Humana (HUM) 10-Q 7 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2018shares
Document And Entity Information [Abstract]
Entity Registrant Name	HUMANA INC
Entity Central Index Key	49,071
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	HUM
Entity Common Stock, Shares Outstanding	137,186,880

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 4,142	$ 4,042
Investment securities	9,695	9,557
Receivables, less allowance for doubtful accounts of $92 in 2018 and $96 in 2017	1,062	854
Other current assets	4,178	2,949
Total current assets	19,077	17,402
Property and equipment, net	1,685	1,584
Long-term investment securities	405	2,745
Equity method investment in Kindred at Home	1,048	0
Goodwill	3,895	3,281
Other long-term assets	1,380	2,166
Total assets	27,490	27,178
Current liabilities:
Benefits payable	5,020	4,668
Trade accounts payable and accrued expenses	5,413	4,069
Book overdraft	199	141
Unearned revenues	294	378
Short-term debt	398	150
Total current liabilities	11,324	9,406
Long-term debt	4,774	4,770
Future policy benefits payable	196	2,923
Other long-term liabilities	603	237
Total liabilities	16,897	17,336
Commitments and contingencies (Note 14)
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; 198,593,361 shares issued at September 30, 2018 and 198,572,458 shares issued at December 31, 2017	33	33
Capital in excess of par value	2,707	2,445
Retained earnings	14,786	13,670
Accumulated other comprehensive (loss) income	(206)	19
Treasury stock, at cost, 61,406,481 shares at September 30, 2018 and 60,893,762 shares at December 31, 2017	(6,727)	(6,325)
Total stockholders’ equity	10,593	9,842
Total liabilities and stockholders’ equity	$ 27,490	$ 27,178

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 92	$ 96
Preferred stock, par (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par (in dollars per share)	$ 0.1667	$ 0.1667
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	198,593,361	198,572,458
Treasury stock, shares (in shares)	61,406,481	60,893,762

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Premiums	$ 13,712	$ 12,955	$ 41,236	$ 39,556
Services	381	223	1,090	706
Investment income	113	104	418	316
Total revenues	14,206	13,282	42,744	40,578
Operating expenses:
Benefits	11,243	10,642	34,449	32,857
Operating costs	1,900	1,688	5,410	4,694
Merger termination fee and related costs, net	0	0	0	(947)
Depreciation and amortization	102	94	302	278
Total operating expenses	13,245	12,424	40,161	36,882
Income (loss) from operations	961	858	2,583	3,696
Loss on sale of business	(4)	0	786	0
Interest expense	53	59	159	166
Other expense, net	11	0	11	0
Income (loss) before income taxes and equity in net earnings	901	799	1,627	3,530
Provision for income taxes	266	300	308	1,266
Equity in net earnings of Kindred at Home	9	0	9	0
Net income	$ 644	$ 499	$ 1,328	$ 2,264
Basic earnings per common share (in dollars per share)	$ 4.68	$ 3.46	$ 9.64	$ 15.56
Diluted earnings per common share (in dollars per share)	4.65	3.44	9.58	15.44
Dividends declared per common share (in dollars per share)	$ 0.5	$ 0.40	$ 1.5	$ 1.20

Condensed Consolidated Statem_2

Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 644	$ 499	$ 1,328	$ 2,264
Other comprehensive (loss) income:
Change in gross unrealized investment gains/losses	(42)	26	(254)	152
Effect of income taxes	10	(9)	64	(56)
Total change in unrealized investment gains/losses, net of tax	(32)	17	(190)	96
Reclassification adjustment for net realized losses (gains)	3	0	(49)	(28)
Effect of income taxes	(1)	0	14	10
Total reclassification adjustment, net of tax	2	0	(35)	(18)
Other comprehensive (loss) income, net of tax	(30)	17	(225)	78
Comprehensive income	$ 614	$ 516	$ 1,103	$ 2,342

Condensed Consolidated Statem_3

Condensed 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	2,264			2,264
Other comprehensive income (loss)	78				78
Common stock repurchases	(1,819)					(1,819)
Dividends and dividend equivalents	(176)			(176)
Stock-based compensation	116		116
Restricted stock unit vesting	0		(100)			100
Stock option exercises	63	$ 0	63
Stock option exercises (in shares)		77
Balances at Sep. 30, 2017	11,211	$ 33	2,641	13,542	12	(5,017)
Balances (in shares) at Sep. 30, 2017		198,572
Balances at Jun. 30, 2017	10,953	$ 33	2,306	13,101	(5)	(4,482)
Balances (in shares) at Jun. 30, 2017		198,570
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	499			499
Other comprehensive income (loss)	17				17
Common stock repurchases	(241)		300			(541)
Dividends and dividend equivalents	(58)			(58)
Stock-based compensation	33		33
Restricted stock unit vesting	0		(6)			6
Stock option exercises	8	$ 0	8
Stock option exercises (in shares)		2
Balances at Sep. 30, 2017	11,211	$ 33	2,641	13,542	12	(5,017)
Balances (in shares) at Sep. 30, 2017		198,572
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	1,328			1,328
Other comprehensive income (loss)	(225)
Other comprehensive loss	(229)			(4)	(225)
Common stock repurchases	(294)		200			(494)
Dividends and dividend equivalents	(208)			(208)
Stock-based compensation	105		105
Restricted stock unit vesting	0		(92)			92
Stock option exercises	49	$ 0	49
Stock option exercises (in shares)		21
Balances at Sep. 30, 2018	10,593	$ 33	2,707	14,786	(206)	(6,727)
Balances (in shares) at Sep. 30, 2018		198,593
Balances at Jun. 30, 2018	10,211	$ 33	2,672	14,211	(176)	(6,529)
Balances (in shares) at Jun. 30, 2018		198,591
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	644			644
Other comprehensive income (loss)	(30)				(30)
Common stock repurchases	(201)					(201)
Dividends and dividend equivalents	(69)			(69)
Stock-based compensation	35		35
Restricted stock unit vesting	0		(3)			3
Stock option exercises	3	$ 0	3
Stock option exercises (in shares)		2
Balances at Sep. 30, 2018	$ 10,593	$ 33	$ 2,707	$ 14,786	$ (206)	$ (6,727)
Balances (in shares) at Sep. 30, 2018		198,593

Condensed Consolidated Statem_4

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income	$ 1,328	$ 2,264
Adjustments to reconcile net income to net cash provided by operating activities:
Loss on sale of business	786	0
Net realized capital gains	(90)	(28)
Equity in net earnings of Kindred at Home	(9)	0
Stock-based compensation	105	116
Depreciation	330	303
Other intangible amortization	70	54
Provision (benefit) for deferred income taxes	165	(54)
Changes in operating assets and liabilities, net of effect of businesses acquired and dispositions:
Receivables	(211)	358
Other assets	(939)	(369)
Benefits payable	410	396
Other liabilities	548	641
Unearned revenues	(84)	3,167
Other, net	97	114
Net cash provided by operating activities	2,506	6,962
Cash flows from investing activities
Cash transferred in sale of business	(805)	0
Acquisitions, net of cash acquired	(354)	(10)
Acquisition, equity method investment in Kindred at Home	(1,095)	0
Purchases of property and equipment, net	(436)	(376)
Purchases of investment securities	(3,379)	(4,337)
Maturities of investment securities	815	919
Proceeds from sales of investment securities	2,614	2,028
Net cash used in investing activities	(2,640)	(1,776)
Cash flows from financing activities
Receipts from contract deposits, net	378	1,931
Proceeds from issuance of senior notes, net	0	985
Proceeds (repayment) from issuance of commercial paper, net	240	(153)
Change in book overdraft	58	(41)
Common stock repurchases	(294)	(1,819)
Dividends paid	(195)	(162)
Proceeds from stock option exercises and other	47	61
Net cash provided by financing activities	234	802
Increase in cash and cash equivalents	100	5,988
Cash and cash equivalents at beginning of period	4,042	3,877
Cash and cash equivalents at end of period	4,142	9,865
Supplemental cash flow disclosures:
Interest payments	120	124
Income tax payments, net	$ 511	$ 1,206

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION AND SIGNIFICANT EVENTS	BASIS OF PRESENTATION AND SIGNIFICANT EVENTS The accompanying condensed consolidated financial statements are presented in accordance with generally accepted accounting principles for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the disclosures normally required by accounting principles generally accepted in the United States of America, or GAAP, or those normally made in an Annual Report on Form 10-K. The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. For further information, the reader of this Form 10-Q should refer to our Form 10-K for the year ended December 31, 2017 , that was filed with the Securities and Exchange Commission, or the SEC, on February 16, 2018 . We refer to the Form 10-K as the “ 2017 Form 10-K” in this document. References throughout this document to “we,” “us,” “our,” “Company,” and “Humana” mean Humana Inc. and its subsidiaries. The preparation of our condensed consolidated financial statements in accordance with GAAP requires us to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. The areas involving the most significant use of estimates are the estimation of benefits payable, future policy 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. Refer to Note 2 to the consolidated financial statements included in our 2017 Form 10-K for information on accounting policies that we consider in preparing our consolidated financial statements. The financial information has been prepared in accordance with our customary accounting practices and has not been audited. In our opinion, the information presented reflects all adjustments necessary for a fair statement of interim results. All such adjustments are of a normal and recurring nature. Workforce Optimization During the third quarter of 2017, we initiated a voluntary early retirement program and an involuntary workforce reduction program . These programs impacted approximately 3,600 associates, or 7.8% , of our workforce in 2017. As a result, in 2017 we recorded charges of $148 million , or $0.64 per diluted common share. At December 31, 2017, $140 million was classified as a current liability, included in our condensed consolidated balance sheet in the trade accounts payable and accrued expenses line. Payments under these programs are being made upon termination during the early retirement or severance pay period . The remaining workforce optimization liability at September 30, 2018 was $29 million and is expected to be substantially paid in 2018. 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." Revenue Recognition Our revenues include premium and service revenues. Service revenues include administrative service fees that are recorded based upon established per member per month rates and the number of members for the month and are recognized as services are provided for the month. Additionally, service revenues include net patient service revenues that are recorded based upon established billing rates, less allowances for contractual adjustments, and are recognized as services are provided. For more information about our revenues, refer to Note 2 to the consolidated financial statements included in our 2017 Form 10-K for information on accounting policies that we consider in preparing our consolidated financial statements. See Note 15 for disaggregation of revenue by segment and type. At September 30, 2018 , accounts receivable related to services were $ 148 million . For the three and nine months ended September 30, 2018 , we had no material bad-debt expense and there were no material contract assets, contract liabilities or deferred contract costs recorded on the condensed consolidated balance sheet at September 30, 2018 . For the three and nine months ended September 30, 2018 , 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.

RECENTLY ISSUED ACCOUNTING PRON

RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS	9 Months Ended
	Sep. 30, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS	RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS In May 2014, the Financial Accounting Standards Board, or FASB, issued new guidance that amends the accounting for revenue recognition. The amendments are intended to provide a more robust framework for addressing revenue issues, improve comparability of revenue recognition practices, and improve disclosure requirements. Insurance contracts are not included in the scope of this new guidance. Accordingly, our premiums revenue and investment income, collectively representing approximately 97% of our consolidated external revenues for the three and nine months ended September 30, 2018 , are not included in the scope of the new guidance. We adopted the new standard effective January 1, 2018, using the modified retrospective approach. As the majority of our revenues are not subject to the new guidance and the remaining revenues’ accounting treatment did not materially differ from pre-existing accounting treatment, the adoption of the new standard did not have a material impact on our consolidated results of operations, financial condition, cash flows, or related disclosures. 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). The new guidance is effective for us beginning with annual and interim periods in 2019, with earlier adoption permitted. We expect to adopt the guidance that allows us not to adjust comparative periods and record a cumulative effect adjustment, if any, to retained earnings. We are in the process of implementing a new lease accounting system and expect to record significant leased assets and corresponding lease obligations based on our existing population of individual leases. We do not expect a material impact on our results of operations or cash flows. 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 of available-for-sale debt securities. We are currently evaluating the impact on our results of operations, financial condition, and cash flows. 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 is effective for us beginning with annual and interim periods in 2019. We do not expect adoption of this guidance will have a material impact on our results of operations, financial condition and 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. In September 2018, the FASB issued new guidance related to accounting for long-duration contracts of insurers which revises key elements of the measurement models and disclosure requirements for long-duration contracts issued by insurers and reinsurers. The new guidance is effective for us beginning with annual and interim periods in 2021, with earlier adoption permitted, and requires retrospective application to previously issued annual and interim financial statements. We are currently evaluating the impact on our results of operations, financial position and cash flows. There are no other recently issued accounting standards that apply to us or that are expected to have a material impact on our results of operations, financial condition, or cash flows.

