Humana (HUM) 10-K 20 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-5975
Entity Registrant Name	HUMANA INC.
Entity Central Index Key	0000049071
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	61-0647538
Entity Address, Address Line One	500 West Main Street
Entity Address, City or Town	Louisville
Entity Address, State or Province	KY
Entity Address, Postal Zip Code	40202
City Area Code	502
Local Phone Number	580-1000
Title of 12(b) Security	Common stock, $0.16 2/3 par value
Trading Symbol	HUM
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 35,478,894,483
Entity Common Stock, Shares Outstanding		132,106,497
Documents Incorporated by Reference	Parts II and III incorporate herein by reference portions of the Registrant’s Proxy Statement to be filed pursuant to Regulation 14A with respect to the Annual Meeting of Stockholders scheduled to be held on April 23, 2020.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 4,054	$ 2,343
Investment securities	10,972	10,026
Receivables, less allowance for doubtful accounts of $69 in 2019 and $79 in 2018	1,056	1,015
Other current assets	3,806	3,564
Total current assets	19,888	16,948
Property and equipment, net	1,955	1,735
Long-term investment securities	406	411
Goodwill	3,928	3,897
Equity method investment in Kindred at Home	1,063	1,047
Other long-term assets	1,834	1,375
Total assets	29,074	25,413
Current liabilities:
Benefits payable	6,004	4,862
Trade accounts payable and accrued expenses	3,754	3,067
Book overdraft	225	171
Unearned revenues	247	283
Short-term debt	699	1,694
Total current liabilities	10,929	10,077
Long-term debt	4,967	4,375
Future policy benefits payable	206	219
Other long-term liabilities	935	581
Total liabilities	17,037	15,252
Commitments and contingencies (Note 17)
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,629,992 shares issued at December 31, 2019 and 198,594,841 shares issued at December 31, 2018	33	33
Capital in excess of par value	2,820	2,535
Retained earnings	17,483	15,072
Accumulated other comprehensive income (loss)	156	(159)
Treasury stock, at cost, 66,524,771 shares at December 31, 2019 and 63,028,169 shares at December 31, 2018	(8,455)	(7,320)
Total stockholders’ equity	12,037	10,161
Total liabilities and stockholders’ equity	$ 29,074	$ 25,413

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 69	$ 79
Preferred stock, par (in USD per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par (in USD per share)	$ 0.1667	$ 0.1667
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	198,629,992	198,594,841
Treasury stock (in shares)	66,524,771	63,028,169

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Premiums									$ 62,948	$ 54,941	$ 52,380
Services									1,439	1,457	982
Investment income									501	514	405
Total revenues	$ 16,295	$ 16,241	$ 16,245	$ 16,107	$ 14,168	$ 14,206	$ 14,259	$ 14,279	64,888	56,912	53,767
Operating expenses:
Benefits									53,857	45,882	43,496
Operating costs									7,381	7,525	6,567
Merger termination fee and related costs, net									0	0	(936)
Depreciation and amortization									458	405	378
Total operating expenses									61,696	53,812	49,505
Income from operations									3,192	3,100	4,262
Loss on sale of business									0	786	0
Interest expense									242	218	242
Other (income) expense, net									(506)	33	0
Income before income taxes and equity in net earnings	593	888	1,229	746	436	901	19	707	3,456	2,063	4,020
Provision for income taxes									763	391	1,572
Equity in net earnings of Kindred at Home									14	11	0
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Basic earnings per common share (in USD per share)	$ 3.87	$ 5.16	$ 6.96	$ 4.18	$ 2.60	$ 4.68	$ 1.40	$ 3.56	$ 20.20	$ 12.24	$ 16.94
Diluted earnings per common share (in USD per share)	$ 3.84	$ 5.14	$ 6.94	$ 4.16	$ 2.58	$ 4.65	$ 1.39	$ 3.53	$ 20.10	$ 12.16	$ 16.81

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Other comprehensive income (loss):
Change in gross unrealized investment losses/gains									450	(189)	149
Effect of income taxes									(105)	51	(55)
Total change in unrealized investment gains/losses, net of tax									345	(138)	94
Reclassification adjustment for net realized gains included in investment income									(34)	(53)	(14)
Effect of income taxes									8	17	5
Total reclassification adjustment, net of tax									(26)	(36)	(9)
Other comprehensive income (loss), net of tax									319	(174)	85
Comprehensive income attributable to our equity method investment in Kindred at Home									(4)	(4)	0
Comprehensive income									$ 3,022	$ 1,505	$ 2,533

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Capital In Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balances at Dec. 31, 2016	$ 10,685	$ 33	$ 2,562	$ 11,454	$ (66)	$ (3,298)
Balances (in shares) at Dec. 31, 2016		198,495
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,448			2,448
Other comprehensive income (loss)	85				85
Common stock repurchases	(3,365)		(200)			(3,165)
Dividends and dividend equivalents	(232)			(232)
Stock-based compensation	157		157
Restricted stock unit vesting	0		(138)			138
Restricted stock unit vesting (in shares)		0
Stock option exercises	64		64
Stock option exercises (in shares)		77
Balances at Dec. 31, 2017	9,842	$ 33	2,445	13,670	19	(6,325)
Balances (in shares) at Dec. 31, 2017		198,572
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,683			1,683
Other comprehensive income (loss)	(182)			(4)	(178)
Common stock repurchases	(1,090)		50			(1,140)
Dividends and dividend equivalents	(277)			(277)
Stock-based compensation	137		137
Restricted stock unit vesting	0		(145)			145
Restricted stock unit vesting (in shares)		0
Stock option exercises	48		48
Stock option exercises (in shares)		23
Balances at Dec. 31, 2018	10,161	$ 33	2,535	15,072	(159)	(7,320)
Balances (in shares) at Dec. 31, 2018		198,595
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,707			2,707
Other comprehensive income (loss)	315				315
Common stock repurchases	(1,070)		150			(1,220)
Dividends and dividend equivalents	(296)			(296)
Stock-based compensation	163		163
Restricted stock unit vesting	0		(48)			48
Restricted stock unit vesting (in shares)		32
Stock option exercises	57		20			37
Stock option exercises (in shares)		3
Balances at Dec. 31, 2019	$ 12,037	$ 33	$ 2,820	$ 17,483	$ 156	$ (8,455)
Balances (in shares) at Dec. 31, 2019		198,630

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income	$ 2,707	$ 1,683	$ 2,448
Adjustments to reconcile net income to net cash provided by operating activities:
Loss on sale of business	0	786	0
Net realized capital gains	(62)	(90)	(14)
Equity in net earnings of Kindred at Home	(14)	(11)	0
Stock compensation	163	137	157
Depreciation	505	444	410
Amortization	70	90	75
Provision for deferred income taxes	162	194	132
Changes in operating assets and liabilities, net of effect of businesses acquired and dispositions:
Receivables	(32)	(164)	426
Other assets	118	(484)	(582)
Benefits payable	1,142	252	105
Other liabilities	471	(676)	641
Unearned revenues	(36)	(95)	98
Other	90	107	155
Net cash provided by operating activities	5,284	2,173	4,051
Cash flows from investing activities
Acquisitions, net of cash acquired	0	(354)	(31)
Purchase of equity method investment in Kindred at Home	0	(1,095)	0
Cash transferred in sale of business	0	(805)	0
Purchases of property and equipment	(736)	(612)	(524)
Purchases of investment securities	(6,361)	(4,687)	(6,265)
Maturities of investment securities	1,733	972	1,111
Proceeds from sales of investment securities	4,086	3,494	2,768
Net cash used in investing activities	(1,278)	(3,087)	(2,941)
Cash flows from financing activities
(Receipts) withdrawals from contract deposits, net	(623)	(640)	1,823
Proceeds from issuance of senior notes, net	987	0	1,779
(Repayments) proceeds from issuance of commercial paper, net	(360)	485	(153)
Proceeds from term loan	0	1,000	0
Repayment of term loan	(650)	(350)	0
Repayment of long-term debt	(400)	0	(800)
Common stock repurchases	(1,070)	(1,090)	(3,365)
Dividends paid	(291)	(265)	(220)
Change in book overdraft	54	30	(71)
Proceeds from stock option exercises & other	58	45	62
Net cash used in financing activities	(2,295)	(785)	(945)
Increase (decrease) in cash and cash equivalents	1,711	(1,699)	165
Cash and cash equivalents at beginning of period	2,343	4,042	3,877
Cash and cash equivalents at end of period	4,054	2,343	4,042
Supplemental cash flow disclosures:
Interest payments	212	195	216
Income tax payments, net	518	631	1,498
Details of businesses acquired in purchase transactions:
Fair value of assets acquired, net of cash acquired	28	392	31
Less: Fair value of liabilities assumed	(28)	(38)	0
Cash paid for acquired businesses, net of cash acquired	$ 0	$ 354	$ 31

REPORTING ENTITY

REPORTING ENTITY	12 Months Ended
	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
REPORTING ENTITY	REPORTING ENTITY Nature of Operations Humana Inc., headquartered in Louisville, Kentucky, is a leading health and well-being company committed to helping our millions of medical and specialty members achieve their best health. Our successful history in care delivery and health plan administration is helping us create a new kind of integrated care with the power to improve health and well‐being and lower costs. Our efforts are leading to a better quality of life for people with Medicare, families, individuals, military service personnel, and communities at large. To accomplish that, we support physicians and other health care professionals as they work to deliver the right care in the right place for their patients, our members. Our range of clinical capabilities, resources and tools, such as in‐home care, behavioral health, pharmacy services, data analytics and wellness solutions, combine to produce a simplified experience that makes health care easier to navigate and more effective. References throughout these notes to consolidated financial statements to “we,” “us,” “our,” “Company,” and “Humana,” mean Humana Inc. and its subsidiaries. We derived approximately 82% of our total premiums and services revenue from contracts with the federal government in 2019 , including 15%

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation Our financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States of America. Our consolidated financial statements include the accounts of Humana Inc. and subsidiaries that the Company controls, including variable interest entities associated with medical practices for which we are the primary beneficiary. We do not own many of our medical practices but instead enter into exclusive management agreements with the affiliated Professional Associations, or P.A.s, that operate these medical practices. Based upon the provisions of these agreements, these affiliated P.A.s are variable interest entities and we are the primary beneficiary, and accordingly we consolidate the affiliated P.A.s. All significant intercompany balances and transactions have been eliminated. The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The areas involving the most significant use of estimates are the estimation of benefits payable, the impact of risk adjustment provisions related to our Medicare contracts, the valuation and related impairment recognition of investment securities, and the valuation and related impairment recognition of long-lived assets, including goodwill. These estimates are based on knowledge of current events and anticipated future events, and accordingly, actual results may ultimately differ materially from those estimates. Workforce Optimization We initiated involuntary workforce reduction programs during 2019 and 2017, as well as a voluntary early retirement program during 2017. These programs impacted approximately 1,000 associates in 2019 and 3,600 associates in 2017. As a result, we recorded charges of $47 million in 2019 and $148 million in 2017. Payments under these programs are made upon termination during the early retirement or severance pay period. The 2017 workforce optimization obligation was $12 million at December 31, 2018 and was fully settled as of December 31, 2019 . The remaining 2019 workforce optimization obligation was $45 million as of December 31, 2019 . Aetna Merger On February 16, 2017, under the terms of the Agreement and Plan of Merger, or Merger Agreement, with Aetna Inc., and certain wholly owned subsidiaries of Aetna Inc., which we collectively refer to as Aetna, we received a breakup fee of $1 billion from Aetna, which is included in our consolidated statement of income in the line captioned "Merger termination fee and related costs, net." Health Care Reform The Patient Protection and Affordable Care Act and The Health Care and Education Reconciliation Act of 2010 (which we collectively refer to as the Health Care Reform Law) enacted significant reforms to various aspects of the U.S. health insurance industry. Certain of these reforms became effective January 1, 2014, including an annual insurance industry premium-based fee and the establishment of federally-facilitated or state-based exchanges. Operating results for our individual commercial medical business compliant with the Health Care Reform Law were challenged primarily due to unanticipated modifications in the program subsequent to the passing of the Health Care Reform Law, resulting in higher covered population morbidity and the ensuing enrollment and claims issues causing volatility in claims experience. As a result of these and other factors, we exited our individual commercial medical business effective January 1, 2018. The annual premium-based fee on health insurers is not deductible for tax purposes. We estimate a liability for the health insurance industry fee and record it in full once qualifying insurance coverage is provided in the applicable calendar year in which the fee is payable with a corresponding deferred cost that is amortized ratably to expense over the same calendar year. We record the liability for the health insurance industry fee in trade accounts payable and accrued expenses and record the deferred cost in other current assets in our consolidated financial statements. We pay the health insurance industry fee in September or October of each year. The Consolidated Appropriations Act enacted on December 18, 2015, included a one year suspension in 2017 of the health insurance industry fee. In 2018, we paid the federal government $1.04 billion for the annual health insurance industry fee attributed to calendar year 2018. The Continuing Resolution bill, H.R. 195, enacted on January 22, 2018, included a one year suspension in 2019 of the health insurance industry fee, but the fee will resume for calendar year 2020. The Further Consolidated Appropriations Act, 2020, enacted on December 20, 2019, permanently repealed the health insurance industry fee beginning in calendar year 2021. Cash and Cash Equivalents Cash and cash equivalents include cash, time deposits, money market funds, commercial paper, other money market instruments, and certain U.S. Government securities with an original maturity of three months or less. Carrying value approximates fair value due to the short-term maturity of the investments. Investment Securities Investment securities, which consist primarily of debt securities, have been categorized as available for sale and, as a result, are stated at fair value. Investment securities available for current operations are classified as current assets. Investment securities available for our long-term insurance products and professional liability funding requirements, as well as restricted statutory deposits, are classified as long-term assets. For the purpose of determining gross realized gains and losses, which are included as a component of investment income in the consolidated statements of income, the cost of investment securities sold is based upon specific identification. Unrealized holding gains and losses, net of applicable deferred taxes, are included as a component of stockholders’ equity and comprehensive income until realized from a sale or other-than-temporary impairment. Under the other-than-temporary impairment model for debt securities held, we recognize an impairment loss in income in an amount equal to the full difference between the amortized cost basis and the fair value when we have the intent to sell the debt security or it is more likely than not we will be required to sell the debt security before recovery of our amortized cost basis. However, if we do not intend to sell the debt security, we evaluate the expected cash flows to be received as compared to amortized cost and determine if a credit loss has occurred. In the event of a credit loss, only the amount of the impairment associated with the credit loss is recognized currently in income with the remainder of the loss recognized in other comprehensive income. When we do not intend to sell a security in an unrealized loss position, potential other-than-temporary impairment is considered using a variety of factors, including the length of time and extent to which the fair value has been less than cost; adverse conditions specifically related to the industry, geographic area or financial condition of the issuer or underlying collateral of a security; payment structure of the security; changes in credit rating of the security by the rating agencies; the volatility of the fair value changes; and changes in fair value of the security after the balance sheet date. For debt securities, we take into account expectations of relevant market and economic data. For example, with respect to mortgage and asset-backed securities, such data includes underlying loan level data and structural features such as seniority and other forms of credit enhancements. A decline in fair value is considered other-than-temporary when we do not expect to recover the entire amortized cost basis of the security. We estimate the amount of the credit loss component of a debt security as the difference between the amortized cost and the present value of the expected cash flows of the security. The present value is determined using the best estimate of future cash flows discounted at the implicit interest rate at the date of purchase. Receivables and Revenue Recognition We generally establish one-year commercial membership contracts with employer groups, subject to cancellation by the employer group on 30 -day written notice. Our Medicare contracts with CMS renew annually. Our military services contracts with the federal government and certain contracts with various state Medicaid programs generally are multi-year contracts subject to annual renewal provisions. Premiums Revenue We receive monthly premiums from the federal government and various states according to government specified payment rates and various contractual terms. We bill and collect premium from employer groups and members in our Medicare and other individual products monthly. Changes in premium revenues resulting from the periodic changes in risk-adjustment scores derived from medical diagnoses for our membership are estimated by projecting the ultimate annual premium and are recognized ratably during the year, with adjustments each period to reflect changes in the ultimate premium. Receivables or payables are classified as current or long-term in our consolidated balance sheet based on the timing of the expected settlement. Premiums revenue is estimated by multiplying the membership covered under the various contracts by the contractual rates. Premiums revenue is recognized as income in the period members are entitled to receive services, and is net of estimated uncollectible amounts, retroactive membership adjustments, and adjustments to recognize rebates under the minimum benefit ratios required under the Health Care Reform Law. We estimate policyholder rebates by projecting calendar year minimum benefit ratios for the small group and large group markets, as defined by the Health Care Reform Law using a methodology prescribed by HHS, separately by state and legal entity. Medicare Advantage and Medicaid products are also subject to minimum benefit ratio requirements. Estimated calendar year rebates recognized ratably during the year are revised each period to reflect current experience. Retroactive membership adjustments result from enrollment changes not yet processed, or not yet reported by an employer group or the government. We routinely monitor the collectability of specific accounts, the aging of receivables, historical retroactivity trends, estimated rebates, as well as prevailing and anticipated economic conditions, and reflect any required adjustments in current operations. Premiums received prior to the service period are recorded as unearned revenues. Medicare Part D We cover prescription drug benefits in accordance with Medicare Part D under multiple contracts with CMS. The payments we receive monthly from CMS and members, which are determined from our annual bid, represent amounts for providing prescription drug insurance coverage. We recognize premiums revenue for providing this insurance coverage ratably over the term of our annual contract. Our CMS payment is subject to risk sharing through the Medicare Part D risk corridor provisions. In addition, receipts for reinsurance and low-income cost subsidies as well as receipts for certain discounts on brand name prescription drugs in the coverage gap represent payments for prescription drug costs for which we are not at risk. The risk corridor provisions compare costs targeted in our bids to actual prescription drug costs, limited to actual costs that would have been incurred under the standard coverage as defined by CMS. Variances exceeding certain thresholds may result in CMS making additional payments to us or require us to refund to CMS a portion of the premiums we received. As risk corridor provisions are considered in our overall annual bid process, we estimate and recognize an adjustment to premiums revenue related to these provisions based upon pharmacy claims experience. We record a receivable or payable at the contract level and classify the amount as current or long-term in our consolidated balance sheets based on the timing of expected settlement. Reinsurance and low-income cost subsidies represent funding from CMS in connection with the Medicare Part D program for which we assume no risk. Reinsurance subsidies represent funding from CMS for its portion of prescription drug costs which exceed the member’s out-of-pocket threshold, or the catastrophic coverage level. Low-income cost subsidies represent funding from CMS for all or a portion of the deductible, the coinsurance and co-payment amounts above the out-of-pocket threshold for low-income beneficiaries. Monthly prospective payments from CMS for reinsurance and low-income cost subsidies are based on assumptions submitted with our annual bid. A reconciliation and related settlement of CMS’s prospective subsidies against actual prescription drug costs we paid is made after the end of the year. The Health Care Reform Law mandates consumer discounts of 50% on brand name prescription drugs for Part D plan participants in the coverage gap. These discounts are funded by CMS and pharmaceutical manufacturers while we administer the application of these funds. We account for these subsidies and discounts as a deposit in our consolidated balance sheets and as a financing activity under receipts (withdrawals) from contract deposits in our consolidated statements of cash flows. For 2019 , subsidy and discount payments of $11.8 billion exceeded reimbursements of $11.2 billion by $0.6 billion . For 2018 , subsidy and discount payments of $10.3 billion exceeded reimbursements of $9.6 billion by $0.7 billion . For 2017 , subsidy and discount reimbursements of $12.1 billion exceeded payments of $10.2 billion by $1.9 billion . We do not recognize premiums revenue or benefit expenses for these subsidies or discounts. Receipt and payment activity is accumulated at the contract level and recorded in our consolidated balance sheets in other current assets or trade accounts payable and accrued expenses depending on the contract balance at the end of the reporting period. Settlement of the reinsurance and low-income cost subsidies as well as the risk corridor payment is based on a reconciliation made approximately 9 months after the close of each calendar year. Settlement with CMS for brand name prescription drug discounts is based on a reconciliation made approximately 14 to 18 months after the close of each calendar year. We continue to revise our estimates with respect to the risk corridor provisions based on subsequent period pharmacy claims data. See Note 7 for detail regarding amounts recorded to our consolidated balance sheets related to the risk corridor settlement and subsidies from CMS with respect to the Medicare Part D program. Services Revenue Patient services revenue Patient services include injury and illness care and related services as well as other healthcare services related to customer needs or as required by law. Patient services revenues are recognized in the period services are provided to the customer and are net of contractual allowances. Administrative services fees Administrative services fees cover the processing of claims, offering access to our provider networks and clinical programs, and responding to customer service inquiries from members of self-funded groups. Revenues from providing administration services, also known as administrative services only, or ASO, are recognized in the period services are performed and are net of estimated uncollectible amounts. ASO fees are estimated by multiplying the membership covered under the various contracts by the contractual rates. Under ASO contracts, self-funded employers retain the risk of financing substantially all of the cost of health benefits. However, many ASO customers purchase stop loss insurance coverage from us to cover catastrophic claims or to limit aggregate annual costs. Accordingly, we have recorded premiums revenue and benefits expense related to these stop loss insurance contracts. We routinely monitor the collectability of specific accounts, the aging of receivables, as well as prevailing and anticipated economic conditions, and reflect any required adjustments in current operations. ASO fees received prior to the service period are recorded as unearned revenues. Under our TRICARE contracts with the Department of Defense (DoD) we provide administrative services, including offering access to our provider networks and clinical programs, claim processing, customer service, enrollment, and other services, while the federal government retains all of the risk of the cost of health benefits. We account for revenues under our contracts net of estimated health care costs similar to an administrative services fee only agreement. Our contracts include fixed administrative services fees and incentive fees and penalties. Administrative services fees are recognized as services are performed. Our TRICARE members are served by both in-network and out-of-network providers in accordance with our contracts. We pay health care costs related to these services to the providers and are subsequently reimbursed by the DoD for such payments. We account for the payments of the federal government’s claims and the related reimbursements under deposit accounting in our consolidated balance sheets and as a financing activity under receipts (withdrawals) from contract deposits in our consolidated statements of cash flows. For 2019, health care cost payments of approximately $6.5 billion exceeded reimbursements of approximately $6.4 billion by $63 million . For 2018, health care cost reimbursements and payments were each approximately $5.6 billion , with reimbursements exceeding payments by $38 million for the year. For 2017, health care cost reimbursements and payments were each approximately $3.4 billion with reimbursements exceeding payments by $11 million for the year. Receivables Receivables, including premium receivables, patient services revenue receivables, and ASO fee receivables, are shown net of allowances for estimated uncollectible accounts, retroactive membership adjustments, and contractual allowances. At December 31, 2019 and 2018, accounts receivable related to services were $141 million and $123 million , respectively. For the year ended December 31, 2019 , we had no material bad-debt expense and there were no material contract assets, contract liabilities or deferred contract costs recorded on the consolidated balance sheet at December 31, 2019 . For the year ended December 31, 2019 , revenue recognized from performance obligations related to prior periods (for example, due to changes in transaction price), was not material. Further, revenue expected to be recognized in any future year related to remaining performance obligations was not material. Other Current Assets Other current assets includes amounts associated with Medicare Part D as discussed above and in Note 7, rebates due from pharmaceutical manufacturers and other amounts due within one year. We accrue pharmaceutical rebates as they are earned based on contractual terms and usage of the product. The balance of pharmaceutical rebates receivable was $1.3 billion at December 31, 2019 and 2018 . Policy Acquisition Costs Policy acquisition costs are those costs that relate directly to the successful acquisition of new and renewal insurance policies. Such costs include commissions, costs of policy issuance and underwriting, and other costs we incur to acquire new business or renew existing business. We expense policy acquisition costs related to our employer-group prepaid health services policies as incurred. These short-duration employer-group prepaid health services policies typically have a 1 -year term and may be canceled upon 30 days notice by the employer group. Life insurance, annuities, certain health and other supplemental, and, prior to the sale of our wholly-owned subsidiary, KMG America Corporation, or KMG, in 2018, long term care policies sold to individuals are accounted for as long-duration insurance products because they are expected to remain in force for an extended period beyond one year and premium received in the earlier years is intended to pay anticipated benefits to be incurred in future years . As a result, we defer policy acquisition costs, primarily consisting of commissions, and amortize them over the estimated life of the policies in proportion to premiums earned. Deferred acquisition costs are reviewed to determine if they are recoverable from future income. Long-Lived Assets Property and equipment is recorded at cost. Gains and losses on sales or disposals of property and equipment are included in operating costs. Certain costs related to the development or purchase of internal-use software are capitalized. Depreciation is computed using the straight-line method over estimated useful lives ranging from 3 to 10 years for equipment, 3 to 5 years for computer software, and 10 to 20 years for buildings. Improvements to leased facilities are depreciated over the shorter of the remaining lease term or the anticipated life of the improvement. We periodically review long-lived assets, including property and equipment and definite-lived intangible assets, for impairment whenever adverse events or changes in circumstances indicate the carrying value of the asset may not be recoverable. Losses are recognized for a long-lived asset to be held and used in our operations when the undiscounted future cash flows expected to result from the use of the asset are less than its carrying value. We recognize an impairment loss based on the excess of the carrying value over the fair value of the asset. A long-lived asset held for sale is reported at the lower of the carrying amount or fair value less costs to sell. Depreciation expense is not recognized on assets held for sale. Losses are recognized for a long-lived asset to be abandoned when the asset ceases to be used. In addition, we periodically review the estimated lives of all long-lived assets for reasonableness. Equity Method Investments We use the equity method of accounting for equity investments in companies where we are able to exercise significant influence, but not control, over operating and financial policies of the investee. Judgment regarding the level of influence over each equity method investment includes considering key factors such as our ownership interest, representation on the board of directors, organizational structure, participation in policy-making decisions and material intra-entity transactions. Generally, under the equity method, original investments in these entities are recorded at cost and subsequently adjusted by our share of equity in income or losses after the date of acquisition as well as capital contributions to and distributions from these companies. Our proportionate share of the net income or loss of these companies is included in consolidated net income. Investment amounts in excess of our share of an investee's net assets are amortized over the life of the related asset creating the excess. Excess goodwill is not amortized. We evaluate equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. Factors considered by us when reviewing an equity method investment for impairment include the length of time (duration) and the extent (severity) to which the fair value of the equity method investment has been less than carrying value, the investee’s financial condition and near-term prospects and the intent and ability to hold the investment for a period of time sufficient to allow for anticipated recovery. An impairment that is other-than-temporary is recognized in the period identified. See Note 4 for further information. Goodwill and Definite-Lived Intangible Assets Goodwill represents the unamortized excess of cost over the fair value of the net tangible and other intangible assets acquired. We are required to test at least annually for impairment at a level of reporting referred to as the reporting unit, and more frequently if adverse events or changes in circumstances indicate that the asset may be impaired. A reporting unit either is our operating segments or one level below the operating segments, referred to as a component, which comprise our reportable segments. A component is considered a reporting unit if the component constitutes a business for which discrete financial information is available that is regularly reviewed by management. We aggregate the components of an operating segment into one reporting unit if they have similar economic characteristics. Goodwill is assigned to the reporting units that are expected to benefit from the specific synergies of the business combination. We use the one-step process to review goodwill for impairment to determine both the existence and amount of goodwill impairment, if any. Impairment tests are performed, at a minimum, in the fourth quarter of each year supported by our long-range business plan and annual planning process. We rely on an evaluation of future discounted cash flows to determine fair value of our reporting units. The fair value of our reporting units with significant goodwill exceeded carrying amounts by a substantial margin. A 100 basis point increase in the discount rate would not have a significant impact on the amount of margin for any of our reporting units with significant goodwill, with the exception of our clinical and provider reporting units in our Healthcare Services segment. Our clinical and provider reporting units primarily provide services to our Retail members. A significant increase in the discount rate, decrease in the long-term growth rate, or substantial reductions in our underlying cash flow assumptions, including revenue growth rates, medical and operating cost trends, and projected operating income, could have a negative impact on the estimated fair value of these reporting units. The clinical reporting unit had a fair value of $544 million which exceeded its carrying value of $533 million by $11 million or 2% . If the discount rate increased 100 basis points, then the clinical reporting unit would incur an impairment loss of approximately $62 million . The provider reporting unit had a fair value of $2.3 billion which exceeded its carrying value of $1.3 billion by $1.0 billion or 78% . The provider reporting unit estimate of fair value relies on multiple assumptions regarding the underlying long-term cash flows, any one of which may be significantly impacted by future changes in estimates and may negatively impact fair value. The clinical and provider reporting units account for $524 million and $761 million , respectively, of goodwill. Impairment tests completed for 2019 , 2018 , and 2017 did not result in an impairment loss. Definite-lived intangible assets primarily relate to acquired customer contracts/relationships and are included with other long-term assets in the consolidated balance sheets. Definite-lived intangible assets are amortized over the useful life generally using the straight-line method. We review definite-lived intangible assets for impairment under our long-lived asset policy. Benefits Payable and Benefits Expense Recognition Benefits expense includes claim payments, capitation payments, pharmacy costs net of rebates, allocations of certain centralized expenses and various other costs incurred to provide health insurance coverage to members, as well as estimates of future payments to hospitals and others for medical care and other supplemental benefits provided on or prior to the balance sheet date. Capitation payments represent monthly contractual fees disbursed to primary care and other providers who are responsible for providing medical care to members. Pharmacy costs represent payments for members’ prescription drug benefits, net of rebates from drug manufacturers. Receivables for such pharmacy rebates are included in other current assets in our consolidated balance sheets. Other supplemental benefits include dental, vision, and other supplemental health products. We estimate the costs of our benefits expense payments using actuarial methods and assumptions based upon claim payment patterns, medical cost inflation, historical developments such as claim inventory levels and claim receipt patterns, and other relevant factors, and record benefit reserves for future payments. We continually review estimates of future payments relating to claims costs for services incurred in the current and prior periods and make necessary adjustments to our reserves. Benefits expense is recognized in the period in which services are provided and includes an estimate of the cost of services which have been incurred but not yet reported, or IBNR. Our reserving practice is to consistently recognize the actuarial best point estimate within a level of confidence required by actuarial standards. Actuarial standards of practice generally require a level of confidence such that the liabilities established for IBNR have a greater probability of being adequate versus being insufficient, or such that the liabilities established for IBNR are sufficient to cover obligations under an assumption of moderately adverse conditions. Adverse conditions are situations in which the actual claims are expected to be higher than the otherwise estimated value of such claims at the time of the estimate. Therefore, in many situations, the claim amounts ultimately settled will be less than the estimate that satisfies the actuarial standards of practice. We develop our estimate for IBNR using actuarial methodologies and assumptions, primarily based upon historical claim experience. Depending on the period for which incurred claims are estimated, we apply a different method in determining our estimate. For periods prior to the most recent two months, the key assumption used in estimating our IBNR is that the completion factor pattern remains consistent over a rolling 12-month period after adjusting for known changes in claim inventory levels and known changes in claim payment processes. Completion factors result from the calculation of the percentage of claims incurred during a given period that have historically been adjudicated as of the reporting period. For the most recent two months, the incurred claims are estimated primarily from a trend analysis based upon per member per month claims trends developed from our historical experience in the preceding months, adjusted for known changes in estimates of recent hospital and drug utilization data, provider contracting changes, changes in benefit levels, changes in member cost sharing, changes in medical management processes, product mix, and workday seasonality. The completion factor method is used for the months of incurred claims prior to the most recent two months because the historical percentage of claims processed for those months is at a level sufficient to produce a consistently reliable result. Conversely, for the most recent two months of incurred claims, the volume of claims processed historically is not at a level sufficient to produce a reliable result, which therefore requires us to examine historical trend patterns as the primary method of evaluation. Changes in claim processes, including recoveries of overpayments, receipt cycle times, claim inventory levels, outsourcing, system conversions, and processing disruptions due to weather or other events affect views regarding the reasonable choice of completion factors. Claim payments to providers for services rendered are often net of overpayment recoveries for claims paid previously, as contractually allowed. Claim overpayment recoveries can result from many different factors, including retroactive enrollment activity, audits of provider billings, and/or payment errors. Changes in patterns of claim overpayment recoveries can be unpredictable and result in completion factor volatility, as they often impact older dates of service. The receipt cycle time measures the average length of time between when a medical claim was initially incurred and when the claim form was received. Increases in electronic claim submissions from providers decrease the receipt cycle time. If claims are submitted or processed on a faster (slower) pace than prior

ACQUISITIONS AND DIVESTITURES

ACQUISITIONS AND DIVESTITURES	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
ACQUISITIONS AND DIVESTITURES	ACQUISITIONS AND DIVESTITURES Recent Transactions In the first quarter of 2020 , we acquired privately held Enclara Healthcare, or Enclara, one of the nation’s largest hospice pharmacy and benefit management providers for cash consideration of approximately $707 million , net of cash received. The purchase accounting is incomplete due to the timing of the availability of information. Also in the first quarter of 2020, our Partners in Primary Care wholly-owned subsidiary entered into a strategic partnership with Welsh, Carson, Anderson & Stowe, or WCAS, to accelerate the expansion of our primary care model. The WCAS partnership is expected to open approximately 50 payor-agnostic, senior-focused primary care centers over 3 years beginning in 2020. Partners in Primary Care committed to the acquisition of a non-controlling interest in the approximately $600 million entity. In addition, the agreement includes a series of put and call options through which WCAS may require us to purchase their interest in the entity and, through which we may acquire WCAS’s interest over the next 5 - 10 years . Sale of Closed Block of Commercial Long-Term Care Insurance Business On August 9, 2018 , we completed the sale of KMG to Continental General Insurance Company, or CGIC, a Texas-based insurance company wholly owned by HC2 Holdings, Inc., a diversified holding company. KMG's subsidiary, Kanawha Insurance Company, or KIC, included our closed block of non-strategic commercial long-term care policies. Upon closing, we funded the transaction with approximately $190 million of parent company cash contributed into KMG, subject to customary adjustments, in addition to the transfer of approximately $160 million of statutory capital with the sale. In connection with the sale of KMG, we recognized a pretax loss, including transaction costs, of $786 million and a corresponding $452 million tax benefit. Prior to the sale of KMG, we entered into reinsurance contracts to transfer the risk associated with certain voluntary benefit and financial protection products previously issued primarily by KIC to a third party. We transferred approximately $245 million of cash to the third party and recorded a commensurate reinsurance recoverable as a result of these transactions. The reinsurance recoverable was included as part of the net assets disposed. There was no material impact to operating results from these reinsurance transactions. KMG revenues and net income for the 2018 period prior to the date of sale was $182 million and $47 million , respectively. KMG revenues and net loss were $261 million and $117 million , respectively, for the year ended December 31, 2017. The assets and liabilities of KMG that were disposed of on August 9, 2018 were as follows: August 9, 2018 Assets (in millions) Cash and cash equivalents $ 805 Receivables, net 3 Investment securities 1,576 Other assets 1,085 Total assets disposed $ 3,469 Liabilities Benefits payable $ 58 Trade accounts payable and accrued expenses 70 Future policy benefits payable 2,573 Total liabilities disposed $ 2,701 Other Acquisitions and Divestitures In the first quarter of 2018, we acquired the remaining equity interest in MCCI Holdings, LLC, or MCCI, a privately held management service organization and healthcare provider headquartered in Miami, Florida, that primarily coordinates medical care for Medicare Advantage beneficiaries in Florida and Texas. The purchase price consisted primarily of $169 million cash, as well as our existing investment in MCCI and a note receivable and a revolving note with an aggregate balance of $383 million . This resulted in a purchase price allocation to goodwill of $483 million , other intangible assets of $80 million , and net tangible assets of $24 million . The goodwill was assigned to the Retail and Healthcare Services segments. The other intangible assets, which primarily consist of customer contracts, have an estimated weighted average useful life of 8 years . Goodwill and other intangible assets are amortizable as deductible expense for tax purposes. In the second quarter of 2018, we acquired Family Physicians Group, or FPG, for cash consideration of approximately $185 million , net of cash received. FPG serves Medicare Advantage and Managed Medicaid HMO patients in Greater Orlando, Florida with a footprint that includes clinics located in Lake, Orange, Osceola and Seminole counties. This resulted in a purchase price allocation to goodwill of $133 million , other intangible assets of $38 million and net tangible assets of $14 million . The goodwill was assigned to the Retail and Healthcare Services segments. The other intangible assets, which primarily consist of customer contracts, have an estimated weighted average useful life of 4.9 years . The purchase price allocations for MCCI and FPG are final. During 2019 and 2018, we acquired other health and wellness related businesses which, individually or in the aggregate, have not had a material impact on our results of operations, financial condition, or cash flows. The results of operations and financial condition of these businesses have been included in our consolidated statements of income and consolidated balance sheets from the respective acquisition dates. Acquisition-related costs recognized in each of 2019, 2018 and 2017 were not material to our results of operations. Goodwill and other intangible assets acquired are partially amortizable as deductible expenses for tax purposes. The pro forma financial information assuming the acquisitions had occurred as of the beginning of the calendar year prior to the year of acquisition, as well as the revenues and earnings generated during the year of acquisition, were not material for disclosure purposes.

