt Instrument, Extension Period Term Draw on term note commitment Schedule of Financial Assets Measured at Fair Value on Recurring Basis Fair Value, Assets Measured on Recurring Basis [Table Text Block] Schedule of Assumptions Used For Inputs In Fair Value Measurement Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Cover [Abstract] Document Type Document Type Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Class of Treasury Stock [Table] Class of Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] December 2017 Authorization December 2017 Authorization [Member] December 2017 Authorization [Member] July 2019 Authorization July 2019 Authorization [Member] July 2019 Authorization [Member] Accelerated Share Repurchases, Date [Axis] Accelerated Share Repurchases, Date [Axis] Accelerated Share Repurchases, Date [Domain] Accelerated Share Repurchases, Date [Domain] July 2019 ASR July 2019 Accelerated Share Repurchase Agreement [Member] July 2019 Accelerated Share Repurchase Agreement [Member] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Share repurchase authorization Stock Repurchase Program, Authorized Amount Remaining share repurchase authorization at replacement Stock Repurchase Program, Remaining Authorized Repurchase Amount Expired Upon Replacement Stock Repurchase Program, Remaining Authorized Repurchase Amount Expired Upon Replacement Accelerated stock repurchase agreement mmount Accelerated Share Repurchases, Agreement Amount Accelerated Share Repurchases, Agreement Amount Accelerated stock repurchase payment Accelerated Share Repurchases, Settlement (Payment) or Receipt Shares received (in shares) Treasury Stock, Shares, Acquired Increase in treasury stock from stock repurchases Decrease in capital in excess of par value Treasury Stock, Decrease In Capital In Excess Of Par Value Treasury Stock, Decrease In Capital In Excess Of Par Value Average daily volume weighted-average share price of common stock during term of agreement (in dollars per share) Accelerated Share Repurchases, Final Price Paid Per Share Reclassification from capital in excess of par value to treasury stock Common Stock Reclassified From Capital In Excess Of Par Value To Treasury Stock Upon Repurchase, Value Common Stock Reclassified From Capital In Excess Of Par Value To Treasury Stock Upon Repurchase, Value Remaining authorized amount Stock Repurchase Program, Remaining Authorized Repurchase Amount Common shares acquired in connection with employee stock plans (in shares) Share Repurchases Related To Employee Stock Based Compensation Awards Shares Number of shares of common stock that were repurchased in the administration of our employee share-based compensation plans. Under the terms of these plans, we accept shares of common stock from option holders if they elect to surrender previously-owned shares upon exercise of the option to cover the exercise price of the options or, in the case of restricted shares of common stock, the withholding of shares to satisfy tax withholding obligations associated with the vesting of such shares. Common shares acquired in connection with employee stock plans, amount Share Repurchases Related To Employee Stock Based Compensation Awards Value Cost of common stock that were repurchased in the administration of our employee share-based compensation plans. Under the terms of these plans, we accept shares of common stock from option holders if they elect to surrender previously-owned shares upon exercise of the option to cover the exercise price of the options or, in the case of restricted shares of common stock, the withholding of shares to satisfy tax withholding obligations associated with the vesting of such shares. Number of reportable segments Number of Reportable Segments Member co-share amounts and government subsidies Government And Health Plan Member Subsidies Amount Amount of member co-share amounts and government subsidies that are excluded from benefits expense because the health plans do not bear responsibility. Depreciation and amortization classified as benefit expense Depreciation And Amortization Classified As Benefit Expense Depreciation and amortization expense that has been reclassified to be included with benefit expenses. The reclassification is the result of depreciation and amortization expense associated primarily from the delivery of pharmacy services by our wholly-owned pharmacy business included in our Healthcare Services segment. ACQUISITIONS AND DIVESTITURES Mergers, Acquisitions and Dispositions Disclosures [Text Block] INCOME TAXES Income Tax Disclosure [Text Block] BASIS OF PRESENTATION AND SIGNIFICANT EVENTS Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Options Option on Securities [Member] Level 3 fair value measurement Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Annualized volatility Measurement Input, Option Volatility [Member] Secured credit rate Measurement Input, Secured Credit Rate [Member] Measurement Input, Secured Credit Rate [Member] NOPAT Measurement Input, Net Operating Profit After Tax [Member] Measurement Input, Net Operating Profit After Tax [Member] Weighted average cost of capital Measurement Input, Discount Rate [Member] Long term growth rate Measurement Input, Long-term Revenue Growth Rate [Member] Option Indexed to Issuer's Equity [Axis] Option Indexed to Issuer's Equity [Axis] Option Indexed to Issuer's Equity, Type [Domain] Option Indexed to Issuer's Equity, Type [Domain] Put option Put Option [Member] Call option Call Option [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other long-term liabilities Other Noncurrent Liabilities [Member] Other long-term assets Other Noncurrent Assets [Member] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair value of financial liability Financial Liabilities Fair Value Disclosure Fair value of financial asset Financial Assets, Fair Value Disclosure Financial Assets, Fair Value Disclosure Significant unobservable inputs Derivative Asset (Liability) Net, Measurement Input STOCKHOLDERS' EQUITY Stockholders' Equity Note Disclosure [Text Block] Amortization expense for other intangible assets Estimated amortization remaining for the years ending December 31, Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract] 2020 Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year 2021 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2022 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2023 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2024 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2025 Finite-Lived Intangible Assets, Amortization Expense, Year Five Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Benefits payable, net of reinsurance Short-duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net Reinsurance recoverable on unpaid claims Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Term loan and commercial paper Notes Payable To Banks And Commercial Paper [Member] Notes Payable To Banks And Commercial Paper [Member] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Debt outstanding Debt Instrument, Fair Value Disclosure Income Statement [Abstract] Revenues: Revenues [Abstract] Services Operating expenses: Operating Expenses [Abstract] Provision for income taxes Income Tax Expense (Benefit) Net income Schedule of Goodwill [Table] Schedule of Goodwill [Table] Goodwill [Line Items] Goodwill [Line Items] Goodwill [Roll Forward] Goodwill [Roll Forward] Goodwill, beginning balance Acquisitions Goodwill, ending balance Schedule of Investment Securities Classified as Current and Long-Term Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of Gross Unrealized Losses and Fair Value of Securities Schedule of Unrealized Loss on Investments [Table Text Block] Schedule of Realized Gains (Losses) Related to Investment Securities Included Within Investment Income Schedule of Realized Gain (Loss) [Table Text Block] Schedule of Contractual Maturity of Debt Securities Available for Sale Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of Details Supporting Computation of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] COMMITMENTS, GUARANTEES AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] SEGMENT INFORMATION Segment Reporting Disclosure [Text Block] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Investment Securities, Available-for-sale Amortized Cost to Fair Value Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract] Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Fair Value EARNINGS PER COMMON SHARE COMPUTATION Earnings Per Share [Text Block] Schedule of Carrying Value of Debt Outstanding Schedule of Debt [Table Text Block] DEBT Debt Disclosure [Text Block]