ACQUISITIONS AND DIVESTITURES

ACQUISITIONS AND DIVESTITURES	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
ACQUISITIONS AND DIVESTITURES	ACQUISITIONS AND DIVESTITURES Acquisition of a 40% Minority Interest in Kindred’s Homecare Business and Curo Health Services On July 2, 2018, we completed the acquisition of a 40% minority interest in the Kindred at Home Division, or Kindred at Home, of Kindred Healthcare, Inc., or Kindred, for cash consideration of approximately $850 million , including our share of transaction and related expenses. TPG Capital, or TPG, and Welsh, Carson, Anderson & Stowe, or WCAS, collectively, the Sponsors, along with us jointly created a consortium to purchase all of the outstanding and issued securities of Kindred. Immediately following the closing of that transaction, Kindred at Home and the Specialty Hospital company were separated, with the result being that the Long Term Acute Care and Rehabilitation businesses (the Specialty Hospital Company) is owned by the Sponsors and Kindred at Home is owned by a joint venture owned by the Sponsors and us. On July 11, 2018, we, along with the same Kindred at Home Sponsors, TPG and WCAS, collectively referred to as the "Consortium," completed the acquisition of privately-held Curo Health Services, or Curo, one of the nation's leading hospice operators providing care to patients at 245 locations in 22 states. The transaction was structured as a merger of Curo with the hospice business of Kindred at Home, and we thereby purchased a 40% minority interest in Curo for cash consideration of approximately $250 million . We account for our 40% investment in Kindred at Home using the equity method of accounting. Investments accounted for under the equity method are initially recorded at cost and subsequently adjusted to our share of the net income or loss from Kindred at Home. This investment is reflected as "Equity method investment in Kindred at Home" in our condensed consolidated balance sheets, with our share of income or loss as "Equity in net earnings of Kindred at Home" in our condensed consolidated statements of income. We entered into a shareholders agreement with the Sponsors that provide 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 year four and ending at the end of year five following the closing. The put and call options, which 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. Both options are exercisable at a fixed EBITDA multiple. 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 $221 million and $265 million , respectively, at September 30, 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 is reflected as "Other expense, net" in our condensed consolidated statements of income. Sale of Closed Block of Commercial Long-Term Care Insurance Business On August 9, 2018, we completed the sale of our wholly-owned subsidiary, KMG America Corporation, or 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, includes 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 which is reported as loss on sale of business in the accompanying condensed consolidated statements of income for the nine months ended September 30, 2018. We recorded a $430 million income tax benefit resulting from the loss which is included in the accompanying condensed consolidated statements of income for the nine months ended September 30, 2018. During the nine months ended September 30, 2018, 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 for the nine months ended September 30, 2018 and 2017 were $182 million and $199 million , respectively. For the nine months ended September 30, 2018 and 2017 KMG pretax income was $47 million and pretax loss was $15 million , respectively. KMG revenues and pretax loss for the three months ended September 30, 2017 were $66 million and $5 million , respectively, and were not material for the three months ended September 30, 2018. 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 On March 1, 2018, we acquired the remaining equity interest in MCCI Holdings, LLC, or MCCI, a privately held management service organization 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 preliminary purchase price allocation to goodwill of $479 million , other intangible assets of $80 million , and net tangible assets of $27 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 expenses for tax purposes. On April 10, 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 preliminary purchase price allocation to goodwill of $135 million , other intangible assets of $38 million and net tangible assets of $17 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 preliminary, subject to completion of valuation analysis, including for example, refining assumptions used to calculate the fair value of intangible assets. During 2018 and 2017 , we also 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 condensed consolidated statements of income and condensed consolidated balance sheets from the respective acquisition dates. Acquisition-related costs recognized in 2018 and 2017 were not material to our results of operations. 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.

INVESTMENT SECURITIES

INVESTMENT SECURITIES	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
INVESTMENT SECURITIES	INVESTMENT SECURITIES Investment securities classified as current and long-term were as follows at September 30, 2018 and December 31, 2017 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) September 30, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 649 $ — $ (5 ) $ 644 Mortgage-backed securities 2,418 — (89 ) 2,329 Tax-exempt municipal securities 2,920 2 (65 ) 2,857 Mortgage-backed securities: Residential 57 — (1 ) 56 Commercial 528 — (18 ) 510 Asset-backed securities 686 — (2 ) 684 Corporate debt securities 3,111 2 (93 ) 3,020 Total debt securities $ 10,369 $ 4 $ (273 ) $ 10,100 December 31, 2017 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 532 $ 1 $ (2 ) $ 531 Mortgage-backed securities 1,625 4 (19 ) 1,610 Tax-exempt municipal securities 3,884 33 (28 ) 3,889 Mortgage-backed securities: Residential 26 — — 26 Commercial 455 3 (2 ) 456 Asset-backed securities 407 1 — 408 Corporate debt securities 5,175 244 (37 ) 5,382 Total debt securities $ 12,104 $ 286 $ (88 ) $ 12,302 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 September 30, 2018 and December 31, 2017 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) September 30, 2018 U.S. Treasury and other U.S. U.S. Treasury and agency $ 476 $ (1 ) $ 143 $ (4 ) $ 619 $ (5 ) Mortgage-backed 1,661 (52 ) 642 (37 ) 2,303 (89 ) Tax-exempt municipal 1,578 (29 ) 1,120 (36 ) 2,698 (65 ) Mortgage-backed securities: Residential 56 (1 ) 1 — 57 (1 ) Commercial 407 (13 ) 74 (5 ) 481 (18 ) Asset-backed securities 480 (2 ) 15 — 495 (2 ) Corporate debt securities 1,835 (43 ) 882 (50 ) 2,717 (93 ) Total debt securities $ 6,493 $ (141 ) $ 2,877 $ (132 ) $ 9,370 $ (273 ) December 31, 2017 U.S. Treasury and other U.S. U.S. Treasury and agency $ 273 $ (1 ) $ 130 $ (1 ) $ 403 $ (2 ) Mortgage-backed 581 (2 ) 672 (17 ) 1,253 (19 ) Tax-exempt municipal 1,590 (16 ) 661 (12 ) 2,251 (28 ) Mortgage-backed securities: Residential 20 — 3 — 23 — Commercial 131 (1 ) 28 (1 ) 159 (2 ) Asset-backed securities 107 — 10 — 117 — Corporate debt securities 1,297 (10 ) 804 (27 ) 2,101 (37 ) Total debt securities $ 3,999 $ (30 ) $ 2,308 $ (58 ) $ 6,307 $ (88 ) Approximately 97% of our debt securities were investment-grade quality, with a weighted average credit rating of AA+ by Standard & Poor's Rating Service, or S&P, at September 30, 2018 . 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 9% . In addition, 2% of our tax-exempt securities were insured by bond insurers and had an equivalent weighted average S&P credit rating of AA exclusive of the bond insurers’ guarantee. Our investment policy limits investments in a single issuer and requires diversification among various asset types. Our unrealized losses from all securities were generated from approximately 1,250 positions out of a total of approximately 1,520 positions at September 30, 2018 . All issuers of securities we own that were trading at an unrealized loss at September 30, 2018 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 September 30, 2018 , 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 September 30, 2018 . The detail of realized gains (losses) related to investment securities and included within investment income was as follows for the three and nine months ended September 30, 2018 and 2017 : Three months ended Nine months ended 2018 2017 2018 2017 (in millions) Gross realized gains $ 10 $ 3 $ 105 $ 34 Gross realized losses (2 ) (3 ) (15 ) (6 ) Net realized capital gains $ 8 $ — $ 90 $ 28 There were no material other-than-temporary impairments for the three and nine months ended September 30, 2018 or 2017 . The contractual maturities of debt securities available for sale at September 30, 2018 , 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 $ 711 $ 709 Due after one year through five years 3,152 3,092 Due after five years through ten years 2,038 1,962 Due after ten years 779 758 Mortgage and asset-backed securities 3,689 3,579 Total debt securities $ 10,369 $ 10,100

FAIR VALUE

FAIR VALUE	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE	FAIR VALUE Financial Assets The following table summarizes our fair value measurements at September 30, 2018 and December 31, 2017 , respectively, for financial assets measured at fair value on a recurring basis: Fair Value Measurements Using Fair Quoted Prices Other Unobservable (in millions) September 30, 2018 Cash equivalents $ 4,990 $ 4,990 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 644 — 644 — Mortgage-backed securities 2,329 — 2,329 — Tax-exempt municipal securities 2,857 — 2,857 — Mortgage-backed securities: Residential 56 — 56 — Commercial 510 — 510 — Asset-backed securities 684 — 684 — Corporate debt securities 3,020 — 3,020 — Total debt securities 10,100 — 10,100 — Total invested assets $ 15,090 $ 4,990 $ 10,100 $ — December 31, 2017 Cash equivalents $ 4,564 $ 4,564 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 531 — 531 — Mortgage-backed securities 1,610 — 1,610 — Tax-exempt municipal securities 3,889 — 3,889 — Mortgage-backed securities: Residential 26 — 26 — Commercial 456 — 456 — Asset-backed securities 408 — 408 — Corporate debt securities 5,382 — 5,381 1 Total debt securities 12,302 — 12,301 1 Total invested assets $ 16,866 $ 4,564 $ 12,301 $ 1 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 $4,774 million at September 30, 2018 and $4,770 million at December 31, 2017 . The fair value of our senior notes debt was $4,879 million at September 30, 2018 and $5,191 million at December 31, 2017 . The fair value of our long-term 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 commercial paper borrowings. There were outstanding commercial paper borrowings of $398 million as of September 30, 2018 and $150 million as of December 31, 2017 . 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 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 2018 or 2017 .

MEDICARE PART D

MEDICARE PART D	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
MEDICARE PART D	MEDICARE PART D We cover prescription drug benefits in accordance with Medicare Part D under multiple contracts with the Centers for Medicare and Medicaid Services, or CMS, as described further in Note 2 to the consolidated financial statements included in our 2017 Form 10-K. The accompanying condensed consolidated balance sheets include the following amounts associated with Medicare Part D at September 30, 2018 and December 31, 2017 . 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. September 30, 2018 December 31, 2017 Risk CMS Risk CMS (in millions) Other current assets $ 6 $ 268 $ 4 $ 101 Trade accounts payable and accrued expenses (214 ) (1,688 ) (255 ) (1,085 ) Net current liability (208 ) (1,420 ) (251 ) (984 ) Other long-term assets 27 — — — Other long-term liabilities (122 ) — (28 ) — Net long-term liability (95 ) — (28 ) — Total net liability $ (303 ) $ (1,420 ) $ (279 ) $ (984 )

HEALTH CARE REFORM

HEALTH CARE REFORM	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
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) established risk spreading premium stabilization programs effective January 1, 2014, including a permanent risk adjustment program and temporary risk corridor and reinsurance programs, which we collectively refer to as the 3Rs. The 3Rs, applicable to certain of our commercial medical insurance products, are further discussed in Note 2 to our 2017 Form 10-K. The temporary programs were only applicable for years 2014 through 2016. As a result of our exit from our individual commercial medical business effective January 1, 2018, the permanent risk adjustment program is currently only applicable to our commercial small group health insurance business. 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 the Health Care Reform Law, for years 2014, 2015 and 2016. Our case has been stayed by the Court, pending resolution of similar cases filed by other insurers. The accompanying condensed consolidated balance sheets include the following amounts associated with the 3Rs at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Premiums receivable $ 68 $ — $ 62 $ — Other current assets — — — 44 Trade accounts payable and (40 ) — (80 ) — Other long-term assets — — 5 — Total net asset (liability) $ 28 $ — $ (13 ) $ 44 Net payments under the 3Rs were $60 million during the nine months ended September 30, 2018 . Net collections were $307 million during the nine months ended September 30, 2017 . In October 2018, we paid the federal government approximately $1.04 billion for our portion of the annual health insurance industry fee attributed to calendar year 2018 in accordance with the Health Care Reform Law. This fee, fixed in amount by law and apportioned to insurance carriers based on market share, is not deductible for tax purposes. Each year on January 1, except for when the fee is suspended, we record a liability for this fee in trade accounts payable and accrued expenses which we carry until the fee is paid. We record a corresponding deferred cost in other current assets in our condensed consolidated financial statements which is amortized ratably to expense over the calendar year. Amortization of the deferred cost was recorded in operating cost expense of approximately $258 million and $778 million for the three and nine months ended September 30, 2018 , resulting from the amortization of the 2018 annual health insurance industry fee. The annual health insurance industry fee was suspended for calendar year 2017, and is also, under current law, suspended for calendar year 2019 .