EQUITY METHOD INVESTMENT

EQUITY METHOD INVESTMENT	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
EQUITY METHOD INVESTMENT	EQUITY METHOD INVESTMENT In the third quarter of 2018, we, along with TPG Capital, or TPG, and Welsh, Carson, Anderson & Stowe, or WCAS (together, the "Sponsors"), completed the acquisitions of Kindred Healthcare, Inc., or Kindred, and privately-held Curo Health Services, or Curo, respectively, merging Curo with the hospice business of the Kindred at Home Division, or Kindred at Home. As part of these transactions, we acquired a 40% minority interest in Kindred at Home, a leading home health and hospice company, for total cash consideration of approximately $1.1 billion . We account for our 40% investment in Kindred at Home using the equity method of accounting. This investment is reflected as "Equity method investment in Kindred at Home" in our consolidated balance sheets, with our share of income or loss reported as "Equity in net earnings of Kindred at Home" in our consolidated statements of income. We entered into a shareholders agreement with the Sponsors that provides for certain rights and obligations of each party. The shareholders agreement with the Sponsors includes a put option under which they have the right to require us to purchase their interest in the joint venture starting at the end of year three and ending at the end of year four following the closing. Likewise, we have a call option under which we have the right to require the Sponsors to sell their interest in the joint venture to Humana beginning at the end of 2022 and ending at the end of 2023 following the closing. The put and call options, which are exercisable at a fixed EBITDA multiple and provide a minimum return on the Sponsor's investment if exercised, are measured at fair value each period using a Monte Carlo simulation. The simulation relies on assumptions around Kindred at Home's equity value, risk free interest rates, volatility, and the details specific to the put and call options. The final purchase price allocation resulted in approximately $1 billion being allocated to the investment and $236 million and $291 million allocated to the put and call options, respectively. The fair values of the put option and call option were $28 million and $557 million , respectively, at December 31, 2019. The fair values of the put option and call option were $224 million and $246 million , respectively, at December 31, 2018. The put option is included within other long-term liabilities and the call option is included within other long term assets. The change in fair value of the put and call options for the years ended December 31, 2019 and 2018 of $(506) million and $33 million , respectively, are reported as "Other (income) expense, net" in our consolidated statements of income. The summarized balance sheets at December 31, 2019 and 2018, and income statement for the year ended December 31, 2019 and period beginning July 2, 2018 through December 31, 2018 of Kindred at Home were as follows: Balance sheets December 31, 2019 December 31, 2018 (in millions) Current assets $ 563 $ 536 Non-current assets 4,967 4,955 Current liabilities 405 351 Non-current liabilities 2,637 2,708 Shareholders' equity 2,488 2,432 Statements of income For the year ended December 31, 2019 July 2, 2018 through December 31, 2018 (in millions) Revenues $ 3,100 $ 1,587 Expenses 2,835 1,451 Net income 54 27

INVESTMENT SECURITIES

INVESTMENT SECURITIES	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
INVESTMENT SECURITIES	INVESTMENT SECURITIES Investment securities classified as current and long-term were as follows at December 31, 2019 and 2018 , respectively: Amortized Gross Gross Fair (in millions) December 31, 2019 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 353 $ 1 $ — $ 354 Mortgage-backed securities 3,628 85 (3 ) 3,710 Tax-exempt municipal securities 1,433 30 — 1,463 Mortgage-backed securities: Commercial 786 18 — 804 Asset-backed securities 1,093 3 (3 ) 1,093 Corporate debt securities 3,867 82 (2 ) 3,947 Total debt securities $ 11,160 $ 219 $ (8 ) $ 11,371 December 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 419 $ 1 $ (3 ) $ 417 Mortgage-backed securities 2,595 3 (54 ) 2,544 Tax-exempt municipal securities 2,805 3 (37 ) 2,771 Mortgage-backed securities: Residential 55 — — 55 Commercial 537 — (14 ) 523 Asset-backed securities 991 1 (7 ) 985 Corporate debt securities 3,239 1 (98 ) 3,142 Total debt securities $ 10,641 $ 9 $ (213 ) $ 10,437 We also held $7 million of equity securities carried at fair value as of December 31, 2019 consisting of common stock. Gross unrealized losses and fair values aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position were as follows at December 31, 2019 and 2018 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) December 31, 2019 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 48 $ — $ 23 $ — $ 71 $ — Mortgage-backed securities 315 (1 ) 204 (2 ) 519 (3 ) Tax-exempt municipal securities 58 — 75 — 133 — Mortgage-backed securities: Commercial 118 — 36 — 154 — Asset-backed securities 20 — 607 (3 ) 627 (3 ) Corporate debt securities 589 (2 ) 155 — 744 (2 ) Total debt securities $ 1,148 $ (3 ) $ 1,100 $ (5 ) $ 2,248 $ (8 ) December 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 179 $ (1 ) $ 153 $ (2 ) $ 332 $ (3 ) Mortgage-backed securities 956 (16 ) 1,019 (38 ) 1,975 (54 ) Tax-exempt municipal securities 809 (9 ) 1,648 (28 ) 2,457 (37 ) Mortgage-backed securities: Residential — — 15 — 15 — Commercial 372 (8 ) 133 (6 ) 505 (14 ) Asset-backed securities 824 (7 ) 40 — 864 (7 ) Corporate debt securities 1,434 (35 ) 1,439 (63 ) 2,873 (98 ) Total debt securities $ 4,574 $ (76 ) $ 4,447 $ (137 ) $ 9,021 $ (213 ) Approximately 96% of our debt securities were investment-grade quality, with a weighted average credit rating of AA by S&P at December 31, 2019 . Most of the debt securities that were below investment-grade were rated BB , the higher end of the below investment-grade rating scale. Tax-exempt municipal securities were diversified among general obligation bonds of states and local municipalities in the United States as well as special revenue bonds issued by municipalities to finance specific public works projects such as utilities, water and sewer, transportation, or education. Our general obligation bonds are diversified across the United States with no individual state exceeding 1% of our total debt securities. Our investment policy limits investments in a single issuer and requires diversification among various asset types. Our unrealized loss from all securities was generated from approximately 235 positions out of a total of approximately 1,515 positions at December 31, 2019 . All issuers of securities we own that were trading at an unrealized loss at December 31, 2019 remain current on all contractual payments. After taking into account these and other factors previously described, we believe these unrealized losses primarily were caused by an increase in market interest rates in the current markets since the time the securities were purchased. At December 31, 2019 , we did not intend to sell the securities with an unrealized loss position in accumulated other comprehensive income, and it is not likely that we will be required to sell these securities before recovery of their amortized cost basis. As a result, we believe that the securities with an unrealized loss were not other-than-temporarily impaired at December 31, 2019 . The detail of realized gains (losses) related to investment securities and included within investment income was as follows for the years ended December 31, 2019 , 2018 , and 2017 : 2019 2018 2017 (in millions) Gross realized gains $ 129 $ 106 $ 35 Gross realized losses (67 ) (16 ) (21 ) Net realized capital gains $ 62 $ 90 $ 14 There were no material other-than-temporary impairments in 2019 , 2018 , or 2017 . The contractual maturities of debt securities available for sale at December 31, 2019 , regardless of their balance sheet classification, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Amortized Fair (in millions) Due within one year $ 1,316 $ 1,317 Due after one year through five years 1,974 2,013 Due after five years through ten years 1,724 1,780 Due after ten years 639 654 Mortgage and asset-backed securities 5,507 5,607 Total debt securities $ 11,160 $ 11,371

FAIR VALUE

FAIR VALUE	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE	FAIR VALUE Financial Assets The following table summarizes our fair value measurements at December 31, 2019 and 2018 , respectively, for financial assets measured at fair value on a recurring basis: Fair Value Measurements Using Fair Value Quoted Prices Other Unobservable (in millions) December 31, 2019 Cash equivalents $ 3,660 $ 3,660 $ — $ — Debt securities: U.S. Treasury and other U.S. government corporations and agencies: U.S. Treasury and agency obligations 354 — 354 — Mortgage-backed securities 3,710 — 3,710 — Tax-exempt municipal securities 1,463 — 1,463 — Mortgage-backed securities: Commercial 804 — 804 — Asset-backed securities 1,093 — 1,093 — Corporate debt securities 3,947 — 3,947 — Total debt securities 11,371 — 11,371 — Common stock 7 7 — — Total invested assets $ 15,038 $ 3,667 $ 11,371 $ — December 31, 2018 Cash equivalents $ 2,024 $ 2,024 $ — $ — Debt securities: U.S. Treasury and other U.S. government corporations and agencies: U.S. Treasury and agency obligations 417 — 417 — Mortgage-backed securities 2,544 — 2,544 — Tax-exempt municipal securities 2,771 — 2,771 — Mortgage-backed securities: Residential 55 — 55 — Commercial 523 — 523 — Asset-backed securities 985 — 985 — Corporate debt securities 3,142 — 3,142 — Total debt securities 10,437 — 10,437 — Total invested assets $ 12,461 $ 2,024 $ 10,437 $ — Financial Liabilities Our debt is recorded at carrying value in our consolidated balance sheets. The carrying value of our senior notes debt outstanding, net of unamortized debt issuance costs, was $5,366 million at December 31, 2019 and $4,774 million at December 31, 2018 . The fair value of our senior note debt was $5,916 million at December 31, 2019 and $4,885 million at December 31, 2018 . The fair value of our senior note debt is determined based on Level 2 inputs, including quoted market prices for the same or similar debt, or if no quoted market prices are available, on the current prices estimated to be available to us for debt with similar terms and remaining maturities. Due to the short-term nature, carrying value approximates fair value for our term note and commercial paper borrowings. The outstanding commercial paper borrowings were $300 million at December 31, 2019 and we repaid the term note balance in August 2019. The term note outstanding and commercial paper borrowings were $1,295 million at December 31, 2018 . Put and Call Options Measured at Fair Value The put and call options fair values, derived from the Monte Carlo simulation, were $28 million and $557 million , respectively at December 31, 2019 and $224 million and $246 million , respectively at December 31, 2018 . The significant unobservable inputs utilized in these Level 3 fair value measurements (and selected values) include the enterprise value of Kindred at Home, annualized volatility ( 19.8% ) and secured credit rate ( 2.2% ). Enterprise value was derived from a discounted cash flow model, which utilized significant unobservable inputs for long-term net operating profit after tax margin, or NOPAT, ( 12.0% ) to measure underlying cash flows, weighted average cost of capital ( 10.0% ) and long term growth rate ( 3.0% ). The calculation of NOPAT utilized net income plus after tax interest expense. We regularly evaluate each of the assumptions used in establishing these assets and liabilities. Significant changes in assumptions for weighted average cost of capital, long term growth rates, NOPAT, volatility, credit spreads, risk free rate, and underlying cash flow estimates, could result in significantly lower or higher fair value measurements. A change in one of these assumptions is not necessarily accompanied by a change in another assumption. Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis As disclosed in Note 3, we acquired MCCI, FPG, and other health and wellness related businesses during 2019 , 2018 , and 2017 . The values of net tangible assets acquired and the resulting goodwill and other intangible assets were recorded at fair value using Level 3 inputs. The majority of the tangible assets acquired and liabilities assumed were recorded at their carrying values as of the respective dates of acquisition, as their carrying values approximated their fair values due to their short-term nature. The fair values of goodwill and other intangible assets acquired in these acquisitions were internally estimated primarily based on the income approach. The income approach estimates fair value based on the present value of the cash flows that the assets are expected to generate in the future. We developed internal estimates for the expected future cash flows and discount rates used in the present value calculations. Other than assets acquired and liabilities assumed in these acquisitions, there were no material assets or liabilities measured at fair value on a nonrecurring basis during 2019 , 2018 , or 2017 .

MEDICARE PART D

MEDICARE PART D	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
MEDICARE PART D	MEDICARE PART D As discussed in Note 2, we cover prescription drug benefits in accordance with Medicare Part D under multiple contracts with CMS. The accompanying consolidated balance sheets include the following amounts associated with Medicare Part D as of December 31, 2019 and 2018 . CMS subsidies/discounts in the table below include the reinsurance and low-income cost subsidies funded by CMS for which we assume no risk as well as brand name prescription drug discounts for Part D plan participants in the coverage gap funded by CMS and pharmaceutical manufacturers. 2019 2018 Risk CMS Risk CMS (in millions) Other current assets $ 5 $ 585 $ 15 $ 172 Trade accounts payable and accrued expenses (120 ) (356 ) (103 ) (503 ) Net current (liability) asset (115 ) 229 (88 ) (331 ) Other long-term assets 6 — 7 — Other long-term liabilities (61 ) — (89 ) — Net long-term liability (55 ) — (82 ) — Total net (liability) asset $ (170 ) $ 229 $ (170 ) $ (331 )

PROPERTY AND EQUIPMENT, NET

PROPERTY AND EQUIPMENT, NET	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT, NET	PROPERTY AND EQUIPMENT, NET Property and equipment was comprised of the following at December 31, 2019 and 2018 . 2019 2018 (in millions) Land $ 20 $ 20 Buildings and leasehold improvements 874 766 Equipment 922 890 Computer software 2,799 2,372 4,615 4,048 Accumulated depreciation (2,660 ) (2,313 ) Property and equipment, net $ 1,955 $ 1,735 Depreciation expense was $505 million in 2019 , $444 million in 2018 , and $410 million in 2017 , including amortization expense for capitalized internally developed and purchased software of $343 million in 2019 , $298 million in 2018 , and $287 million in 2017 .

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS Changes in the carrying amount of goodwill for our reportable segments for the years ended December 31, 2019 and 2018 were as follows: Retail Group and Specialty Healthcare Services Total (in millions) Balance at January 1, 2018 $ 1,059 $ 261 $ 1,961 $ 3,281 Acquisitions 476 — 140 616 Balance at December 31, 2018 1,535 261 2,101 3,897 Acquisitions — — 31 31 Balance at December 31, 2019 $ 1,535 $ 261 $ 2,132 $ 3,928 The following table presents details of our other intangible assets included in other long-term assets in the accompanying consolidated balance sheets at December 31, 2019 and 2018 . Weighted 2019 2018 Cost Accumulated Net Cost Accumulated Net (in millions) Other intangible assets: Customer contracts/relationships 8.7 years $ 646 $ 496 $ 150 $ 646 $ 434 $ 212 Trade names and technology 6.4 years 84 84 — 84 83 1 Provider contracts 11.8 years 70 44 26 68 37 31 Noncompetes and other 7.3 years 29 28 1 29 28 1 Total other intangible assets 8.7 years $ 829 $ 652 $ 177 $ 827 $ 582 $ 245 Amortization expense for other intangible assets was approximately $70 million in 2019 , $90 million in 2018 , and $75 million in 2017 . Amortization expense for 2018 included $12 million associated with the write-off of a trade name value reflecting the re-branding of certain provider assets. The following table presents our estimate of amortization expense for each of the five next succeeding fiscal years: (in millions) For the years ending December 31, 2020 $ 68 2021 34 2022 31 2023 18 2024 11

LEASES

LEASES	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
LEASES	LEASES We determine if a contract contains a lease by evaluating the nature and substance of the agreement. We lease facilities, computer hardware, and other furniture and equipment. Leases with an initial term of 12 months or less are not recorded on the balance sheet; we recognize lease expense for these leases on a straight-line basis over the lease term. For new lease agreements, we combine lease and nonlease components for all of our asset classes. See Note 2 for further information. When portions of the lease payments are not fixed or depend on an index or rate, we consider those payments to be variable in nature. Our variable lease payments include, but are not limited to, common area maintenance, taxes and insurance which are not dependent upon an index or rate. Variable lease payments are recorded in the period in which the obligation for the payment is incurred. Most leases include options to renew, with renewal terms that can extend the lease term. The exercise of lease renewal options is at our sole discretion. Certain leases also include options to purchase the leased property. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option reasonably certain of exercise. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants. At December 31, 2019 , $410 million of operating ROU assets are included within other long-term assets in our consolidated balance sheet. Additionally, at December 31, 2019 , $116 million and $332 million of operating lease liabilities are included within trade accounts payable and accrued expenses and other long-term liabilities, respectively, in our consolidated balance sheet based on the remaining lease term. For the year-ended December 31, 2019 , total fixed operating lease costs, excluding short-term lease costs, were $154 million and are included within operating costs in our consolidated statement of income. Short-term lease costs were not material. In addition, for the year-ended December 31, 2019 , total variable operating lease costs were $82 million and are included within operating costs in our consolidated statement of income. We sublease facilities or partial facilities to third party tenants for space not used in our operations. For the year-ended December 31, 2019 , sublease rental income was $45 million and is included within operating costs in our consolidated statement of income. The weighted average remaining lease term is 4.9 years with a weighted average discount rate of 4.1% at December 31, 2019 . For the year-ended December 31, 2019 , cash paid for amounts included in the measurement of lease liabilities included within our operating cash flows was $151 million . Maturity of Lease Liabilities December 31, 2019 (in millions) 2020 $ 133 2021 117 2022 97 2023 52 2024 31 After 2024 70 Total lease payments 500 Less: Interest 52 Present value of lease liabilities $ 448 As most of our leases do not provide an implicit rate, we use our incremental borrowing rate, as adjusted for collateralized borrowings, based on the information available at date of adoption or commencement date in determining the present value of lease payments. For the year ended 2018, under prior lease disclosure requirements We lease facilities, computer hardware, and other furniture and equipment under long-term operating leases that are noncancelable and expire on various dates through 2046. We sublease facilities or partial facilities to third party tenants for space not used in our operations. Rent with scheduled escalation terms are accounted for on a straight-line basis over the lease term. Rent expense and sublease rental income, which are recorded net as an operating cost, for all operating leases were as follows for the years ended December 31, 2018 and 2017: 2018 2017 (in millions) Rent expense $ 167 $ 204 Sublease rental income (32 ) (33 ) Net rent expense $ 135 $ 171 Future annual minimum payments due subsequent to December 31, 2018 under all of our noncancelable operating leases with initial terms in excess of one year are as follows: Minimum Sublease Net Lease (in millions) For the years ending December 31,: 2019 $ 147 $ (13 ) $ 134 2020 113 (12 ) 101 2021 96 (10 ) 86 2022 79 (9 ) 70 2023 34 (9 ) 25 Thereafter 50 (23 ) 27 Total $ 519 $ (76 ) $ 443

BENEFITS PAYABLE

BENEFITS PAYABLE	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
BENEFITS PAYABLE	BENEFITS PAYABLE On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 4,862 $ 4,668 $ 4,563 Less: Reinsurance recoverables (95 ) (70 ) (76 ) Balances at January 1, net 4,767 4,598 4,487 Incurred related to: Current year 54,193 46,385 44,001 Prior years (336 ) (503 ) (483 ) Total incurred 53,857 45,882 43,518 Paid related to: Current year (48,421 ) (41,736 ) (39,496 ) Prior years (4,267 ) (3,977 ) (3,911 ) Total paid (52,688 ) (45,713 ) (43,407 ) Reinsurance recoverable 68 95 70 Balances at December 31 $ 6,004 $ 4,862 $ 4,668 Amounts incurred related to prior years vary from previously estimated liabilities as the claims ultimately are settled. Negative amounts reported for incurred related to prior years result from claims being ultimately settled for amounts less than originally estimated (favorable development). As previously discussed, our reserving practice is to consistently recognize the actuarial best estimate of our ultimate liability for claims. Actuarial standards require the use of assumptions based on moderately adverse experience, which generally results in favorable reserve development, or reserves that are considered redundant. We experienced favorable medical claims reserve development related to prior fiscal years of $336 million in 2019 , $503 million in 2018 , and $483 million in 2017 . The table below details our favorable medical claims reserve development related to prior fiscal years by segment for 2019 , 2018 , and 2017 . (Favorable) Unfavorable Medical Claims Reserve 2019 2018 2017 Retail Segment $ (386 ) $ (398 ) $ (386 ) Group and Specialty Segment 50 (46 ) (40 ) Individual Commercial Segment — (57 ) (56 ) Other Businesses — (2 ) (1 ) Total $ (336 ) $ (503 ) $ (483 ) The medical claims reserve development for 2019 , 2018 , and 2017 primarily reflects the consistent application of trend and completion factors estimated using an assumption of moderately adverse conditions. Favorable prior period development primarily resulted from our Medicare Advantage medical business. The unfavorable Group and Specialty medical claims reserve development for 2019 reflects higher than expected claims trend and provider settlements. Benefits expense reduction of $22 million associated with long-duration future policy benefits for the year ended December 31, 2017 was excluded from the previous short duration benefits payable rollforward table. Incurred and Paid Claims Development The following discussion provides information about incurred and paid claims development for our segments as of December 31, 2019 , net of reinsurance, as well as cumulative claim frequency and the total of IBNR included within the net incurred claims amounts. The information about incurred and paid claims development for the years ended December 31, 2017 and 2018 is presented as supplementary information. Claims frequency is measured as medical fee-for-service claims for each service encounter with a unique provider identification number. Our claims frequency measure includes claims covered by deductibles as well as claims under capitated arrangements. Claim counts may vary based on product mix and the percentage of delegated capitation arrangements. Retail Segment Activity in benefits payable for our Retail segment was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 4,338 $ 3,963 $ 3,506 Less: Reinsurance recoverables (95 ) (70 ) (76 ) Balances at January 1, net 4,243 3,893 3,430 Incurred related to: Current year 48,983 41,323 38,604 Prior years (386 ) (398 ) (386 ) Total incurred 48,597 40,925 38,218 Paid related to: Current year (43,831 ) (37,189 ) (34,781 ) Prior years (3,714 ) (3,386 ) (2,974 ) Total paid (47,545 ) (40,575 ) (37,755 ) Reinsurance recoverable 68 95 70 Balances at December 31 $ 5,363 $ 4,338 $ 3,963 At December 31, 2019 , benefits payable for our Retail segment included IBNR of approximately $3.6 billion , primarily associated with claims incurred in 2019 . The cumulative number of reported claims as of December 31, 2019 was approximately 123.0 million for claims incurred in 2019 , 109.6 million for claims incurred in 2018 , and 104.7 million for claims incurred in 2017 . The following tables provide information about incurred and paid claims development for the Retail segment as of December 31, 2019 , net of reinsurance. Incurred Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 38,604 $ 38,341 $ 38,310 2018 41,323 40,984 2019 48,983 Total $ 128,277 Cumulative Paid Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 34,781 $ 38,232 $ 38,310 2018 37,189 40,841 2019 43,831 Total $ 122,982 All outstanding benefit liabilities before 2017, net of reinsurance N/A Benefits payable, net of reinsurance $ 5,295 Group and Specialty Segment Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 517 $ 568 $ 579 Incurred related to: Current year 5,708 5,466 5,403 Prior years 50 (46 ) (40 ) Total incurred 5,758 5,420 5,363 Paid related to: Current year (5,081 ) (4,957 ) (4,843 ) Prior years (553 ) (514 ) (531 ) Total paid (5,634 ) (5,471 ) (5,374 ) Balances at December 31 $ 641 $ 517 $ 568 At December 31, 2019 , benefits payable for our Group and Specialty segment included IBNR of approximately $567 million , primarily associated with claims incurred in 2019 . The cumulative number of reported claims as of December 31, 2019 was approximately 9.7 million for claims incurred in 2019 , 10.8 million for claims incurred in 2018 , and 11.1 million for claims incurred in 2017 . The following tables provide information about incurred and paid claims development for the Group and Specialty segment as of December 31, 2019 , net of reinsurance. Incurred Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 5,403 $ 5,358 $ 5,372 2018 5,466 5,501 2019 5,708 Total $ 16,581 Cumulative Paid Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 4,843 $ 5,351 $ 5,372 2018 4,957 5,487 2019 5,081 Total $ 15,940 All outstanding benefit liabilities before 2017, net of reinsurance N/A Benefits payable, net of reinsurance $ 641 Reconciliation to Consolidated The reconciliation of the net incurred and paid claims development tables to benefits payable in the consolidated statement of financial position is as follows: December 31, Net outstanding liabilities Retail $ 5,295 Group and Specialty 641 Benefits payable, net of reinsurance 5,936 Reinsurance recoverable on unpaid claims Retail 68 Total benefits payable, gross $ 6,004

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The provision for income taxes consisted of the following for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Current provision: Federal $ 560 $ 139 $ 1,324 States and Puerto Rico 41 58 116 Total current provision 601 197 1,440 Deferred expense 162 194 132 Provision for income taxes $ 763 $ 391 $ 1,572 The provision for income taxes was different from the amount computed using the federal statutory rate for the years ended December 31, 2019 , 2018 and 2017 due to the following: 2019 2018 2017 (in millions) Income tax provision at federal statutory rate $ 729 $ 436 $ 1,407 States, net of federal benefit, and Puerto Rico 49 42 80 Tax exempt investment income (6 ) (11 ) (22 ) Health insurance industry fee — 243 — Nondeductible executive compensation 25 17 36 Tax reform — (39 ) 133 KMG sale — (272 ) — Other, net (34 ) (25 ) (62 ) Provision for income taxes $ 763 $ 391 $ 1,572 The tax reform law enacted on December 22, 2017 (the "Tax Reform Law") reduced the statutory federal corporate income tax rate to 21 percent from 35 percent, beginning in 2018, and required a mandatory deemed repatriation of undistributed foreign earnings. The rate reduction required a remeasurement of our net deferred tax asset . These items resulted in an estimated increase in our 2017 tax provision of approximately $133 million , including approximately $10 million for the deemed repatriation tax imposed on the undistributed earnings of our Puerto Rico operations. Revisions to our prior estimate for the income tax effects of the Tax Reform Law decreased our 2018 tax provision by approximately $39 million . The incremental tax benefit on the sale of KMG of $272 million resulted from a tax loss higher than the loss recorded in the statement of income for the year ended December 31, 2018 due to a higher tax basis in KMG than book basis. In addition, the amount reflects our ability to carryback the capital loss to tax years 2015, 2016 and 2017 at the historical tax rate of 35 percent instead of the current tax rate of 21 percent. Deferred income tax balances reflect the impact of temporary differences between the tax bases of assets or liabilities and their reported amounts in our consolidated financial statements, and are stated at enacted tax rates expected to be in effect when the reported amounts are actually recovered or settled. Principal components of our net deferred tax balances at December 31, 2019 and 2018 were as follows: Assets (Liabilities) 2019 2018 (in millions) Compensation and other accrued expense $ 111 $ 89 Benefits payable 89 79 Net operating loss carryforward 42 38 Deferred acquisition costs 22 17 Unearned revenues 8 9 Other 8 8 Capital loss carryforward 1 15 Investment securities — 44 Total deferred income tax assets 281 299 Valuation allowance (45 ) (54 ) Total deferred income tax assets, net of valuation allowance 236 245 Depreciable property and intangible assets (329 ) (273 ) Investment securities (181 ) — Prepaid expenses (64 ) (52 ) Future policy benefits payable (3 ) (5 ) Total deferred income tax liabilities (577 ) (330 ) Total net deferred income tax liabilities $ (341 ) $ (85 ) All deferred tax liabilities and assets are classified as noncurrent in our consolidated balance sheets as other long-term liabilities at December 31, 2019 and 2018. At December 31, 2019 , we had approximately $114 million of net operating losses and $2 million of capital losses to carry forward. These loss carryforwards, if not used to offset future taxable income or capital gain, will expire from 2020 through 2033 . Due to limitations and uncertainty regarding our ability to use some of the loss carryforwards and certain other deferred tax assets, a valuation allowance of $45 million was established. For the remainder of the net operating loss carryforwards and other cumulative temporary differences, based on our historical record of producing taxable income and profitability, we have concluded that future operating income will be sufficient to give rise to tax expense to recover these deferred tax assets. We file income tax returns in the United States and Puerto Rico. The U.S. Internal Revenue Service, or IRS, has completed its examinations of our consolidated income tax returns for 2017 and prior years. Our 2018 tax return is in the post-filing review period under the Compliance Assurance Process, or CAP. Our 2019 tax return is under advance review by the IRS under CAP. With a few exceptions, which are immaterial in the aggregate, we no longer are subject to state, local and foreign tax examinations for years before 2016. We are not aware of any material adjustments that may be proposed as a result of any ongoing or future examinations. We do not have material uncertain tax positions reflected in our consolidated balance sheets.