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2018
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 nine months ended September 30, 2018 were as follows: Retail Group and Specialty Healthcare Total (in millions) Balance at January 1, 2018 $ 1,059 $ 261 $ 1,961 $ 3,281 Acquisitions 476 — 138 614 Balance at September 30, 2018 $ 1,535 $ 261 $ 2,099 $ 3,895 The following table presents details of our other intangible assets included in other long-term assets in the accompanying condensed consolidated balance sheets at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 8.7 years $ 646 $ 419 $ 227 $ 566 $ 401 $ 165 Trade names and 6.4 years 84 82 2 104 84 20 Provider contracts 11.9 years 68 36 32 68 30 38 Noncompetes and 7.3 years 29 27 2 32 29 3 Total other intangible 8.7 years $ 827 $ 564 $ 263 $ 770 $ 544 $ 226 Amortization expense for other intangible assets was approximately $19 million for the three months ended September 30, 2018 and $18 million for the three months ended September 30, 2017 . For the nine months ended September 30, 2018 and 2017 , amortization expense for other intangible assets was approximately $70 million and $54 million , respectively. Amortization expense for the nine months ended September 30, 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 2018 and each of the five next succeeding years: (in millions) For the years ending December 31, 2018 $ 90 2019 70 2020 67 2021 34 2022 31 2023 18

BENEFITS PAYABLE

BENEFITS PAYABLE	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
BENEFITS PAYABLE	BENEFITS PAYABLE On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 4,668 $ 4,563 Less: Reinsurance recoverables (70 ) (76 ) Balances, beginning of period, net 4,598 4,487 Incurred related to: Current year 34,915 33,318 Prior years (467 ) (430 ) Total incurred 34,448 32,888 Paid related to: Current year (30,204 ) (28,741 ) Prior years (3,920 ) (3,745 ) Total paid (34,124 ) (32,486 ) Reinsurance recoverable 98 70 Balances, end of period $ 5,020 $ 4,959 Amounts incurred related to prior periods 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). 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. Benefits expense excluded from the previous table was as follows for the nine months ended September 30, 2018 and 2017 . For the nine months ended September 30, 2018 2017 (in millions) Future policy benefits: Individual Commercial $ (14 ) $ (67 ) Other Businesses 15 36 Total future policy benefits $ 1 $ (31 ) Incurred and Paid Claims Development The following discussion provides information about incurred and paid claims development for our Retail, Group and Specialty, and Individual Commercial segments as of September 30, 2018 and 2017 , net of reinsurance, and the total of IBNR included within the net incurred claims amounts. Retail Segment Activity in benefits payable for our Retail segment was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 3,963 $ 3,507 Less: Reinsurance recoverables (70 ) (76 ) Balances, beginning of period, net 3,893 3,431 Incurred related to: Current year 31,209 29,356 Prior years (367 ) (339 ) Total incurred 30,842 29,017 Paid related to: Current year (27,062 ) (25,460 ) Prior years (3,334 ) (2,822 ) Total paid (30,396 ) (28,282 ) Reinsurance recoverable 98 70 Balances, end of period $ 4,437 $ 4,236 At September 30, 2018 , benefits payable for our Retail segment included IBNR of approximately $2.8 billion , primarily associated with claims incurred in 2018. Group and Specialty Segment Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 568 $ 578 Incurred related to: Current year 4,018 3,996 Prior years (41 ) (44 ) Total incurred 3,977 3,952 Paid related to: Current year (3,462 ) (3,452 ) Prior years (509 ) (517 ) Total paid (3,971 ) (3,969 ) Balances, end of period $ 574 $ 561 At September 30, 2018 , benefits payable for our Group and Specialty segment included IBNR of approximately $490 million , primarily associated with claims incurred in 2018. Individual Commercial Segment Activity in benefits payable for our Individual Commercial segment was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 101 $ 454 Incurred related to: Current year — 502 Prior years (58 ) (46 ) Total incurred (58 ) 456 Paid related to: Current year — (393 ) Prior years (34 ) (383 ) Total paid (34 ) (776 ) Balance, end of period $ 9 $ 134 At September 30, 2018 , benefits payable for our Individual Commercial segment included IBNR of approximately $2 million , associated with claims incurred in 2017 and prior. 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: Reconciliation of the Disclosure of Incurred and Paid Claims Development to Benefits Payable, net of reinsurance September 30, 2018 Net outstanding liabilities Retail $ 4,339 Group and Specialty 574 Individual Commercial 9 Other Businesses — Benefits payable, net of reinsurance 4,922 Reinsurance recoverable on unpaid claims Retail 98 Total benefits payable, gross $ 5,020

EARNINGS PER COMMON SHARE COMPU

EARNINGS PER COMMON SHARE COMPUTATION	9 Months Ended
	Sep. 30, 2018
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 three and nine months ended September 30, 2018 and 2017 : Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 644 $ 499 $ 1,328 $ 2,264 Weighted average outstanding shares of common stock 137,709 144,215 137,792 145,546 Dilutive effect of: Employee stock options 186 165 199 174 Restricted stock 783 980 704 902 Shares used to compute diluted earnings per common share 138,678 145,360 138,695 146,622 Basic earnings per common share $ 4.68 $ 3.46 $ 9.64 $ 15.56 Diluted earnings per common share $ 4.65 $ 3.44 $ 9.58 $ 15.44 Number of antidilutive stock options and restricted stock 36 399 284 595

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Dividends The following table provides details of dividend payments, excluding dividend equivalent rights for unvested stock awards, in 2017 and 2018 under our Board approved quarterly cash dividend policy: Record Payment Amount Total (in millions) 2017 payments 1/12/2017 1/27/2017 $ 0.29 $ 43 3/31/2017 4/28/2017 $ 0.40 $ 58 6/30/2017 7/31/2017 $ 0.40 $ 58 9/29/2017 10/27/2017 $ 0.40 $ 57 2018 payments 12/29/2017 1/26/2018 $ 0.40 $ 55 3/30/2018 4/27/2018 $ 0.50 $ 69 6/29/2018 7/27/2018 $ 0.50 $ 69 9/28/2018 10/26/2018 $ 0.50 $ 69 On November 2, 2018 , the Board declared a cash dividend of $0.50 per share payable on January 25, 2019 , to stockholders of record on December 31, 2018 . Stock Repurchases 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. Under the share repurchase authorization, shares may be 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 December 21, 2017 , we entered into an accelerated stock repurchase agreement, or ASR, 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 authorization from our Board of Directors. 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 reflects 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 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. Excluding the 0.46 million shares received in March 2018 upon final settlement of our ASR Agreement for which no cash was paid during the period, as well as any prior year ASR activity, share repurchases were as follows during the nine months ended September 30, 2018 and 2017 : Nine months ended September 30, 2018 2017 Authorization Date Purchase Not to Exceed Shares Cost Shares Cost (in millions) February 2017 $ 2,250 — $ — 0.96 $ 240 December 2017 $ 3,000 0.68 224 — — Total repurchases 0.68 $ 224 0.96 $ 240 Our remaining repurchase authorization was approximately $1.8 billion as of November 6, 2018. In connection with employee stock plans, we acquired 0.26 million common shares for $70 million and 0.37 million common shares for $79 million during the nine months ended September 30, 2018 and 2017 , respectively. Treasury Stock Reissuance We reissued 0.87 million shares of treasury stock during the nine months ended September 30, 2018 at a cost of $92 million associated with restricted stock unit vestings and option exercises. Accumulated Other Comprehensive Income Accumulated other comprehensive income included net unrealized losses, net of tax, on our investment securities of $206 million at September 30, 2018 and net unrealized gains, net of tax, on our investment securities of $125 million at December 31, 2017 . In addition, accumulated other comprehensive income included $106 million , net of tax, at December 31, 2017 for an additional liability that would exist on our closed block of long-term care insurance policies if unrealized gains on the sale of the investments backing such products had been realized and the proceeds reinvested at then current yields. Refer to Note 18 to the consolidated financial statements in our 2017 Form 10-K for further discussion of our long-term care insurance policies.

INCOME TAXES

INCOME TAXES	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The effective income tax rate was 29.1% for the three months ended September 30, 2018 , compared to 37.5% for the three months ended September 30, 2017 and was 18.8% for the nine months ended September 30, 2018 , compared to 35.9% for the nine months ended September 30, 2017 , primarily due to the tax benefit recognized from the loss on the sale of KMG and the tax reform law enacted on December 22, 2017 (the "Tax Reform Law") , which was partially offset by the impact of the reinstatement of the non-deductible health insurance industry fee in 2018. The income tax rate for the nine months ended September 30, 2017 included previously non-deductible transaction costs that, as a result of the termination of the Merger Agreement, became deductible for tax purposes. The Tax Reform Law reduced the statutory federal corporate income tax rate to 21 percent from 35 percent, beginning in 2018. The accounting for certain income tax effects of the Tax Reform Law is provisional. Revisions to prior estimates are recorded as additional analysis is completed using information available at each measurement date during 2018, with adjustments to the income tax provision recorded as new information becomes known. Revisions to our prior estimates for the income tax effects of the Tax Reform Law decreased our tax expense for the nine months ended September 30, 2018 by $39.3 million .

DEBT

DEBT	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
DEBT	DEBT The carrying value of long-term debt outstanding, net of unamortized debt issuance costs, was as follows at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in millions) Senior notes: $400 million, 2.625% due October 1, 2019 $ 399 $ 399 $400 million, 2.50% due December 15, 2020 398 397 $400 million, 2.90% due December 15, 2022 396 396 $600 million, 3.15% due December 1, 2022 597 595 $600 million, 3.85% due October 1, 2024 596 595 $600 million, 3.95% due March 15, 2027 595 594 $250 million, 8.15% due June 15, 2038 263 263 $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 395 396 Total long-term debt $ 4,774 $ 4,770 Senior Notes In December 2017, we issued $400 million of 2.50% senior notes due December 15, 2020 and $400 million of 2.90% senior notes due December 15, 2022. Our net proceeds, reduced for the underwriters' discount and commission and offering expenses paid as of December 31, 2017, were $794 million . We used the net proceeds, together with available cash, to fund the redemption of our $300 million aggregate principal amount of 6.30% senior notes maturing in August 2018 and our $500 million aggregate principal amount of 7.20% senior notes maturing in June 2018 at 100% of the principal amount plus applicable premium for early redemption and accrued and unpaid interest to the redemption date, for cash totaling approximately $829 million . We recognized a loss on extinguishment of debt of approximately $17 million in December 2017 for the redemption of these senior notes, which is included in interest expense in the consolidated statements of income. In March 2017, we issued $600 million of 3.95% senior notes due March 15, 2027 and $400 million of 4.80% senior notes due March 15, 2047. Our net proceeds, reduced for the underwriters' discount and commission and offering expenses paid as of March 31, 2017, were $991 million . 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. 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. 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 actual debt to capitalization of 32.8% as measured in accordance with the credit agreement as of September 30, 2018. 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 $500.0 million incremental loan facility. At September 30, 2018 , we had no borrowings and no letters of credit outstanding under the credit agreement . Accordingly, as of September 30, 2018 , we had $2.0 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 nine months ended September 30, 2018 was $442 million . There were outstanding borrowings of $398 million at September 30, 2018 and $150 million at December 31, 2017 .