DEBT

DEBT	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
DEBT	DEBT The carrying value of debt outstanding was as follows at December 31, 2019 and 2018 : 2019 2018 (in millions) Short-term debt: Commercial paper $ 300 $ 645 Term note — 650 Senior notes: $400 million, 2.625% due October 1, 2019 — 399 $400 million, 2.50% due December 15, 2020 399 — Total short-term debt $ 699 $ 1,694 Long-term debt: Senior notes: $400 million, 2.50% due December 15, 2020 $ — $ 398 $600 million, 3.15% due December 1, 2022 598 596 $400 million, 2.90% due December 15, 2022 397 396 $600 million, 3.85% due October 1, 2024 597 597 $600 million, 3.95% due March 15, 2027 595 594 $500 million, 3.125% due August 15, 2029 495 — $250 million, 8.15% due June 15, 2038 262 263 $400 million, 4.625% due December 1, 2042 396 396 $750 million, 4.95% due October 1, 2044 739 739 $400 million, 4.80% due March 15, 2047 396 396 $500 million, 3.95% due August 15, 2049 492 — Total long-term debt $ 4,967 $ 4,375 Maturities of the short-term and long-term debt for the years ending December 31, are as follows: For the years ending December 31, (in millions) 2020 $ 700 2021 — 2022 1,000 2023 — 2024 600 Thereafter 3,400 Senior Notes In August 2019, we issued $500 million of 3.125% senior notes due August 15, 2029 and $500 million of 3.950% senior notes due August 15, 2049. Our net proceeds, reduced for the underwriters' discount and commission and offering expenses paid were $987 million . We used the net proceeds from this offering, together with available cash, to repay the $650 million outstanding amount due under our term note in August 2019, and the $400 million aggregate principal amount of our 2.625% senior notes due on its maturity date of October 1, 2019. Our senior notes, which are unsecured, may be redeemed at our option at any time at 100% of the principal amount plus accrued interest and a specified make-whole amount. The 8.15% senior notes are subject to an interest rate adjustment if the debt ratings assigned to the notes are downgraded (or subsequently upgraded). In addition, our senior notes contain a change of control provision that may require us to purchase the notes under certain circumstances. We recognized a loss on extinguishment of debt of approximately $17 million in 2017 for the early redemption of senior notes, which is included in interest expense in the consolidated statements of income. Credit Agreement Our 5 -year, $2.0 billion unsecured revolving credit agreement expires May 2022. Under the credit agreement, at our option, we can borrow on either a competitive advance basis or a revolving credit basis. The revolving credit portion bears interest at either LIBOR plus a spread or the base rate plus a spread. If drawn upon, the revolving credit would revert to using the alternative base rate once LIBOR is discontinued. The LIBOR spread, currently 110.0 basis points, varies depending on our credit ratings ranging from 91.0 to 150.0 basis points. We also pay an annual facility fee regardless of utilization. This facility fee, currently 15.0 basis points, may fluctuate between 9.0 and 25.0 basis points, depending upon our credit ratings. The competitive advance portion of any borrowings will bear interest at market rates prevailing at the time of borrowing on either a fixed rate or a floating rate based on LIBOR, at our option. The terms of the credit agreement include standard provisions related to conditions of borrowing which could limit our ability to borrow additional funds. In addition, the credit agreement contains customary restrictive covenants and a financial covenant regarding maximum debt to capitalization of 50% as well as customary events of default. We are in compliance with this financial covenant, with an actual debt to capitalization of 32% as measured in accordance with the credit agreement as of December 31, 2019 . Upon our agreement with one or more financial institutions, we may expand the aggregate commitments under the credit agreement to a maximum of $2.5 billion , through a $500 million incremental loan facility. At December 31, 2019 , we had no borrowings and no letters of credit outstanding under the credit agreement. Accordingly, as of December 31, 2019 , we had $2 billion of remaining borrowing capacity (which excludes the uncommitted $500 million incremental loan facility under the credit agreement), none of which would be restricted by our financial covenant compliance requirement. We have other customary, arms-length relationships, including financial advisory and banking, with some parties to the credit agreement. Commercial Paper Under our commercial paper program we may issue short-term, unsecured commercial paper notes privately placed on a discount basis through certain broker dealers at any time not to exceed $2 billion . Amounts available under the program may be borrowed, repaid and re-borrowed from time to time. The net proceeds of issuances have been and are expected to be used for general corporate purposes. The maximum principal amount outstanding at any one time during the year ended December 31, 2019 was $801 million , with $300 million outstanding at December 31, 2019 compared to $645 million outstanding at December 31, 2018 . The outstanding commercial paper at December 31, 2019 had a weighted average annual interest rate of 2% . Term Note In November 2018, we entered into a $1.0 billion term note agreement with a bank at a variable rate of interest due within one year . We may elect to incur interest at either the bank's base rate or LIBOR plus 115 basis points. The base rate is defined as the higher of the daily federal funds rate plus 50 basis points; or the bank's prime rate; or LIBOR plus 100 basis points. The term note shares the customary terms and provisions as well as financial covenants of our credit agreement, as discussed above. The note was prepayable without penalty. We repaid $350 million prior to December 31, 2018 and repaid the outstanding balance of $650 million in August 2019. In February 2020, we entered into a new $1 billion term loan commitment with a bank that allows for up to three draws with the initial draw at a minimum of $300 million that matures 1 year after the first draw, subject to a 1 year extension. Following any initial draw, any unused commitments in excess of $300 million expire on June 30, 2020, with the remaining commitments of up to $300 million available until September 30, 2020. If the initial draw has not been made by June 30, 2020, then all commitments expire on June 30, 2020. The facility fee, interest rate and financial covenants are consistent with those of our revolving credit agreement. There is no prepayment penalty.

EMPLOYEE BENEFIT PLANS

EMPLOYEE BENEFIT PLANS	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS Employee Savings Plan We have defined contribution retirement savings plans covering eligible employees which include matching contributions based on the amount of our employees’ contributions to the plans. The cost of these plans amounted to approximately $221 million in 2019 , $197 million in 2018 , and $217 million in 2017 . The Company’s cash match is invested pursuant to the participant’s contribution direction. Based on the closing price of our common stock of $366.52 on December 31, 2019 , approximately 11% of the retirement and savings plan’s assets were invested in our common stock, or approximately 1.6 million shares, representing approximately 1.2% of the shares outstanding as of December 31, 2019 . At December 31, 2019 , approximately 1.8 million shares of our common stock were reserved for issuance under our defined contribution retirement savings plans. Stock-Based Compensation We have plans under which options to purchase our common stock and restricted stock units have been granted to executive officers, directors and key employees. Awards generally require both a change in control and termination of employment within 2 years of the date of the change in control to accelerate the vesting, including those granted to retirement-eligible participants. The terms and vesting schedules for stock-based awards vary by type of grant. Generally, the awards vest upon time-based conditions. We have also granted awards to certain employees that vest upon a combination of time and performance-based conditions. The stock awards of retirement-eligible participants are generally earned ratably over the service period for each tranche. Accordingly, upon retirement the earned portion of the current tranche will continue to vest on the originally scheduled vest date and any remaining unearned portion of the award will be forfeited. Our equity award program includes a retirement provision that generally treats employees with a combination of age and years of services with the Company totaling 65 or greater, with a minimum required age of 55 and a minimum requirement of 5 years of service, as retirement-eligible. Upon exercise, stock-based compensation awards are settled with authorized but unissued company stock or treasury stock. The compensation expense that has been charged against income for these plans was as follows for the years ended December 31, 2019 , 2018 , and 2017 : 2019 2018 2017 (in millions) Stock-based compensation expense by type: Restricted stock $ 152 $ 124 $ 145 Stock options 11 13 12 Total stock-based compensation expense 163 137 157 Tax benefit recognized (35 ) (21 ) (32 ) Stock-based compensation expense, net of tax $ 128 $ 116 $ 125 Stock-based compensation expense for certain restricted stock in 2017 included a $29 million modification expense for certain awards. The tax benefit recognized in our consolidated financial statements is based on the amount of compensation expense recorded for book purposes, subject to limitations on the deductibility of annual compensation in excess of $500,000 per employee as mandated by the Health Care Reform Law. The actual tax benefit realized in our tax return is based on the intrinsic value, or the excess of the market value over the exercise or purchase price, of stock options exercised and restricted stock vested during the period, subject to limitations on the deductibility of annual compensation in excess of $500,000 per employee as mandated by the Health Care Reform Law. The actual tax benefit realized for the deductions taken on our tax returns from option exercises and restricted stock vesting totaled $25 million in 2019 , $49 million in 2018 , and $68 million in 2017 . There was no capitalized stock-based compensation expense during these years. At December 31, 2019 , there were 12.5 million shares reserved for stock award plans under the Humana Inc. 2011 Stock Incentive Plan, or 2011 Plan, and 16.0 million shares reserved for stock award plans under the Humana Inc. 2019 Stock Incentive Plan, or 2019 Plan. These reserved shares included giving effect to, under the 2011 Plan, 3.8 million shares of common stock available for future grants assuming all stock options were granted or 1.7 million shares available for future grants assuming all restricted stock were granted. These reserved shares included giving effect to, under the 2019 Plan, 15.8 million shares of common stock available for future grants assuming all stock options were granted or 4.7 million shares available for future grants assuming all restricted stock were granted. Shares may be issued from authorized but unissued company stock or treasury stock. Restricted Stock Restricted stock is granted with a fair value equal to the market price of our common stock on the date of grant and generally vests in equal annual tranches over a three year period from the date of grant. Certain of our restricted stock grants also include performance-based conditions generally associated with return on invested capital and strategic membership growth. Restricted stock units have forfeitable dividend equivalent rights equal to the dividend paid on common stock. The weighted-average grant date fair value of our restricted stock was $302.09 in 2019 , $276.62 in 2018 , and $222.35 in 2017 . Activity for our restricted stock was as follows for the year ended December 31, 2019 : Shares Weighted- (shares in thousands) Nonvested restricted stock at December 31, 2018 964 $ 213.99 Granted 503 302.09 Vested (421 ) 239.42 Forfeited (70 ) 269.06 Nonvested restricted stock at December 31, 2019 976 $ 245.21 Approximately 22% of the nonvested restricted stock at December 31, 2019 included performance-based conditions. The fair value of shares vested was $141 million during 2019 , $298 million during 2018 , and $306 million during 2017 . Total compensation expense not yet recognized related to nonvested restricted stock was $164 million at December 31, 2019 . We expect to recognize this compensation expense over a weighted-average period of approximately 1.7 years. There are no other contractual terms covering restricted stock once vested. Stock Options Stock options are granted with an exercise price equal to the fair market value of the underlying common stock on the date of grant. Our stock plans, as approved by the Board of Directors and stockholders, define fair market value as the average of the highest and lowest stock prices reported on the composite tape by the New York Stock Exchange on a given date. Exercise provisions vary, but most options vest in whole or in part 1 to 3 years after grant and expire 7 years after grant. The weighted-average fair value of each option granted during 2019 , 2018 , and 2017 is provided below. The fair value was estimated on the date of grant using the Black-Scholes pricing model with the weighted-average assumptions indicated below: 2019 2018 2017 Weighted-average fair value at grant date $ 68.53 $ 63.67 $ 49.81 Expected option life (years) 4.1 years 4.1 years 4.1 years Expected volatility 25.5 % 26.1 % 27.1 % Risk-free interest rate at grant date 2.4 % 2.5 % 2.0 % Dividend yield 0.7 % 0.7 % 0.7 % When valuing employee stock options, we stratify the employee population into three homogeneous groups that historically have exhibited similar exercise behaviors. These groups are executive officers, directors, and all other employees. We value the stock options based on the unique assumptions for each of these employee groups. We calculate the expected term for our employee stock options based on historical employee exercise behavior and base the risk-free interest rate on a traded zero-coupon U.S. Treasury bond with a term substantially equal to the option’s expected term. The volatility used to value employee stock options is based on historical volatility. We calculate historical volatility using a simple-average calculation methodology based on daily price intervals as measured over the expected term of the option. Activity for our option plans was as follows for the year ended December 31, 2019 : Shares Under Weighted-Average (shares in thousands) Options outstanding at December 31, 2018 677 $ 213.17 Granted 121 304.59 Exercised (305 ) 189.24 Forfeited — — Options outstanding at December 31, 2019 493 $ 250.46 Options exercisable at December 31, 2019 109 $ 216.49 As of December 31, 2019 , outstanding stock options, substantially all of which are expected to vest, had an aggregate intrinsic value of $56 million , and a weighted-average remaining contractual term of 4.8 years. As of December 31, 2019 , exercisable stock options had an aggregate intrinsic value of $16 million , and a weighted-average remaining contractual term of 3.9 years. The total intrinsic value of stock options exercised during 2019 was $43 million , compared with $43 million during 2018 and $44 million during 2017 . Cash received from stock option exercises totaled $58 million in 2019 , $50 million in 2018 , and $63 million in 2017 . Total compensation expense not yet recognized related to nonvested options was $11 million at December 31, 2019 . We expect to recognize this compensation expense over a weighted-average period of approximately 1.7 years.

EARNINGS PER COMMON SHARE COMPU

EARNINGS PER COMMON SHARE COMPUTATION	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE COMPUTATION	EARNINGS PER COMMON SHARE COMPUTATION Detail supporting the computation of basic and diluted earnings per common share was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (dollars in millions, except per Net income available for common stockholders $ 2,707 $ 1,683 $ 2,448 Weighted-average outstanding shares of common stock used to 134,055 137,486 144,493 Dilutive effect of: Employee stock options 107 194 172 Restricted stock 565 723 920 Shares used to compute diluted earnings per common share 134,727 138,403 145,585 Basic earnings per common share $ 20.20 $ 12.24 $ 16.94 Diluted earnings per common share $ 20.10 $ 12.16 $ 16.81 Number of antidilutive stock options and restricted stock awards 478 223 539

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Dividends The following table provides details of dividend payments, excluding dividend equivalent rights, in 2017 , 2018 , and 2019 under our Board approved quarterly cash dividend policy: Payment Amount Total (in millions) 2017 $1.49 $216 2018 $1.90 $262 2019 $2.15 $289 On October 24, 2019 , the Board declared a cash dividend of $0.55 per share that was paid on January 31, 2020 to stockholders of record on December 31, 2019 , for an aggregate amount of $73 million . Declaration and payment of future quarterly dividends is at the discretion of our Board and may be adjusted as business needs or market conditions change. In February 2020, the Board declared a cash dividend of $0.625 per share payable on April 24, 2020 to stockholders of record on March 31, 2020. Stock Repurchases Our Board of Directors may authorize the purchase of our common shares. Under our share repurchase authorization, shares may have been purchased from time to time at prevailing prices in the open market, by block purchases, through plans designed to comply with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended, or in privately-negotiated transactions (including pursuant to accelerated share repurchase agreements with investment banks), subject to certain regulatory restrictions on volume, pricing, and timing. On February 14, 2017, our Board of Directors authorized the repurchase of up to $2.25 billion of our common shares expiring on December 31, 2017, exclusive of shares repurchased in connection with employee stock plans. On February 16, 2017, we entered into an accelerated share repurchase agreement, the February 2017 ASR, with Goldman, Sachs & Co. LLC, or Goldman Sachs, to repurchase $1.5 billion of our common stock as part of the $2.25 billion share repurchase authorized on February 14, 2017. On February 22, 2017, we made a payment of $1.5 billion to Goldman Sachs from available cash on hand and received an initial delivery of 5.83 million shares of our common stock from Goldman Sachs based on the then current market price of Humana common stock. The payment to Goldman Sachs was recorded as a reduction to stockholders’ equity, consisting of a $1.2 billion increase in treasury stock, which reflected the value of the initial 5.83 million shares received upon initial settlement, and a $300 million decrease in capital in excess of par value, which reflected the value of stock held back by Goldman Sachs pending final settlement of the February 2017 ASR. Upon settlement of the February 2017 ASR on August 28, 2017, we received an additional 0.84 million shares as determined by the average daily volume weighted-average share price of our common stock during the term of the agreement, less a discount, of $224.81 , bringing the total shares received under this program to 6.67 million . In addition, upon settlement we reclassified the $300 million value of stock initially held back by Goldman Sachs from capital in excess of par value to treasury stock. Subsequent to settlement of the February 2017 ASR, we repurchased an additional 3.04 million shares in the open market, utilizing the remaining $750 million of the $2.25 billion authorization prior to expiration. On December 14, 2017, our Board of Directors authorized the repurchase of up to $3.0 billion of our common shares expiring on December 31, 2020, exclusive of shares repurchased in connection with employee stock plans. On December 21, 2017, we entered into an accelerated stock repurchase agreement, the December 2017 ASR, with Bank of America, N.A., or BofA, to repurchase $1.0 billion of our common stock as part of the $3.0 billion share repurchase program authorized on December 14, 2017. On December 22, 2017, we made a payment of $1.0 billion to BofA from available cash on hand and received an initial delivery of 3.28 million shares of our common stock from BofA based on the then current market price of Humana common stock. The payment to BofA was recorded as a reduction to stockholders’ equity, consisting of an $800 million increase in treasury stock, which reflected the value of the initial 3.28 million shares received upon initial settlement, and a $200 million decrease in capital in excess of par value, which reflected the value of stock held back by BofA pending final settlement of the December 2017 ASR. Upon settlement of the ASR on March 26, 2018, we received an additional 0.46 million shares as determined by the average daily volume weighted-average share price of our common stock during the term of the ASR Agreement, less a discount, of $267.55 , bringing the total shares received under this program to 3.74 million . In addition, upon settlement we reclassified the $200 million value of stock initially held back by BofA from capital in excess of par value to treasury stock. On November 28, 2018, we entered into an accelerated stock repurchase agreement, the November 2018 ASR, with Goldman Sachs to repurchase $750 million of our common stock as part of the $3.0 billion share repurchase program authorized by the Board of Directors on December 14, 2017. On November 29, 2018, we made a payment of $750 million to Goldman Sachs from available cash on hand and received an initial delivery of 1.94 million shares of our common stock from Goldman Sachs. The payment to Goldman Sachs was recorded as a reduction to stockholders’ equity, consisting of a $600 million increase in treasury stock, which reflected the value of the initial 1.94 million shares received upon initial settlement, and a $150 million decrease in capital in excess of par value, which reflected the value of stock held back by Goldman Sachs pending final settlement of the November 2018 ASR. Upon final settlement of the November 2018 ASR on February 28, 2019, we received an additional 0.6 million shares as determined by the average daily volume weighted-averages share price of our common stock during the term of the agreement, less a discount, of $295.15 , bringing the total shares received under this program to 2.54 million . In addition, upon settlement we reclassified the $150 million value of stock initially held back by Goldman Sachs from capital in excess of par value to treasury stock. On July 30, 2019, the Board of Directors replaced a previous share repurchase authorization of up to $3 billion (of which approximately $1.03 billion remained unused) with a new authorization for repurchases of up to $3 billion of our common shares exclusive of shares repurchased in connection with employee stock plans, expiring on June 30, 2022. On July 31, 2019, we entered into an accelerated stock repurchase agreement, the July 2019 ASR, with Citibank, N.A., or Citi, to repurchase $1 billion of our common stock. On August 2, 2019, we made a payment of $1 billion to Citi and received an initial delivery of 2.7 million shares of our common stock. We recorded the payment to Citi as a reduction to stockholders’ equity, consisting of an $800 million increase in treasury stock, which reflected the value of the initial 2.7 million shares received upon initial settlement, and a $200 million decrease in capital in excess of par value, which reflected the value of stock held back by Citi pending final settlement of the July 2019 ASR. Upon final settlement of the July 2019 ASR on December 26, 2019, we received an additional 0.7 million shares as determined by the average daily volume weighted-averages share price of our common stock during the term of the agreement, less a discount, of $296.19 , bringing the total shares received under the July 2019 ASR to 3.4 million . In addition, upon settlement we reclassified the $200 million value of stock initially held back by Citi from capital in excess of par value to treasury stock. Our remaining repurchase authorization was approximately $2.0 billion as of February 19, 2020. Excluding shares acquired in connection with employee stock plans, share repurchases were as follows during the years ended December 31, 2019 , 2018 and 2017 . 2019 2018 2017 Authorization Date Purchase Not to Exceed Shares Cost Shares Cost Shares Cost (in millions) February 2017 2,250 — — — — 9.71 2,250 December 2017 3,000 — — 3.07 1,024 3.28 800 July 2019 3,000 3.40 1,000 — — — — Total repurchases 3.40 $ 1,000 3.07 $ 1,024 12.99 $ 3,050 In connection with employee stock plans, we acquired 0.2 million common shares for $70 million in 2019 , 0.4 million common shares for $116 million in 2018 , and 0.5 million common shares for $115 million in 2017 . Regulatory Requirements Certain of our subsidiaries operate in states that regulate the payment of dividends, loans, or other cash transfers to Humana Inc., our parent company, and require minimum levels of equity as well as limit investments to approved securities. The amount of dividends that may be paid to Humana Inc. by these subsidiaries, without prior approval by state regulatory authorities, or ordinary dividends, is limited based on the entity’s level of statutory income and statutory capital and surplus. If the dividend, together with other dividends paid within the preceding twelve months, exceeds a specified statutory limit or is paid from sources other than earned surplus, it is generally considered an extraordinary dividend requiring prior regulatory approval. In most states, prior notification is provided before paying a dividend even if approval is not required. Although minimum required levels of equity are largely based on premium volume, product mix, and the quality of assets held, minimum requirements vary significantly at the state level. Our state regulated insurances subsidiaries had aggregate statutory capital and surplus of approximately $8.0 billion and $7.6 billion as of December 31, 2019 and 2018 , respectively, which exceeded aggregate minimum regulatory requirements of $5.9 billion and $5.2 billion , respectively. The amount of ordinary dividends that may be paid to our parent company in 2020 is approximately $1.0 billion in the aggregate. The amount, timing and mix of ordinary and extraordinary dividend payments will vary due to state regulatory requirements, the level of excess statutory capital and surplus and expected future surplus requirements related to, for example, premium volume and product mix. Actual dividends that were paid to our parent company were approximately $1.8 billion in 2019 , $2.3 billion in 2018 , and $1.4 billion in 2017 .

COMMITMENTS, GUARANTEES AND CON

COMMITMENTS, GUARANTEES AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS, GUARANTEES AND CONTINGENCIES	COMMITMENTS, GUARANTEES AND CONTINGENCIES Purchase Obligations We have agreements to purchase services, primarily information technology related services, or to make improvements to real estate, in each case that are enforceable and legally binding on us and that specify all significant terms, including: fixed or minimum levels of service to be purchased; fixed, minimum or variable price provisions; and the appropriate timing of the transaction. We have purchase obligation commitments of $922 million in 2020 , $647 million in 2021 , $489 million in 2022 , $246 million in 2023 , and $100 million in 2024. Purchase obligations exclude agreements that are cancelable without penalty. Off-Balance Sheet Arrangements As part of our ongoing business, we do not participate or knowingly seek to participate in transactions that generate relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities, or SPEs, which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes. As of December 31, 2019 , we were not involved in any SPE transactions. Guarantees and Indemnifications Through indemnity agreements approved by the state regulatory authorities, certain of our regulated subsidiaries generally are guaranteed by Humana Inc., our parent company, in the event of insolvency for (1) member coverage for which premium payment has been made prior to insolvency; (2) benefits for members then hospitalized until discharged; and (3) payment to providers for services rendered prior to insolvency. Our parent also has guaranteed the obligations of certain of our non-regulated subsidiaries and funding to maintain required statutory capital levels of certain regulated subsidiaries. In the ordinary course of business, we enter into contractual arrangements under which we may agree to indemnify a third party to such arrangement from any losses incurred relating to the services they perform on behalf of us, or for losses arising from certain events as defined within the particular contract, which may include, for example, litigation or claims relating to past performance. Such indemnification obligations may not be subject to maximum loss clauses. Historically, payments made related to these indemnifications have been immaterial. Government Contracts Our Medicare products, which accounted for approximately 82% of our total premiums and services revenue for the year ended December 31, 2019 , primarily consisted of products covered under the Medicare Advantage and Medicare Part D Prescription Drug Plan contracts with the federal government. These contracts are renewed generally for a calendar year term unless CMS notifies us of its decision not to renew by May 1 of the calendar year in which the contract would end, or we notify CMS of our decision not to renew by the first Monday in June of the calendar year in which the contract would end. All material contracts between Humana and CMS relating to our Medicare products have been renewed for 2020 , and all of our product offerings filed with CMS for 2020 have been approved. CMS uses a risk-adjustment model which adjusts premiums paid to Medicare Advantage, or MA, plans according to health status of covered members. The risk-adjustment model, which CMS implemented pursuant to the Balanced Budget Act of 1997 (BBA) and the Benefits Improvement and Protection Act of 2000 (BIPA), generally pays more where a plan's membership has higher expected costs. Under this model, rates paid to MA plans are based on actuarially determined bids, which include a process whereby our prospective payments are based on our estimated cost of providing standard Medicare-covered benefits to an enrollee with a "national average risk profile." That baseline payment amount is adjusted to reflect the health status of our enrolled membership. Under the risk-adjustment methodology, all MA plans must collect and submit the necessary diagnosis code information from hospital inpatient, hospital outpatient, and physician providers to CMS within prescribed deadlines. The CMS risk-adjustment model uses the diagnosis data to calculate the risk-adjusted premium payment to MA plans, which CMS adjusts for coding pattern differences between the health plans and the government fee-for-service program. We generally rely on providers, including certain providers in our network who are our employees, to code their claim submissions with appropriate diagnoses, which we send to CMS as the basis for our payment received from CMS under the actuarial risk-adjustment model. We also rely on these providers to document appropriately all medical data, including the diagnosis data submitted with claims. In addition, we conduct medical record reviews as part of our data and payment accuracy compliance efforts, to more accurately reflect diagnosis conditions under the risk adjustment model. These compliance efforts include the internal contract level audits described in more detail below, as well as ordinary course reviews of our internal business processes. CMS is phasing-in the process of calculating risk scores using diagnoses data from the Risk Adjustment Processing System, or RAPS, to diagnoses data from the Encounter Data System, or EDS. The RAPS process requires MA plans to apply a filter logic based on CMS guidelines and only submit diagnoses that satisfy those guidelines. For submissions through EDS, CMS requires MA plans to submit all the encounter data and CMS will apply the risk adjustment filtering logic to determine the risk scores. For 2019 , 25% of the risk score was calculated from claims data submitted through EDS. CMS will increase that percentage to 50% in 2020 and has proposed to increase that percentage to 75% in 2021 . The phase-in from RAPS to EDS could result in different risk scores from each dataset as a result of plan processing issues, CMS processing issues, or filtering logic differences between RAPS and EDS, and could have a material adverse effect on our results of operations, financial position, or cash flows. CMS and the Office of the Inspector General of Health and Human Services, or HHS-OIG, are continuing to perform audits of various companies’ selected MA contracts related to this risk adjustment diagnosis data. We refer to these audits as Risk-Adjustment Data Validation Audits, or RADV audits. RADV audits review medical records in an attempt to validate provider medical record documentation and coding practices which influence the calculation of premium payments to MA plans. In 2012, CMS released a “Notice of Final Payment Error Calculation Methodology for Part C Medicare Advantage Risk Adjustment Data Validation (RADV) Contract-Level Audits.” The payment error calculation methodology provided that, in calculating the economic impact of audit results for an MA contract, if any, the results of the RADV audit sample would be extrapolated to the entire MA contract after a comparison of the audit results to a similar audit of the government’s traditional fee-for-service Medicare program, or Medicare FFS. We refer to the process of accounting for errors in FFS claims as the "FFS Adjuster." This comparison of RADV audit results to the FFS error rate is necessary to determine the economic impact, if any, of RADV audit results because the government used the Medicare FFS program data set, including any attendant errors that are present in that data set, to estimate the costs of various health status conditions and to set the resulting adjustments to MA plans’ payment rates in order to establish actuarial equivalence in payment rates as required under the Medicare statute. CMS already makes other adjustments to payment rates based on a comparison of coding pattern differences between MA plans and Medicare FFS data (such as for frequency of coding for certain diagnoses in MA plan data versus the Medicare FFS program dataset). The final RADV extrapolation methodology, including the first application of extrapolated audit results to determine audit settlements, is expected to be applied to CMS RADV contract level audits conducted for contract year 2011 and subsequent years. CMS is currently conducting RADV contract level audits for certain of our Medicare Advantage plans. Estimated audit settlements are recorded as a reduction of premiums revenue in our consolidated statements of income, based upon available information. We perform internal contract level audits based on the RADV audit methodology prescribed by CMS. Included in these internal contract level audits is an audit of our Private Fee-For Service business which we used to represent a proxy of the FFS Adjuster which has not yet been finalized. We based our accrual of estimated audit settlements for each contract year on the results of these internal contract level audits and update our estimates as each audit is completed. Estimates derived from these results were not material to our results of operations, financial position, or cash flows. We report the results of these internal contract level audits to CMS, including identified overpayments, if any. On October 26, 2018, CMS issued a proposed rule and accompanying materials (which we refer to as the “Proposed Rule”) related to, among other things, the RADV audit methodology described above. If implemented, the Proposed Rule would use extrapolation in RADV audits applicable to payment year 2011 contract-level audits and all subsequent audits, without the application of a FFS Adjuster to audit findings. We believe that the Proposed Rule fails to address adequately the statutory requirement of actuarial equivalence, and have provided substantive comments to CMS on the Proposed Rule as part of the notice-and-comment rulemaking process. Whether, and to what extent, CMS finalizes the Proposed Rule, and any related regulatory, industry or company reactions, could have a material adverse effect on our results of operations, financial position, or cash flows. In addition, as part of our internal compliance efforts, we routinely perform ordinary course reviews of our internal business processes related to, among other things, our risk coding and data submissions in connection with the risk- adjustment model. These reviews may also result in the identification of errors and the submission of corrections to CMS, that may, either individually or in the aggregate, be material. As such, the result of these reviews may have a material adverse effect on our results of operations, financial position, or cash flows. We believe that CMS' statements and policies regarding the requirement to report and return identified overpayments received by MA plans are inconsistent with CMS' 2012 RADV audit methodology, and the Medicare statute's requirements. These statements and policies, such as certain statements contained in the preamble to CMS’ final rule release regarding Medicare Advantage and Part D prescription drug benefit program regulations for Contract Year 2015 (which we refer to as the "Overpayment Rule"), and the Proposed Rule, appear to equate each Medicare Advantage risk adjustment data error with an “overpayment” without addressing the principles underlying the FFS Adjuster referenced above. On September 7, 2018, the Federal District Court for the District of Columbia vacated CMS's Overpayment Rule, concluding that it violated the Medicare statute, including the requirement for actuarial equivalence, and that the Overpayment Rule was also arbitrary and capricious in departing from CMS's RADV methodology without adequate explanation (among other reasons). CMS has appealed the decision to the Circuit Court of Appeals. We will continue to work with CMS to ensure that MA plans are paid accurately and that payment model principles are in accordance with the requirements of the Social Security Act, which, if not implemented correctly could have a material adverse effect on our results of operations, financial position, or cash flows. At December 31, 2019, our military services business, which accounted for approximately 1% of our total premiums and services revenue for the year ended December 31, 2019 , primarily consisted of the TRICARE T2017 East Region contract. The T2017 East Region contract is a consolidation of the former T3 North and South Regions, comprising thirty-two states and approximately 6 million TRICARE beneficiaries, under which delivery of health care services commenced on January 1, 2018. The T2017 East Region contract is a 5 -year contract set to expire on December 31, 2022 and is subject to renewals on January 1 of each year during its term at the government's option. Our state-based Medicaid business accounted for approximately 4% of our total premiums and services revenue for the year ended December 31, 2019 . In addition to our state-based Temporary Assistance for Needy Families, or TANF, Medicaid contracts in Florida and Kentucky, we have contracts in Florida for Long Term Support Services (LTSS), and in Illinois for stand-alone dual eligible demonstration programs serving individuals dually eligible for both the federal Medicare program and the applicable state-based Medicaid program. The loss of any of the contracts above or significant changes in these programs as a result of legislative or regulatory action, including reductions in premium payments to us, regulatory restrictions on profitability, including reviews by regulatory bodies that may compare our Medicare Advantage profitability to our non-Medicare Advantage business profitability, or compare the profitability of various products within our Medicare Advantage business, and require that they remain within certain ranges of each other, or increases in member benefits or member eligibility criteria without corresponding increases in premium payments to us, may have a material adverse effect on our results of operations, financial position, and cash flows. Legal Proceedings and Certain Regulatory Matters As previously disclosed, the Civil Division of the United States Department of Justice provided us with an information request in December 2014, concerning our Medicare Part C risk adjustment practices. The request relates to our oversight and submission of risk adjustment data generated by providers in our Medicare Advantage network, as well as to our business and compliance practices related to risk adjustment data generated by our providers and by us, including medical record reviews conducted as part of our data and payment accuracy compliance efforts, the use of health and well-being assessments, and our fraud detection efforts. We believe that this request for information is in connection with a wider review of Medicare Risk Adjustment generally that includes a number of Medicare Advantage plans, providers and vendors. We continue to cooperate with and voluntarily respond to the information requests from the Department of Justice. These matters are expected to result in additional qui tam litigation. As previously disclosed, on January 19, 2016, an individual filed a qui tam suit captioned United States of America ex rel. Steven Scott v. Humana, Inc., in United States District Court, Central District of California, Western Division. The complaint alleges certain civil violations by us in connection with the actuarial equivalence of the plan benefits under Humana’s Basic PDP plan, a prescription drug plan offered by us under Medicare Part D. The action seeks damages and penalties on behalf of the United States under the False Claims Act. The court ordered the qui tam action unsealed on September 13, 2017, so that the relator could proceed, following notice from the U.S. Government that it was not intervening at that time. On January 29, 2018, the suit was transferred to the United States District Court, Western District of Kentucky, Louisville Division. We take seriously our obligations to comply with applicable CMS requirements and actuarial standards of practice, and continue to vigorously defend against these allegations since the transfer to the Western District of Kentucky. We have engaged in active discovery with the relator who has pursued the matter on behalf of the United States following its unsealing, and expect that discovery process to conclude in the near future and for the Court to consider our motion for summary judgment. On November 2, 2017, we filed suit against the United States of America in the United States Court of Federal Claims, on behalf of our health plans seeking recovery from the federal government of approximately $611 million in payments under the risk corridor premium stabilization program established under Health Care Reform , for years 2014, 2015 and 2016. Our case has been stayed by the Court, pending resolution of similar cases filed by other insurers. We have not recognized revenue, nor have we recorded a receivable, for any amount due from the federal government for unpaid risk corridor payments as of December 31, 2019. We have fully recognized all liabilities due to the federal government that we have incurred under the risk corridor program, and have paid all amounts due to the federal government as required. There is no assurance that we will prevail in the lawsuit. Other Lawsuits and Regulatory Matters Our current and past business practices are subject to review or other investigations by various state insurance and health care regulatory authorities and other state and federal regulatory authorities. These authorities regularly scrutinize the business practices of health insurance, health care delivery and benefits companies. These reviews focus on numerous facets of our business, including claims payment practices, statutory capital requirements, provider contracting, risk adjustment, competitive practices, commission payments, privacy issues, utilization management practices, pharmacy benefits, access to care, and sales practices, among others. Some of these reviews have historically resulted in fines imposed on us and some have required changes to some of our practices. We continue to be subject to these reviews, which could result in additional fines or other sanctions being imposed on us or additional changes in some of our practices. We also are involved in various other lawsuits that arise, for the most part, in the ordinary course of our business operations, certain of which may be styled as class-action lawsuits. Among other matters, this litigation may include employment matters, claims of medical malpractice, bad faith, nonacceptance or termination of providers, anticompetitive practices, improper rate setting, provider contract rate and payment disputes, including disputes over reimbursement rates required by statute, general contractual matters, intellectual property matters, and challenges to subrogation practices. Under state guaranty assessment laws, including those related to state cooperative failures in the industry, we may be assessed (up to prescribed limits) for certain obligations to the policyholders and claimants of insolvent insurance companies that write the same line or lines of business as we do. As a government contractor, we may also be subject to qui tam litigation brought by individuals who seek to sue on behalf of the government, alleging that the government contractor submitted false claims to the government including, among other allegations, those resulting from coding and review practices under the Medicare risk adjustment model. Qui tam litigation is filed under seal to allow the government an opportunity to investigate and to decide if it wishes to intervene and assume control of the litigation. If the government does not intervene, the individual may continue to prosecute the action on his or her own, on behalf of the government. We also are subject to other allegations of non-performance of contractual obligations to providers, members, and others, including failure to properly pay claims, improper policy terminations, challenges to our implementation of the Medicare Part D prescription drug program and other litigation. A limited number of the claims asserted against us are subject to insurance coverage. Personal injury claims, claims for extra contractual damages, care delivery malpractice, and claims arising from medical benefit denials are covered by insurance from our wholly owned captive insurance subsidiary and excess carriers, except to the extent that claimants seek punitive damages, which may not be covered by insurance in certain states in which insurance coverage for punitive damages is not permitted. In addition, insurance coverage for all or certain forms of liability has become increasingly costly and may become unavailable or prohibitively expensive in the future. We record accruals for the contingencies discussed in the sections above to the extent that we conclude it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. No estimate of the possible loss or range of loss in excess of amounts accrued, if any, can be made at this time regarding the matters specifically described above because of the inherently unpredictable nature of legal proceedings, which also may be exacerbated by various factors, including: (i) the damages sought in the proceedings are unsubstantiated or indeterminate; (ii) discovery is not complete; (iii) the proceeding is in its early stages; (iv) the matters present legal uncertainties; (v) there are significant facts in dispute; (vi) there are a large number of parties (including where it is uncertain how liability, if any, will be shared among multiple defendants); or (vii) there is a wide range of potential outcomes. The outcome of any current or future litigation or governmental or internal investigations, including the matters described above, cannot be accurately predicted, nor can we predict any resulting judgments, penalties, fines or other sanctions that may be imposed at the discretion of federal or state regulatory authorities or as a result of actions by third parties. Nevertheless, it is reasonably possible that any such outcome of litigation, judgments, penalties, fines or other sanctions could be substantial, and the outcome of these matters may have a material adverse effect on our results of operations, financial position, and cash flows, and may also affect our reputation.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION We manage our business with three reportable segments: Retail, Group and Specialty, and Healthcare Services. Beginning January 1, 2018, we exited the individual commercial fully-insured medical health insurance business, as well as certain other business in 2018, and therefore no longer report separately the Individual Commercial segment and the Other Businesses category in the current year. Previously, the Other Businesses category included businesses that were not individually reportable because they did not meet the quantitative thresholds required by generally accepted accounting principles, primarily our closed-block of commercial long-term care insurance policies which were sold in 2018. The reportable segments are based on a combination of the type of health plan customer and adjacent businesses centered on well-being solutions for our health plans and other customers, as described below. These segment groupings are consistent with information used by our Chief Executive Officer, the chief operating decision maker, to assess performance and allocate resources. The Retail segment consists of Medicare benefits, marketed to individuals or directly via group Medicare accounts. In addition, the Retail segment also includes our contract with CMS to administer the Limited Income Newly Eligible Transition, or LI-NET, prescription drug plan program and contracts with various states to provide Medicaid, dual eligible, and Long-Term Support Services benefits, which we refer to collectively as our state-based contracts. The Group and Specialty segment consists of employer group commercial fully-insured medical and specialty health insurance benefits marketed to individuals and employer groups, including dental, vision, and other supplemental health benefits, as well as administrative services only, or ASO products. In addition, our Group and Specialty segment includes our military services business, primarily our TRICARE T2017 East Region contract. The Healthcare Services segment includes our services offered to our health plan members as well as to third parties, including pharmacy solutions, provider services, and clinical care service, such as home health and other services and capabilities to promote wellness and advance population health, including our minority investment in Kindred at Home. Our Healthcare Services intersegment revenues primarily relate to managing prescription drug coverage for members of our other segments through Humana Pharmacy Solutions®, or HPS, and includes the operations of Humana Pharmacy, Inc., our mail order pharmacy business. These revenues consist of the prescription price (ingredient cost plus dispensing fee), including the portion to be settled with the member (co-share) or with the government (subsidies), plus any associated administrative fees. Services revenues related to the distribution of prescriptions by third party retail pharmacies in our networks are recognized when the claim is processed and product revenues from dispensing prescriptions from our mail order pharmacies are recorded when the prescription or product is shipped. Our pharmacy operations, which are responsible for designing pharmacy benefits, including defining member co-share responsibilities, determining formulary listings, contracting with retail pharmacies, confirming member eligibility, reviewing drug utilization, and processing claims, act as a principal in the arrangement on behalf of members in our other segments. As principal, our Healthcare Services segment reports revenues on a gross basis, including co-share amounts from members collected by third party retail pharmacies at the point of service. In addition, our Healthcare Services intersegment revenues include revenues earned by certain owned providers derived from risk-based and non-risk-based managed care agreements with our health plans. Under risk based agreements, the provider receives a monthly capitated fee that varies depending on the demographics and health status of the member, for each member assigned to these owned providers by our health plans. The owned provider assumes the economic risk of funding the assigned members’ healthcare services. Under non risk-based agreements, our health plans retain the economic risk of funding the assigned members' healthcare services. Our Healthcare Services segment reports provider services revenues associated with risk-based agreements on a gross basis, whereby capitation fee revenue is recognized in the period in which the assigned members are entitled to receive healthcare services. Provider services revenues associated with non-risk-based agreements are presented net of associated healthcare costs. We present our consolidated results of operations from the perspective of the health plans. As a result, the cost of providing benefits to our members, whether provided via a third party provider or internally through a stand-alone subsidiary, is classified as benefits expense and excludes the portion of the cost for which the health plans do not bear responsibility, including member co-share amounts and government subsidies of $14.9 billion in 2019 , $13.4 billion in 2018 , and $13.5 billion in 2017 . In addition, depreciation and amortization expense associated with certain businesses in our Healthcare Services segment delivering benefits to our members, primarily associated with our provider services and pharmacy operations, are included with benefits expense. The amount of this expense was $117 million in 2019 , $129 million in 2018 , and $107 million in 2017 . Other than those described previously, the accounting policies of each segment are the same and are described in Note 2. Transactions between reportable segments primarily consist of sales of services rendered by our Healthcare Services segment, primarily pharmacy, provider, and clinical care services, to our Retail and Group and Specialty segment customers . Intersegment sales and expenses are recorded at fair value and eliminated in consolidation. Members served by our segments often use the same provider networks, enabling us in some instances to obtain more favorable contract terms with providers. Our segments also share indirect costs and assets. As a result, the profitability of each segment is interdependent. We allocate most operating expenses to our segments. Assets and certain corporate income and expenses are not allocated to the segments, including the portion of investment income not supporting segment operations, interest expense on corporate debt, and certain other corporate expenses. These items are managed at a corporate level. These corporate amounts are reported separately from our reportable segments and are included with intersegment eliminations in the tables presenting segment results below. Retail Group and Specialty Healthcare Services Eliminations/ Consolidated (in millions) 2019 External revenues Premiums: Individual Medicare Advantage $ 43,128 $ — $ — $ — $ 43,128 Group Medicare Advantage 6,475 — — — 6,475 Medicare stand-alone PDP 3,165 — — — 3,165 Total Medicare 52,768 — — — 52,768 Fully-insured 588 5,123 — — 5,711 Specialty — 1,571 — — 1,571 Medicaid and other 2,898 — — — 2,898 Total premiums 56,254 6,694 — — 62,948 Services revenue: Provider — — 446 — 446 ASO and other 17 790 — — 807 Pharmacy — — 186 — 186 Total services revenue 17 790 632 — 1,439 Total external revenues 56,271 7,484 632 — 64,387 Intersegment revenues Services — 18 18,255 (18,273 ) — Products — — 6,894 (6,894 ) — Total intersegment revenues — 18 25,149 (25,167 ) — Investment income 195 23 2 281 501 Total revenues 56,466 7,525 25,783 (24,886 ) 64,888 Operating expenses: Benefits 48,602 5,758 — (503 ) 53,857 Operating costs 5,306 1,651 24,852 (24,428 ) 7,381 Depreciation and amortization 323 88 156 (109 ) 458 Total operating expenses 54,231 7,497 25,008 (25,040 ) 61,696 Income from operations 2,235 28 775 154 3,192 Interest expense — — — 242 242 Other income, net — — — (506 ) (506 ) Income before income taxes and equity in net earnings 2,235 28 775 418 3,456 Equity in net earnings of Kindred at Home — — 14 — 14 Segment earnings $ 2,235 $ 28 $ 789 $ 418 $ 3,470 Premium and services revenues derived from our contracts with the federal government, as a percentage of our total premium and services revenues, was approximately 82% for 2019 , compared to 81% for 2018 , and 79% for 2017 . Retail Group and Specialty Healthcare Services Individual Commercial Other Businesses Eliminations/ Consolidated (in millions) 2018 External revenues Premiums: Individual Medicare Advantage $ 35,656 $ — $ — $ — $ — $ — $ 35,656 Group Medicare Advantage 6,103 — — — — — 6,103 Medicare stand-alone PDP 3,584 — — — — — 3,584 Total Medicare 45,343 — — — — — 45,343 Fully-insured 510 5,444 — 8 — — 5,962 Specialty — 1,359 — — — — 1,359 Medicaid and other 2,255 — — — 22 — 2,277 Total premiums 48,108 6,803 — 8 22 — 54,941 Services revenue: Provider — — 404 — — — 404 ASO and other 11 835 — — 4 — 850 Pharmacy — — 203 — — — 203 Total services revenue 11 835 607 — 4 — 1,457 Total external revenues 48,119 7,638 607 8 26 — 56,398 Intersegment revenues Services — 18 16,840 — — (16,858 ) — Products — — 6,330 — — (6,330 ) — Total intersegment revenues — 18 23,170 — — (23,188 ) — Investment income 136 23 34 — 110 211 514 Total revenues 48,255 7,679 23,811 8 136 (22,977 ) 56,912 Operating expenses: Benefits 40,925 5,420 — (70 ) 77 (470 ) 45,882 Operating costs 5,327 1,810 22,905 4 6 (22,527 ) 7,525 Depreciation and amortization 270 88 163 — — (116 ) 405 Total operating expenses 46,522 7,318 23,068 (66 ) 83 (23,113 ) 53,812 Income from operations 1,733 361 743 74 53 136 3,100 Loss on sale of business — — — — — 786 786 Interest expense — — — — — 218 218 Other expense, net — — — — — 33 33 Income (loss) before income taxes and equity in net earnings 1,733 361 743 74 53 (901 ) 2,063 Equity in net earnings of Kindred at Home — — 11 — — — 11 Segment earnings (losses) $ 1,733 $ 361 $ 754 $ 74 $ 53 $ (901 ) $ 2,074 Retail Group and Specialty Healthcare Services Individual Commercial Other Businesses Eliminations/ Consolidated (in millions) 2017 External revenues Premiums: Individual Medicare Advantage $ 32,720 $ — $ — $ — $ — $ — $ 32,720 Group Medicare Advantage 5,155 — — — — — 5,155 Medicare stand-alone PDP 3,702 — — — — — 3,702 Total Medicare 41,577 — — — — — 41,577 Fully-insured 478 5,462 — 947 — — 6,887 Specialty — 1,310 — — — — 1,310 Medicaid and other 2,571 — — — 35 — 2,606 Total premiums 44,626 6,772 — 947 35 — 52,380 Services revenue: Provider — — 258 — — — 258 ASO and other 10 626 — — 8 — 644 Pharmacy — — 80 — — — 80 Total services revenue 10 626 338 — 8 — 982 Total external revenues 44,636 7,398 338 947 43 — 53,362 Intersegment revenues Services — 20 17,293 — — (17,313 ) — Products — — 6,292 — — (6,292 ) — Total intersegment revenues — 20 23,585 — — (23,605 ) — Investment income 90 31 35 4 87 158 405 Total revenues 44,726 7,449 23,958 951 130 (23,447 ) 53,767 Operating expenses: Benefits 38,218 5,363 — 544 131 (760 ) 43,496 Operating costs 4,292 1,590 22,848 201 12 (22,376 ) 6,567 Merger termination fee and related costs, net — — — — — (936 ) (936 ) Depreciation and amortization 238 84 143 13 — (100 ) 378 Total operating expenses 42,748 7,037 22,991 758 143 (24,172 ) 49,505 Income (loss) from operations 1,978 412 967 193 (13 ) 725 4,262 Interest expense — — — — — 242 242 Income (loss) before income taxes and equity in net earnings 1,978 412 967 193 (13 ) 483 4,020 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings (losses) $ 1,978 $ 412 $ 967 $ 193 $ (13 ) $ 483 $ 4,020

REINSURANCE

REINSURANCE	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
REINSURANCE	REINSURANCE Certain blocks of insurance assumed in acquisitions, primarily life and annuities in run-off status and, prior to its sale in 2018, long-term care, are subject to reinsurance where some or all of the underwriting risk related to these policies has been ceded to a third party. In addition, a large portion of our reinsurance takes the form of 100% coinsurance agreements where, in addition to all of the underwriting risk, all administrative responsibilities, including premium collections and claim payment, have also been ceded to a third party. We acquired these policies and related reinsurance agreements with the purchase of stock of companies in which the policies were originally written. We acquired these companies for business reasons unrelated to these particular policies, including the companies’ other products and licenses necessary to fulfill strategic plans. A reinsurance agreement between two entities transfers the underwriting risk of policyholder liabilities to a reinsurer while the primary insurer retains the contractual relationship with the ultimate insured. As such, these reinsurance agreements do not completely relieve us of our potential liability to the ultimate insured. However, given the transfer of underwriting risk, our potential liability is limited to the credit exposure which exists should the reinsurer be unable to meet its obligations assumed under these reinsurance agreements. Reinsurance recoverables represent the portion of future policy benefits payable and benefits payable that are covered by reinsurance. Amounts recoverable from reinsurers are estimated in a manner consistent with the methods used to determine future policy benefits payable as detailed in Note 2. Reinsurance recoverables, included in other current and long-term assets, were $267 million at December 31, 2019 and $314 million at December 31, 2018 . The amount of these reinsurance recoverables resulting from 100% coinsurance agreements was approximately $267 million at December 31, 2019 and approximately $313 million at December 31, 2018 . Premiums ceded were $1 billion in 2019 , $976 million in 2018 and $969 million in 2017 . Benefits ceded were $881 million in 2019 , $980 million in 2018 , and $844 million in 2017 . Historical ceded premium and benefits reflect the activity associated with ceding all risk under a Medicaid contract to a third party reinsurer. The reinsurance agreement ceding all risk under the Medicaid contract was terminated effective January 1, 2020. We evaluate the financial condition of our reinsurers on a regular basis. Protective Life Insurance Company with $174 million in reinsurance recoverables is well-known and well-established with a AM Best rating of A+ (superior) at December 31, 2019 . The remaining reinsurance recoverables of $94 million are divided between 11 other reinsurers, with $72 million subject to funds withheld accounts or other financial guarantees supporting the repayment of these amounts.

QUARTERLY FINANCIAL INFORMATION

QUARTERLY FINANCIAL INFORMATION (Unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
QUARTERLY FINANCIAL INFORMATION (Unaudited)	QUARTERLY FINANCIAL INFORMATION (Unaudited) A summary of our quarterly unaudited results of operations for the years ended December 31, 2019 and 2018 follows: 2019 First Second Third Fourth (in millions, except per share results) Total revenues $ 16,107 $ 16,245 $ 16,241 $ 16,295 Income before income taxes and equity in net earnings 746 1,229 888 593 Net income 566 940 689 512 Basic earnings per common share (1) $ 4.18 $ 6.96 $ 5.16 $ 3.87 Diluted earnings per common share (1) $ 4.16 $ 6.94 $ 5.14 $ 3.84 2018 First Second Third Fourth (in millions, except per share results) Total revenues $ 14,279 $ 14,259 $ 14,206 $ 14,168 Income before income taxes and equity in net earnings 707 19 901 436 Net income 491 193 644 355 Basic earnings per common share (1) $ 3.56 $ 1.40 $ 4.68 $ 2.60 Diluted earnings per common share (1) $ 3.53 $ 1.39 $ 4.65 $ 2.58 (1)

SCHEDULE I - PARENT COMPANY FIN

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION	SCHEDULE I—PARENT COMPANY FINANCIAL INFORMATION CONDENSED BALANCE SHEETS December 31, 2019 2018 (in millions, except share ASSETS Current assets: Cash and cash equivalents $ 1,006 $ 265 Investment securities 355 313 Receivable from operating subsidiaries 1,248 1,306 Other current assets 778 628 Total current assets 3,387 2,512 Property and equipment, net 1,403 1,209 Investments in subsidiaries 14,763 16,951 Equity method investment in Kindred at Home 1,063 1,047 Other long-term assets 778 359 Total assets $ 21,394 $ 22,078 LIABILITIES AND STOCKHOLDERS’ EQUITY Current liabilities: Payable to operating subsidiaries $ 1,975 $ 4,487 Current portion of notes payable to operating subsidiaries 36 28 Book overdraft 40 38 Short-term debt 699 1,694 Other current liabilities 1,128 791 Total current liabilities 3,878 7,038 Long-term debt 4,967 4,375 Other long-term liabilities 512 504 Total liabilities 9,357 11,917 Commitments and contingencies Stockholders’ equity: Preferred stock, $1 par; 10,000,000 shares authorized; none issued — — Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 33 33 Capital in excess of par value 2,820 2,535 Retained earnings 17,483 15,072 Accumulated other comprehensive income (loss) 156 (159 ) Treasury stock, at cost, 66,524,771 shares at December 31, 2019 (8,455 ) (7,320 ) Total stockholders’ equity 12,037 10,161 Total liabilities and stockholders’ equity $ 21,394 $ 22,078 See accompanying notes to the parent company financial statements. SCHEDULE I—PARENT COMPANY FINANCIAL INFORMATION CONDENSED STATEMENTS OF INCOME For the year ended December 31, 2019 2018 2017 (in millions) Revenues: Management fees charged to operating subsidiaries $ 1,789 $ 1,666 $ 1,864 Investment and other income, net 28 30 57 1,817 1,696 1,921 Expenses: Operating costs 1,578 1,468 1,801 Merger termination fee and related costs, net — — (936 ) Depreciation 387 342 332 Interest 242 218 243 2,207 2,028 1,440 Other (income) expense, net (507 ) 33 — Loss on sale of business — 782 — Income (loss) before income taxes and equity in net earnings of subsidiaries 117 (1,147 ) 481 Provision (benefit) for income taxes 27 (542 ) 61 Income (loss) before equity in net earnings of subsidiaries 90 (605 ) 420 Equity in net earnings of subsidiaries 2,603 2,277 2,028 Equity in net earnings of Kindred at Home 14 11 — Net income $ 2,707 $ 1,683 $ 2,448 See accompanying notes to the parent company financial statements. SCHEDULE I—PARENT COMPANY FINANCIAL INFORMATION CONDENSED STATEMENTS OF COMPREHENSIVE INCOME For the year ended December 31, 2019 2018 2017 (in millions) Net income $ 2,707 $ 1,683 $ 2,448 Other comprehensive income (loss): Change in gross unrealized investment losses/gains 450 (189 ) 149 Effect of income taxes (105 ) 51 (55 ) Total change in unrealized investment 345 (138 ) 94 Reclassification adjustment for net realized (34 ) (53 ) (14 ) Effect of income taxes 8 17 5 Total reclassification adjustment, net of tax (26 ) (36 ) (9 ) Other comprehensive income (loss), net of tax 319 (174 ) 85 Comprehensive income attributable to our equity method (4 ) (4 ) — Comprehensive income $ 3,022 $ 1,505 $ 2,533 See accompanying notes to the parent company financial statements. SCHEDULE I—PARENT COMPANY FINANCIAL INFORMATION CONDENSED STATEMENTS OF CASH FLOWS For the year ended December 31, 2019 2018 2017 (in millions) Net cash provided by operating activities $ 3,529 $ 2,719 $ 2,423 Cash flows from investing activities: Acquisitions, net of cash acquired — (354 ) — Acquisitions, equity method investment in Kindred at Home — (1,095 ) — Capital contributions to operating subsidiaries (423 ) (697 ) (695 ) Purchases of investment securities (204 ) (145 ) (53 ) Proceeds from sale of investment securities 15 35 — Maturities of investment securities 134 59 51 Purchases of property and equipment, net (585 ) (465 ) (359 ) Net cash used in investing activities (1,063 ) (2,662 ) (1,056 ) Cash flows from financing activities: Proceeds from issuance of senior notes, net 987 — 1,779 (Repayments) proceeds from issuance of commercial paper, net (360 ) 485 (153 ) Proceeds from term loan — 1,000 — Repayment of term loan (650 ) (350 ) — Repayment of long-term debt (400 ) — (800 ) Change in book overdraft 2 (3 ) 3 Common stock repurchases (1,070 ) (1,090 ) (3,365 ) Dividends paid (291 ) (265 ) (220 ) Proceeds from stock option exercises and other 57 48 62 Net cash used in financing activities (1,725 ) (175 ) (2,694 ) Increase (decrease) in cash and cash equivalents 741 (118 ) (1,327 ) Cash and cash equivalents at beginning of year 265 383 1,710 Cash and cash equivalents at end of year $ 1,006 $ 265 $ 383 See accompanying notes to the parent company financial statements. SCHEDULE I—PARENT COMPANY FINANCIAL INFORMATION NOTES TO CONDENSED FINANCIAL STATEMENTS Parent company financial information has been derived from our consolidated financial statements and excludes the accounts of all operating subsidiaries. This information should be read in conjunction with our consolidated financial statements. Management Fee Through intercompany service agreements approved, if required, by state regulatory authorities, Humana Inc., our parent company, charges a management fee for reimbursement of certain centralized services provided to its subsidiaries including information systems, disbursement, investment and cash administration, marketing, legal, finance, and medical and executive management oversight. Dividends Cash dividends received from subsidiaries and included as a component of net cash provided by operating activities were $1.8 billion in 2019 , $2.3 billion in 2018 , and $1.4 billion in 2017 . Guarantee Through indemnity agreements approved by state regulatory authorities, certain of our regulated subsidiaries generally are guaranteed by our parent company in the event of insolvency for: (1) member coverage for which premium payment has been made prior to insolvency; (2) benefits for members then hospitalized until discharged; and (3) payment to providers for services rendered prior to insolvency. Our parent has also guaranteed the obligations of our military services subsidiaries and funding to maintain required statutory capital levels of certain other regulated subsidiaries. Certain of our subsidiaries operate in states that regulate the payment of dividends, loans, or other cash transfers to Humana Inc., our parent company, and require minimum levels of equity as well as limit investments to approved securities. The amount of dividends that may be paid to Humana Inc. by these subsidiaries, without prior approval by state regulatory authorities, or ordinary dividends, is limited based on the entity’s level of statutory income and statutory capital and surplus. If the dividend, together with other dividends paid within the preceding twelve months, exceeds a specified statutory limit or is paid from sources other than earned surplus, it is generally considered an extraordinary dividend requiring prior regulatory approval. In most states, prior notification is provided before paying a dividend even if approval is not required. Although minimum required levels of equity are largely based on premium volume, product mix, and the quality of assets held, minimum requirements vary significantly at the state level. Our state regulated insurances subsidiaries had aggregate statutory capital and surplus of approximately $8.0 billion and $7.6 billion as of December 31, 2019 and 2018 , respectively, which exceeded aggregate minimum regulatory requirements of $5.9 billion and $5.2 billion , respectively. The amount of ordinary dividends that may be paid to our parent company in 2020 is approximately $1 billion in the aggregate. The amount, timing and mix of ordinary and extraordinary dividend payments will vary due to state regulatory requirements, the level of excess statutory capital and surplus and expected future surplus requirements related to, for example, premium volume and product mix. Actual dividends that were paid to our parent company were approximately $1.8 billion in 2019 , $2.3 billion in 2018 , and $1.4 billion in 2017 . Our use of operating cash flows derived from our non-insurance subsidiaries, such as in our Healthcare Services segment, is generally not restricted by state departments of insurance (or comparable state regulators). Refer to Notes 3 and 4 of the notes to consolidated financial statements in this Annual Report on Form 10-K for a description of certain acquisitions and divestitures. During 2019 , 2018 and 2017 Refer to Note 12 of the notes to consolidated financial statements included in this Annual Report on Form 10-K for a description of income taxes. Refer to Note 13 of the notes to consolidated financial statements included in this Annual Report on Form 10-K for a description of debt. Refer to Note 16 of the notes to consolidated financial statements included in this Annual Report on Form 10-K for a description of stockholders’ equity, including stock repurchases and stockholder dividends.