GUARANTEES AND CONTINGENCIES

GUARANTEES AND CONTINGENCIES	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
GUARANTEES AND CONTINGENCIES	GUARANTEES AND CONTINGENCIES Government Contracts Our Medicare products, which accounted for approximately 80% of our total premiums and services revenue for the nine months ended September 30, 2018 , 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 2019, and all of our product offerings filed with CMS for 2019 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 2017, 25% of the risk score was calculated from claims data submitted through EDS. CMS has revised the pace of the phase-in and, for 2018 and 2019, 15% and 25%, respectively, of the risk score will be calculated from claims data submitted through EDS. 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 is 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 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 RADV contract level audits conducted for contract year 2011 and subsequent years. CMS is currently conducting RADV contract level audits for contract years 2011, 2012, and 2013 in which two, five and five of our Medicare Advantage plans are being audited, respectively. Per CMS guidance, selected MA contracts will be notified of an audit at some point after the close of the final reconciliation for the payment year being audited. 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 are studying the Proposed Rule and CMS’ underlying analysis contained therein. We believe, however, that the Proposed Rule fails to address adequately the statutory requirement of actuarial equivalence, and we expect to provide substantive comments to CMS on the Proposed Rule as part of the notice-and-comment rulemaking process. We are also evaluating the potential impact of the Proposed Rule, if adopted as proposed, which 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. In addition, 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 filed a motion for reconsideration related to certain aspects of the Federal District Court's opinion and has simultaneously filed a notice to appeal 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 September 30, 2018 , our military services business, which accounted for approximately 1% of our total premiums and services revenue for the nine months ended September 30, 2018 , 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 5.9 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. On October 11, 2018, we received notice from the Defense Health Agency of its intent to exercise the second option period under the East Region contract, with delivery of health care services commencing on January 1, 2019. Our state-based Medicaid business accounted for approximately 4% of our total premiums and services revenue for the nine months ended September 30, 2018 . 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 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 we are vigorously defending against these allegations. 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 September 30, 2018. 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. For example, a number of hospitals and other providers have asserted that, under their network provider contracts, we are not entitled to reduce Medicare Advantage payments to these providers in connection with changes in Medicare payment systems and in accordance with the Balanced Budget and Emergency Deficit Control Act of 1985, as amended (commonly referred to as “sequestration”). Those challenges have led and could lead to arbitration demands or other litigation. Also, 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	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION We manage our business with four reportable segments: Retail, Group and Specialty, Healthcare Services and Individual Commercial. In addition, the Other Businesses category includes businesses that are not individually reportable because they do not meet the quantitative thresholds required by generally accepted accounting principles. These 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 to assess performance and allocate resources. The Retail segment consists of Medicare benefits, marketed to individuals or directly via group 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 military services business, primarily our TRICARE T2017 East Region contract. The Healthcare Services segment includes 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 investment in Kindred at Home. The Individual Commercial segment consisted of our individual commercial fully-insured medical health insurance benefits. We report under the category of Other Businesses those businesses that do not align with the reportable segments described above, primarily our closed-block long-term care insurance policies, which were sold. 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 $3.5 billion and $3.6 billion for the three months ended September 30, 2018 and 2017 , respectively. For the nine months ended September 30, 2018 and 2017 these amounts were $9.7 billion and $9.8 billion , respectively. 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 $29 million and $26 million for the three months ended September 30, 2018 and 2017 , respectively. For the nine months ended September 30, 2018 and 2017 , the amount of this expense was $98 million and $79 million , respectively. Other than those described previously, the accounting policies of each segment are the same and are described in Note 2 to the consolidated financial statements included in our 2017 Form 10-K. 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, Group and Specialty, and Individual Commercial 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. Our segment results were as follows for the three and nine months ended September 30, 2018 and 2017 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended September 30, 2018 External revenues Premiums: Individual Medicare Advantage $ 8,912 $ — $ — $ — $ — $ — $ 8,912 Group Medicare Advantage 1,542 — — — — — 1,542 Medicare stand-alone PDP 893 — — — — — 893 Total Medicare 11,347 — — — — — 11,347 Fully-insured 129 1,345 — 1 — — 1,475 Specialty — 325 — — — — 325 Medicaid and other 561 — — — 4 — 565 Total premiums 12,037 1,670 — 1 4 — 13,712 Services revenue: Provider — — 113 — — — 113 ASO and other 1 215 — — — — 216 Pharmacy — — 52 — — — 52 Total services revenue 1 215 165 — — — 381 Total external revenues 12,038 1,885 165 1 4 — 14,093 Intersegment revenues Services — 4 4,214 — — (4,218 ) — Products — — 1,576 — — (1,576 ) — Total intersegment revenues — 4 5,790 — — (5,794 ) — Investment income 35 5 11 — 10 52 113 Total revenues 12,073 1,894 5,966 1 14 (5,742 ) 14,206 Operating expenses: Benefits 10,020 1,347 — (4 ) 12 (132 ) 11,243 Operating costs 1,352 445 5,720 — 2 (5,619 ) 1,900 Depreciation and amortization 67 21 40 — — (26 ) 102 Total operating expenses 11,439 1,813 5,760 (4 ) 14 (5,777 ) 13,245 Income from operations 634 81 206 5 — 35 961 Loss on sale of business — — — — — (4 ) (4 ) Interest expense — — — — — 53 53 Other expense, net — — — — — 11 11 Income (loss) before income taxes and equity in net earnings 634 81 206 5 — (25 ) 901 Equity in net earnings of Kindred at Home — — 9 — — — 9 Segment earnings $ 634 $ 81 $ 215 $ 5 $ — $ (25 ) $ 910 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended September 30, 2017 External revenues Premiums: Individual Medicare Advantage $ 8,077 $ — $ — $ — $ — $ — $ 8,077 Group Medicare Advantage 1,272 — — — — — 1,272 Medicare stand-alone PDP 921 — — — — — 921 Total Medicare 10,270 — — — — — 10,270 Fully-insured 121 1,370 — 224 — — 1,715 Specialty — 331 — — — — 331 Medicaid and other 630 — — — 9 — 639 Total premiums 11,021 1,701 — 224 9 — 12,955 Services revenue: Provider — — 60 — — — 60 ASO and other 2 140 — — 1 — 143 Pharmacy — — 20 — — — 20 Total services revenue 2 140 80 — 1 — 223 Total external revenues 11,023 1,841 80 224 10 — 13,178 Intersegment revenues Services — 5 4,339 — — (4,344 ) — Products — — 1,572 — — (1,572 ) — Total intersegment revenues — 5 5,911 — — (5,916 ) — Investment income 23 7 9 1 22 42 104 Total revenues 11,046 1,853 6,000 225 32 (5,874 ) 13,282 Operating expenses: Benefits 9,294 1,354 — 147 34 (187 ) 10,642 Operating costs 1,081 385 5,726 49 3 (5,556 ) 1,688 Depreciation and amortization 61 21 34 3 — (25 ) 94 Total operating expenses 10,436 1,760 5,760 199 37 (5,768 ) 12,424 Income (loss) from operations 610 93 240 26 (5 ) (106 ) 858 Interest expense — — — — — 59 59 Income (loss) before income taxes and equity in net earnings 610 93 240 26 (5 ) (165 ) 799 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings $ 610 $ 93 $ 240 $ 26 $ (5 ) $ (165 ) $ 799 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Nine months ended September 30, 2018 External revenues Premiums: Individual Medicare Advantage $ 26,790 $ — $ — $ — $ — $ — $ 26,790 Group Medicare Advantage 4,575 — — — — — 4,575 Medicare stand-alone PDP 2,703 — — — — — 2,703 Total Medicare 34,068 — — — — — 34,068 Fully-insured 379 4,083 — 6 — — 4,468 Specialty — 1,014 — — — — 1,014 Medicaid and other 1,664 — — — 22 — 1,686 Total premiums 36,111 5,097 — 6 22 — 41,236 Services revenue: Provider — — 290 — — — 290 ASO and other 6 642 — — 4 — 652 Pharmacy — — 148 — — — 148 Total services revenue 6 642 438 — 4 — 1,090 Total external revenues 36,117 5,739 438 6 26 — 42,326 Intersegment revenues Services — 13 12,426 — — (12,439 ) — Products — — 4,722 — — (4,722 ) — Total intersegment revenues — 13 17,148 — — (17,161 ) — Investment income 102 18 34 — 110 154 418 Total revenues 36,219 5,770 17,620 6 136 (17,007 ) 42,744 Operating expenses: Benefits 30,842 3,977 — (73 ) 77 (374 ) 34,449 Operating costs 3,784 1,355 16,910 3 6 (16,648 ) 5,410 Depreciation and amortization 199 66 125 — — (88 ) 302 Total operating expenses 34,825 5,398 17,035 (70 ) 83 (17,110 ) 40,161 Income from operations 1,394 372 585 76 53 103 2,583 Loss on sale of business — — — — — 786 786 Interest expense — — — — — 159 159 Other expense, net — — — — — 11 11 Income (loss) before income taxes and equity in net earnings 1,394 372 585 76 53 (853 ) 1,627 Equity in net earnings of Kindred at Home — — 9 — — — 9 Segment earnings $ 1,394 $ 372 $ 594 $ 76 $ 53 $ (853 ) $ 1,636 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Nine months ended September 30, 2017 External Revenues Premiums: Individual Medicare Advantage $ 24,735 $ — $ — $ — $ — $ — $ 24,735 Group Medicare Advantage 3,867 — — — — — 3,867 Medicare stand-alone PDP 2,787 — — — — — 2,787 Total Medicare 31,389 — — — — — 31,389 Fully-insured 357 4,098 — 754 — — 5,209 Specialty — 976 — — — — 976 Medicaid and other 1,954 — — — 28 — 1,982 Total premiums 33,700 5,074 — 754 28 — 39,556 Services revenue: Provider — — 193 — — — 193 ASO and other 6 444 — — 5 — 455 Pharmacy — — 58 — — — 58 Total services revenue 6 444 251 — 5 — 706 Total external revenues 33,706 5,518 251 754 33 — 40,262 Intersegment revenues Services — 15 12,958 — — (12,973 ) — Products — — 4,706 — — (4,706 ) — Total intersegment revenues — 15 17,664 — — (17,679 ) — Investment income 72 25 25 3 64 127 316 Total revenues 33,778 5,558 17,940 757 97 (17,552 ) 40,578 Operating expenses: Benefits 29,017 3,952 — 389 95 (596 ) 32,857 Operating costs 2,998 1,178 17,083 151 9 (16,725 ) 4,694 Merger termination fee and related costs, net — — — — — (947 ) (947 ) Depreciation and amortization 176 63 103 10 — (74 ) 278 Total operating expenses 32,191 5,193 17,186 550 104 (18,342 ) 36,882 Income (loss) from operations 1,587 365 754 207 (7 ) 790 3,696 Interest expense — — — — — 166 166 Income (loss) before income taxes and equity in net earnings 1,587 365 754 207 (7 ) 624 3,530 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings $ 1,587 $ 365 $ 754 $ 207 $ (7 ) $ 624 $ 3,530

ACQUISITIONS AND DIVESTITURES (

ACQUISITIONS AND DIVESTITURES (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Disposal Groups, Including Discontinued Operations	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

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2018
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 September 30, 2018 and December 31, 2017 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) September 30, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 649 $ — $ (5 ) $ 644 Mortgage-backed securities 2,418 — (89 ) 2,329 Tax-exempt municipal securities 2,920 2 (65 ) 2,857 Mortgage-backed securities: Residential 57 — (1 ) 56 Commercial 528 — (18 ) 510 Asset-backed securities 686 — (2 ) 684 Corporate debt securities 3,111 2 (93 ) 3,020 Total debt securities $ 10,369 $ 4 $ (273 ) $ 10,100 December 31, 2017 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 532 $ 1 $ (2 ) $ 531 Mortgage-backed securities 1,625 4 (19 ) 1,610 Tax-exempt municipal securities 3,884 33 (28 ) 3,889 Mortgage-backed securities: Residential 26 — — 26 Commercial 455 3 (2 ) 456 Asset-backed securities 407 1 — 408 Corporate debt securities 5,175 244 (37 ) 5,382 Total debt securities $ 12,104 $ 286 $ (88 ) $ 12,302
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 September 30, 2018 and December 31, 2017 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) September 30, 2018 U.S. Treasury and other U.S. U.S. Treasury and agency $ 476 $ (1 ) $ 143 $ (4 ) $ 619 $ (5 ) Mortgage-backed 1,661 (52 ) 642 (37 ) 2,303 (89 ) Tax-exempt municipal 1,578 (29 ) 1,120 (36 ) 2,698 (65 ) Mortgage-backed securities: Residential 56 (1 ) 1 — 57 (1 ) Commercial 407 (13 ) 74 (5 ) 481 (18 ) Asset-backed securities 480 (2 ) 15 — 495 (2 ) Corporate debt securities 1,835 (43 ) 882 (50 ) 2,717 (93 ) Total debt securities $ 6,493 $ (141 ) $ 2,877 $ (132 ) $ 9,370 $ (273 ) December 31, 2017 U.S. Treasury and other U.S. U.S. Treasury and agency $ 273 $ (1 ) $ 130 $ (1 ) $ 403 $ (2 ) Mortgage-backed 581 (2 ) 672 (17 ) 1,253 (19 ) Tax-exempt municipal 1,590 (16 ) 661 (12 ) 2,251 (28 ) Mortgage-backed securities: Residential 20 — 3 — 23 — Commercial 131 (1 ) 28 (1 ) 159 (2 ) Asset-backed securities 107 — 10 — 117 — Corporate debt securities 1,297 (10 ) 804 (27 ) 2,101 (37 ) Total debt securities $ 3,999 $ (30 ) $ 2,308 $ (58 ) $ 6,307 $ (88 )
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 three and nine months ended September 30, 2018 and 2017 : Three months ended Nine months ended 2018 2017 2018 2017 (in millions) Gross realized gains $ 10 $ 3 $ 105 $ 34 Gross realized losses (2 ) (3 ) (15 ) (6 ) Net realized capital gains $ 8 $ — $ 90 $ 28
Schedule of Contractual Maturity of Debt Securities Available for Sale	The contractual maturities of debt securities available for sale at September 30, 2018 , 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 $ 711 $ 709 Due after one year through five years 3,152 3,092 Due after five years through ten years 2,038 1,962 Due after ten years 779 758 Mortgage and asset-backed securities 3,689 3,579 Total debt securities $ 10,369 $ 10,100

FAIR VALUE (Tables)

FAIR VALUE (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Assets Measured at Fair Value on Recurring Basis	The following table summarizes our fair value measurements at September 30, 2018 and December 31, 2017 , respectively, for financial assets measured at fair value on a recurring basis: Fair Value Measurements Using Fair Quoted Prices Other Unobservable (in millions) September 30, 2018 Cash equivalents $ 4,990 $ 4,990 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 644 — 644 — Mortgage-backed securities 2,329 — 2,329 — Tax-exempt municipal securities 2,857 — 2,857 — Mortgage-backed securities: Residential 56 — 56 — Commercial 510 — 510 — Asset-backed securities 684 — 684 — Corporate debt securities 3,020 — 3,020 — Total debt securities 10,100 — 10,100 — Total invested assets $ 15,090 $ 4,990 $ 10,100 $ — December 31, 2017 Cash equivalents $ 4,564 $ 4,564 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 531 — 531 — Mortgage-backed securities 1,610 — 1,610 — Tax-exempt municipal securities 3,889 — 3,889 — Mortgage-backed securities: Residential 26 — 26 — Commercial 456 — 456 — Asset-backed securities 408 — 408 — Corporate debt securities 5,382 — 5,381 1 Total debt securities 12,302 — 12,301 1 Total invested assets $ 16,866 $ 4,564 $ 12,301 $ 1