SCHEDULE II - VALUATION AND QUA

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS	12 Months Ended
	Dec. 31, 2019
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS	SCHEDULE II—VALUATION AND QUALIFYING ACCOUNTS For the Years Ended December 31, 2019 , 2018 , and 2017 (in millions) Additions Balance at Acquired/(Disposed) Charged Charged to Deductions Balance at Allowance for loss on receivables: 2019 $ 79 $ — $ (1 ) $ — $ (9 ) $ 69 2018 96 — 36 (29 ) (24 ) 79 2017 118 — 20 (10 ) (32 ) 96 Deferred tax asset valuation allowance: 2019 (54 ) — 9 — — (45 ) 2018 (49 ) — (5 ) — — (54 ) 2017 (49 ) — — — — (49 ) (1) Represents changes in retroactive membership adjustments to premiums revenue and contractual allowances adjustments to services revenue as more fully described in Note 2 to the consolidated financial statements included in this annual report on Form 10-K.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Our financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States of America. Our consolidated financial statements include the accounts of Humana Inc. and subsidiaries that the Company controls, including variable interest entities associated with medical practices for which we are the primary beneficiary. We do not own many of our medical practices but instead enter into exclusive management agreements with the affiliated Professional Associations, or P.A.s, that operate these medical practices. Based upon the provisions of these agreements, these affiliated P.A.s are variable interest entities and we are the primary beneficiary, and accordingly we consolidate the affiliated P.A.s. All significant intercompany balances and transactions have been eliminated. The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. The areas involving the most significant use of estimates are the estimation of benefits payable, the impact of risk adjustment provisions related to our Medicare contracts, the valuation and related impairment recognition of investment securities, and the valuation and related impairment recognition of long-lived assets, including goodwill. These estimates are based on knowledge of current events and anticipated future events, and accordingly, actual results may ultimately differ materially from those estimates.
Health Care Reform	Health Care Reform The Patient Protection and Affordable Care Act and The Health Care and Education Reconciliation Act of 2010 (which we collectively refer to as the Health Care Reform Law) enacted significant reforms to various aspects of the U.S. health insurance industry. Certain of these reforms became effective January 1, 2014, including an annual insurance industry premium-based fee and the establishment of federally-facilitated or state-based exchanges. Operating results for our individual commercial medical business compliant with the Health Care Reform Law were challenged primarily due to unanticipated modifications in the program subsequent to the passing of the Health Care Reform Law, resulting in higher covered population morbidity and the ensuing enrollment and claims issues causing volatility in claims experience. As a result of these and other factors, we exited our individual commercial medical business effective January 1, 2018. The annual premium-based fee on health insurers is not deductible for tax purposes. We estimate a liability for the health insurance industry fee and record it in full once qualifying insurance coverage is provided in the applicable calendar year in which the fee is payable with a corresponding deferred cost that is amortized ratably to expense over the same calendar year. We record the liability for the health insurance industry fee in trade accounts payable and accrued expenses and record the deferred cost in other current assets in our consolidated financial statements. We pay the health insurance industry fee in September or October of each year. The Consolidated Appropriations Act enacted on December 18, 2015, included a one year suspension in 2017 of the health insurance industry fee. In 2018, we paid the federal government $1.04 billion for the annual health insurance industry fee attributed to calendar year 2018. The Continuing Resolution bill, H.R. 195, enacted on January 22, 2018, included a one year suspension in 2019 of the health insurance industry fee, but the fee will resume for calendar year 2020. The Further Consolidated Appropriations Act, 2020, enacted on December 20, 2019, permanently repealed the health insurance industry fee beginning in calendar year 2021.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash, time deposits, money market funds, commercial paper, other money market instruments, and certain U.S. Government securities with an original maturity of three months or less. Carrying value approximates fair value due to the short-term maturity of the investments.
Investment Securities	Investment Securities Investment securities, which consist primarily of debt securities, have been categorized as available for sale and, as a result, are stated at fair value. Investment securities available for current operations are classified as current assets. Investment securities available for our long-term insurance products and professional liability funding requirements, as well as restricted statutory deposits, are classified as long-term assets. For the purpose of determining gross realized gains and losses, which are included as a component of investment income in the consolidated statements of income, the cost of investment securities sold is based upon specific identification. Unrealized holding gains and losses, net of applicable deferred taxes, are included as a component of stockholders’ equity and comprehensive income until realized from a sale or other-than-temporary impairment. Under the other-than-temporary impairment model for debt securities held, we recognize an impairment loss in income in an amount equal to the full difference between the amortized cost basis and the fair value when we have the intent to sell the debt security or it is more likely than not we will be required to sell the debt security before recovery of our amortized cost basis. However, if we do not intend to sell the debt security, we evaluate the expected cash flows to be received as compared to amortized cost and determine if a credit loss has occurred. In the event of a credit loss, only the amount of the impairment associated with the credit loss is recognized currently in income with the remainder of the loss recognized in other comprehensive income. When we do not intend to sell a security in an unrealized loss position, potential other-than-temporary impairment is considered using a variety of factors, including the length of time and extent to which the fair value has been less than cost; adverse conditions specifically related to the industry, geographic area or financial condition of the issuer or underlying collateral of a security; payment structure of the security; changes in credit rating of the security by the rating agencies; the volatility of the fair value changes; and changes in fair value of the security after the balance sheet date. For debt securities, we take into account expectations of relevant market and economic data. For example, with respect to mortgage and asset-backed securities, such data includes underlying loan level data and structural features such as seniority and other forms of credit enhancements. A decline in fair value is considered other-than-temporary when we do not expect to recover the entire amortized cost basis of the security. We estimate the amount of the credit loss component of a debt security as the difference between the amortized cost and the present value of the expected cash flows of the security. The present value is determined using the best estimate of future cash flows discounted at the implicit interest rate at the date of purchase.
Receivables and Revenue Recognition	Receivables and Revenue Recognition We generally establish one-year commercial membership contracts with employer groups, subject to cancellation by the employer group on 30 -day written notice. Our Medicare contracts with CMS renew annually. Our military services contracts with the federal government and certain contracts with various state Medicaid programs generally are multi-year contracts subject to annual renewal provisions. Premiums Revenue We receive monthly premiums from the federal government and various states according to government specified payment rates and various contractual terms. We bill and collect premium from employer groups and members in our Medicare and other individual products monthly. Changes in premium revenues resulting from the periodic changes in risk-adjustment scores derived from medical diagnoses for our membership are estimated by projecting the ultimate annual premium and are recognized ratably during the year, with adjustments each period to reflect changes in the ultimate premium. Receivables or payables are classified as current or long-term in our consolidated balance sheet based on the timing of the expected settlement. Premiums revenue is estimated by multiplying the membership covered under the various contracts by the contractual rates. Premiums revenue is recognized as income in the period members are entitled to receive services, and is net of estimated uncollectible amounts, retroactive membership adjustments, and adjustments to recognize rebates under the minimum benefit ratios required under the Health Care Reform Law. We estimate policyholder rebates by projecting calendar year minimum benefit ratios for the small group and large group markets, as defined by the Health Care Reform Law using a methodology prescribed by HHS, separately by state and legal entity. Medicare Advantage and Medicaid products are also subject to minimum benefit ratio requirements. Estimated calendar year rebates recognized ratably during the year are revised each period to reflect current experience. Retroactive membership adjustments result from enrollment changes not yet processed, or not yet reported by an employer group or the government. We routinely monitor the collectability of specific accounts, the aging of receivables, historical retroactivity trends, estimated rebates, as well as prevailing and anticipated economic conditions, and reflect any required adjustments in current operations. Premiums received prior to the service period are recorded as unearned revenues. Medicare Part D We cover prescription drug benefits in accordance with Medicare Part D under multiple contracts with CMS. The payments we receive monthly from CMS and members, which are determined from our annual bid, represent amounts for providing prescription drug insurance coverage. We recognize premiums revenue for providing this insurance coverage ratably over the term of our annual contract. Our CMS payment is subject to risk sharing through the Medicare Part D risk corridor provisions. In addition, receipts for reinsurance and low-income cost subsidies as well as receipts for certain discounts on brand name prescription drugs in the coverage gap represent payments for prescription drug costs for which we are not at risk. The risk corridor provisions compare costs targeted in our bids to actual prescription drug costs, limited to actual costs that would have been incurred under the standard coverage as defined by CMS. Variances exceeding certain thresholds may result in CMS making additional payments to us or require us to refund to CMS a portion of the premiums we received. As risk corridor provisions are considered in our overall annual bid process, we estimate and recognize an adjustment to premiums revenue related to these provisions based upon pharmacy claims experience. We record a receivable or payable at the contract level and classify the amount as current or long-term in our consolidated balance sheets based on the timing of expected settlement. Reinsurance and low-income cost subsidies represent funding from CMS in connection with the Medicare Part D program for which we assume no risk. Reinsurance subsidies represent funding from CMS for its portion of prescription drug costs which exceed the member’s out-of-pocket threshold, or the catastrophic coverage level. Low-income cost subsidies represent funding from CMS for all or a portion of the deductible, the coinsurance and co-payment amounts above the out-of-pocket threshold for low-income beneficiaries. Monthly prospective payments from CMS for reinsurance and low-income cost subsidies are based on assumptions submitted with our annual bid. A reconciliation and related settlement of CMS’s prospective subsidies against actual prescription drug costs we paid is made after the end of the year. The Health Care Reform Law mandates consumer discounts of 50% on brand name prescription drugs for Part D plan participants in the coverage gap. These discounts are funded by CMS and pharmaceutical manufacturers while we administer the application of these funds. We account for these subsidies and discounts as a deposit in our consolidated balance sheets and as a financing activity under receipts (withdrawals) from contract deposits in our consolidated statements of cash flows. For 2019 , subsidy and discount payments of $11.8 billion exceeded reimbursements of $11.2 billion by $0.6 billion . For 2018 , subsidy and discount payments of $10.3 billion exceeded reimbursements of $9.6 billion by $0.7 billion . For 2017 , subsidy and discount reimbursements of $12.1 billion exceeded payments of $10.2 billion by $1.9 billion . We do not recognize premiums revenue or benefit expenses for these subsidies or discounts. Receipt and payment activity is accumulated at the contract level and recorded in our consolidated balance sheets in other current assets or trade accounts payable and accrued expenses depending on the contract balance at the end of the reporting period. Settlement of the reinsurance and low-income cost subsidies as well as the risk corridor payment is based on a reconciliation made approximately 9 months after the close of each calendar year. Settlement with CMS for brand name prescription drug discounts is based on a reconciliation made approximately 14 to 18 months after the close of each calendar year. We continue to revise our estimates with respect to the risk corridor provisions based on subsequent period pharmacy claims data. See Note 7 for detail regarding amounts recorded to our consolidated balance sheets related to the risk corridor settlement and subsidies from CMS with respect to the Medicare Part D program. Services Revenue Patient services revenue Patient services include injury and illness care and related services as well as other healthcare services related to customer needs or as required by law. Patient services revenues are recognized in the period services are provided to the customer and are net of contractual allowances. Administrative services fees Administrative services fees cover the processing of claims, offering access to our provider networks and clinical programs, and responding to customer service inquiries from members of self-funded groups. Revenues from providing administration services, also known as administrative services only, or ASO, are recognized in the period services are performed and are net of estimated uncollectible amounts. ASO fees are estimated by multiplying the membership covered under the various contracts by the contractual rates. Under ASO contracts, self-funded employers retain the risk of financing substantially all of the cost of health benefits. However, many ASO customers purchase stop loss insurance coverage from us to cover catastrophic claims or to limit aggregate annual costs. Accordingly, we have recorded premiums revenue and benefits expense related to these stop loss insurance contracts. We routinely monitor the collectability of specific accounts, the aging of receivables, as well as prevailing and anticipated economic conditions, and reflect any required adjustments in current operations. ASO fees received prior to the service period are recorded as unearned revenues. Under our TRICARE contracts with the Department of Defense (DoD) we provide administrative services, including offering access to our provider networks and clinical programs, claim processing, customer service, enrollment, and other services, while the federal government retains all of the risk of the cost of health benefits. We account for revenues under our contracts net of estimated health care costs similar to an administrative services fee only agreement. Our contracts include fixed administrative services fees and incentive fees and penalties. Administrative services fees are recognized as services are performed. Our TRICARE members are served by both in-network and out-of-network providers in accordance with our contracts. We pay health care costs related to these services to the providers and are subsequently reimbursed by the DoD for such payments. We account for the payments of the federal government’s claims and the related reimbursements under deposit accounting in our consolidated balance sheets and as a financing activity under receipts (withdrawals) from contract deposits in our consolidated statements of cash flows. For 2019, health care cost payments of approximately $6.5 billion exceeded reimbursements of approximately $6.4 billion by $63 million . For 2018, health care cost reimbursements and payments were each approximately $5.6 billion , with reimbursements exceeding payments by $38 million for the year. For 2017, health care cost reimbursements and payments were each approximately $3.4 billion with reimbursements exceeding payments by $11 million for the year. Receivables Receivables, including premium receivables, patient services revenue receivables, and ASO fee receivables, are shown net of allowances for estimated uncollectible accounts, retroactive membership adjustments, and contractual allowances.
Other Current Assets	Other Current Assets
Policy Acquisition Costs	Policy Acquisition Costs Policy acquisition costs are those costs that relate directly to the successful acquisition of new and renewal insurance policies. Such costs include commissions, costs of policy issuance and underwriting, and other costs we incur to acquire new business or renew existing business. We expense policy acquisition costs related to our employer-group prepaid health services policies as incurred. These short-duration employer-group prepaid health services policies typically have a 1 -year term and may be canceled upon 30 days notice by the employer group. Life insurance, annuities, certain health and other supplemental, and, prior to the sale of our wholly-owned subsidiary, KMG America Corporation, or KMG, in 2018, long term care policies sold to individuals are accounted for as long-duration insurance products because they are expected to remain in force for an extended period beyond one year and premium received in the earlier years is intended to pay anticipated benefits to be incurred in future years . As a result, we defer policy acquisition costs, primarily consisting of commissions, and amortize them over the estimated life of the policies in proportion to premiums earned. Deferred acquisition costs are reviewed to determine if they are recoverable from future income.
Long-Lived Assets	Long-Lived Assets Property and equipment is recorded at cost. Gains and losses on sales or disposals of property and equipment are included in operating costs. Certain costs related to the development or purchase of internal-use software are capitalized. Depreciation is computed using the straight-line method over estimated useful lives ranging from 3 to 10 years for equipment, 3 to 5 years for computer software, and 10 to 20 years for buildings. Improvements to leased facilities are depreciated over the shorter of the remaining lease term or the anticipated life of the improvement. We periodically review long-lived assets, including property and equipment and definite-lived intangible assets, for impairment whenever adverse events or changes in circumstances indicate the carrying value of the asset may not be recoverable. Losses are recognized for a long-lived asset to be held and used in our operations when the undiscounted future cash flows expected to result from the use of the asset are less than its carrying value. We recognize an impairment loss based on the excess of the carrying value over the fair value of the asset. A long-lived asset held for sale is reported at the lower of the carrying amount or fair value less costs to sell. Depreciation expense is not recognized on assets held for sale. Losses are recognized for a long-lived asset to be abandoned when the asset ceases to be used. In addition, we periodically review the estimated lives of all long-lived assets for reasonableness.
Equity Method Investments	Equity Method Investments We use the equity method of accounting for equity investments in companies where we are able to exercise significant influence, but not control, over operating and financial policies of the investee. Judgment regarding the level of influence over each equity method investment includes considering key factors such as our ownership interest, representation on the board of directors, organizational structure, participation in policy-making decisions and material intra-entity transactions. Generally, under the equity method, original investments in these entities are recorded at cost and subsequently adjusted by our share of equity in income or losses after the date of acquisition as well as capital contributions to and distributions from these companies. Our proportionate share of the net income or loss of these companies is included in consolidated net income. Investment amounts in excess of our share of an investee's net assets are amortized over the life of the related asset creating the excess. Excess goodwill is not amortized. We evaluate equity method investments for impairment whenever events or changes in circumstances indicate that the carrying amount of the investment might not be recoverable. Factors considered by us when reviewing an equity method investment for impairment include the length of time (duration) and the extent (severity) to which the fair value of the equity method investment has been less than carrying value, the investee’s financial condition and near-term prospects and the intent and ability to hold the investment for a period of time sufficient to allow for anticipated recovery. An impairment that is other-than-temporary is recognized in the period identified.
Goodwill and Definite-Lived Intangible Assets	Goodwill and Definite-Lived Intangible Assets Goodwill represents the unamortized excess of cost over the fair value of the net tangible and other intangible assets acquired. We are required to test at least annually for impairment at a level of reporting referred to as the reporting unit, and more frequently if adverse events or changes in circumstances indicate that the asset may be impaired. A reporting unit either is our operating segments or one level below the operating segments, referred to as a component, which comprise our reportable segments. A component is considered a reporting unit if the component constitutes a business for which discrete financial information is available that is regularly reviewed by management. We aggregate the components of an operating segment into one reporting unit if they have similar economic characteristics. Goodwill is assigned to the reporting units that are expected to benefit from the specific synergies of the business combination. We use the one-step process to review goodwill for impairment to determine both the existence and amount of goodwill impairment, if any. Impairment tests are performed, at a minimum, in the fourth quarter of each year supported by our long-range business plan and annual planning process. We rely on an evaluation of future discounted cash flows to determine fair value of our reporting units. The fair value of our reporting units with significant goodwill exceeded carrying amounts by a substantial margin. A 100 basis point increase in the discount rate would not have a significant impact on the amount of margin for any of our reporting units with significant goodwill, with the exception of our clinical and provider reporting units in our Healthcare Services segment. Our clinical and provider reporting units primarily provide services to our Retail members. A significant increase in the discount rate, decrease in the long-term growth rate, or substantial reductions in our underlying cash flow assumptions, including revenue growth rates, medical and operating cost trends, and projected operating income, could have a negative impact on the estimated fair value of these reporting units. The clinical reporting unit had a fair value of $544 million which exceeded its carrying value of $533 million by $11 million or 2% . If the discount rate increased 100 basis points, then the clinical reporting unit would incur an impairment loss of approximately $62 million . The provider reporting unit had a fair value of $2.3 billion which exceeded its carrying value of $1.3 billion by $1.0 billion or 78% . The provider reporting unit estimate of fair value relies on multiple assumptions regarding the underlying long-term cash flows, any one of which may be significantly impacted by future changes in estimates and may negatively impact fair value. The clinical and provider reporting units account for $524 million and $761 million , respectively, of goodwill. Impairment tests completed for 2019 , 2018 , and 2017 did not result in an impairment loss. Definite-lived intangible assets primarily relate to acquired customer contracts/relationships and are included with other long-term assets in the consolidated balance sheets. Definite-lived intangible assets are amortized over the useful life generally using the straight-line method. We review definite-lived intangible assets for impairment under our long-lived asset policy.
Benefits Payable and Benefits Expense Recognition	Benefits Payable and Benefits Expense Recognition Benefits expense includes claim payments, capitation payments, pharmacy costs net of rebates, allocations of certain centralized expenses and various other costs incurred to provide health insurance coverage to members, as well as estimates of future payments to hospitals and others for medical care and other supplemental benefits provided on or prior to the balance sheet date. Capitation payments represent monthly contractual fees disbursed to primary care and other providers who are responsible for providing medical care to members. Pharmacy costs represent payments for members’ prescription drug benefits, net of rebates from drug manufacturers. Receivables for such pharmacy rebates are included in other current assets in our consolidated balance sheets. Other supplemental benefits include dental, vision, and other supplemental health products. We estimate the costs of our benefits expense payments using actuarial methods and assumptions based upon claim payment patterns, medical cost inflation, historical developments such as claim inventory levels and claim receipt patterns, and other relevant factors, and record benefit reserves for future payments. We continually review estimates of future payments relating to claims costs for services incurred in the current and prior periods and make necessary adjustments to our reserves. Benefits expense is recognized in the period in which services are provided and includes an estimate of the cost of services which have been incurred but not yet reported, or IBNR. Our reserving practice is to consistently recognize the actuarial best point estimate within a level of confidence required by actuarial standards. Actuarial standards of practice generally require a level of confidence such that the liabilities established for IBNR have a greater probability of being adequate versus being insufficient, or such that the liabilities established for IBNR are sufficient to cover obligations under an assumption of moderately adverse conditions. Adverse conditions are situations in which the actual claims are expected to be higher than the otherwise estimated value of such claims at the time of the estimate. Therefore, in many situations, the claim amounts ultimately settled will be less than the estimate that satisfies the actuarial standards of practice. We develop our estimate for IBNR using actuarial methodologies and assumptions, primarily based upon historical claim experience. Depending on the period for which incurred claims are estimated, we apply a different method in determining our estimate. For periods prior to the most recent two months, the key assumption used in estimating our IBNR is that the completion factor pattern remains consistent over a rolling 12-month period after adjusting for known changes in claim inventory levels and known changes in claim payment processes. Completion factors result from the calculation of the percentage of claims incurred during a given period that have historically been adjudicated as of the reporting period. For the most recent two months, the incurred claims are estimated primarily from a trend analysis based upon per member per month claims trends developed from our historical experience in the preceding months, adjusted for known changes in estimates of recent hospital and drug utilization data, provider contracting changes, changes in benefit levels, changes in member cost sharing, changes in medical management processes, product mix, and workday seasonality. The completion factor method is used for the months of incurred claims prior to the most recent two months because the historical percentage of claims processed for those months is at a level sufficient to produce a consistently reliable result. Conversely, for the most recent two months of incurred claims, the volume of claims processed historically is not at a level sufficient to produce a reliable result, which therefore requires us to examine historical trend patterns as the primary method of evaluation. Changes in claim processes, including recoveries of overpayments, receipt cycle times, claim inventory levels, outsourcing, system conversions, and processing disruptions due to weather or other events affect views regarding the reasonable choice of completion factors. Claim payments to providers for services rendered are often net of overpayment recoveries for claims paid previously, as contractually allowed. Claim overpayment recoveries can result from many different factors, including retroactive enrollment activity, audits of provider billings, and/or payment errors. Changes in patterns of claim overpayment recoveries can be unpredictable and result in completion factor volatility, as they often impact older dates of service. The receipt cycle time measures the average length of time between when a medical claim was initially incurred and when the claim form was received. Increases in electronic claim submissions from providers decrease the receipt cycle time. If claims are submitted or processed on a faster (slower) pace than prior periods, the actual claim may be more (less) complete than originally estimated using our completion factors, which may result in reserves that are higher (lower) than required. Medical cost trends potentially are more volatile than other segments of the economy. The drivers of medical cost trends include increases in the utilization of hospital facilities, physician services, new higher priced technologies and medical procedures, and new prescription drugs and therapies, as well as the inflationary effect on the cost per unit of each of these expense components. Other external factors such as government-mandated benefits or other regulatory changes, the tort liability system, increases in medical services capacity, direct to consumer advertising for prescription drugs and medical services, an aging population, lifestyle changes including diet and smoking, catastrophes, and epidemics also may impact medical cost trends. Internal factors such as system conversions, claims processing cycle times, changes in medical management practices and changes in provider contracts also may impact our ability to accurately predict estimates of historical completion factors or medical cost trends. All of these factors are considered in estimating IBNR and in estimating the per member per month claims trend for purposes of determining the reserve for the most recent two months. Additionally, we continually prepare and review follow-up studies to assess the reasonableness of the estimates generated by our process and methods over time. The results of these studies are also considered in determining the reserve for the most recent two months. Each of these factors requires significant judgment by management. We reassess the profitability of our contracts for providing insurance coverage to our members when current operating results or forecasts indicate probable future losses. We establish a premium deficiency reserve in current operations to the extent that the sum of expected future costs, claim adjustment expenses, and maintenance costs exceeds related future premiums under contracts without consideration of investment income. For purposes of determining premium deficiencies, contracts are grouped in a manner consistent with our method of acquiring, servicing, and measuring the profitability of such contracts. Losses recognized as a premium deficiency result in a beneficial effect in subsequent periods as operating losses under these contracts are charged to the liability previously established. Because the majority of our member contracts renew annually, we would not record a material premium deficiency reserve, except when unanticipated adverse events or changes in circumstances indicate otherwise. We believe our benefits payable are adequate to cover future claims payments required. However, such estimates are based on knowledge of current events and anticipated future events. Therefore, the actual liability could differ materially from the amounts provided.
Future policy benefits payable	Future policy benefits payable Future policy benefits payable include liabilities for long-duration insurance policies including life insurance, annuities, certain health and other supplemental, and prior to the sale of KMG in 2018, long-term care policies sold to individuals for which some of the premium received in the earlier years is intended to pay anticipated benefits to be incurred in future years. At policy issuance, these reserves are recognized on a net level premium method based on interest rates, mortality, morbidity, and maintenance expense assumptions. Interest rates are based on our expected net investment returns on the investment portfolio supporting the reserves for these blocks of business. Mortality, a measure of expected death, and morbidity, a measure of health status, assumptions are based on industry actuarial tables, modified based upon actual experience. Changes in estimates of these reserves are recognized as an adjustment to benefits expense in the period the changes occur. We perform loss recognition tests at least annually in the fourth quarter, and more frequently if adverse events or changes in circumstances indicate that the level of the liability, together with the present value of future gross premiums, may not be adequate to provide for future expected policy benefits and maintenance costs. We adjust future policy benefits payable for the additional liability that would have been recorded if investment securities backing the liability had been sold at their stated aggregate fair value and the proceeds reinvested at current yields. We include the impact of this adjustment, if any, net of applicable deferred taxes, with the change in unrealized investment gain (loss) in accumulated other comprehensive income in stockholders’ equity. Health policies sold to individuals that conform to the Health Care Reform Law are accounted for under a short-duration model under which policy reserves are not established because premiums received in the current year are intended to pay anticipated benefits in that year . In addition, as previously underwritten members transition to plans compliant with the Health Care Reform Law, it results in policy lapses and the release of reserves for future policy benefits.
Book Overdraft	Book Overdraft Under our cash management system, checks issued but not yet presented to banks that would result in negative bank balances when presented are classified as a current liability in the consolidated balance sheets. Changes in book overdrafts from period to period are reported in the consolidated statement of cash flows as a financing activity.
Income Taxes	Income Taxes We recognize an asset or liability for the deferred tax consequences of temporary differences between the tax bases of assets or liabilities and their reported amounts in the consolidated financial statements. These temporary differences will result in taxable or deductible amounts in future years when the reported amounts of the assets or liabilities are recovered or settled. We also recognize the future tax benefits such as net operating and capital loss carryforwards as deferred tax assets. A valuation allowance is provided against these deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized. Future years’ tax expense may be increased or decreased by adjustments to the valuation allowance or to the estimated accrual for income taxes. Deferred tax assets and deferred tax liabilities are further adjusted for changes in the enacted tax rates. We record tax benefits when it is more likely than not that the tax return position taken with respect to a particular transaction will be sustained. A liability, if recorded, is not considered resolved until the statute of limitations for the relevant taxing authority to examine and challenge the tax position has expired, or the tax position is ultimately settled through examination, negotiation, or litigation. We classify interest and penalties associated with uncertain tax positions in our provision for income taxes.
Stock-Based Compensation	Stock-Based Compensation We generally recognize stock-based compensation expense, as determined on the date of grant at fair value, on a straight-line basis over the period during which an employee is required to provide service in exchange for the award (the vesting period). In addition, for awards with both time and performance-based conditions, we generally recognize compensation expense on a straight line basis over the vesting period when it is probable that the performance condition will be achieved. We estimate expected forfeitures and recognize compensation expense only for those awards which are expected to vest. We estimate the grant-date fair value of stock options using the Black-Scholes option-pricing model.
Earnings Per Common Share	Earnings Per Common Share We compute basic earnings per common share on the basis of the weighted-average number of unrestricted common shares outstanding. Diluted earnings per common share is computed on the basis of the weighted-average number of unrestricted common shares outstanding plus the dilutive effect of outstanding employee stock options and restricted shares, or units, using the treasury stock method.
Fair Value	Fair Value Assets and liabilities measured at fair value are categorized into a fair value hierarchy based on whether the inputs to valuation techniques are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our own assumptions about the assumptions market participants would use. The fair value hierarchy includes three levels of inputs that may be used to measure fair value as described below. Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 1 assets and liabilities include securities that are traded in an active exchange market. Level 2 – Observable inputs other than Level 1 prices such as quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 2 assets and liabilities include debt securities with quoted prices that are traded less frequently than exchange-traded instruments as well as debt securities whose value is determined using a pricing model with inputs that are observable in the market or can be derived principally from or corroborated by observable market data. Level 3 – Unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Level 3 includes assets and liabilities whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques reflecting our own assumptions about the assumptions market participants would use as well as those requiring significant management judgment. Fair value of actively traded debt securities are based on quoted market prices. Fair value of other debt securities are based on quoted market prices of identical or similar securities or based on observable inputs like interest rates generally using a market valuation approach, or, less frequently, an income valuation approach and are generally classified as Level 2. We obtain at least one price for each security from a third party pricing service. These prices are generally derived from recently reported trades for identical or similar securities, including adjustments through the reporting date based upon observable market information. When quoted prices are not available, the third party pricing service may use quoted market prices of comparable securities or discounted cash flow analysis, incorporating inputs that are currently observable in the markets for similar securities. Inputs that are often used in the valuation methodologies include benchmark yields, reported trades, credit spreads, broker quotes, default rates, and prepayment speeds. We are responsible for the determination of fair value and as such we perform analysis on the prices received from the third party pricing service to determine whether the prices are reasonable estimates of fair value. Our analysis includes a review of monthly price fluctuations as well as a quarterly comparison of the prices received from the pricing service to prices reported by our third party investment adviser. In addition, on a quarterly basis we examine the underlying inputs and assumptions for a sample of individual securities across asset classes, credit rating levels, and various durations. Fair value of privately held debt securities are estimated using a variety of valuation methodologies, including both market and income approaches, where an observable quoted market does not exist and are generally classified as Level 3. For privately-held debt securities, such methodologies include reviewing the value ascribed to the most recent financing, comparing the security with securities of publicly-traded companies in similar lines of business, and reviewing the underlying financial performance including estimating discounted cash flows.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements Recently Adopted Accounting Pronouncements In February 2016, the FASB issued new guidance related to accounting for leases which requires lessees to record assets and liabilities reflecting the leased assets and lease obligations, respectively, while following the dual model for recognition in statements of income requiring leases to be classified as either operating or finance. Operating leases will result in straight-line expense (similar to current operating leases) while finance leases will result in a front-loaded expense pattern (similar to current capital leases). We adopted the new standard effective January 1, 2019, as allowed, using the modified retrospective approach. We elected the practical expedients of not reassessing whether any expired or existing contracts are or contain leases, not reassessing the lease classification for any expired or existing leases and not reassessing any initial direct costs for existing leases. In addition, we elected the practical expedient to not separate lease and nonlease components for all of our asset classes. We made a permitted accounting policy election to not apply the new guidance to leases with an initial term of 12 months or less. We recognize those lease payments in the condensed consolidated statement of income on a straight-line basis over the lease term. As of January 1, 2019, the adoption of the standard resulted in recognition of lease liabilities of approximately $470 million and right-of-use, or ROU, assets of $436 million , which equals the lease liabilities net of accrued rent and lease incentives. The standard does not materially affect our results of operations, cash flows and liquidity. See Note 10 for further information. In March 2017, the FASB issued new guidance that amends the accounting for premium amortization on purchased callable debt securities by shortening the amortization period. This amended guidance requires the premium to be amortized to the earliest call date instead of maturity date. The new guidance was effective for us beginning with annual and interim periods in 2019. This guidance did not have a material impact on our results of operations, financial condition or cash flows. In February 2018, the FASB issued guidance which allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the December 22, 2017 enactment of the Tax Cuts and Jobs Act. The new guidance is effective for us beginning January 1, 2019, with early adoption permitted. We early adopted this guidance in the first quarter of 2018 and it did not have a material impact on our results of operations, financial condition or cash flows. Accounting Pronouncements Effective in Future Periods In June 2016, the FASB issued guidance introducing a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses. The guidance is effective for us beginning January 1, 2020. The new current expected credit losses (CECL) model generally calls for the immediate recognition of all expected credit losses and applies to loans, accounts and trade receivables as well as other financial assets measured at amortized cost, loan commitments and off-balance sheet credit exposures, debt securities and other financial assets measured at fair value through other comprehensive income, and beneficial interests in securitized financial assets. The new guidance replaces the current incurred loss model for measuring expected credit losses, requires expected losses on available for sale debt securities to be recognized through an allowance for credit losses rather than as reductions in the amortized cost of the securities, and provides for additional disclosure requirements. Our investment portfolio consists primarily of available for sale debt securities. We adopted the new standard effective January 1, 2020. Due to the high concentration of our financial assets measured at amortized cost being with the federal government resulting in zero nonpayment risk as well as our available for sale debt securities primarily being in an unrealized gain position, the adoption of the new standard did not have a material impact on our results of operations, financial condition, or cash flows.