MEDICARE PART D (Tables)

MEDICARE PART D (Tables)	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
Balance Sheet Amounts Associated With Medicare Part D	The accompanying condensed consolidated balance sheets include the following amounts associated with Medicare Part D at September 30, 2018 and December 31, 2017 . 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. September 30, 2018 December 31, 2017 Risk CMS Risk CMS (in millions) Other current assets $ 6 $ 268 $ 4 $ 101 Trade accounts payable and accrued expenses (214 ) (1,688 ) (255 ) (1,085 ) Net current liability (208 ) (1,420 ) (251 ) (984 ) Other long-term assets 27 — — — Other long-term liabilities (122 ) — (28 ) — Net long-term liability (95 ) — (28 ) — Total net liability $ (303 ) $ (1,420 ) $ (279 ) $ (984 )

HEALTH CARE REFORM (Tables)

HEALTH CARE REFORM (Tables)	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
Schedule Of Risk Adjustment, Reinsurance Recoverable And Risk Corridor Settlement	The accompanying condensed consolidated balance sheets include the following amounts associated with the 3Rs at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Premiums receivable $ 68 $ — $ 62 $ — Other current assets — — — 44 Trade accounts payable and (40 ) — (80 ) — Other long-term assets — — 5 — Total net asset (liability) $ 28 $ — $ (13 ) $ 44

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Amount of Goodwill By Reportable Segments	Changes in the carrying amount of goodwill for our reportable segments for the nine months ended September 30, 2018 were as follows: Retail Group and Specialty Healthcare Total (in millions) Balance at January 1, 2018 $ 1,059 $ 261 $ 1,961 $ 3,281 Acquisitions 476 — 138 614 Balance at September 30, 2018 $ 1,535 $ 261 $ 2,099 $ 3,895
Details 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 condensed consolidated balance sheets at September 30, 2018 and December 31, 2017 . September 30, 2018 December 31, 2017 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 8.7 years $ 646 $ 419 $ 227 $ 566 $ 401 $ 165 Trade names and 6.4 years 84 82 2 104 84 20 Provider contracts 11.9 years 68 36 32 68 30 38 Noncompetes and 7.3 years 29 27 2 32 29 3 Total other intangible 8.7 years $ 827 $ 564 $ 263 $ 770 $ 544 $ 226
Schedule of Estimated Amortization Expense	The following table presents our estimate of amortization expense for 2018 and each of the five next succeeding years: (in millions) For the years ending December 31, 2018 $ 90 2019 70 2020 67 2021 34 2022 31 2023 18

BENEFITS PAYABLE (Tables)

BENEFITS PAYABLE (Tables)	9 Months Ended
	Sep. 30, 2018
Insurance [Abstract]
Activity in Benefits Payable	Activity in benefits payable for our Individual Commercial segment was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 101 $ 454 Incurred related to: Current year — 502 Prior years (58 ) (46 ) Total incurred (58 ) 456 Paid related to: Current year — (393 ) Prior years (34 ) (383 ) Total paid (34 ) (776 ) Balance, end of period $ 9 $ 134 On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 4,668 $ 4,563 Less: Reinsurance recoverables (70 ) (76 ) Balances, beginning of period, net 4,598 4,487 Incurred related to: Current year 34,915 33,318 Prior years (467 ) (430 ) Total incurred 34,448 32,888 Paid related to: Current year (30,204 ) (28,741 ) Prior years (3,920 ) (3,745 ) Total paid (34,124 ) (32,486 ) Reinsurance recoverable 98 70 Balances, end of period $ 5,020 $ 4,959 Activity in benefits payable for our Retail segment was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 3,963 $ 3,507 Less: Reinsurance recoverables (70 ) (76 ) Balances, beginning of period, net 3,893 3,431 Incurred related to: Current year 31,209 29,356 Prior years (367 ) (339 ) Total incurred 30,842 29,017 Paid related to: Current year (27,062 ) (25,460 ) Prior years (3,334 ) (2,822 ) Total paid (30,396 ) (28,282 ) Reinsurance recoverable 98 70 Balances, end of period $ 4,437 $ 4,236 Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the nine months ended September 30, 2018 and 2017 : For the nine months ended September 30, 2018 2017 (in millions) Balances, beginning of period $ 568 $ 578 Incurred related to: Current year 4,018 3,996 Prior years (41 ) (44 ) Total incurred 3,977 3,952 Paid related to: Current year (3,462 ) (3,452 ) Prior years (509 ) (517 ) Total paid (3,971 ) (3,969 ) Balances, end of period $ 574 $ 561
Benefit Expenses Excluded From Activity in Benefits Payable	Benefits expense excluded from the previous table was as follows for the nine months ended September 30, 2018 and 2017 . For the nine months ended September 30, 2018 2017 (in millions) Future policy benefits: Individual Commercial $ (14 ) $ (67 ) Other Businesses 15 36 Total future policy benefits $ 1 $ (31 )
Schedule Of 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: Reconciliation of the Disclosure of Incurred and Paid Claims Development to Benefits Payable, net of reinsurance September 30, 2018 Net outstanding liabilities Retail $ 4,339 Group and Specialty 574 Individual Commercial 9 Other Businesses — Benefits payable, net of reinsurance 4,922 Reinsurance recoverable on unpaid claims Retail 98 Total benefits payable, gross $ 5,020

EARNINGS PER COMMON SHARE COM_2

EARNINGS PER COMMON SHARE COMPUTATION (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Details Supporting Computation of Earnings Per Share	Detail supporting the computation of basic and diluted earnings per common share was as follows for the three and nine months ended September 30, 2018 and 2017 : Three months ended September 30, Nine months ended September 30, 2018 2017 2018 2017 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 644 $ 499 $ 1,328 $ 2,264 Weighted average outstanding shares of common stock 137,709 144,215 137,792 145,546 Dilutive effect of: Employee stock options 186 165 199 174 Restricted stock 783 980 704 902 Shares used to compute diluted earnings per common share 138,678 145,360 138,695 146,622 Basic earnings per common share $ 4.68 $ 3.46 $ 9.64 $ 15.56 Diluted earnings per common share $ 4.65 $ 3.44 $ 9.58 $ 15.44 Number of antidilutive stock options and restricted stock 36 399 284 595

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Schedule of Details of Dividend Payments	The following table provides details of dividend payments, excluding dividend equivalent rights for unvested stock awards, in 2017 and 2018 under our Board approved quarterly cash dividend policy: Record Payment Amount Total (in millions) 2017 payments 1/12/2017 1/27/2017 $ 0.29 $ 43 3/31/2017 4/28/2017 $ 0.40 $ 58 6/30/2017 7/31/2017 $ 0.40 $ 58 9/29/2017 10/27/2017 $ 0.40 $ 57 2018 payments 12/29/2017 1/26/2018 $ 0.40 $ 55 3/30/2018 4/27/2018 $ 0.50 $ 69 6/29/2018 7/27/2018 $ 0.50 $ 69 9/28/2018 10/26/2018 $ 0.50 $ 69
Class of Treasury Stock	Excluding the 0.46 million shares received in March 2018 upon final settlement of our ASR Agreement for which no cash was paid during the period, as well as any prior year ASR activity, share repurchases were as follows during the nine months ended September 30, 2018 and 2017 : Nine months ended September 30, 2018 2017 Authorization Date Purchase Not to Exceed Shares Cost Shares Cost (in millions) February 2017 $ 2,250 — $ — 0.96 $ 240 December 2017 $ 3,000 0.68 224 — — Total repurchases 0.68 $ 224 0.96 $ 240

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of carrying value of long-term debt outstanding	The carrying value of long-term debt outstanding, net of unamortized debt issuance costs, was as follows at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in millions) Senior notes: $400 million, 2.625% due October 1, 2019 $ 399 $ 399 $400 million, 2.50% due December 15, 2020 398 397 $400 million, 2.90% due December 15, 2022 396 396 $600 million, 3.15% due December 1, 2022 597 595 $600 million, 3.85% due October 1, 2024 596 595 $600 million, 3.95% due March 15, 2027 595 594 $250 million, 8.15% due June 15, 2038 263 263 $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 395 396 Total long-term debt $ 4,774 $ 4,770

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, By Segment	Our segment results were as follows for the three and nine months ended September 30, 2018 and 2017 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended September 30, 2018 External revenues Premiums: Individual Medicare Advantage $ 8,912 $ — $ — $ — $ — $ — $ 8,912 Group Medicare Advantage 1,542 — — — — — 1,542 Medicare stand-alone PDP 893 — — — — — 893 Total Medicare 11,347 — — — — — 11,347 Fully-insured 129 1,345 — 1 — — 1,475 Specialty — 325 — — — — 325 Medicaid and other 561 — — — 4 — 565 Total premiums 12,037 1,670 — 1 4 — 13,712 Services revenue: Provider — — 113 — — — 113 ASO and other 1 215 — — — — 216 Pharmacy — — 52 — — — 52 Total services revenue 1 215 165 — — — 381 Total external revenues 12,038 1,885 165 1 4 — 14,093 Intersegment revenues Services — 4 4,214 — — (4,218 ) — Products — — 1,576 — — (1,576 ) — Total intersegment revenues — 4 5,790 — — (5,794 ) — Investment income 35 5 11 — 10 52 113 Total revenues 12,073 1,894 5,966 1 14 (5,742 ) 14,206 Operating expenses: Benefits 10,020 1,347 — (4 ) 12 (132 ) 11,243 Operating costs 1,352 445 5,720 — 2 (5,619 ) 1,900 Depreciation and amortization 67 21 40 — — (26 ) 102 Total operating expenses 11,439 1,813 5,760 (4 ) 14 (5,777 ) 13,245 Income from operations 634 81 206 5 — 35 961 Loss on sale of business — — — — — (4 ) (4 ) Interest expense — — — — — 53 53 Other expense, net — — — — — 11 11 Income (loss) before income taxes and equity in net earnings 634 81 206 5 — (25 ) 901 Equity in net earnings of Kindred at Home — — 9 — — — 9 Segment earnings $ 634 $ 81 $ 215 $ 5 $ — $ (25 ) $ 910 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended September 30, 2017 External revenues Premiums: Individual Medicare Advantage $ 8,077 $ — $ — $ — $ — $ — $ 8,077 Group Medicare Advantage 1,272 — — — — — 1,272 Medicare stand-alone PDP 921 — — — — — 921 Total Medicare 10,270 — — — — — 10,270 Fully-insured 121 1,370 — 224 — — 1,715 Specialty — 331 — — — — 331 Medicaid and other 630 — — — 9 — 639 Total premiums 11,021 1,701 — 224 9 — 12,955 Services revenue: Provider — — 60 — — — 60 ASO and other 2 140 — — 1 — 143 Pharmacy — — 20 — — — 20 Total services revenue 2 140 80 — 1 — 223 Total external revenues 11,023 1,841 80 224 10 — 13,178 Intersegment revenues Services — 5 4,339 — — (4,344 ) — Products — — 1,572 — — (1,572 ) — Total intersegment revenues — 5 5,911 — — (5,916 ) — Investment income 23 7 9 1 22 42 104 Total revenues 11,046 1,853 6,000 225 32 (5,874 ) 13,282 Operating expenses: Benefits 9,294 1,354 — 147 34 (187 ) 10,642 Operating costs 1,081 385 5,726 49 3 (5,556 ) 1,688 Depreciation and amortization 61 21 34 3 — (25 ) 94 Total operating expenses 10,436 1,760 5,760 199 37 (5,768 ) 12,424 Income (loss) from operations 610 93 240 26 (5 ) (106 ) 858 Interest expense — — — — — 59 59 Income (loss) before income taxes and equity in net earnings 610 93 240 26 (5 ) (165 ) 799 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings $ 610 $ 93 $ 240 $ 26 $ (5 ) $ (165 ) $ 799 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Nine months ended September 30, 2018 External revenues Premiums: Individual Medicare Advantage $ 26,790 $ — $ — $ — $ — $ — $ 26,790 Group Medicare Advantage 4,575 — — — — — 4,575 Medicare stand-alone PDP 2,703 — — — — — 2,703 Total Medicare 34,068 — — — — — 34,068 Fully-insured 379 4,083 — 6 — — 4,468 Specialty — 1,014 — — — — 1,014 Medicaid and other 1,664 — — — 22 — 1,686 Total premiums 36,111 5,097 — 6 22 — 41,236 Services revenue: Provider — — 290 — — — 290 ASO and other 6 642 — — 4 — 652 Pharmacy — — 148 — — — 148 Total services revenue 6 642 438 — 4 — 1,090 Total external revenues 36,117 5,739 438 6 26 — 42,326 Intersegment revenues Services — 13 12,426 — — (12,439 ) — Products — — 4,722 — — (4,722 ) — Total intersegment revenues — 13 17,148 — — (17,161 ) — Investment income 102 18 34 — 110 154 418 Total revenues 36,219 5,770 17,620 6 136 (17,007 ) 42,744 Operating expenses: Benefits 30,842 3,977 — (73 ) 77 (374 ) 34,449 Operating costs 3,784 1,355 16,910 3 6 (16,648 ) 5,410 Depreciation and amortization 199 66 125 — — (88 ) 302 Total operating expenses 34,825 5,398 17,035 (70 ) 83 (17,110 ) 40,161 Income from operations 1,394 372 585 76 53 103 2,583 Loss on sale of business — — — — — 786 786 Interest expense — — — — — 159 159 Other expense, net — — — — — 11 11 Income (loss) before income taxes and equity in net earnings 1,394 372 585 76 53 (853 ) 1,627 Equity in net earnings of Kindred at Home — — 9 — — — 9 Segment earnings $ 1,394 $ 372 $ 594 $ 76 $ 53 $ (853 ) $ 1,636 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Nine months ended September 30, 2017 External Revenues Premiums: Individual Medicare Advantage $ 24,735 $ — $ — $ — $ — $ — $ 24,735 Group Medicare Advantage 3,867 — — — — — 3,867 Medicare stand-alone PDP 2,787 — — — — — 2,787 Total Medicare 31,389 — — — — — 31,389 Fully-insured 357 4,098 — 754 — — 5,209 Specialty — 976 — — — — 976 Medicaid and other 1,954 — — — 28 — 1,982 Total premiums 33,700 5,074 — 754 28 — 39,556 Services revenue: Provider — — 193 — — — 193 ASO and other 6 444 — — 5 — 455 Pharmacy — — 58 — — — 58 Total services revenue 6 444 251 — 5 — 706 Total external revenues 33,706 5,518 251 754 33 — 40,262 Intersegment revenues Services — 15 12,958 — — (12,973 ) — Products — — 4,706 — — (4,706 ) — Total intersegment revenues — 15 17,664 — — (17,679 ) — Investment income 72 25 25 3 64 127 316 Total revenues 33,778 5,558 17,940 757 97 (17,552 ) 40,578 Operating expenses: Benefits 29,017 3,952 — 389 95 (596 ) 32,857 Operating costs 2,998 1,178 17,083 151 9 (16,725 ) 4,694 Merger termination fee and related costs, net — — — — — (947 ) (947 ) Depreciation and amortization 176 63 103 10 — (74 ) 278 Total operating expenses 32,191 5,193 17,186 550 104 (18,342 ) 36,882 Income (loss) from operations 1,587 365 754 207 (7 ) 790 3,696 Interest expense — — — — — 166 166 Income (loss) before income taxes and equity in net earnings 1,587 365 754 207 (7 ) 624 3,530 Equity in net earnings of Kindred at Home — — — — — — — Segment earnings $ 1,587 $ 365 $ 754 $ 207 $ (7 ) $ 624 $ 3,530

BASIS OF PRESENTATION AND SIG_2

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS - Narrative (Details) $ / shares in Units, $ in Millions	Feb. 16, 2017USD ($)	Dec. 31, 2017USD ($)employee$ / shares	Sep. 30, 2018USD ($)
Business Acquisition [Line Items]
Number of associates impacted | employee		3,600
Percentage of workforce associated impacted		7.80%
Restructuring charges		$ 148
Restructuring charges per diluted share (in dollars per share) | $ / shares		$ 0.64
Restructuring liability, current		$ 140	$ 29
Break up fee received	$ 1,000
Accounts receivable		$ 854	1,062
Services Accounts Receivable
Business Acquisition [Line Items]
Accounts receivable			$ 148

RECENTLY ISSUED ACCOUNTING PR_2

RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018
Revenue From Premiums and Investment Income | Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage	97.00%	97.00%

ACQUISITIONS AND DIVESTITURES -

ACQUISITIONS AND DIVESTITURES - Narrative (Details) $ in Millions	Jul. 11, 2018USD ($)locationState	Jul. 02, 2018USD ($)	Apr. 10, 2018USD ($)	Mar. 01, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Aug. 09, 2018USD ($)	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Payments to acquire equity method investments						$ 1,095	$ 0
Equity method investment in Kindred at Home						1,048			$ 0
Goodwill, acquired during period						614
MCCI
Business Acquisition [Line Items]
Notes receivable and revolving note, related party				$ 383
MCCI
Business Acquisition [Line Items]
Payments to acquire business				169
Goodwill, acquired during period				479
Other intangible assets acquired				80
Net tangible assets acquired				$ 27
Other intangible assets, weighted average useful life				8 years
FPG
Business Acquisition [Line Items]
Payments to acquire business			$ 185
Goodwill, acquired during period			135
Other intangible assets acquired			38
Net tangible assets acquired			$ 17
Other intangible assets, weighted average useful life			4 years 10 months 25 days
KMG America Corporation | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Business Acquisition [Line Items]
Parent company cash contributed to sale of subsidiary								$ 190
Transfer of statutory capital with sale of subsidiary								$ 160
Pretax loss on sale of subsidiary						786
Tax benefit on sale of subsidiary						430
Disposal group, revenue					$ 66	182	199
Disposal group, pretax income (loss)					$ (5)	47	$ (15)
KIC
Business Acquisition [Line Items]
Payments for reinsurance						245
Kindred at Home
Business Acquisition [Line Items]
Equity method investment, ownership percentage		40.00%
Payments to acquire equity method investments		$ 850
Equity method investment in Kindred at Home		1,000
Curo Health Services
Business Acquisition [Line Items]
Equity method investment, ownership percentage	40.00%
Payments to acquire equity method investments	$ 250
Equity method investment, number of locations | location	245
Equity method investment, number of states | State	22
Equity Option | Put Option
Business Acquisition [Line Items]
Purchase price allocation, financial asset		236
Equity Option | Put Option | Other long-term assets
Business Acquisition [Line Items]
Financial asset, fair value						221
Equity Option | Call Option
Business Acquisition [Line Items]
Purchase price allocation, financial liability		$ 291
Equity Option | Call Option | Other long-term liabilities
Business Acquisition [Line Items]
Financial liability, fair value						$ 265

ACQUISITIONS AND DIVESTITURES_2

ACQUISITIONS AND DIVESTITURES - Assets and Liabilities Held-for-sale (Details) - KMG America Corporation - Disposal Group, Disposed of by Sale, Not Discontinued Operations $ in Millions	Aug. 09, 2018USD ($)
Assets
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

INVESTMENT SECURITIES - Securit

INVESTMENT SECURITIES - Securities Classified as Current and Long-Term (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Investment [Line Items]
Amortized Cost	$ 10,369	$ 12,104
Gross Unrealized Gains	4	286
Gross Unrealized Losses	(273)	(88)
Fair Value	10,100	12,302
Tax-exempt municipal securities
Investment [Line Items]
Amortized Cost	2,920	3,884
Gross Unrealized Gains	2	33
Gross Unrealized Losses	(65)	(28)
Fair Value	2,857	3,889
Residential mortgage-backed securities
Investment [Line Items]
Amortized Cost	57	26
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	56	26
Commercial mortgage-backed securities
Investment [Line Items]
Amortized Cost	528	455
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(18)	(2)
Fair Value	510	456
Asset-backed securities
Investment [Line Items]
Amortized Cost	686	407
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(2)	0
Fair Value	684	408
Corporate debt securities
Investment [Line Items]
Amortized Cost	3,111	5,175
Gross Unrealized Gains	2	244
Gross Unrealized Losses	(93)	(37)
Fair Value	3,020	5,382
U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Investment [Line Items]
Amortized Cost	649	532
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(5)	(2)
Fair Value	644	531
U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Investment [Line Items]
Amortized Cost	2,418	1,625
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(89)	(19)
Fair Value	$ 2,329	$ 1,610

INVESTMENT SECURITIES - Gross U

INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value
Less than 12 months	$ 6,493	$ 3,999
12 months or more	2,877	2,308
Total	9,370	6,307
Gross Unrealized Losses
Less than 12 months	(141)	(30)
12 months or more	(132)	(58)
Total	(273)	(88)
U.S. Treasury and agency obligations | U.S. Treasury and other U.S. government corporations and agencies
Fair Value
Less than 12 months	476	273
12 months or more	143	130
Total	619	403
Gross Unrealized Losses
Less than 12 months	(1)	(1)
12 months or more	(4)	(1)
Total	(5)	(2)
Mortgage-backed securities | U.S. Treasury and other U.S. government corporations and agencies
Fair Value
Less than 12 months	1,661	581
12 months or more	642	672
Total	2,303	1,253
Gross Unrealized Losses
Less than 12 months	(52)	(2)
12 months or more	(37)	(17)
Total	(89)	(19)
Tax-exempt municipal securities
Fair Value
Less than 12 months	1,578	1,590
12 months or more	1,120	661
Total	2,698	2,251
Gross Unrealized Losses
Less than 12 months	(29)	(16)
12 months or more	(36)	(12)
Total	(65)	(28)
Residential mortgage-backed securities
Fair Value
Less than 12 months	56	20
12 months or more	1	3
Total	57	23
Gross Unrealized Losses
Less than 12 months	(1)	0
12 months or more	0	0
Total	(1)	0
Commercial mortgage-backed securities
Fair Value
Less than 12 months	407	131
12 months or more	74	28
Total	481	159
Gross Unrealized Losses
Less than 12 months	(13)	(1)
12 months or more	(5)	(1)
Total	(18)	(2)
Asset-backed securities
Fair Value
Less than 12 months	480	107
12 months or more	15	10
Total	495	117
Gross Unrealized Losses
Less than 12 months	(2)	0
12 months or more	0	0
Total	(2)	0
Corporate debt securities
Fair Value
Less than 12 months	1,835	1,297
12 months or more	882	804
Total	2,717	2,101
Gross Unrealized Losses
Less than 12 months	(43)	(10)
12 months or more	(50)	(27)
Total	$ (93)	$ (37)

INVESTMENT SECURITIES - Additio

INVESTMENT SECURITIES - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)position	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)position	Sep. 30, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Percentage of debt securities considered to be of investment-grade	97.00%		97.00%
Maximum percentage of any general obligation bonds in one state			9.00%
Percent of tax exempt securities insured	2.00%		2.00%
Securities in unrealized loss positions, number of positions	1,250		1,250
Number of positions	1,520		1,520
Other-than-temporary impairments | $	$ 0	$ 0	$ 0	$ 0

INVESTMENT SECURITIES - Realize

INVESTMENT SECURITIES - Realized Gains (Losses) Within Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 10	$ 3	$ 105	$ 34
Gross realized losses	(2)	(3)	(15)	(6)
Net realized capital gains	$ 8	$ 0	$ 90	$ 28

INVESTMENT SECURITIES - Contrac

INVESTMENT SECURITIES - Contractual Maturities, Available for Sale (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Due within one year	$ 711
Due after one year through five years	3,152
Due after five years through ten years	2,038
Due after ten years	779
Mortgage and asset-backed securities	3,689
Amortized Cost	10,369	$ 12,104
Fair Value
Due within one year	709
Due after one year through five years	3,092
Due after five years through ten years	1,962
Due after ten years	758
Mortgage and asset-backed securities	3,579
Fair Value	$ 10,100	$ 12,302

FAIR VALUE - Financial Assets M

FAIR VALUE - Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 10,100	$ 12,302
Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	2,857	3,889
Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	56	26
Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	510	456
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	684	408
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,020	5,382
U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	644	531
U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	2,329	1,610
Measured On Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	4,990	4,564
Debt securities	10,100	12,302
Total invested assets	15,090	16,866
Measured On Recurring Basis | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	2,857	3,889
Measured On Recurring Basis | Residential mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	56	26
Measured On Recurring Basis | Commercial mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	510	456
Measured On Recurring Basis | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	684	408
Measured On Recurring Basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,020	5,382
Measured On Recurring Basis | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	644	531
Measured On Recurring Basis | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	2,329	1,610
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	4,990	4,564
Debt securities	0	0
Total invested assets	4,990	4,564
Measured On 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
Measured On 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	0
Measured On 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
Measured On 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
Measured On 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
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On 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	10,100	12,301
Total invested assets	10,100	12,301
Measured On 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	2,857	3,889
Measured On 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	56	26
Measured On 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	510	456
Measured On 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	684	408
Measured On 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	3,020	5,381
Measured On Recurring Basis | Other Observable Inputs (Level 2) | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	644	531
Measured On Recurring Basis | Other Observable Inputs (Level 2) | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	2,329	1,610
Measured On 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	1
Total invested assets	0	1
Measured On 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
Measured On 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	0
Measured On 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
Measured On 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
Measured On 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	1
Measured On Recurring Basis | Unobservable Inputs (Level 3) | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Unobservable Inputs (Level 3) | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 0	$ 0