ACQUISITIONS AND DIVESTITURES (

ACQUISITIONS AND DIVESTITURES (Tables)	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Schedule of Assets and Liabilities Disposed	The assets and liabilities of KMG that were disposed of on August 9, 2018 were as follows: August 9, 2018 Assets (in millions) Cash and cash equivalents $ 805 Receivables, net 3 Investment securities 1,576 Other assets 1,085 Total assets disposed $ 3,469 Liabilities Benefits payable $ 58 Trade accounts payable and accrued expenses 70 Future policy benefits payable 2,573 Total liabilities disposed $ 2,701

EQUITY METHOD INVESTMENT (Table

EQUITY METHOD INVESTMENT (Tables)	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Equity Method Investments	The summarized balance sheets at December 31, 2019 and 2018, and income statement for the year ended December 31, 2019 and period beginning July 2, 2018 through December 31, 2018 of Kindred at Home were as follows: Balance sheets December 31, 2019 December 31, 2018 (in millions) Current assets $ 563 $ 536 Non-current assets 4,967 4,955 Current liabilities 405 351 Non-current liabilities 2,637 2,708 Shareholders' equity 2,488 2,432 Statements of income For the year ended December 31, 2019 July 2, 2018 through December 31, 2018 (in millions) Revenues $ 3,100 $ 1,587 Expenses 2,835 1,451 Net income 54 27

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of Investment Securities Classified as Current and Long-Term	Investment securities classified as current and long-term were as follows at December 31, 2019 and 2018 , respectively: Amortized Gross Gross Fair (in millions) December 31, 2019 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 353 $ 1 $ — $ 354 Mortgage-backed securities 3,628 85 (3 ) 3,710 Tax-exempt municipal securities 1,433 30 — 1,463 Mortgage-backed securities: Commercial 786 18 — 804 Asset-backed securities 1,093 3 (3 ) 1,093 Corporate debt securities 3,867 82 (2 ) 3,947 Total debt securities $ 11,160 $ 219 $ (8 ) $ 11,371 December 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 419 $ 1 $ (3 ) $ 417 Mortgage-backed securities 2,595 3 (54 ) 2,544 Tax-exempt municipal securities 2,805 3 (37 ) 2,771 Mortgage-backed securities: Residential 55 — — 55 Commercial 537 — (14 ) 523 Asset-backed securities 991 1 (7 ) 985 Corporate debt securities 3,239 1 (98 ) 3,142 Total debt securities $ 10,641 $ 9 $ (213 ) $ 10,437
Schedule of Gross Unrealized Losses and Fair Value of Securities	Gross unrealized losses and fair values aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position were as follows at December 31, 2019 and 2018 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) December 31, 2019 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 48 $ — $ 23 $ — $ 71 $ — Mortgage-backed securities 315 (1 ) 204 (2 ) 519 (3 ) Tax-exempt municipal securities 58 — 75 — 133 — Mortgage-backed securities: Commercial 118 — 36 — 154 — Asset-backed securities 20 — 607 (3 ) 627 (3 ) Corporate debt securities 589 (2 ) 155 — 744 (2 ) Total debt securities $ 1,148 $ (3 ) $ 1,100 $ (5 ) $ 2,248 $ (8 ) December 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 179 $ (1 ) $ 153 $ (2 ) $ 332 $ (3 ) Mortgage-backed securities 956 (16 ) 1,019 (38 ) 1,975 (54 ) Tax-exempt municipal securities 809 (9 ) 1,648 (28 ) 2,457 (37 ) Mortgage-backed securities: Residential — — 15 — 15 — Commercial 372 (8 ) 133 (6 ) 505 (14 ) Asset-backed securities 824 (7 ) 40 — 864 (7 ) Corporate debt securities 1,434 (35 ) 1,439 (63 ) 2,873 (98 ) Total debt securities $ 4,574 $ (76 ) $ 4,447 $ (137 ) $ 9,021 $ (213 )
Schedule of Realized Gains (Losses) Related to Investment Securities Included Within Investment Income	The detail of realized gains (losses) related to investment securities and included within investment income was as follows for the years ended December 31, 2019 , 2018 , and 2017 : 2019 2018 2017 (in millions) Gross realized gains $ 129 $ 106 $ 35 Gross realized losses (67 ) (16 ) (21 ) Net realized capital gains $ 62 $ 90 $ 14
Schedule of Contractual Maturity of Debt Securities Available for Sale	The contractual maturities of debt securities available for sale at December 31, 2019 , regardless of their balance sheet classification, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Amortized Fair (in millions) Due within one year $ 1,316 $ 1,317 Due after one year through five years 1,974 2,013 Due after five years through ten years 1,724 1,780 Due after ten years 639 654 Mortgage and asset-backed securities 5,507 5,607 Total debt securities $ 11,160 $ 11,371

FAIR VALUE (Tables)

FAIR VALUE (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value Measurements	The following table summarizes our fair value measurements at December 31, 2019 and 2018 , respectively, for financial assets measured at fair value on a recurring basis: Fair Value Measurements Using Fair Value Quoted Prices Other Unobservable (in millions) December 31, 2019 Cash equivalents $ 3,660 $ 3,660 $ — $ — Debt securities: U.S. Treasury and other U.S. government corporations and agencies: U.S. Treasury and agency obligations 354 — 354 — Mortgage-backed securities 3,710 — 3,710 — Tax-exempt municipal securities 1,463 — 1,463 — Mortgage-backed securities: Commercial 804 — 804 — Asset-backed securities 1,093 — 1,093 — Corporate debt securities 3,947 — 3,947 — Total debt securities 11,371 — 11,371 — Common stock 7 7 — — Total invested assets $ 15,038 $ 3,667 $ 11,371 $ — December 31, 2018 Cash equivalents $ 2,024 $ 2,024 $ — $ — Debt securities: U.S. Treasury and other U.S. government corporations and agencies: U.S. Treasury and agency obligations 417 — 417 — Mortgage-backed securities 2,544 — 2,544 — Tax-exempt municipal securities 2,771 — 2,771 — Mortgage-backed securities: Residential 55 — 55 — Commercial 523 — 523 — Asset-backed securities 985 — 985 — Corporate debt securities 3,142 — 3,142 — Total debt securities 10,437 — 10,437 — Total invested assets $ 12,461 $ 2,024 $ 10,437 $ —

MEDICARE PART D (Tables)

MEDICARE PART D (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Schedule of Balance Sheet Amounts Associated With Medicare Part D	The accompanying consolidated balance sheets include the following amounts associated with Medicare Part D as of December 31, 2019 and 2018 . CMS subsidies/discounts in the table below include the reinsurance and low-income cost subsidies funded by CMS for which we assume no risk as well as brand name prescription drug discounts for Part D plan participants in the coverage gap funded by CMS and pharmaceutical manufacturers. 2019 2018 Risk CMS Risk CMS (in millions) Other current assets $ 5 $ 585 $ 15 $ 172 Trade accounts payable and accrued expenses (120 ) (356 ) (103 ) (503 ) Net current (liability) asset (115 ) 229 (88 ) (331 ) Other long-term assets 6 — 7 — Other long-term liabilities (61 ) — (89 ) — Net long-term liability (55 ) — (82 ) — Total net (liability) asset $ (170 ) $ 229 $ (170 ) $ (331 )

PROPERTY AND EQUIPMENT, NET (Ta

PROPERTY AND EQUIPMENT, NET (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment was comprised of the following at December 31, 2019 and 2018 . 2019 2018 (in millions) Land $ 20 $ 20 Buildings and leasehold improvements 874 766 Equipment 922 890 Computer software 2,799 2,372 4,615 4,048 Accumulated depreciation (2,660 ) (2,313 ) Property and equipment, net $ 1,955 $ 1,735

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Carrying Amount of Goodwill By Reportable Segments	Changes in the carrying amount of goodwill for our reportable segments for the years ended December 31, 2019 and 2018 were as follows: Retail Group and Specialty Healthcare Services Total (in millions) Balance at January 1, 2018 $ 1,059 $ 261 $ 1,961 $ 3,281 Acquisitions 476 — 140 616 Balance at December 31, 2018 1,535 261 2,101 3,897 Acquisitions — — 31 31 Balance at December 31, 2019 $ 1,535 $ 261 $ 2,132 $ 3,928
Schedule of Intangible Assets Included in Other Long-Term Assets	The following table presents details of our other intangible assets included in other long-term assets in the accompanying consolidated balance sheets at December 31, 2019 and 2018 . Weighted 2019 2018 Cost Accumulated Net Cost Accumulated Net (in millions) Other intangible assets: Customer contracts/relationships 8.7 years $ 646 $ 496 $ 150 $ 646 $ 434 $ 212 Trade names and technology 6.4 years 84 84 — 84 83 1 Provider contracts 11.8 years 70 44 26 68 37 31 Noncompetes and other 7.3 years 29 28 1 29 28 1 Total other intangible assets 8.7 years $ 829 $ 652 $ 177 $ 827 $ 582 $ 245
Schedule of Estimate of Amortization Expense	The following table presents our estimate of amortization expense for each of the five next succeeding fiscal years: (in millions) For the years ending December 31, 2020 $ 68 2021 34 2022 31 2023 18 2024 11

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Schedule of Maturity of Lease Liabilities	Maturity of Lease Liabilities December 31, 2019 (in millions) 2020 $ 133 2021 117 2022 97 2023 52 2024 31 After 2024 70 Total lease payments 500 Less: Interest 52 Present value of lease liabilities $ 448
Schedule of Rent Expense and Sublease Rental Income in Prior Years	Rent expense and sublease rental income, which are recorded net as an operating cost, for all operating leases were as follows for the years ended December 31, 2018 and 2017: 2018 2017 (in millions) Rent expense $ 167 $ 204 Sublease rental income (32 ) (33 ) Net rent expense $ 135 $ 171
Schedule of Future Annual Minimum Payments Due at Prior Year End	Future annual minimum payments due subsequent to December 31, 2018 under all of our noncancelable operating leases with initial terms in excess of one year are as follows: Minimum Sublease Net Lease (in millions) For the years ending December 31,: 2019 $ 147 $ (13 ) $ 134 2020 113 (12 ) 101 2021 96 (10 ) 86 2022 79 (9 ) 70 2023 34 (9 ) 25 Thereafter 50 (23 ) 27 Total $ 519 $ (76 ) $ 443

BENEFITS PAYABLE (Tables)

BENEFITS PAYABLE (Tables)	12 Months Ended
	Dec. 31, 2019
Insurance [Abstract]
Schedule of Activity in Benefits Payable	Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 517 $ 568 $ 579 Incurred related to: Current year 5,708 5,466 5,403 Prior years 50 (46 ) (40 ) Total incurred 5,758 5,420 5,363 Paid related to: Current year (5,081 ) (4,957 ) (4,843 ) Prior years (553 ) (514 ) (531 ) Total paid (5,634 ) (5,471 ) (5,374 ) Balances at December 31 $ 641 $ 517 $ 568 On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 4,862 $ 4,668 $ 4,563 Less: Reinsurance recoverables (95 ) (70 ) (76 ) Balances at January 1, net 4,767 4,598 4,487 Incurred related to: Current year 54,193 46,385 44,001 Prior years (336 ) (503 ) (483 ) Total incurred 53,857 45,882 43,518 Paid related to: Current year (48,421 ) (41,736 ) (39,496 ) Prior years (4,267 ) (3,977 ) (3,911 ) Total paid (52,688 ) (45,713 ) (43,407 ) Reinsurance recoverable 68 95 70 Balances at December 31 $ 6,004 $ 4,862 $ 4,668 Activity in benefits payable for our Retail segment was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Balances at January 1 $ 4,338 $ 3,963 $ 3,506 Less: Reinsurance recoverables (95 ) (70 ) (76 ) Balances at January 1, net 4,243 3,893 3,430 Incurred related to: Current year 48,983 41,323 38,604 Prior years (386 ) (398 ) (386 ) Total incurred 48,597 40,925 38,218 Paid related to: Current year (43,831 ) (37,189 ) (34,781 ) Prior years (3,714 ) (3,386 ) (2,974 ) Total paid (47,545 ) (40,575 ) (37,755 ) Reinsurance recoverable 68 95 70 Balances at December 31 $ 5,363 $ 4,338 $ 3,963
Schedule of Favorable Medical Claims Reserve Development Related to Prior Fiscal Years by Segment	The table below details our favorable medical claims reserve development related to prior fiscal years by segment for 2019 , 2018 , and 2017 . (Favorable) Unfavorable Medical Claims Reserve 2019 2018 2017 Retail Segment $ (386 ) $ (398 ) $ (386 ) Group and Specialty Segment 50 (46 ) (40 ) Individual Commercial Segment — (57 ) (56 ) Other Businesses — (2 ) (1 ) Total $ (336 ) $ (503 ) $ (483 )
Schedule of Incurred and Paid Claims Development	The following tables provide information about incurred and paid claims development for the Group and Specialty segment as of December 31, 2019 , net of reinsurance. Incurred Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 5,403 $ 5,358 $ 5,372 2018 5,466 5,501 2019 5,708 Total $ 16,581 Cumulative Paid Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 4,843 $ 5,351 $ 5,372 2018 4,957 5,487 2019 5,081 Total $ 15,940 All outstanding benefit liabilities before 2017, net of reinsurance N/A Benefits payable, net of reinsurance $ 641 The following tables provide information about incurred and paid claims development for the Retail segment as of December 31, 2019 , net of reinsurance. Incurred Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 38,604 $ 38,341 $ 38,310 2018 41,323 40,984 2019 48,983 Total $ 128,277 Cumulative Paid Claims, Net of Reinsurance For the Years Ended December 31, Claims Incurred Year 2017 2018 2019 (in millions) 2017 $ 34,781 $ 38,232 $ 38,310 2018 37,189 40,841 2019 43,831 Total $ 122,982 All outstanding benefit liabilities before 2017, net of reinsurance N/A Benefits payable, net of reinsurance $ 5,295
Schedule of Reconciliation of Net Incurred and Paid Claims to Benefits Payable	The reconciliation of the net incurred and paid claims development tables to benefits payable in the consolidated statement of financial position is as follows: December 31, Net outstanding liabilities Retail $ 5,295 Group and Specialty 641 Benefits payable, net of reinsurance 5,936 Reinsurance recoverable on unpaid claims Retail 68 Total benefits payable, gross $ 6,004

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Provision for Income Taxes	The provision for income taxes consisted of the following for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (in millions) Current provision: Federal $ 560 $ 139 $ 1,324 States and Puerto Rico 41 58 116 Total current provision 601 197 1,440 Deferred expense 162 194 132 Provision for income taxes $ 763 $ 391 $ 1,572
Provision for Income Taxes Using Federal Statutory Rate	The provision for income taxes was different from the amount computed using the federal statutory rate for the years ended December 31, 2019 , 2018 and 2017 due to the following: 2019 2018 2017 (in millions) Income tax provision at federal statutory rate $ 729 $ 436 $ 1,407 States, net of federal benefit, and Puerto Rico 49 42 80 Tax exempt investment income (6 ) (11 ) (22 ) Health insurance industry fee — 243 — Nondeductible executive compensation 25 17 36 Tax reform — (39 ) 133 KMG sale — (272 ) — Other, net (34 ) (25 ) (62 ) Provision for income taxes $ 763 $ 391 $ 1,572
Principal Components of Net Deferred Tax Balances	Principal components of our net deferred tax balances at December 31, 2019 and 2018 were as follows: Assets (Liabilities) 2019 2018 (in millions) Compensation and other accrued expense $ 111 $ 89 Benefits payable 89 79 Net operating loss carryforward 42 38 Deferred acquisition costs 22 17 Unearned revenues 8 9 Other 8 8 Capital loss carryforward 1 15 Investment securities — 44 Total deferred income tax assets 281 299 Valuation allowance (45 ) (54 ) Total deferred income tax assets, net of valuation allowance 236 245 Depreciable property and intangible assets (329 ) (273 ) Investment securities (181 ) — Prepaid expenses (64 ) (52 ) Future policy benefits payable (3 ) (5 ) Total deferred income tax liabilities (577 ) (330 ) Total net deferred income tax liabilities $ (341 ) $ (85 )

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Carrying Value of Debt Outstanding	The carrying value of debt outstanding was as follows at December 31, 2019 and 2018 : 2019 2018 (in millions) Short-term debt: Commercial paper $ 300 $ 645 Term note — 650 Senior notes: $400 million, 2.625% due October 1, 2019 — 399 $400 million, 2.50% due December 15, 2020 399 — Total short-term debt $ 699 $ 1,694 Long-term debt: Senior notes: $400 million, 2.50% due December 15, 2020 $ — $ 398 $600 million, 3.15% due December 1, 2022 598 596 $400 million, 2.90% due December 15, 2022 397 396 $600 million, 3.85% due October 1, 2024 597 597 $600 million, 3.95% due March 15, 2027 595 594 $500 million, 3.125% due August 15, 2029 495 — $250 million, 8.15% due June 15, 2038 262 263 $400 million, 4.625% due December 1, 2042 396 396 $750 million, 4.95% due October 1, 2044 739 739 $400 million, 4.80% due March 15, 2047 396 396 $500 million, 3.95% due August 15, 2049 492 — Total long-term debt $ 4,967 $ 4,375
Schedule of Maturities of Long-term Debt	Maturities of the short-term and long-term debt for the years ending December 31, are as follows: For the years ending December 31, (in millions) 2020 $ 700 2021 — 2022 1,000 2023 — 2024 600 Thereafter 3,400

EMPLOYEE BENEFIT PLANS (Tables)

EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2019
Retirement Benefits [Abstract]
Stock-Based Compensation Expense	The compensation expense that has been charged against income for these plans was as follows for the years ended December 31, 2019 , 2018 , and 2017 : 2019 2018 2017 (in millions) Stock-based compensation expense by type: Restricted stock $ 152 $ 124 $ 145 Stock options 11 13 12 Total stock-based compensation expense 163 137 157 Tax benefit recognized (35 ) (21 ) (32 ) Stock-based compensation expense, net of tax $ 128 $ 116 $ 125
Activity for Restricted Stock Awards	Activity for our restricted stock was as follows for the year ended December 31, 2019 : Shares Weighted- (shares in thousands) Nonvested restricted stock at December 31, 2018 964 $ 213.99 Granted 503 302.09 Vested (421 ) 239.42 Forfeited (70 ) 269.06 Nonvested restricted stock at December 31, 2019 976 $ 245.21
Weighted-Average Fair Value of Stock Options	The fair value was estimated on the date of grant using the Black-Scholes pricing model with the weighted-average assumptions indicated below: 2019 2018 2017 Weighted-average fair value at grant date $ 68.53 $ 63.67 $ 49.81 Expected option life (years) 4.1 years 4.1 years 4.1 years Expected volatility 25.5 % 26.1 % 27.1 % Risk-free interest rate at grant date 2.4 % 2.5 % 2.0 % Dividend yield 0.7 % 0.7 % 0.7 %
Activity for Option Plans	Activity for our option plans was as follows for the year ended December 31, 2019 : Shares Under Weighted-Average (shares in thousands) Options outstanding at December 31, 2018 677 $ 213.17 Granted 121 304.59 Exercised (305 ) 189.24 Forfeited — — Options outstanding at December 31, 2019 493 $ 250.46 Options exercisable at December 31, 2019 109 $ 216.49

EARNINGS PER COMMON SHARE COM_2

EARNINGS PER COMMON SHARE COMPUTATION (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Earnings Per Common Share	Detail supporting the computation of basic and diluted earnings per common share was as follows for the years ended December 31, 2019 , 2018 and 2017 : 2019 2018 2017 (dollars in millions, except per Net income available for common stockholders $ 2,707 $ 1,683 $ 2,448 Weighted-average outstanding shares of common stock used to 134,055 137,486 144,493 Dilutive effect of: Employee stock options 107 194 172 Restricted stock 565 723 920 Shares used to compute diluted earnings per common share 134,727 138,403 145,585 Basic earnings per common share $ 20.20 $ 12.24 $ 16.94 Diluted earnings per common share $ 20.10 $ 12.16 $ 16.81 Number of antidilutive stock options and restricted stock awards 478 223 539

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Schedule of Details of Dividend Payments	The following table provides details of dividend payments, excluding dividend equivalent rights, in 2017 , 2018 , and 2019 under our Board approved quarterly cash dividend policy: Payment Amount Total (in millions) 2017 $1.49 $216 2018 $1.90 $262 2019 $2.15 $289
Class of Treasury Stock	Excluding shares acquired in connection with employee stock plans, share repurchases were as follows during the years ended December 31, 2019 , 2018 and 2017 . 2019 2018 2017 Authorization Date Purchase Not to Exceed Shares Cost Shares Cost Shares Cost (in millions) February 2017 2,250 — — — — 9.71 2,250 December 2017 3,000 — — 3.07 1,024 3.28 800 July 2019 3,000 3.40 1,000 — — — — Total repurchases 3.40 $ 1,000 3.07 $ 1,024 12.99 $ 3,050

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, By Segment	Retail Group and Specialty Healthcare Services Eliminations/ Consolidated (in millions) 2019 External revenues Premiums: Individual Medicare Advantage $ 43,128 $ — $ — $ — $ 43,128 Group Medicare Advantage 6,475 — — — 6,475 Medicare stand-alone PDP 3,165 — — — 3,165 Total Medicare 52,768 — — — 52,768 Fully-insured 588 5,123 — — 5,711 Specialty — 1,571 — — 1,571 Medicaid and other 2,898 — — — 2,898 Total premiums 56,254 6,694 — — 62,948 Services revenue: Provider — — 446 — 446 ASO and other 17 790 — — 807 Pharmacy — — 186 — 186 Total services revenue 17 790 632 — 1,439 Total external revenues 56,271 7,484 632 — 64,387 Intersegment revenues Services — 18 18,255 (18,273 ) — Products — — 6,894 (6,894 ) — Total intersegment revenues — 18 25,149 (25,167 ) — Investment income 195 23 2 281 501 Total revenues 56,466 7,525 25,783 (24,886 ) 64,888 Operating expenses: Benefits 48,602 5,758 — (503 ) 53,857 Operating costs 5,306 1,651 24,852 (24,428 ) 7,381 Depreciation and amortization 323 88 156 (109 ) 458 Total operating expenses 54,231 7,497 25,008 (25,040 ) 61,696 Income from operations 2,235 28 775 154 3,192 Interest expense — — — 242 242 Other income, net — — — (506 ) (506 ) Income before income taxes and equity in net earnings 2,235 28 775 418 3,456 Equity in net earnings of Kindred at Home — — 14 — 14 Segment earnings $ 2,235 $ 28 $ 789 $ 418 $ 3,470 Premium and services revenues derived from our contracts with the federal government, as a percentage of our total premium and services revenues, was approximately 82% for 2019 , compared to 81% for 2018 , and 79% for 2017 . Retail Group and Specialty Healthcare Services Individual Commercial Other Businesses Eliminations/ Consolidated (in millions) 2018 External revenues Premiums: Individual Medicare Advantage $ 35,656 $ — $ — $ — $ — $ — $ 35,656 Group Medicare Advantage 6,103 — — — — — 6,103 Medicare stand-alone PDP 3,584 — — — — — 3,584 Total Medicare 45,343 — — — — — 45,343 Fully-insured 510 5,444 — 8 — — 5,962 Specialty — 1,359 — — — — 1,359 Medicaid and other 2,255 — — — 22 — 2,277 Total premiums 48,108 6,803 — 8 22 — 54,941 Services revenue: Provider — — 404 — — — 404 ASO and other 11 835 — — 4 — 850 Pharmacy — — 203 — — — 203 Total services revenue 11 835 607 — 4 — 1,457 Total external revenues 48,119 7,638 607 8 26 — 56,398 Intersegment revenues Services — 18 16,840 — — (16,858 ) — Products — — 6,330 — — (6,330 ) — Total intersegment revenues — 18 23,170 — — (23,188 ) — Investment income 136 23 34 — 110 211 514 Total revenues 48,255 7,679 23,811 8 136 (22,977 ) 56,912 Operating expenses: Benefits 40,925 5,420 — (70 ) 77 (470 ) 45,882 Operating costs 5,327 1,810 22,905 4 6 (22,527 ) 7,525 Depreciation and amortization 270 88 163 — — (116 ) 405 Total operating expenses 46,522 7,318 23,068 (66 ) 83 (23,113 ) 53,812 Income from operations 1,733 361 743 74 53 136 3,100 Loss on sale of business — — — — — 786 786 Interest expense — — — — — 218 218 Other expense, net — — — — — 33 33 Income (loss) before income taxes and equity in net earnings 1,733 361 743 74 53 (901 ) 2,063 Equity in net earnings of Kindred at Home — — 11 — — — 11 Segment earnings (losses) $ 1,733 $ 361 $ 754 $ 74 $ 53 $ (901 ) $ 2,074 Retail Group and Specialty Healthcare Services Individual Commercial Other Businesses Eliminations/ Consolidated (in millions) 2017 External revenues Premiums: Individual Medicare Advantage $ 32,720 $ — $ — $ — $ — $ — $ 32,720 Group Medicare Advantage 5,155 — — — — — 5,155 Medicare stand-alone PDP 3,702 — — — — — 3,702 Total Medicare 41,577 — — — — — 41,577 Fully-insured 478 5,462 — 947 — — 6,887 Specialty — 1,310 — — — — 1,310 Medicaid and other 2,571 — — — 35 — 2,606 Total premiums 44,626 6,772 — 947 35 — 52,380 Services revenue: Provider — — 258 — — — 258 ASO and other 10 626 — — 8 — 644 Pharmacy — — 80 — — — 80 Total services revenue 10 626 338 — 8 — 982 Total external revenues 44,636 7,398 338 947 43 — 53,362 Intersegment revenues Services — 20 17,293 — — (17,313 ) — Products — — 6,292 — — (6,292 ) — Total intersegment revenues — 20 23,585 — — (23,605 ) — Investment income 90 31 35 4 87 158 405 Total revenues 44,726 7,449 23,958 951 130 (23,447 ) 53,767 Operating expenses: Benefits 38,218 5,363 — 544 131 (760 ) 43,496 Operating costs 4,292 1,590 22,848 201 12 (22,376 ) 6,567 Merger termination fee and related costs, net — — — — — (936 ) (936 ) Depreciation and amortization 238 84 143 13 — (100 ) 378 Total operating expenses 42,748 7,037 22,991 758 143 (24,172 ) 49,505 Income (loss) from operations 1,978 412 967 193 (13 ) 725 4,262 Interest expense — — — — — 242 242 Income (loss) before income taxes and equity in net earnings 1,978 412 967 193 (13 ) 483 4,020 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings (losses) $ 1,978 $ 412 $ 967 $ 193 $ (13 ) $ 483 $ 4,020

QUARTERLY FINANCIAL INFORMATI_2

QUARTERLY FINANCIAL INFORMATION (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	A summary of our quarterly unaudited results of operations for the years ended December 31, 2019 and 2018 follows: 2019 First Second Third Fourth (in millions, except per share results) Total revenues $ 16,107 $ 16,245 $ 16,241 $ 16,295 Income before income taxes and equity in net earnings 746 1,229 888 593 Net income 566 940 689 512 Basic earnings per common share (1) $ 4.18 $ 6.96 $ 5.16 $ 3.87 Diluted earnings per common share (1) $ 4.16 $ 6.94 $ 5.14 $ 3.84 2018 First Second Third Fourth (in millions, except per share results) Total revenues $ 14,279 $ 14,259 $ 14,206 $ 14,168 Income before income taxes and equity in net earnings 707 19 901 436 Net income 491 193 644 355 Basic earnings per common share (1) $ 3.56 $ 1.40 $ 4.68 $ 2.60 Diluted earnings per common share (1) $ 3.53 $ 1.39 $ 4.65 $ 2.58 (1) The calculation of earnings per common share is based on the weighted average shares outstanding during each quarter and, accordingly, the sum may not equal the total for the year.

REPORTING ENTITY (Details)

REPORTING ENTITY (Details) - Premiums and services revenue - Government Contracts Concentration Risk	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Federal government contracts
Concentration Risk [Line Items]
Premiums and services revenue (percent)	82.00%	81.00%	79.00%
CMS, coverage for individual Medicare Advantage members in Florida
Concentration Risk [Line Items]
Premiums and services revenue (percent)	15.00%

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)	Feb. 16, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Number of days notice for employer group to cancel short-duration prepaid health services policies		30 days
Consumer discounts on brand name prescription drugs		50.00%
Contract liabilities		$ 0
Deferred costs		0
Pharmaceutical rebates		$ 1,300,000,000	$ 1,300,000,000
Typical term (in years) of short-duration employer-group prepaid health services policies		1 year
Lease liabilities		$ 448,000,000
Right-of-use assets		410,000,000
Aetna
Significant Accounting Policies [Line Items]
Merger breakup fee received	$ 1,000,000,000
Tricare South Region Contract
Significant Accounting Policies [Line Items]
TRICARE health care cost reimbursements		6,400,000,000	5,600,000,000	$ 3,400,000,000
TRICARE health care cost payments		6,500,000,000
Difference between TRICARE health care costs payments and reimbursements		$ 63,000,000	(38,000,000)	(11,000,000)
Equipment | Minimum
Significant Accounting Policies [Line Items]
Useful life		3 years
Equipment | Maximum
Significant Accounting Policies [Line Items]
Useful life		10 years
Computer Software | Minimum
Significant Accounting Policies [Line Items]
Useful life		3 years
Computer Software | Maximum
Significant Accounting Policies [Line Items]
Useful life		5 years
Building | Minimum
Significant Accounting Policies [Line Items]
Useful life		10 years
Building | Maximum
Significant Accounting Policies [Line Items]
Useful life		20 years
Health Care Reform
Significant Accounting Policies [Line Items]
Payment of annual health insurance industry fee			1,040,000,000
CMS reinsurance subsidies and discounts
Significant Accounting Policies [Line Items]
Subsidy and discount payments		$ 11,800,000,000	10,300,000,000	10,200,000,000
Subsidy reimbursements		11,200,000,000	9,600,000,000	12,100,000,000
Subsidy and discount payments in excess of reimbursements		$ 600,000,000	700,000,000	$ 1,900,000,000
Settlement period after close		9 months
CMS brand name prescription drug discounts | Minimum
Significant Accounting Policies [Line Items]
Settlement period after close		14 months
CMS brand name prescription drug discounts | Maximum
Significant Accounting Policies [Line Items]
Settlement period after close		18 months
Services
Significant Accounting Policies [Line Items]
Accounts receivable, net, current		$ 141,000,000	$ 123,000,000
Bad-debt expense		0
Contract with customer, asset, net		$ 0
ASU 2016-02
Significant Accounting Policies [Line Items]
Lease liabilities					$ 470,000,000
Right-of-use assets					$ 436,000,000

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Workforce Optimization (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)employee	Dec. 31, 2017USD ($)employee	Dec. 31, 2018USD ($)
Accounting Policies [Abstract]
Expected number of associates impacted | employee	1,000	3,600
Estimated charges	$ 47	$ 148
Workforce optimization obligation	$ 45		$ 12

SUMMARY OF SIGNIFICANT ACCOUN_5

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill	$ 3,928,000,000	$ 3,897,000,000	$ 3,281,000,000
Goodwill impairment loss	0	$ 0	$ 0
Healthcare Services | Clinical
Goodwill [Line Items]
Fair value of reporting unit	544,000,000
Carrying value of reporting unit	533,000,000
Fair value in excess of carrying value	$ 11,000,000
Fair value in excess of carrying value (percent)	2.00%
Hypothetical goodwill impairment if 100 basis point increase in discount rate	$ 62,000,000
Goodwill	524,000,000
Healthcare Services | Provider
Goodwill [Line Items]
Fair value of reporting unit	2,300,000,000
Carrying value of reporting unit	1,300,000,000
Fair value in excess of carrying value	$ 1,000,000,000
Fair value in excess of carrying value (percent)	78.00%
Goodwill	$ 761,000,000

ACQUISITIONS AND DIVESTITURES -

ACQUISITIONS AND DIVESTITURES - Narrative (Details) $ in Millions	Aug. 09, 2018USD ($)	Aug. 08, 2018USD ($)	Feb. 20, 2020USD ($)primary_care_center	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Aug. 08, 2018USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Disclosures by Disposal Groups [Line Items]
Purchase price allocated to goodwill							$ 31	$ 616
Disposed of by sale | KMG America Corporation
Disclosures by Disposal Groups [Line Items]
Cash contribution from parent to disposal group to fund transaction	$ 190
Statutory capital transferred with sale	160
Loss, including transaction costs, on disposal	786
Tax benefit on disposal transaction	$ 452
Cash transferred to third party prior to sale		$ 245
Disposal group revenues						$ 182			$ 261
Disposal group income						$ 47			$ 117
Enclara | Subsequent Event
Disclosures by Disposal Groups [Line Items]
Cash consideration for acquisition			$ 707
MCCI Holdings LLC
Disclosures by Disposal Groups [Line Items]
Cash consideration for acquisition					$ 169
Purchase price allocated to goodwill					483
Purchase price allocated to other intangible assets					80
Purchase price allocated to net tangible assets					$ 24
Estimated weighted average useful life of acquired intangible assets (in years)					8 years
Family Physicians Group
Disclosures by Disposal Groups [Line Items]
Cash consideration for acquisition				$ 185
Purchase price allocated to goodwill				133
Purchase price allocated to other intangible assets				38
Purchase price allocated to net tangible assets				$ 14
Estimated weighted average useful life of acquired intangible assets (in years)				4 years 10 months 24 days
WCAS | Subsequent Event
Disclosures by Disposal Groups [Line Items]
Expected number of payor-agnostic, senior-focused primary care centers to be opened by strategic partnership | primary_care_center			50
Expected time frame for opening primary care centers			3 years
Value of partnership entity			$ 600
Time frame for put and call option activity per partnership agreement, minimum			5 years
Time frame for put and call option activity per partnership agreement, maximum			10 years
MCCI Holdings LLC
Disclosures by Disposal Groups [Line Items]
Note receivable					$ 383

ACQUISITIONS AND DIVESTITURES_2

ACQUISITIONS AND DIVESTITURES - Assets and Liabilities Disposed Of (Details) - Disposed of by sale - KMG America Corporation $ in Millions	Aug. 09, 2018USD ($)
Disclosures by Disposal Groups [Line Items]
Cash and cash equivalents	$ 805
Receivables, net	3
Investment securities	1,576
Other assets	1,085
Total assets disposed	3,469
Benefits payable	58
Trade accounts payable and accrued expenses	70
Future policy benefits payable	2,573
Total liabilities disposed	$ 2,701

EQUITY METHOD INVESTMENT - Narr

EQUITY METHOD INVESTMENT - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Purchase of equity method investment		$ 0	$ 1,095	$ 0
Equity method investment		1,063	1,047
Put option
Schedule of Equity Method Investments [Line Items]
Purchase price allocated to put options	$ 236
Call option
Schedule of Equity Method Investments [Line Items]
Purchase price allocated to call options	$ 291
Options
Schedule of Equity Method Investments [Line Items]
(Income) expense on put and call options		(506)	33
Other long-term liabilities | Put option
Schedule of Equity Method Investments [Line Items]
Fair value of financial liability		28	224
Other long-term assets | Call option
Schedule of Equity Method Investments [Line Items]
Fair value of financial asset		$ 557	$ 246
Kindred at Home
Schedule of Equity Method Investments [Line Items]
Equity method investment ownership (percent)	40.00%
Purchase of equity method investment	$ 1,100
Equity method investment	$ 1,000