FAIR VALUE - Additional Informa

FAIR VALUE - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 398	$ 150
Commercial Paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	398	150
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of debt outstanding	4,774	4,770
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of debt outstanding	$ 4,879	$ 5,191

MEDICARE PART D (Detail)

MEDICARE PART D (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Other current assets	$ 4,178	$ 2,949
Trade accounts payable and accrued expenses	(5,413)	(4,069)
Other long-term assets	1,380	2,166
Other long-term liabilities	(603)	(237)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	6	4
Trade accounts payable and accrued expenses	(214)	(255)
Net current (liability) asset	(208)	(251)
Other long-term assets	27	0
Other long-term liabilities	(122)	(28)
Net long-term liability	(95)	(28)
Total net asset (liability)	(303)	(279)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	268	101
Trade accounts payable and accrued expenses	(1,688)	(1,085)
Net current (liability) asset	(1,420)	(984)
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term liability	0	0
Total net asset (liability)	$ (1,420)	$ (984)

HEALTH CARE REFORM (Details)

HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Nov. 02, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Litigation recoveries sought						$ 611
Other current assets		$ 4,178	$ 4,178		$ 2,949
Trade accounts payable and accrued expenses		(5,413)	(5,413)		(4,069)
Other long-term assets		1,380	1,380		2,166
Payments for risk corridor settlements			(60)
Proceeds from risk corridor settlements				$ 307
Health Care Reform
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Amortization of deferred charges		258	778
Health Care Reform | Subsequent Event
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Payment of annual health insurance industry fee	$ 1,040
Risk Adjustment Settlement
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums receivable		68	68		62
Other current assets		0	0		0
Trade accounts payable and accrued expenses		(40)	(40)		(80)
Other long-term assets		0	0		5
Total net asset (liability)		28	28		(13)
Reinsurance Recoverables
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Premiums receivable		0	0		0
Other current assets		0	0		44
Trade accounts payable and accrued expenses		0	0		0
Other long-term assets		0	0		0
Total net asset (liability)		$ 0	$ 0		$ 44

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill by Segments (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 3,281
Acquisitions	614
Ending balance	3,895
Retail
Goodwill [Roll Forward]
Beginning balance	1,059
Acquisitions	476
Ending balance	1,535
Group and Specialty
Goodwill [Roll Forward]
Beginning balance	261
Acquisitions	0
Ending balance	261
Healthcare Services
Goodwill [Roll Forward]
Beginning balance	1,961
Acquisitions	138
Ending balance	$ 2,099

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months
Cost	$ 827	$ 770
Accumulated Amortization	564	544
Net	$ 263	226
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 8 months
Cost	$ 646	566
Accumulated Amortization	419	401
Net	$ 227	165
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 5 months
Cost	$ 84	104
Accumulated Amortization	82	84
Net	$ 2	20
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 11 months
Cost	$ 68	68
Accumulated Amortization	36	30
Net	$ 32	38
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	7 years 4 months
Cost	$ 29	32
Accumulated Amortization	27	29
Net	$ 2	$ 3

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Estimated Amortization Expense (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for other intangible assets	$ 19	$ 18	$ 70	$ 54
Amortization expense, trade name write-off			12
For the years ending December 31,
2,018	90		90
2,019	70		70
2,020	67		67
2,021	34		34
2,022	31		31
2,023	$ 18		$ 18

BENEFITS PAYABLE - Activity in

BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	$ 4,668	$ 4,563
Less: Reinsurance recoverables	(98)	(70)	$ (70)	$ (76)
Balances, beginning of period, net	4,598	4,487
Incurred related to:
Current year	34,915	33,318
Prior years	(467)	(430)
Total incurred	34,448	32,888
Paid related to:
Current year	(30,204)	(28,741)
Prior years	(3,920)	(3,745)
Total paid	(34,124)	(32,486)
Reinsurance recoverable	98	70	70	76
Balances, end of period	5,020	4,959
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	3,963	3,507
Less: Reinsurance recoverables	(98)	(70)	(70)	(76)
Balances, beginning of period, net	3,893	3,431
Incurred related to:
Current year	31,209	29,356
Prior years	(367)	(339)
Total incurred	30,842	29,017
Paid related to:
Current year	(27,062)	(25,460)
Prior years	(3,334)	(2,822)
Total paid	(30,396)	(28,282)
Reinsurance recoverable	98	70	$ 70	$ 76
Balances, end of period	4,437	4,236
Total IBNR	2,800
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	568	578
Incurred related to:
Current year	4,018	3,996
Prior years	(41)	(44)
Total incurred	3,977	3,952
Paid related to:
Current year	(3,462)	(3,452)
Prior years	(509)	(517)
Total paid	(3,971)	(3,969)
Balances, end of period	574	561
Total IBNR	490
Individual Commercial
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balances, beginning of period	101	454
Incurred related to:
Current year	0	502
Prior years	(58)	(46)
Total incurred	(58)	456
Paid related to:
Current year	0	(393)
Prior years	(34)	(383)
Total paid	(34)	(776)
Balances, end of period	9	$ 134
Total IBNR	$ 2

BENEFITS PAYABLE - Benefit Expe

BENEFITS PAYABLE - Benefit Expenses Excluded From Activity in Benefits Payable (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	$ 1	$ (31)
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	(14)	(67)
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	$ 15	$ 36

BENEFITS PAYABLE - Reconciliati

BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 4,922
Reinsurance recoverable on unpaid claims	98	$ 70	$ 70	$ 76
Benefits payable	5,020	4,668	4,959	4,563
Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reinsurance recoverable on unpaid claims	98	70	70	76
Benefits payable	4,437	3,963	4,236	3,507
Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	574	568	561	578
Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	9	$ 101	$ 134	$ 454
Operating Segments | Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	4,339
Operating Segments | Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	574
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	9
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 0

EARNINGS PER COMMON SHARE COM_3

EARNINGS PER COMMON SHARE COMPUTATION (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 644	$ 499	$ 1,328	$ 2,264
Weighted average outstanding shares of common stock used to compute basic earnings per common share (in shares)	137,709	144,215	137,792	145,546
Shares used to compute diluted earnings per common share (in shares)	138,678	145,360	138,695	146,622
Basic earnings per common share (in dollars per share)	$ 4.68	$ 3.46	$ 9.64	$ 15.56
Diluted earnings per common share (in dollars per share)	$ 4.65	$ 3.44	$ 9.58	$ 15.44
Number of antidilutive stock options and restricted stock excluded from computation (in shares)	36	399	284	595
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)	186	165	199	174
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)	783	980	704	902

STOCKHOLDERS' EQUITY - Schedule

STOCKHOLDERS' EQUITY - Schedule of Details of Dividend Payments (Detail) - USD ($) $ / shares in Units, $ in Millions	Oct. 26, 2018	Jul. 27, 2018	Apr. 27, 2018	Jan. 26, 2018	Oct. 27, 2017	Jul. 31, 2017	Apr. 28, 2017	Jan. 27, 2017
Subsequent Event [Line Items]
Amount per Share (in dollars per share)		$ 0.50	$ 0.50	$ 0.40	$ 0.40	$ 0.40	$ 0.40	$ 0.29
Total Amount		$ 69	$ 69	$ 55	$ 57	$ 58	$ 58	$ 43
Subsequent Event
Subsequent Event [Line Items]
Amount per Share (in dollars per share)	$ 0.50
Total Amount	$ 69

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	Nov. 02, 2018	Mar. 26, 2018	Dec. 22, 2017	Sep. 30, 2018	Mar. 26, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Nov. 06, 2018	Dec. 31, 2017	Dec. 21, 2017	Dec. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Dividends declared per common share (in dollars per share)				$ 0.5		$ 0.40	$ 1.5	$ 1.20
Stock repurchase program, authorized amount												$ 3,000,000,000
Common stock repurchases				$ 201,000,000		$ 241,000,000	$ 294,000,000	$ 1,819,000,000
Common shares acquired in connection with employee stock plans (in shares)							260	370
Common shares acquired in connection with employee stock plans, amount							$ 70,000,000	$ 79,000,000
Treasury stock reissued (in shares)							870
Treasury stock reissued							$ 92,000,000
Accumulated other comprehensive gain (loss)				(206,000,000)			(206,000,000)			$ 19,000,000
Net unrealized (losses) gains on investment securities
Equity, Class of Treasury Stock [Line Items]
Accumulated other comprehensive gain (loss)				$ (206,000,000)			$ (206,000,000)			125,000,000
Additional liability that would exist on closed block of long-term care policies assuming unrealized gains on investments backing such products were realized and reinvested at current yields
Equity, Class of Treasury Stock [Line Items]
Accumulated other comprehensive gain (loss)										$ 106,000,000
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Dividends declared per common share (in dollars per share)	$ 0.50
Remaining authorized amount									$ 1,800,000,000
December 2017 ASR
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount											$ 1,000,000,000
Share repurchase payment			$ 1,000,000,000
Shares		460	3,280		3,740
Common stock repurchases		$ 200,000,000	$ 800,000,000
Decrease in capital in excess of par value			$ 200,000,000
Average cost per share (in dollars per share)					$ 267.55

STOCKHOLDERS' EQUITY - Share Re

STOCKHOLDERS' EQUITY - Share Repurchases (Details) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Purchase Not to Exceed					$ 3,000,000,000
Cost	$ 201,000,000	$ 241,000,000	$ 294,000,000	$ 1,819,000,000
February 2,017
Equity, Class of Treasury Stock [Line Items]
Purchase Not to Exceed	2,250,000,000		$ 2,250,000,000
Shares			0	960
Cost			$ 0	$ 240,000,000
December 2,017
Equity, Class of Treasury Stock [Line Items]
Purchase Not to Exceed	$ 3,000,000,000		$ 3,000,000,000
Shares			680	0
Cost			$ 224,000,000	$ 0
Total Excluding ASR Activity
Equity, Class of Treasury Stock [Line Items]
Shares			680	960
Cost			$ 224,000,000	$ 240,000,000

INCOME TAXES (Detail)

INCOME TAXES (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	29.10%	37.50%	18.80%	35.90%
Provisional income tax benefit, Tax Reform Law			$ 39.3

DEBT - Senior Notes (Details)

DEBT - Senior Notes (Details) - Senior Notes - USD ($)	1 Months Ended		9 Months Ended
	Dec. 31, 2017	Mar. 31, 2017	Sep. 30, 2018
Debt Instrument [Line Items]
Long-term debt	$ 4,770,000,000		$ 4,774,000,000
Proceeds from debt, net of discounts and offering expenses	$ 794,000,000	$ 991,000,000
Percentage of principal amount redeemed	100.00%
Early repayment of senior debt	$ 829,000,000
Loss on extinguishment of debt	17,000,000
Redemption price, percentage			100.00%
$400 million, 2.625% due October 1, 2019
Debt Instrument [Line Items]
Long-term debt	399,000,000		$ 399,000,000
Face amount			$ 400,000,000
Stated interest rate			2.625%
$400 million, 2.50% due December 15, 2020
Debt Instrument [Line Items]
Long-term debt	397,000,000		$ 398,000,000
Face amount	$ 400,000,000		$ 400,000,000
Stated interest rate	2.50%		2.50%
$400 million, 2.90% due December 15, 2022
Debt Instrument [Line Items]
Long-term debt	$ 396,000,000		$ 396,000,000
Face amount	$ 400,000,000		$ 400,000,000
Stated interest rate	2.90%		2.90%
$600 million, 3.15% due December 1, 2022
Debt Instrument [Line Items]
Long-term debt	$ 595,000,000		$ 597,000,000
Face amount			$ 600,000,000
Stated interest rate			3.15%
$600 million, 3.85% due October 1, 2024
Debt Instrument [Line Items]
Long-term debt	595,000,000		$ 596,000,000
Face amount			$ 600,000,000
Stated interest rate			3.85%
$600 million, 3.95% due March 15, 2027
Debt Instrument [Line Items]
Long-term debt	594,000,000		$ 595,000,000
Face amount		$ 600,000,000	$ 600,000,000
Stated interest rate		3.95%	3.95%
$250 million, 8.15% due June 15, 2038
Debt Instrument [Line Items]
Long-term debt	263,000,000		$ 263,000,000
Face amount			$ 250,000,000
Stated interest rate			8.15%
$400 million, 4.625% due December 1, 2042
Debt Instrument [Line Items]
Long-term debt	396,000,000		$ 396,000,000
Face amount			$ 400,000,000
Stated interest rate			4.625%
$750 million, 4.95% due October 1, 2044
Debt Instrument [Line Items]
Long-term debt	739,000,000		$ 739,000,000
Face amount			$ 750,000,000
Stated interest rate			4.95%
$400 million, 4.80% due March 15, 2047
Debt Instrument [Line Items]
Long-term debt	396,000,000		$ 395,000,000
Face amount		$ 400,000,000	$ 400,000,000
Stated interest rate		4.80%	4.80%
$300 million, 6.30% due August 2018
Debt Instrument [Line Items]
Face amount	$ 300,000,000
Stated interest rate	6.30%
$500 million, 7.20% due June 2018
Debt Instrument [Line Items]
Face amount	$ 500,000,000
Stated interest rate	7.20%

DEBT - Credit Agreement (Detail

DEBT - Credit Agreement (Details) - Line of Credit	9 Months Ended
	Sep. 30, 2018USD ($)
Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 2,500,000,000
Debt to capitalization percentage, maximum	50.00%
Actual debt to capitalization percentage	32.80%
Uncommitted incremental loan facility	$ 500,000,000
Line of credit, outstanding borrowings	0
Credit Agreement | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit, outstanding borrowings	$ 0
Credit Agreement | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Line of Credit Facility [Line Items]
Interest rate spread	1.10%
Facility fee (percentage)	0.15%
Credit Agreement | Minimum | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Line of Credit Facility [Line Items]
Interest rate spread	0.91%
Facility fee (percentage)	0.09%
Credit Agreement | Maximum | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Line of Credit Facility [Line Items]
Interest rate spread	1.50%
Facility fee (percentage)	0.25%
Unsecured Revolving Credit Agreement, Expires May 2022 | Revolving Credit Facility
Line of Credit Facility [Line Items]
Term	5 years
Maximum borrowing capacity	$ 2,000,000,000
Remaining borrowing capacity	$ 2,000,000,000

DEBT - Commercial Paper (Detail

DEBT - Commercial Paper (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Short-term Debt [Line Items]
Outstanding borrowings	$ 398,000,000	$ 150,000,000
Commercial Paper
Short-term Debt [Line Items]
Maximum borrowing capacity	2,000,000,000
Maximum amount outstanding during period	442,000,000
Outstanding borrowings	$ 398,000,000	$ 150,000,000

GUARANTEES AND CONTINGENCIES (D

GUARANTEES AND CONTINGENCIES (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Nov. 02, 2017
Loss Contingencies [Line Items]
Litigation recoveries sought		$ 611
Medicare
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	80.00%
Military service
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%

SEGMENT INFORMATION - Additiona

SEGMENT INFORMATION - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)Segment	Sep. 30, 2017USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment			4
Member co-share amounts and government subsidies	$ 3,500	$ 3,600	$ 9,700	$ 9,800
Depreciation and amortization classified as benefit expense	$ 29	$ 26	$ 98	$ 79

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Premiums	$ 13,712	$ 12,955	$ 41,236	$ 39,556
Services revenue	381	223	1,090	706
Investment income	113	104	418	316
Total revenues	14,206	13,282	42,744	40,578
Benefits	11,243	10,642	34,449	32,857
Operating costs	1,900	1,688	5,410	4,694
Merger termination fee and related costs, net	0	0	0	(947)
Depreciation and amortization	102	94	302	278
Total operating expenses	13,245	12,424	40,161	36,882
Income (loss) from operations	961	858	2,583	3,696
Loss on sale of business	(4)	0	786	0
Interest expense	53	59	159	166
Other expense, net	11	0	11	0
Income (loss) before income taxes and equity in net earnings	901	799	1,627	3,530
Equity in net earnings of Kindred at Home	9	0	9	0
Segment earnings	910	799	1,636	3,530
Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	8,912	8,077	26,790	24,735
Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	1,542	1,272	4,575	3,867
Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	893	921	2,703	2,787
Total Medicare
Segment Reporting Information [Line Items]
Premiums	11,347	10,270	34,068	31,389
Fully-insured
Segment Reporting Information [Line Items]
Premiums	1,475	1,715	4,468	5,209
Specialty
Segment Reporting Information [Line Items]
Premiums	325	331	1,014	976
Medicaid and other
Segment Reporting Information [Line Items]
Premiums	565	639	1,686	1,982
Total external revenues
Segment Reporting Information [Line Items]
Total revenues	14,093	13,178	42,326	40,262
Services
Segment Reporting Information [Line Items]
Services revenue	381	223	1,090	706
Services | Provider
Segment Reporting Information [Line Items]
Services revenue	113	60	290	193
Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	216	143	652	455
Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	52	20	148	58
Operating Segments | Retail
Segment Reporting Information [Line Items]
Premiums	12,037	11,021	36,111	33,700
Investment income	35	23	102	72
Total revenues	12,073	11,046	36,219	33,778
Benefits	10,020	9,294	30,842	29,017
Operating costs	1,352	1,081	3,784	2,998
Merger termination fee and related costs, net				0
Depreciation and amortization	67	61	199	176
Total operating expenses	11,439	10,436	34,825	32,191
Income (loss) from operations	634	610	1,394	1,587
Loss on sale of business	0		0
Interest expense	0	0	0	0
Other expense, net	0		0
Income (loss) before income taxes and equity in net earnings	634	610	1,394	1,587
Equity in net earnings of Kindred at Home	0	0	0	0
Segment earnings	634	610	1,394	1,587
Operating Segments | Retail | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	8,912	8,077	26,790	24,735
Operating Segments | Retail | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	1,542	1,272	4,575	3,867
Operating Segments | Retail | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	893	921	2,703	2,787
Operating Segments | Retail | Total Medicare
Segment Reporting Information [Line Items]
Premiums	11,347	10,270	34,068	31,389
Operating Segments | Retail | Fully-insured
Segment Reporting Information [Line Items]
Premiums	129	121	379	357
Operating Segments | Retail | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Retail | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	561	630	1,664	1,954
Operating Segments | Retail | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	12,038	11,023	36,117	33,706
Operating Segments | Retail | Services
Segment Reporting Information [Line Items]
Services revenue	1	2	6	6
Operating Segments | Retail | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Retail | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	1	2	6	6
Operating Segments | Retail | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	1,670	1,701	5,097	5,074
Investment income	5	7	18	25
Total revenues	1,894	1,853	5,770	5,558
Benefits	1,347	1,354	3,977	3,952
Operating costs	445	385	1,355	1,178
Merger termination fee and related costs, net				0
Depreciation and amortization	21	21	66	63
Total operating expenses	1,813	1,760	5,398	5,193
Income (loss) from operations	81	93	372	365
Loss on sale of business	0		0
Interest expense	0	0	0	0
Other expense, net	0		0
Income (loss) before income taxes and equity in net earnings	81	93	372	365
Equity in net earnings of Kindred at Home	0	0	0	0
Segment earnings	81	93	372	365
Operating Segments | Group and Specialty | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Group and Specialty | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Group and Specialty | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Group and Specialty | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Group and Specialty | Fully-insured
Segment Reporting Information [Line Items]
Premiums	1,345	1,370	4,083	4,098
Operating Segments | Group and Specialty | Specialty
Segment Reporting Information [Line Items]
Premiums	325	331	1,014	976
Operating Segments | Group and Specialty | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Group and Specialty | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	1,885	1,841	5,739	5,518
Operating Segments | Group and Specialty | Services
Segment Reporting Information [Line Items]
Services revenue	215	140	642	444
Operating Segments | Group and Specialty | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Group and Specialty | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	215	140	642	444
Operating Segments | Group and Specialty | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Healthcare Services
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Investment income	11	9	34	25
Total revenues	5,966	6,000	17,620	17,940
Benefits	0	0	0	0
Operating costs	5,720	5,726	16,910	17,083
Merger termination fee and related costs, net				0
Depreciation and amortization	40	34	125	103
Total operating expenses	5,760	5,760	17,035	17,186
Income (loss) from operations	206	240	585	754
Loss on sale of business	0		0
Interest expense	0	0	0	0
Other expense, net	0		0
Income (loss) before income taxes and equity in net earnings	206	240	585	754
Equity in net earnings of Kindred at Home	9	0	9	0
Segment earnings	215	240	594	754
Operating Segments | Healthcare Services | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Healthcare Services | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	165	80	438	251
Operating Segments | Healthcare Services | Services
Segment Reporting Information [Line Items]
Services revenue	165	80	438	251
Operating Segments | Healthcare Services | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	113	60	290	193
Operating Segments | Healthcare Services | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Healthcare Services | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	52	20	148	58
Operating Segments | Individual Commercial
Segment Reporting Information [Line Items]
Premiums	1	224	6	754
Investment income	0	1	0	3
Total revenues	1	225	6	757
Benefits	(4)	147	(73)	389
Operating costs	0	49	3	151
Merger termination fee and related costs, net				0
Depreciation and amortization	0	3	0	10
Total operating expenses	(4)	199	(70)	550
Income (loss) from operations	5	26	76	207
Loss on sale of business	0		0
Interest expense	0	0	0	0
Other expense, net	0		0
Income (loss) before income taxes and equity in net earnings	5	26	76	207
Equity in net earnings of Kindred at Home	0	0	0	0
Segment earnings	5	26	76	207
Operating Segments | Individual Commercial | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Fully-insured
Segment Reporting Information [Line Items]
Premiums	1	224	6	754
Operating Segments | Individual Commercial | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Operating Segments | Individual Commercial | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	1	224	6	754
Operating Segments | Individual Commercial | Services
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Individual Commercial | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Individual Commercial | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Operating Segments | Individual Commercial | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Intersegment revenues
Segment Reporting Information [Line Items]
Total revenues	(5,794)	(5,916)	(17,161)	(17,679)
Intersegment revenues | Services
Segment Reporting Information [Line Items]
Total revenues	(4,218)	(4,344)	(12,439)	(12,973)
Intersegment revenues | Products
Segment Reporting Information [Line Items]
Total revenues	(1,576)	(1,572)	(4,722)	(4,706)
Intersegment revenues | Retail
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Retail | Services
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Retail | Products
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Group and Specialty
Segment Reporting Information [Line Items]
Total revenues	4	5	13	15
Intersegment revenues | Group and Specialty | Services
Segment Reporting Information [Line Items]
Total revenues	4	5	13	15
Intersegment revenues | Group and Specialty | Products
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Healthcare Services
Segment Reporting Information [Line Items]
Total revenues	5,790	5,911	17,148	17,664
Intersegment revenues | Healthcare Services | Services
Segment Reporting Information [Line Items]
Total revenues	4,214	4,339	12,426	12,958
Intersegment revenues | Healthcare Services | Products
Segment Reporting Information [Line Items]
Total revenues	1,576	1,572	4,722	4,706
Intersegment revenues | Individual Commercial
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Individual Commercial | Services
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Intersegment revenues | Individual Commercial | Products
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Other Businesses
Segment Reporting Information [Line Items]
Premiums	4	9	22	28
Investment income	10	22	110	64
Total revenues	14	32	136	97
Benefits	12	34	77	95
Operating costs	2	3	6	9
Merger termination fee and related costs, net				0
Depreciation and amortization	0	0	0	0
Total operating expenses	14	37	83	104
Income (loss) from operations	0	(5)	53	(7)
Loss on sale of business	0		0
Interest expense	0	0	0	0
Other expense, net	0		0
Income (loss) before income taxes and equity in net earnings	0	(5)	53	(7)
Equity in net earnings of Kindred at Home	0	0	0	0
Segment earnings	0	(5)	53	(7)
Other Businesses | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0	0	0
Other Businesses | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	4	9	22	28
Other Businesses | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	4	10	26	33
Other Businesses | Services
Segment Reporting Information [Line Items]
Services revenue	0	1	4	5
Other Businesses | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Other Businesses | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	1	4	5
Other Businesses | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	0	0	0	0
Eliminations/ Corporate
Segment Reporting Information [Line Items]
Premiums	0	0
Investment income	52	42	154	127
Total revenues	(5,742)	(5,874)	(17,007)	(17,552)
Benefits	(132)	(187)	(374)	(596)
Operating costs	(5,619)	(5,556)	(16,648)	(16,725)
Merger termination fee and related costs, net				(947)
Depreciation and amortization	(26)	(25)	(88)	(74)
Total operating expenses	(5,777)	(5,768)	(17,110)	(18,342)
Income (loss) from operations	35	(106)	103	790
Loss on sale of business	(4)		786
Interest expense	53	59	159	166
Other expense, net	11		11
Income (loss) before income taxes and equity in net earnings	(25)	(165)	(853)	624
Equity in net earnings of Kindred at Home	0	0	0	0
Segment earnings	(25)	(165)	$ (853)	$ 624
Eliminations/ Corporate | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Total external revenues
Segment Reporting Information [Line Items]
Total revenues	0	0
Eliminations/ Corporate | Services
Segment Reporting Information [Line Items]
Services revenue	0	0
Eliminations/ Corporate | Services | Provider
Segment Reporting Information [Line Items]
Services revenue	0	0
Eliminations/ Corporate | Services | ASO and other
Segment Reporting Information [Line Items]
Services revenue	0	0
Eliminations/ Corporate | Services | Pharmacy
Segment Reporting Information [Line Items]
Services revenue	$ 0	$ 0