EQUITY METHOD INVESTMENT - Summ

EQUITY METHOD INVESTMENT - Summary of Balances Sheets and Income Statement (Details) - Kindred at Home - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Balance sheets
Current assets	$ 536	$ 563
Non-current assets	4,955	4,967
Current liabilities	351	405
Non-current liabilities	2,708	2,637
Shareholders' equity	2,432	2,488
Statements of income
Revenues	1,587	3,100
Expenses	1,451	2,835
Net income	$ 27	$ 54

INVESTMENT SECURITIES - Investm

INVESTMENT SECURITIES - Investment Securities Classified as Current and Long-Term (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost to Fair Value
Amortized Cost	$ 11,160	$ 10,641
Gross Unrealized Gains	219	9
Gross Unrealized Losses	(8)	(213)
Fair Value	11,371	10,437
U.S. Treasury and agency obligations
Amortized Cost to Fair Value
Amortized Cost	353	419
Gross Unrealized Gains	1	1
Gross Unrealized Losses	0	(3)
Fair Value	354	417
Mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost	3,628	2,595
Gross Unrealized Gains	85	3
Gross Unrealized Losses	(3)	(54)
Fair Value	3,710	2,544
Tax-exempt municipal securities
Amortized Cost to Fair Value
Amortized Cost	1,433	2,805
Gross Unrealized Gains	30	3
Gross Unrealized Losses	0	(37)
Fair Value	1,463	2,771
Residential mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost		55
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		55
Commercial mortgage-backed securities
Amortized Cost to Fair Value
Amortized Cost	786	537
Gross Unrealized Gains	18	0
Gross Unrealized Losses	0	(14)
Fair Value	804	523
Asset-backed securities
Amortized Cost to Fair Value
Amortized Cost	1,093	991
Gross Unrealized Gains	3	1
Gross Unrealized Losses	(3)	(7)
Fair Value	1,093	985
Corporate debt securities
Amortized Cost to Fair Value
Amortized Cost	3,867	3,239
Gross Unrealized Gains	82	1
Gross Unrealized Losses	(2)	(98)
Fair Value	$ 3,947	$ 3,142

INVESTMENT SECURITIES - Gross U

INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value
Less than 12 months	$ 1,148	$ 4,574
12 months or more	1,100	4,447
Total	2,248	9,021
Gross Unrealized Losses
Less than 12 months	(3)	(76)
12 months or more	(5)	(137)
Total	(8)	(213)
U.S. Treasury and agency obligations
Fair Value
Less than 12 months	48	179
12 months or more	23	153
Total	71	332
Gross Unrealized Losses
Less than 12 months	0	(1)
12 months or more	0	(2)
Total	0	(3)
Mortgage-backed securities
Fair Value
Less than 12 months	315	956
12 months or more	204	1,019
Total	519	1,975
Gross Unrealized Losses
Less than 12 months	(1)	(16)
12 months or more	(2)	(38)
Total	(3)	(54)
Tax-exempt municipal securities
Fair Value
Less than 12 months	58	809
12 months or more	75	1,648
Total	133	2,457
Gross Unrealized Losses
Less than 12 months	0	(9)
12 months or more	0	(28)
Total	0	(37)
Residential mortgage-backed securities
Fair Value
Less than 12 months		0
12 months or more		15
Total		15
Gross Unrealized Losses
Less than 12 months		0
12 months or more		0
Total		0
Commercial mortgage-backed securities
Fair Value
Less than 12 months	118	372
12 months or more	36	133
Total	154	505
Gross Unrealized Losses
Less than 12 months	0	(8)
12 months or more	0	(6)
Total	0	(14)
Asset-backed securities
Fair Value
Less than 12 months	20	824
12 months or more	607	40
Total	627	864
Gross Unrealized Losses
Less than 12 months	0	(7)
12 months or more	(3)	0
Total	(3)	(7)
Corporate debt securities
Fair Value
Less than 12 months	589	1,434
12 months or more	155	1,439
Total	744	2,873
Gross Unrealized Losses
Less than 12 months	(2)	(35)
12 months or more	0	(63)
Total	$ (2)	$ (98)

INVESTMENT SECURITIES - Narrati

INVESTMENT SECURITIES - Narrative (Details)	12 Months Ended
	Dec. 31, 2019USD ($)position	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Equity securities | $	$ 7,000,000
Percentage of debt securities considered to be of investment-grade (percent)	96.00%
Maximum individual state general bond obligation as a percentage of total debt securities (percent)	1.00%
Securities in unrealized loss position, number of positions | position	235
Securities, number of positions | position	1,515
Other-than-temporary impairments | $	$ 0	$ 0	$ 0

INVESTMENT SECURITIES - Realize

INVESTMENT SECURITIES - Realized Gains (Losses) Included Within Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 129	$ 106	$ 35
Gross realized losses	(67)	(16)	(21)
Net realized capital gains	$ 62	$ 90	$ 14

INVESTMENT SECURITIES - Contrac

INVESTMENT SECURITIES - Contractual Maturities of Debt Securities Available for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 1,316
Due after one year through five years	1,974
Due after five years through ten years	1,724
Due after ten years	639
Mortgage and asset-backed securities	5,507
Amortized Cost	11,160	$ 10,641
Fair Value
Due within one year	1,317
Due after one year through five years	2,013
Due after five years through ten years	1,780
Due after ten years	654
Mortgage and asset-backed securities	5,607
Fair Value	$ 11,371	$ 10,437

FAIR VALUE - Financial Assets M

FAIR VALUE - Financial Assets Measured on Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 11,371	$ 10,437
Common stock	7
U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	354	417
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,710	2,544
Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,463	2,771
Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities		55
Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	804	523
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,093	985
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,947	3,142
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,660	2,024
Debt securities	11,371	10,437
Common stock	7
Total invested assets	15,038	12,461
Recurring Basis | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	354	417
Recurring Basis | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,710	2,544
Recurring Basis | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,463	2,771
Recurring Basis | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities		55
Recurring Basis | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	804	523
Recurring Basis | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,093	985
Recurring Basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,947	3,142
Recurring Basis | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,660	2,024
Debt securities	0	0
Common stock	7
Total invested assets	3,667	2,024
Recurring Basis | Quoted Prices in Active Markets (Level 1) | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities		0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Quoted Prices in Active Markets (Level 1) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Debt securities	11,371	10,437
Common stock	0
Total invested assets	11,371	10,437
Recurring Basis | Other Observable Inputs (Level 2) | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	354	417
Recurring Basis | Other Observable Inputs (Level 2) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,710	2,544
Recurring Basis | Other Observable Inputs (Level 2) | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,463	2,771
Recurring Basis | Other Observable Inputs (Level 2) | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities		55
Recurring Basis | Other Observable Inputs (Level 2) | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	804	523
Recurring Basis | Other Observable Inputs (Level 2) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	1,093	985
Recurring Basis | Other Observable Inputs (Level 2) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,947	3,142
Recurring Basis | Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Debt securities	0	0
Common stock	0
Total invested assets	0	0
Recurring Basis | Unobservable Inputs (Level 3) | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Unobservable Inputs (Level 3) | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Unobservable Inputs (Level 3) | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Unobservable Inputs (Level 3) | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities		0
Recurring Basis | Unobservable Inputs (Level 3) | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Unobservable Inputs (Level 3) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Recurring Basis | Unobservable Inputs (Level 3) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 0	$ 0

FAIR VALUE - Narrative (Details

FAIR VALUE - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt outstanding	$ 5,366	$ 4,774
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt outstanding	5,916	4,885
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 300	645
Term loan and commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt		$ 1,295

FAIR VALUE - Put and Call Optio

FAIR VALUE - Put and Call Options Measured at Fair Value (Details) $ in Millions	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Put option | Other long-term liabilities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of financial liability	$ 28	$ 224
Call option | Other long-term assets
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of financial asset	$ 557	$ 246
Options | Level 3 fair value measurement | Annualized volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.198
Options | Level 3 fair value measurement | Secured credit rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.022
Options | Level 3 fair value measurement | Long-term net operating profit after tax
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.120
Options | Level 3 fair value measurement | Weighted average cost of capital
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.100
Options | Level 3 fair value measurement | Long term growth rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Significant unobservable inputs	0.030

MEDICARE PART D (Details)

MEDICARE PART D (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Other current assets	$ 3,806	$ 3,564
Trade accounts payable and accrued expenses	(3,754)	(3,067)
Other long-term assets	1,834	1,375
Other long-term liabilities	(935)	(581)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	5	15
Trade accounts payable and accrued expenses	(120)	(103)
Net current (liability) asset	(115)	(88)
Other long-term assets	6	7
Other long-term liabilities	(61)	(89)
Net long-term liability	(55)	(82)
Total net (liability) asset	(170)	(170)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	585	172
Trade accounts payable and accrued expenses	(356)	(503)
Net current (liability) asset	229	(331)
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term liability	0	0
Total net (liability) asset	$ 229	$ (331)

PROPERTY AND EQUIPMENT, NET - S

PROPERTY AND EQUIPMENT, NET - Schedule of Property and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Land	$ 20	$ 20
Buildings and leasehold improvements	874	766
Equipment	922	890
Computer software	2,799	2,372
Property and equipment, gross	4,615	4,048
Accumulated depreciation	(2,660)	(2,313)
Property and equipment, net	$ 1,955	$ 1,735

PROPERTY AND EQUIPMENT, NET - N

PROPERTY AND EQUIPMENT, NET - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 505	$ 444	$ 410
Amortization expense for capitalized internally developed and purchased software	$ 343	$ 298	$ 287

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - Changes in Carrying Amount of Goodwill by Reportable Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 3,897	$ 3,281
Acquisitions	31	616
Ending balance	3,928	3,897
Retail
Goodwill [Roll Forward]
Beginning balance	1,535	1,059
Acquisitions	0	476
Ending balance	1,535	1,535
Group and Specialty
Goodwill [Roll Forward]
Beginning balance	261	261
Acquisitions	0	0
Ending balance	261	261
Healthcare Services
Goodwill [Roll Forward]
Beginning balance	2,101	1,961
Acquisitions	31	140
Ending balance	$ 2,132	$ 2,101

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Intangible Assets
Weighted Average Life	8 years 8 months 12 days
Cost	$ 829	$ 827
Accumulated Amortization	652	582
Net	$ 177	245
Customer contracts/relationships
Intangible Assets
Weighted Average Life	8 years 8 months 12 days
Cost	$ 646	646
Accumulated Amortization	496	434
Net	$ 150	212
Trade names and technology
Intangible Assets
Weighted Average Life	6 years 4 months 24 days
Cost	$ 84	84
Accumulated Amortization	84	83
Net	$ 0	1
Provider contracts
Intangible Assets
Weighted Average Life	11 years 9 months 18 days
Cost	$ 70	68
Accumulated Amortization	44	37
Net	$ 26	31
Noncompetes and other
Intangible Assets
Weighted Average Life	7 years 3 months 18 days
Cost	$ 29	29
Accumulated Amortization	28	28
Net	$ 1	$ 1

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for other intangible assets	$ 70	$ 90	$ 75
Impairment of intangible assets, finite-lived		$ 12

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLE ASSETS - Estimate of Amortization Expense (Details) $ in Millions	Dec. 31, 2019USD ($)
Estimate of Amortization Expense
2020	$ 68
2021	34
2022	31
2023	18
2024	$ 11

LEASES - Narrative (Details)

LEASES - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Leases [Abstract]
Operating right-of-use lease assets included within other long-term assets	$ 410
Operating lease liabilities included within trade accounts payable and accrued expenses	116
Operating lease liabilities included within other long-term liabilities	332
Fixed operating lease costs	154
Variable lease costs	82
Sublease rental income	$ 45
Weighted average remaining lease term (in years)	4 years 10 months 24 days
Weighted average discount rate (percent)	4.10%
Operating lease cash payments	$ 151

LEASES - Maturity of Lease Liab

LEASES - Maturity of Lease Liabilities (Details) $ in Millions	Dec. 31, 2019USD ($)
Maturity of Lease Liabilities
2020	$ 133
2021	117
2022	97
2023	52
2024	31
After 2024	70
Total lease payments	500
Less: Interest	52
Present value of lease liabilities	$ 448

LEASES - Rent Expense and Suble

LEASES - Rent Expense and Sublease Rental Income in Prior Years (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Rent Expense and Sublease Rental Income
Rent expense	$ 167	$ 204
Sublease rental income	(32)	(33)
Net rent expense	$ 135	$ 171

LEASES - Future Annual Minimum

LEASES - Future Annual Minimum Payments Due at Prior Year End (Details) $ in Millions	Dec. 31, 2018USD ($)
Minimum Lease Payments
2019	$ 147
2020	113
2021	96
2022	79
2023	34
Thereafter	50
Total	519
Sublease Rental Receipts
2019	(13)
2020	(12)
2021	(10)
2022	(9)
2023	(9)
Thereafter	(23)
Total	(76)
Net Lease Commitments
2019	134
2020	101
2021	86
2022	70
2023	25
Thereafter	27
Total	$ 443

BENEFITS PAYABLE - Activity in

BENEFITS PAYABLE - Activity in Benefits Payable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	$ 4,862	$ 4,668	$ 4,563
Less: Reinsurance recoverables	(95)	(70)	(76)
Balances, beginning of period, net	4,767	4,598	4,487
Incurred related to:
Current year	54,193	46,385	44,001
Prior years	(336)	(503)	(483)
Total incurred	53,857	45,882	43,518
Paid related to:
Current year	(48,421)	(41,736)	(39,496)
Prior years	(4,267)	(3,977)	(3,911)
Total paid	(52,688)	(45,713)	(43,407)
Reinsurance recoverable	68	95	70
Balances, end of period	6,004	4,862	4,668
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	4,338	3,963	3,506
Less: Reinsurance recoverables	(95)	(70)	(76)
Balances, beginning of period, net	4,243	3,893	3,430
Incurred related to:
Current year	48,983	41,323	38,604
Prior years	(386)	(398)	(386)
Total incurred	48,597	40,925	38,218
Paid related to:
Current year	(43,831)	(37,189)	(34,781)
Prior years	(3,714)	(3,386)	(2,974)
Total paid	(47,545)	(40,575)	(37,755)
Reinsurance recoverable	68	95	70
Balances, end of period	5,363	4,338	3,963
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	517	568	579
Incurred related to:
Current year	5,708	5,466	5,403
Prior years	50	(46)	(40)
Total incurred	5,758	5,420	5,363
Paid related to:
Current year	(5,081)	(4,957)	(4,843)
Prior years	(553)	(514)	(531)
Total paid	(5,634)	(5,471)	(5,374)
Balances, end of period	$ 641	$ 517	$ 568

BENEFITS PAYABLE - Favorable Me

BENEFITS PAYABLE - Favorable Medical Claims Reserve Development (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	$ (336)	$ (503)	$ (483)
Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	(386)	(398)	(386)
Group and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	50	(46)	(40)
Operating Segments | Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	(386)	(398)	(386)
Operating Segments | Group and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	50	(46)	(40)
Operating Segments | Individual Commercial
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	0	(57)	(56)
Other Businesses
Liability for Claims and Claims Adjustment Expense [Line Items]
(Favorable) unfavorable medical claims reserve development	$ 0	$ (2)	$ (1)

BENEFITS PAYABLE - Narrative (D

BENEFITS PAYABLE - Narrative (Details) claim in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)claim	Dec. 31, 2018USD ($)claim	Dec. 31, 2017USD ($)claim
Claims Development [Line Items]
Favorable medical claims reserve development related to prior fiscal years | $	$ 336	$ 503	$ 483
Benefit expense reduction excluded from previous short duration benefits payable rollforward | $			$ (22)
Retail
Claims Development [Line Items]
Total IBNR | $	3,600
Group and Specialty
Claims Development [Line Items]
Total IBNR | $	$ 567
2019 Claims Incurred Year | Retail
Claims Development [Line Items]
Cumulative number of reported claims	123
2019 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Cumulative number of reported claims	9.7
2018 Claims Incurred Year | Retail
Claims Development [Line Items]
Cumulative number of reported claims		109.6
2018 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Cumulative number of reported claims		10.8
2017 Claims Incurred Year | Retail
Claims Development [Line Items]
Cumulative number of reported claims			104.7
2017 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Cumulative number of reported claims			11.1

BENEFITS PAYABLE - Incurred and

BENEFITS PAYABLE - Incurred and Paid Claims Development (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Claims Development [Line Items]
Benefits payable, net of reinsurance	$ 5,936
Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	128,277
Cumulative Paid Claims, Net of Reinsurance	122,982
Benefits payable, net of reinsurance	5,295
Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	16,581
Cumulative Paid Claims, Net of Reinsurance	15,940
Benefits payable, net of reinsurance	641
2017 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	38,310	$ 38,341	$ 38,604
Cumulative Paid Claims, Net of Reinsurance	38,310	38,232	34,781
2017 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,372	5,358	5,403
Cumulative Paid Claims, Net of Reinsurance	5,372	5,351	$ 4,843
2018 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	40,984	41,323
Cumulative Paid Claims, Net of Reinsurance	40,841	37,189
2018 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,501	5,466
Cumulative Paid Claims, Net of Reinsurance	5,487	$ 4,957
2019 Claims Incurred Year | Retail
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	48,983
Cumulative Paid Claims, Net of Reinsurance	43,831
2019 Claims Incurred Year | Group and Specialty
Claims Development [Line Items]
Incurred Claims, Net of Reinsurance	5,708
Cumulative Paid Claims, Net of Reinsurance	$ 5,081

BENEFITS PAYABLE - Reconciliati

BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	$ 5,936
Reinsurance recoverable on unpaid claims	68	$ 95	$ 70	$ 76
Total benefits payable, gross	6,004	4,862	4,668	4,563
Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	5,295
Reinsurance recoverable on unpaid claims	68	95	70	76
Total benefits payable, gross	5,363	4,338	3,963	3,506
Group and Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Benefits payable, net of reinsurance	641
Total benefits payable, gross	641	$ 517	$ 568	$ 579
Operating Segments | Retail
Liability for Claims and Claims Adjustment Expense [Line Items]
Reinsurance recoverable on unpaid claims	$ 68

INCOME TAXES - Provision for In

INCOME TAXES - Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal	$ 560	$ 139	$ 1,324
States and Puerto Rico	41	58	116
Total current provision	601	197	1,440
Deferred expense	162	194	132
Provision for income taxes	$ 763	$ 391	$ 1,572

INCOME TAXES - Provision for _2

INCOME TAXES - Provision for Income Taxes Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax provision at federal statutory rate	$ 729	$ 436	$ 1,407
States, net of federal benefit, and Puerto Rico	49	42	80
Tax exempt investment income	(6)	(11)	(22)
Health insurance industry fee	0	243	0
Nondeductible executive compensation	25	17	36
Tax reform	0	(39)	133
KMG sale	0	(272)	0
Other, net	(34)	(25)	(62)
Provision for income taxes	$ 763	$ 391	$ 1,572

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Increase in tax provision from remeasurement to deferred tax asset due to Tax Reform Law			$ 133
Decrease to tax provision from revisions of Tax Reform Law estimates		$ 39
Benefit on sale of business	$ 0	272	0
Net operating losses to carryforward related to prior acquisitions	114
Valuation allowances on net operating loss carryforwards related to prior acquisitions	45	$ 54
Puerto Rico
Operating Loss Carryforwards [Line Items]
Repatriation tax for undistributed foreign earnings			$ 10
Capital Loss Carryforward
Operating Loss Carryforwards [Line Items]
Capital loss carryforward	$ 2

INCOME TAXES - Principal Compon

INCOME TAXES - Principal Components of Net Deferred Tax Balances (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Compensation and other accrued expense	$ 111	$ 89
Benefits payable	89	79
Net operating loss carryforward	42	38
Deferred acquisition costs	22	17
Unearned revenues	8	9
Other	8	8
Capital loss carryforward	1	15
Investment securities	0	44
Total deferred income tax assets	281	299
Valuation allowance	(45)	(54)
Total deferred income tax assets, net of valuation allowance	236	245
Depreciable property and intangible assets	(329)	(273)
Investment securities	(181)	0
Prepaid expenses	(64)	(52)
Future policy benefits payable	(3)	(5)
Total deferred income tax liabilities	(577)	(330)
Total net deferred income tax liabilities	$ (341)	$ (85)

DEBT - Debt Outstanding (Detail

DEBT - Debt Outstanding (Details) - USD ($)	Dec. 31, 2019	Oct. 01, 2019	Aug. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total short-term debt	$ 699,000,000			$ 1,694,000,000
Long-term debt	4,967,000,000			4,375,000,000
$500 million, 3.95% due August 15, 2049
Debt Instrument [Line Items]
Face amount	$ 500,000,000
Stated interest rate (percent)	3.95%
Commercial paper
Debt Instrument [Line Items]
Short-term debt	$ 300,000,000			645,000,000
Term note
Debt Instrument [Line Items]
Short-term debt	0			650,000,000
Senior notes | $400 million, 2.625% due October 1, 2019
Debt Instrument [Line Items]
Face amount	$ 400,000,000
Stated interest rate (percent)	2.625%	2.625%
Long-term debt, current maturities	$ 0			399,000,000
Senior notes | $400 million, 2.50% due December 15, 2020
Debt Instrument [Line Items]
Face amount	$ 400,000,000
Stated interest rate (percent)	2.50%
Long-term debt, current maturities	$ 399,000,000			0
Long-term debt	0			398,000,000
Senior notes | $600 million, 3.15% due December 1, 2022
Debt Instrument [Line Items]
Face amount	$ 600,000,000
Stated interest rate (percent)	3.15%
Long-term debt	$ 598,000,000			596,000,000
Senior notes | $400 million, 2.90% due December 15, 2022
Debt Instrument [Line Items]
Face amount	$ 400,000,000
Stated interest rate (percent)	2.90%
Long-term debt	$ 397,000,000			396,000,000
Senior notes | $600 million, 3.85% due October 1, 2024
Debt Instrument [Line Items]
Face amount	$ 600,000,000
Stated interest rate (percent)	3.85%
Long-term debt	$ 597,000,000			597,000,000
Senior notes | $600 million, 3.95% due March 15, 2027
Debt Instrument [Line Items]
Face amount	$ 600,000,000
Stated interest rate (percent)	3.95%
Long-term debt	$ 595,000,000			594,000,000
Senior notes | $500 million, 3.125% due August 15, 2029
Debt Instrument [Line Items]
Face amount	$ 500,000,000		$ 500,000,000
Stated interest rate (percent)	3.125%		3.125%
Long-term debt	$ 495,000,000			0
Senior notes | $250 million, 8.15% due June 15, 2038
Debt Instrument [Line Items]
Face amount	$ 250,000,000
Stated interest rate (percent)	8.15%
Long-term debt	$ 262,000,000			263,000,000
Senior notes | $400 million, 4.625% due December 1, 2042
Debt Instrument [Line Items]
Face amount	$ 400,000,000
Stated interest rate (percent)	4.625%
Long-term debt	$ 396,000,000			396,000,000
Senior notes | $750 million, 4.95% due October 1, 2044
Debt Instrument [Line Items]
Face amount	$ 750,000,000
Stated interest rate (percent)	4.95%
Long-term debt	$ 739,000,000			739,000,000
Senior notes | $400 million, 4.80% due March 15, 2047
Debt Instrument [Line Items]
Face amount	$ 400,000,000
Stated interest rate (percent)	4.80%
Long-term debt	$ 396,000,000			396,000,000
Senior notes | $500 million, 3.95% due August 15, 2049
Debt Instrument [Line Items]
Face amount			$ 500,000,000
Stated interest rate (percent)			3.95%
Long-term debt	$ 492,000,000			$ 0

DEBT - Maturities of Debt (Deta

DEBT - Maturities of Debt (Details) $ in Millions	Dec. 31, 2019USD ($)
Maturities of debt
2020	$ 700
2021	0
2022	1,000
2023	0
2024	600
Thereafter	$ 3,400

DEBT - Senior Notes (Details)

DEBT - Senior Notes (Details) - USD ($)	Oct. 01, 2019	Aug. 31, 2019	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repayment of short-term debt				$ 650,000,000	$ 350,000,000	$ 0
Repayment of long-term debt				400,000,000	$ 0	800,000,000
$500 million, 3.95% due August 15, 2049
Debt Instrument [Line Items]
Face amount			$ 500,000,000	$ 500,000,000
Stated interest rate (percent)			3.95%	3.95%
Senior notes
Debt Instrument [Line Items]
Debt redemption price (percent)				100.00%
Proceeds from issuance of debt, net			$ 987,000,000
Loss on extinguishment of debt						$ 17,000,000
Senior notes | $500 million, 3.125% due August 15, 2029
Debt Instrument [Line Items]
Face amount		$ 500,000,000	$ 500,000,000	$ 500,000,000
Stated interest rate (percent)		3.125%	3.125%	3.125%
Senior notes | $500 million, 3.95% due August 15, 2049
Debt Instrument [Line Items]
Face amount		$ 500,000,000
Stated interest rate (percent)		3.95%
Senior notes | $400 million, 2.625% due October 1, 2019
Debt Instrument [Line Items]
Face amount			$ 400,000,000	$ 400,000,000
Stated interest rate (percent)	2.625%		2.625%	2.625%
Repayment of long-term debt	$ 400,000,000
Senior notes | $250 million, 8.15% due June 15, 2038
Debt Instrument [Line Items]
Face amount			$ 250,000,000	$ 250,000,000
Stated interest rate (percent)			8.15%	8.15%
Term note
Debt Instrument [Line Items]
Repayment of short-term debt		$ 650,000,000

DEBT - Credit Agreement (Detail

DEBT - Credit Agreement (Details)	12 Months Ended
	Dec. 31, 2019USD ($)
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument term (in years)	5 years
Maximum borrowing capacity	$ 2,000,000,000
Facility fee (percent)	0.15%
Debt to capitalization percentage, maximum	50.00%
Actual debt to capitalization percentage	32.00%
Maximum borrowing capacity including uncommitted incremental loan facility	$ 2,500,000,000
Uncommitted incremental loan facility	500,000,000
Line of credit, outstanding borrowings	0
Remaining borrowing capacity	$ 2,000,000,000
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Facility fee (percent)	0.09%
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Facility fee (percent)	0.25%
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis points spread on variable rate (percent)	1.10%
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis points spread on variable rate (percent)	0.91%
Line of Credit | Unsecured Revolving Credit Agreement | Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis points spread on variable rate (percent)	1.50%
Line of Credit | Unsecured Revolving Credit Agreement | Letter of Credit
Debt Instrument [Line Items]
Line of credit, outstanding borrowings	$ 0
Commercial paper
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 2,000,000,000

DEBT - Commercial Paper (Detail

DEBT - Commercial Paper (Details) - Commercial paper - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Maximum borrowing capacity	$ 2,000,000,000
Maximum amount outstanding during period	801,000,000
Short-term debt outstanding	$ 300,000,000	$ 645,000,000
Weighted average annual interest rate (percent)	2.00%

DEBT - Term Note (Details)

DEBT - Term Note (Details)	1 Months Ended			2 Months Ended	12 Months Ended
	Feb. 20, 2020USD ($)draw	Aug. 31, 2019USD ($)	Nov. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Short-term Debt [Line Items]
Repayment of short-term debt					$ 650,000,000	$ 350,000,000	$ 0
Term note
Short-term Debt [Line Items]
Repayment of short-term debt		$ 650,000,000
2018 Term Note | Term note
Short-term Debt [Line Items]
Face amount			$ 1,000,000,000
Debt instrument term (in years)			1 year
Repayment of short-term debt		$ 650,000,000		$ 350,000,000
2018 Term Note | Term note | LIBOR
Short-term Debt [Line Items]
Basis points spread on variable rate (percent)					1.15%
Base rate component, basis spread on variable rate (percent)					1.00%
2018 Term Note | Term note | Federal Funds Rate
Short-term Debt [Line Items]
Base rate component, basis spread on variable rate (percent)					0.50%
2020 Term Loan Commitment | Subsequent Event | Term note
Short-term Debt [Line Items]
Face amount	$ 1,000,000,000
Debt instrument term (in years)	1 year
Extension period term (in years)	1 year
Number of draws on term loan commitment allowable per agreement | draw	3
Minimum draw amount on term loan commitment allowable per agreement	$ 300,000,000
Unused commitment threshold for expiration	$ 300,000,000
2020 Term Loan Commitment | Subsequent Event | Term note | LIBOR
Short-term Debt [Line Items]
Basis points spread on variable rate (percent)	1.15%
Base rate component, basis spread on variable rate (percent)	1.00%
2020 Term Loan Commitment | Subsequent Event | Term note | Federal Funds Rate
Short-term Debt [Line Items]
Base rate component, basis spread on variable rate (percent)	0.50%

EMPLOYEE BENEFIT PLANS - Narrat

EMPLOYEE BENEFIT PLANS - Narrative (Details) $ / shares in Units, shares in Millions	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2019USD ($)employee_group$ / sharesshares	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee retirement and savings plan cost		$ 221,000,000	$ 197,000,000	$ 217,000,000
Closing stock price (in USD per share) | $ / shares	$ 366.52
Percentage of retirement and savings plan's assets invested in our company common stock		11.00%
Shares of retirement and savings plans invested in company's common stock (in shares) | shares	1.6	1.6
Percentage of the retirement and savings plan's assets invested in our common stock as compared to company's outstanding shares at year-end		1.20%
Number of shares of our common stock reserved for issuance (in shares) | shares	1.8	1.8
Combination of age and years necessary for retirement provision as related to our equity award program		65 years
Minimum age required for retirement eligibility as related to our equity award program		55 years
Minimum number of years of service for retirement eligibility as related to our equity award program		5 years
Limitations on deductibility of excess annual employee compensation as mandated by health insurance reforms		$ 500,000
Employee service share based compensation tax benefit realized from exercise of stock options and restricted stock vesting		25,000,000	49,000,000	68,000,000
Fair value of shares vested		$ 141,000,000	298,000,000	306,000,000
Stratified homogeneous employee groups in stock option valuation | employee_group		3
Outstanding intrinsic value of stock options	$ 56,000,000	$ 56,000,000
Weighted-average remaining contractual term (in years)		4 years 9 months 18 days
Exercisable stock options intrinsic value	$ 16,000,000	$ 16,000,000
Exercisable stock options weighted-average remaining contractual term (in years)		3 years 10 months 24 days
Total intrinsic value of stock options exercised		$ 43,000,000	43,000,000	44,000,000
Proceeds from stock options exercised		$ 58,000,000	$ 50,000,000	63,000,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation modification expense				$ 29,000,000
Vesting period (in years)		3 years
Weighted-average grant date fair value of restricted stock awards (in USD per share) | $ / shares		$ 302.09	$ 276.62	$ 222.35
Percent of stock with performance-based conditions	22.00%	22.00%
Total compensation expense not yet recognized related to nonvested restricted stock	$ 164,000,000	$ 164,000,000
Compensation expense over a weighted-average period (in years)		1 year 8 months 12 days
Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense not yet recognized related to nonvested restricted stock	$ 11,000,000	$ 11,000,000
Compensation expense over a weighted-average period (in years)		1 year 8 months 12 days
Minimum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		1 year
Expiration period (in years)		7 years
Maximum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		3 years
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for stock award plans (in shares) | shares	12.5	12.5
2011 Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants assuming all stock options or restricted stock are granted (in shares) | shares	1.7	1.7
2011 Plan | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants assuming all stock options or restricted stock are granted (in shares) | shares	3.8	3.8
2019 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares reserved for stock award plans (in shares) | shares	16	16
2019 Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants assuming all stock options or restricted stock are granted (in shares) | shares	4.7	4.7
2019 Plan | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grants assuming all stock options or restricted stock are granted (in shares) | shares	15.8	15.8

EMPLOYEE BENEFIT PLANS - Stock-

EMPLOYEE BENEFIT PLANS - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-based compensation expense by type:
Restricted stock	$ 152	$ 124	$ 145
Stock options	11	13	12
Total stock-based compensation expense	163	137	157
Tax benefit recognized	(35)	(21)	(32)
Stock-based compensation expense, net of tax	$ 128	$ 116	$ 125

EMPLOYEE BENEFIT PLANS - Restri

EMPLOYEE BENEFIT PLANS - Restricted Stock Activity (Details) - Restricted Stock - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Nonvested restricted stock, beginning balance (in shares)	964
Granted (in shares)	503
Vested (in shares)	(421)
Forfeited (in shares)	(70)
Nonvested restricted stock, ending balance (in shares)	976	964
Weighted- Average Grant-Date Fair Value
Nonvested restricted stock, beginning balance (in USD per share)	$ 213.99
Granted (in USD per share)	302.09	$ 276.62	$ 222.35
Vested (in USD per share)	239.42
Forfeited (in USD per share)	269.06
Nonvested restricted stock, ending balance (in USD per share)	$ 245.21	$ 213.99

EMPLOYEE BENEFIT PLANS - Weight

EMPLOYEE BENEFIT PLANS - Weighted-Average Fair Value Assumptions for Stock Options (Details) - Employee Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value at grant date (in dollars per share)	$ 68.53	$ 63.67	$ 49.81
Expected option life (years)	4 years 1 month 6 days	4 years 1 month 6 days	4 years 1 month 6 days
Expected volatility (percent)	25.50%	26.10%	27.10%
Risk-free interest rate at grant date (percent)	2.40%	2.50%	2.00%
Dividend yield (percent)	0.70%	0.70%	0.70%

EMPLOYEE BENEFIT PLANS - Option

EMPLOYEE BENEFIT PLANS - Option Plans Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Shares Under Option
Options outstanding, beginning balance (in shares) | shares	677
Granted (in shares) | shares	121
Exercised (in shares) | shares	(305)
Forfeited (in shares) | shares	0
Options outstanding, ending balance (in shares) | shares	493
Options exercisable, ending balance (in shares) | shares	109
Weighted-Average Exercise Price
Options outstanding, beginning balance (in dollars per share) | $ / shares	$ 213.17
Granted (in dollars per share) | $ / shares	304.59
Exercised (in dollars per share) | $ / shares	189.24
Forfeited (in dollars per share) | $ / shares	0
Options outstanding, ending balance (in dollars per share) | $ / shares	250.46
Options exercisable, ending balance (in dollars per share) | $ / shares	$ 216.49

EARNINGS PER COMMON SHARE COM_3

EARNINGS PER COMMON SHARE COMPUTATION - Details Supporting Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Weighted-average outstanding shares of common stock used to compute basic earnings per common share (in shares)									134,055	137,486	144,493
Shares used to compute diluted earnings per common share (in shares)									134,727	138,403	145,585
Basic earnings per common share (in USD per share)	$ 3.87	$ 5.16	$ 6.96	$ 4.18	$ 2.60	$ 4.68	$ 1.40	$ 3.56	$ 20.20	$ 12.24	$ 16.94
Diluted earnings per common share (in USD per share)	$ 3.84	$ 5.14	$ 6.94	$ 4.16	$ 2.58	$ 4.65	$ 1.39	$ 3.53	$ 20.10	$ 12.16	$ 16.81
Number of antidilutive stock options and restricted stock awards excluded from computation (in shares)									478	223	539
Employee stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock (in shares)									107	194	172
Restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dilutive effect of employee stock options and restricted stock (in shares)									565	723	920

STOCKHOLDERS' EQUITY - Dividend

STOCKHOLDERS' EQUITY - Dividend Payments (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 31, 2020	Oct. 24, 2019	Feb. 20, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Dividends
Amount per Share (in USD per share)				$ 2.15	$ 1.90	$ 1.49
Total Amount				$ 289	$ 262	$ 216
Cash dividend declared (in USD per share)		$ 0.55
Subsequent Event
Dividends
Total Amount	$ 73
Cash dividend declared (in USD per share)			$ 0.625

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands	Dec. 26, 2019	Aug. 02, 2019	Feb. 28, 2019	Nov. 29, 2018	Mar. 26, 2018	Dec. 22, 2017	Aug. 28, 2017	Feb. 22, 2017	Feb. 28, 2019	Mar. 26, 2018	Dec. 31, 2017	Dec. 26, 2019	Aug. 28, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 19, 2020	Jul. 31, 2019	Jul. 30, 2019	Nov. 28, 2018	Dec. 21, 2017	Dec. 14, 2017	Feb. 16, 2017	Feb. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization																			$ 3,000,000,000	$ 3,000,000,000	$ 3,000,000,000	$ 3,000,000,000	$ 2,250,000,000	$ 2,250,000,000
Shares received (in shares)											3,040
Increase in treasury stock from share repurchases											$ 750,000,000			$ 1,070,000,000	$ 1,090,000,000	$ 3,365,000,000
Remaining share repurchase authorization at replacement																			$ 1,030,000,000
Common shares acquired in connection with employee stock plans (in shares)														200	400	500
Common shares acquired in connection with employee stock plans, amount														$ 70,000,000	$ 116,000,000	$ 115,000,000
Aggregate statutory capital and surplus in our state regulated insurance subsidiaries														8,000,000,000	7,600,000,000
Aggregate minimum regulatory requirements of statutory capital and surplus														5,900,000,000	5,200,000,000
Dividends that may be paid to the parent company without prior approval by state regulatory authorities in 2014														1,000,000,000
Dividends that were paid to the parent company without prior approval by state regulatory authorities														$ 1,800,000,000	$ 2,300,000,000	$ 1,400,000,000
February 2017 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated share repurchase agreement amount																							$ 1,500,000,000
Accelerated share repurchase payment								$ 1,500,000,000
Shares received (in shares)							840	5,830					6,670
Increase in treasury stock from share repurchases								$ 1,200,000,000
Decrease in capital in excess of par value								$ 300,000,000
Average daily volume weighted-average share price of common stock during term of agreement (in USD per share)													$ 224.81
Reclassification from capital in excess of par value to treasury stock							$ 300,000,000
December 2017 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated share repurchase agreement amount																					$ 1,000,000,000
Accelerated share repurchase payment						$ 1,000,000,000
Shares received (in shares)					460	3,280				3,740
Increase in treasury stock from share repurchases						$ 800,000,000
Decrease in capital in excess of par value						$ 200,000,000
Average daily volume weighted-average share price of common stock during term of agreement (in USD per share)										$ 267.55
Reclassification from capital in excess of par value to treasury stock					$ 200,000,000
November 2018 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated share repurchase agreement amount																				$ 750,000,000
Accelerated share repurchase payment				$ 750,000,000
Shares received (in shares)			600	1,940					2,540
Increase in treasury stock from share repurchases				$ 600,000,000
Decrease in capital in excess of par value				$ 150,000,000
Average daily volume weighted-average share price of common stock during term of agreement (in USD per share)									$ 295.15
Reclassification from capital in excess of par value to treasury stock			$ 150,000,000
July 2019 ASR
Equity, Class of Treasury Stock [Line Items]
Accelerated share repurchase agreement amount																		$ 1,000,000,000
Accelerated share repurchase payment		$ 1,000,000,000
Shares received (in shares)	700	2,700										3,400
Increase in treasury stock from share repurchases		$ 800,000,000
Decrease in capital in excess of par value		$ 200,000,000
Average daily volume weighted-average share price of common stock during term of agreement (in USD per share)												$ 296.19
Reclassification from capital in excess of par value to treasury stock	$ 200,000,000
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Remaining authorized amount																	$ 2,000,000,000

STOCKHOLDERS' EQUITY - Share Re

STOCKHOLDERS' EQUITY - Share Repurchases (Details) - USD ($) shares in Thousands	4 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 30, 2019	Nov. 28, 2018	Dec. 21, 2017	Dec. 14, 2017	Feb. 16, 2017	Feb. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization					$ 3,000,000,000	$ 3,000,000,000	$ 3,000,000,000	$ 3,000,000,000	$ 2,250,000,000	$ 2,250,000,000
Shares repurchased (in shares)	3,040
Cost of repurchases	$ 750,000,000	$ 1,070,000,000	$ 1,090,000,000	$ 3,365,000,000
February 2017 Authorization
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization		$ 2,250,000,000
Shares repurchased (in shares)		0	0	9,710
Cost of repurchases		$ 0	$ 0	$ 2,250,000,000
December 2017 Authorization
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization		$ 3,000,000,000
Shares repurchased (in shares)		0	3,070	3,280
Cost of repurchases		$ 0	$ 1,024,000,000	$ 800,000,000
July 2019 Authorization
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization		$ 3,000,000,000
Shares repurchased (in shares)		3,400	0	0
Cost of repurchases		$ 1,000,000,000	$ 0	$ 0
Excluding Employee Stock Plans and ASR
Equity, Class of Treasury Stock [Line Items]
Shares repurchased (in shares)		3,400	3,070	12,990
Cost of repurchases		$ 1,000,000,000	$ 1,024,000,000	$ 3,050,000,000

COMMITMENTS, GUARANTEES AND C_2

COMMITMENTS, GUARANTEES AND CONTINGENCIES - Narrative (Details) beneficiary in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019USD ($)beneficiaryState	Nov. 02, 2017USD ($)
Loss Contingencies [Line Items]
Purchase obligations in 2020			$ 922
Purchase obligations in 2021			647
Purchase obligations in 2022			489
Purchase obligations in 2023			246
Purchase obligations in 2024			$ 100
Percentage of risk score calculated from claims submitted through EDS			25.00%
Number of states comprising TRICARE beneficiaries | State			32
Number of TRICARE beneficiaries | beneficiary			6
Litigation recoveries sought				$ 611
Tricare East Region Contract
Loss Contingencies [Line Items]
Contract term years			5 years
Medicare
Loss Contingencies [Line Items]
Percentage of premiums and services revenue			82.00%
Military services
Loss Contingencies [Line Items]
Percentage of premiums and services revenue			1.00%
Medicaid
Loss Contingencies [Line Items]
Percentage of premiums and services revenue			4.00%
Forecast
Loss Contingencies [Line Items]
Percentage of risk score calculated from claims submitted through EDS	75.00%	50.00%

SEGMENT INFORMATION - Narrative

SEGMENT INFORMATION - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	3
Member co-share amounts and government subsidies	$ 14,900	$ 13,400	$ 13,500
Depreciation and amortization classified as benefit expense	$ 117	$ 129	$ 107
Government Contracts Concentration Risk | Premiums and services revenue | Federal government contracts
Segment Reporting Information [Line Items]
Premiums and services revenue (percent)	82.00%	81.00%	79.00%

SEGMENT INFORMATION - Segment R

SEGMENT INFORMATION - Segment Results (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Premiums									$ 62,948	$ 54,941	$ 52,380
Services revenue									1,439	1,457	982
Total external revenues									64,387	56,398	53,362
Intersegment revenues									0	0	0
Investment income									501	514	405
Total revenues	$ 16,295	$ 16,241	$ 16,245	$ 16,107	$ 14,168	$ 14,206	$ 14,259	$ 14,279	64,888	56,912	53,767
Benefits									53,857	45,882	43,496
Operating costs									7,381	7,525	6,567
Merger termination fee and related costs, net									0	0	(936)
Depreciation and amortization									458	405	378
Total operating expenses									61,696	53,812	49,505
Income from operations									3,192	3,100	4,262
Loss on sale of business									0	786	0
Interest expense									242	218	242
Other (income) expense, net									(506)	33	0
Income before income taxes and equity in net earnings	$ 593	$ 888	$ 1,229	$ 746	$ 436	$ 901	$ 19	$ 707	3,456	2,063	4,020
Equity in net earnings of Kindred at Home									14	11	0
Segment earnings									3,470	2,074	4,020
Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									43,128	35,656	32,720
Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									6,475	6,103	5,155
Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums									3,165	3,584	3,702
Total Medicare
Segment Reporting Information [Line Items]
Premiums									52,768	45,343	41,577
Fully-insured
Segment Reporting Information [Line Items]
Premiums									5,711	5,962	6,887
Specialty
Segment Reporting Information [Line Items]
Premiums									1,571	1,359	1,310
Medicaid and other
Segment Reporting Information [Line Items]
Premiums									2,898	2,277	2,606
Provider
Segment Reporting Information [Line Items]
Services revenue									446	404	258
ASO and other
Segment Reporting Information [Line Items]
Services revenue									807	850	644
Pharmacy
Segment Reporting Information [Line Items]
Services revenue									186	203	80
Services
Segment Reporting Information [Line Items]
Intersegment revenues									0	0	0
Products
Segment Reporting Information [Line Items]
Intersegment revenues									0	0	0
Operating Segments | Retail
Segment Reporting Information [Line Items]
Premiums									56,254	48,108	44,626
Services revenue									17	11	10
Total external revenues									56,271	48,119	44,636
Intersegment revenues									0	0	0
Investment income									195	136	90
Total revenues									56,466	48,255	44,726
Benefits									48,602	40,925	38,218
Operating costs									5,306	5,327	4,292
Merger termination fee and related costs, net											0
Depreciation and amortization									323	270	238
Total operating expenses									54,231	46,522	42,748
Income from operations									2,235	1,733	1,978
Loss on sale of business										0
Interest expense									0	0	0
Other (income) expense, net									0	0
Income before income taxes and equity in net earnings									2,235	1,733	1,978
Equity in net earnings of Kindred at Home									0	0	0
Segment earnings									2,235	1,733	1,978
Operating Segments | Retail | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									43,128	35,656	32,720
Operating Segments | Retail | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									6,475	6,103	5,155
Operating Segments | Retail | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums									3,165	3,584	3,702
Operating Segments | Retail | Total Medicare
Segment Reporting Information [Line Items]
Premiums									52,768	45,343	41,577
Operating Segments | Retail | Fully-insured
Segment Reporting Information [Line Items]
Premiums									588	510	478
Operating Segments | Retail | Specialty
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Retail | Medicaid and other
Segment Reporting Information [Line Items]
Premiums									2,898	2,255	2,571
Operating Segments | Retail | Provider
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Operating Segments | Retail | ASO and other
Segment Reporting Information [Line Items]
Services revenue									17	11	10
Operating Segments | Retail | Pharmacy
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Operating Segments | Retail | Services
Segment Reporting Information [Line Items]
Intersegment revenues									0	0	0
Operating Segments | Retail | Products
Segment Reporting Information [Line Items]
Intersegment revenues									0	0	0
Operating Segments | Group and Specialty
Segment Reporting Information [Line Items]
Premiums									6,694	6,803	6,772
Services revenue									790	835	626
Total external revenues									7,484	7,638	7,398
Intersegment revenues									18	18	20
Investment income									23	23	31
Total revenues									7,525	7,679	7,449
Benefits									5,758	5,420	5,363
Operating costs									1,651	1,810	1,590
Merger termination fee and related costs, net											0
Depreciation and amortization									88	88	84
Total operating expenses									7,497	7,318	7,037
Income from operations									28	361	412
Loss on sale of business										0
Interest expense									0	0	0
Other (income) expense, net									0	0
Income before income taxes and equity in net earnings									28	361	412
Equity in net earnings of Kindred at Home									0	0	0
Segment earnings									28	361	412
Operating Segments | Group and Specialty | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Group and Specialty | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Group and Specialty | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Group and Specialty | Total Medicare
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Group and Specialty | Fully-insured
Segment Reporting Information [Line Items]
Premiums									5,123	5,444	5,462
Operating Segments | Group and Specialty | Specialty
Segment Reporting Information [Line Items]
Premiums									1,571	1,359	1,310
Operating Segments | Group and Specialty | Medicaid and other
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Group and Specialty | Provider
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Operating Segments | Group and Specialty | ASO and other
Segment Reporting Information [Line Items]
Services revenue									790	835	626
Operating Segments | Group and Specialty | Pharmacy
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Operating Segments | Group and Specialty | Services
Segment Reporting Information [Line Items]
Intersegment revenues									18	18	20
Operating Segments | Group and Specialty | Products
Segment Reporting Information [Line Items]
Intersegment revenues									0	0	0
Operating Segments | Healthcare Services
Segment Reporting Information [Line Items]
Premiums									0	0	0
Services revenue									632	607	338
Total external revenues									632	607	338
Intersegment revenues									25,149	23,170	23,585
Investment income									2	34	35
Total revenues									25,783	23,811	23,958
Benefits									0	0	0
Operating costs									24,852	22,905	22,848
Merger termination fee and related costs, net											0
Depreciation and amortization									156	163	143
Total operating expenses									25,008	23,068	22,991
Income from operations									775	743	967
Loss on sale of business										0
Interest expense									0	0	0
Other (income) expense, net									0	0
Income before income taxes and equity in net earnings									775	743	967
Equity in net earnings of Kindred at Home									14	11	0
Segment earnings									789	754	967
Operating Segments | Healthcare Services | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Total Medicare
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Fully-insured
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Specialty
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Medicaid and other
Segment Reporting Information [Line Items]
Premiums									0	0	0
Operating Segments | Healthcare Services | Provider
Segment Reporting Information [Line Items]
Services revenue									446	404	258
Operating Segments | Healthcare Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Operating Segments | Healthcare Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue									186	203	80
Operating Segments | Healthcare Services | Services
Segment Reporting Information [Line Items]
Intersegment revenues									18,255	16,840	17,293
Operating Segments | Healthcare Services | Products
Segment Reporting Information [Line Items]
Intersegment revenues									6,894	6,330	6,292
Operating Segments | Individual Commercial
Segment Reporting Information [Line Items]
Premiums										8	947
Services revenue										0	0
Total external revenues										8	947
Intersegment revenues										0	0
Investment income										0	4
Total revenues										8	951
Benefits										(70)	544
Operating costs										4	201
Merger termination fee and related costs, net											0
Depreciation and amortization										0	13
Total operating expenses										(66)	758
Income from operations										74	193
Loss on sale of business										0
Interest expense										0	0
Other (income) expense, net										0
Income before income taxes and equity in net earnings										74	193
Equity in net earnings of Kindred at Home										0	0
Segment earnings										74	193
Operating Segments | Individual Commercial | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Total Medicare
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Fully-insured
Segment Reporting Information [Line Items]
Premiums										8	947
Operating Segments | Individual Commercial | Specialty
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Medicaid and other
Segment Reporting Information [Line Items]
Premiums										0	0
Operating Segments | Individual Commercial | Provider
Segment Reporting Information [Line Items]
Services revenue										0	0
Operating Segments | Individual Commercial | ASO and other
Segment Reporting Information [Line Items]
Services revenue										0	0
Operating Segments | Individual Commercial | Pharmacy
Segment Reporting Information [Line Items]
Services revenue										0	0
Operating Segments | Individual Commercial | Services
Segment Reporting Information [Line Items]
Intersegment revenues										0	0
Operating Segments | Individual Commercial | Products
Segment Reporting Information [Line Items]
Intersegment revenues										0	0
Other Businesses
Segment Reporting Information [Line Items]
Premiums										22	35
Services revenue										4	8
Total external revenues										26	43
Intersegment revenues										0	0
Investment income										110	87
Total revenues										136	130
Benefits										77	131
Operating costs										6	12
Merger termination fee and related costs, net											0
Depreciation and amortization										0	0
Total operating expenses										83	143
Income from operations										53	(13)
Loss on sale of business										0
Interest expense										0	0
Other (income) expense, net										0
Income before income taxes and equity in net earnings										53	(13)
Equity in net earnings of Kindred at Home										0	0
Segment earnings										53	(13)
Other Businesses | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Total Medicare
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Fully-insured
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Specialty
Segment Reporting Information [Line Items]
Premiums										0	0
Other Businesses | Medicaid and other
Segment Reporting Information [Line Items]
Premiums										22	35
Other Businesses | Provider
Segment Reporting Information [Line Items]
Services revenue										0	0
Other Businesses | ASO and other
Segment Reporting Information [Line Items]
Services revenue										4	8
Other Businesses | Pharmacy
Segment Reporting Information [Line Items]
Services revenue										0	0
Other Businesses | Services
Segment Reporting Information [Line Items]
Intersegment revenues										0	0
Other Businesses | Products
Segment Reporting Information [Line Items]
Intersegment revenues										0	0
Eliminations/Corporate
Segment Reporting Information [Line Items]
Premiums									0	0	0
Services revenue									0	0	0
Total external revenues									0	0	0
Intersegment revenues									(25,167)	(23,188)	(23,605)
Investment income									281	211	158
Total revenues									(24,886)	(22,977)	(23,447)
Benefits									(503)	(470)	(760)
Operating costs									(24,428)	(22,527)	(22,376)
Merger termination fee and related costs, net											(936)
Depreciation and amortization									(109)	(116)	(100)
Total operating expenses									(25,040)	(23,113)	(24,172)
Income from operations									154	136	725
Loss on sale of business										786
Interest expense									242	218	242
Other (income) expense, net									(506)	33
Income before income taxes and equity in net earnings									418	(901)	483
Equity in net earnings of Kindred at Home									0	0	0
Segment earnings									418	(901)	483
Eliminations/Corporate | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Total Medicare
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Fully-insured
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Specialty
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Medicaid and other
Segment Reporting Information [Line Items]
Premiums									0	0	0
Eliminations/Corporate | Provider
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Eliminations/Corporate | ASO and other
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Eliminations/Corporate | Pharmacy
Segment Reporting Information [Line Items]
Services revenue									0	0	0
Eliminations/Corporate | Services
Segment Reporting Information [Line Items]
Intersegment revenues									(18,273)	(16,858)	(17,313)
Eliminations/Corporate | Products
Segment Reporting Information [Line Items]
Intersegment revenues									$ (6,894)	$ (6,330)	$ (6,292)

REINSURANCE - Narrative (Detail

REINSURANCE - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)Reinsurer	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 267	$ 314
Premiums ceded	1,000	976	$ 969
Benefits ceded	$ 881	980	$ 844
Number of reinsurers comprising other reinsurance recoverables balance | Reinsurer	11
Cash and securities in trusts held by certain reinsurers	$ 72
100% Coinsurance Agreements
Effects of Reinsurance [Line Items]
Percentage of coinsurance agreement	100.00%
Reinsurance Recoverables | Reinsurer Concentration Risk
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 267	$ 313
Protective Life Insurance Company
Effects of Reinsurance [Line Items]
Reinsurance recoverables	174
All others
Effects of Reinsurance [Line Items]
Reinsurance recoverables	$ 94

QUARTERLY FINANCIAL INFORMATI_3

QUARTERLY FINANCIAL INFORMATION (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 16,295	$ 16,241	$ 16,245	$ 16,107	$ 14,168	$ 14,206	$ 14,259	$ 14,279	$ 64,888	$ 56,912	$ 53,767
Income (loss) before income taxes	593	888	1,229	746	436	901	19	707	3,456	2,063	4,020
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Basic earnings per common share (in USD per share)	$ 3.87	$ 5.16	$ 6.96	$ 4.18	$ 2.60	$ 4.68	$ 1.40	$ 3.56	$ 20.20	$ 12.24	$ 16.94
Diluted earnings per common share (in USD per share)	$ 3.84	$ 5.14	$ 6.94	$ 4.16	$ 2.58	$ 4.65	$ 1.39	$ 3.53	$ 20.10	$ 12.16	$ 16.81

SCHEDULE I - PARENT COMPANY F_2

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Balance Sheets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 4,054	$ 2,343
Investment securities	10,972	10,026
Other current assets	3,806	3,564
Total current assets	19,888	16,948
Property and equipment, net	1,955	1,735
Equity method investment in Kindred at Home	1,063	1,047
Other long-term assets	1,834	1,375
Total assets	29,074	25,413
Current liabilities:
Total current liabilities	10,929	10,077
Long-term debt	4,967	4,375
Other long-term liabilities	935	581
Total liabilities	17,037	15,252
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,629,992 shares issued at December 31, 2019 and 198,594,841 shares issued at December 31, 2018	33	33
Capital in excess of par value	2,820	2,535
Retained earnings	17,483	15,072
Accumulated other comprehensive income (loss)	156	(159)
Treasury stock, at cost, 66,524,771 shares at December 31, 2019 and 63,028,169 shares at December 31, 2018	(8,455)	(7,320)
Total stockholders’ equity	12,037	10,161	$ 9,842	$ 10,685
Total liabilities and stockholders’ equity	29,074	25,413
Parent Company
Current assets:
Cash and cash equivalents	1,006	265
Investment securities	355	313
Receivable from operating subsidiaries	1,248	1,306
Other current assets	778	628
Total current assets	3,387	2,512
Property and equipment, net	1,403	1,209
Investments in subsidiaries	14,763	16,951
Equity method investment in Kindred at Home	1,063	1,047
Other long-term assets	778	359
Total assets	21,394	22,078
Current liabilities:
Payable to operating subsidiaries	1,975	4,487
Current portion of notes payable to operating subsidiaries	36	28
Book overdraft	40	38
Short-term debt	699	1,694
Other current liabilities	1,128	791
Total current liabilities	3,878	7,038
Long-term debt	4,967	4,375
Other long-term liabilities	512	504
Total liabilities	9,357	11,917
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,629,992 shares issued at December 31, 2019 and 198,594,841 shares issued at December 31, 2018	33	33
Capital in excess of par value	2,820	2,535
Retained earnings	17,483	15,072
Accumulated other comprehensive income (loss)	156	(159)
Treasury stock, at cost, 66,524,771 shares at December 31, 2019 and 63,028,169 shares at December 31, 2018	(8,455)	(7,320)
Total stockholders’ equity	12,037	10,161
Total liabilities and stockholders’ equity	$ 21,394	$ 22,078

SCHEDULE I - PARENT COMPANY F_3

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Balance Sheets Share Data) (Details) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par (in USD per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par (in USD per share)	$ 0.1667	$ 0.1667
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	198,629,992	198,594,841
Treasury stock (in shares)	66,524,771	63,028,169
Parent Company
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par (in USD per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Common stock, par (in USD per share)	$ 0.1667	$ 0.1667
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	198,629,992	198,594,841
Treasury stock (in shares)	66,524,771	63,028,169

SCHEDULE I - PARENT COMPANY F_4

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues	$ 16,295	$ 16,241	$ 16,245	$ 16,107	$ 14,168	$ 14,206	$ 14,259	$ 14,279	$ 64,888	$ 56,912	$ 53,767
Expenses:
Operating costs									7,381	7,525	6,567
Merger termination fee and related costs, net									0	0	(936)
Depreciation									505	444	410
Interest									242	218	242
Other expense, net									(506)	33	0
Loss on sale of business									0	786	0
(Benefit) provision for income taxes									763	391	1,572
Equity in net earnings of Kindred at Home									14	11	0
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	2,707	1,683	2,448
Parent Company
Revenues:
Management fees charged to operating subsidiaries									1,789	1,666	1,864
Investment and other income, net									28	30	57
Total revenues									1,817	1,696	1,921
Expenses:
Operating costs									1,578	1,468	1,801
Merger termination fee and related costs, net									0	0	(936)
Depreciation									387	342	332
Interest									242	218	243
Total operating expenses									2,207	2,028	1,440
Other expense, net									(507)	33	0
Loss on sale of business									0	782	0
(Loss) income before income taxes and equity in net earnings of subsidiaries									117	(1,147)	481
(Benefit) provision for income taxes									27	(542)	61
(Loss) income before equity in net earnings of subsidiaries									90	(605)	420
Equity in net earnings of subsidiaries									2,603	2,277	2,028
Equity in net earnings of Kindred at Home									14	11	0
Net income									$ 2,707	$ 1,683	$ 2,448

SCHEDULE I - PARENT COMPANY F_5

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net income	$ 512	$ 689	$ 940	$ 566	$ 355	$ 644	$ 193	$ 491	$ 2,707	$ 1,683	$ 2,448
Other comprehensive income (loss):
Change in gross unrealized investment losses/gains									450	(189)	149
Effect of income taxes									(105)	51	(55)
Total change in unrealized investment gains/losses, net of tax									345	(138)	94
Reclassification adjustment for net realized gains included in investment income									(34)	(53)	(14)
Effect of income taxes									8	17	5
Total reclassification adjustment, net of tax									(26)	(36)	(9)
Other comprehensive income (loss), net of tax									319	(174)	85
Comprehensive income attributable to our equity method investment in Kindred at Home									(4)	(4)	0
Comprehensive income									3,022	1,505	2,533
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net income									2,707	1,683	2,448
Other comprehensive income (loss):
Change in gross unrealized investment losses/gains									450	(189)	149
Effect of income taxes									(105)	51	(55)
Total change in unrealized investment gains/losses, net of tax									345	(138)	94
Reclassification adjustment for net realized gains included in investment income									(34)	(53)	(14)
Effect of income taxes									8	17	5
Total reclassification adjustment, net of tax									(26)	(36)	(9)
Other comprehensive income (loss), net of tax									319	(174)	85
Comprehensive income attributable to our equity method investment in Kindred at Home									(4)	(4)	0
Comprehensive income									$ 3,022	$ 1,505	$ 2,533

SCHEDULE I - PARENT COMPANY F_6

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 5,284	$ 2,173	$ 4,051
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	(354)	(31)
Purchase of equity method investment in Kindred at Home	0	(1,095)	0
Purchases of investment securities	(6,361)	(4,687)	(6,265)
Proceeds from sale of investment securities	4,086	3,494	2,768
Maturities of investment securities	1,733	972	1,111
Purchases of property and equipment, net	(736)	(612)	(524)
Net cash used in investing activities	(1,278)	(3,087)	(2,941)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	987	0	1,779
(Repayments) proceeds from issuance of commercial paper, net	(360)	485	(153)
Proceeds from term loan	0	1,000	0
Repayment of term loan	(650)	(350)	0
Repayment of long-term debt	(400)	0	(800)
Change in book overdraft	54	30	(71)
Common stock repurchases	(1,070)	(1,090)	(3,365)
Dividends paid	(291)	(265)	(220)
Proceeds From Stock Options Exercised And Other	58	45	62
Net cash used in financing activities	(2,295)	(785)	(945)
Increase (decrease) in cash and cash equivalents	1,711	(1,699)	165
Cash and cash equivalents at beginning of period	2,343	4,042	3,877
Cash and cash equivalents at end of period	4,054	2,343	4,042
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	3,529	2,719	2,423
Cash flows from investing activities:
Acquisitions, net of cash acquired	0	(354)	0
Purchase of equity method investment in Kindred at Home	0	(1,095)	0
Capital contributions to operating subsidiaries	(423)	(697)	(695)
Purchases of investment securities	(204)	(145)	(53)
Proceeds from sale of investment securities	15	35	0
Maturities of investment securities	134	59	51
Purchases of property and equipment, net	(585)	(465)	(359)
Net cash used in investing activities	(1,063)	(2,662)	(1,056)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	987	0	1,779
(Repayments) proceeds from issuance of commercial paper, net	(360)	485	(153)
Proceeds from term loan	0	1,000	0
Repayment of term loan	(650)	(350)	0
Repayment of long-term debt	(400)	0	(800)
Change in book overdraft	2	(3)	3
Common stock repurchases	(1,070)	(1,090)	(3,365)
Dividends paid	(291)	(265)	(220)
Proceeds From Stock Options Exercised And Other	57	48	62
Net cash used in financing activities	(1,725)	(175)	(2,694)
Increase (decrease) in cash and cash equivalents	741	(118)	(1,327)
Cash and cash equivalents at beginning of period	265	383	1,710
Cash and cash equivalents at end of period	$ 1,006	$ 265	$ 383

SCHEDULE I - PARENT COMPANY F_7

SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Notes to Condensed Financial Statements) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Information Disclosure [Abstract]
Cash dividends received from subsidiary	$ 1.8	$ 2.3	$ 1.4
Aggregate statutory capital and surplus in our state regulated insurance subsidiaries	8	7.6
Aggregate minimum regulatory requirements of statutory capital and surplus	5.9	5.2
Dividends that may be paid to the parent company without prior approval by state regulatory authorities in 2014	1
Dividends that were paid to the parent company without prior approval by state regulatory authorities	$ 1.8	$ 2.3	$ 1.4

SCHEDULE II - VALUATION AND Q_2

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for loss on receivables:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 79	$ 96	$ 118
Acquired/(Disposed) Balances	0	0	0
Charged (Credited) to Costs and Expenses	(1)	36	20
Charged to Other Accounts	0	(29)	(10)
Deductions or Write-offs	(9)	(24)	(32)
Balance at End of Period	69	79	96
Deferred tax asset valuation allowance:
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	54	49	49
Acquired/(Disposed) Balances	0	0	0
Charged (Credited) to Costs and Expenses	9	(5)	0
Charged to Other Accounts	0	0	0
Deductions or Write-offs	0	0	0
Balance at End of Period	$ 45	$ 54	$ 49