Humana (HUM) 10-Q 2 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2018shares
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	HUM
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 Common Stock, Shares Outstanding	137,682,171

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 8,855	$ 4,042
Investment securities	9,742	9,557
Receivables, less allowance for doubtful accounts of $87 in 2018 and $96 in 2017	1,276	854
Other current assets	4,059	2,949
Total current assets	23,932	17,402
Property and equipment, net	1,595	1,584
Long-term investment securities	2,361	2,745
Goodwill	3,760	3,281
Other long-term assets	1,805	2,166
Total assets	33,453	27,178
Current liabilities:
Benefits payable	4,961	4,668
Trade accounts payable and accrued expenses	6,266	4,069
Book overdraft	124	141
Unearned revenues	3,706	378
Short-term debt	398	150
Total current liabilities	15,455	9,406
Long-term debt	4,772	4,770
Future policy benefits payable	2,842	2,923
Other long-term liabilities	303	237
Total liabilities	23,372	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; 198,585,156 shares issued at March 31, 2018 and 198,572,458 shares issued at December 31, 2017	33	33
Capital in excess of par value	2,626	2,445
Retained earnings	14,086	13,670
Accumulated other comprehensive (loss) income	(154)	19
Treasury stock, at cost, 60,902,985 shares at March 31, 2018 and 60,893,762 shares at December 31, 2017	(6,510)	(6,325)
Total stockholders’ equity	10,081	9,842
Total liabilities and stockholders’ equity	$ 33,453	$ 27,178

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 87	$ 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)	198,585,156	198,572,458
Treasury stock, shares (in shares)	60,902,985	60,893,762

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Premiums	$ 13,811	$ 13,398
Services	327	253
Investment income	141	111
Total revenues	14,279	13,762
Operating expenses:
Benefits	11,670	11,326
Operating costs	1,749	1,553
Merger termination fee and related costs, net	0	(947)
Depreciation and amortization	100	92
Total operating expenses	13,519	12,024
Income (loss) from operations	760	1,738
Interest expense	53	49
Income (loss) before income taxes	707	1,689
Provision for income taxes	216	574
Net income	$ 491	$ 1,115
Basic earnings per common share (in dollars per share)	$ 3.56	$ 7.54
Diluted earnings per common share (in dollars per share)	3.53	7.49
Dividends declared per common share (in dollars per share)	$ 0.5	$ 0.40

Condensed Consolidated Stateme5

Condensed Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 491	$ 1,115
Other comprehensive (loss) income:
Change in gross unrealized investment gains/losses	(203)	38
Effect of income taxes	52	(14)
Total change in unrealized investment gains/losses, net of tax	(151)	24
Reclassification adjustment for net realized gains included in investment income	(29)	(26)
Effect of income taxes	7	10
Total reclassification adjustment, net of tax	(22)	(16)
Other comprehensive (loss) income, net of tax	(173)	8
Comprehensive income	$ 318	$ 1,123

Condensed Consolidated Stateme6

Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 491	$ 1,115
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized capital gains	(29)	(26)
Stock-based compensation	35	26
Depreciation	109	100
Other intangible amortization	30	18
Provision for deferred income taxes	83	29
Changes in operating assets and liabilities, net of effect of businesses acquired and dispositions:
Receivables	(422)	(558)
Other assets	(1,164)	(415)
Benefits payable	293	198
Other liabilities	885	542
Unearned revenues	3,328	3,140
Other, net	47	36
Net cash provided by operating activities	3,686	4,205
Cash flows from investing activities
Acquisitions, net of cash acquired	(169)	(7)
Purchases of property and equipment	(134)	(122)
Purchases of investment securities	(1,711)	(1,876)
Maturities of investment securities	217	284
Proceeds from sales of investment securities	1,392	795
Net cash used in investing activities	(405)	(926)
Cash flows from financing activities
Receipts from contract deposits, net	1,401	1,730
Proceeds from issuance of senior notes, net	0	991
Proceeds from issuance of commercial paper, net	245	169
Change in book overdraft	(17)	(34)
Common stock repurchases	(51)	(1,574)
Dividends paid	(57)	(47)
Proceeds from stock option exercises and other	11	34
Net cash provided by financing activities	1,532	1,269
Increase in cash and cash equivalents	4,813	4,548
Cash and cash equivalents at beginning of period	4,042	3,877
Cash and cash equivalents at end of period	8,855	8,425
Supplemental cash flow disclosures:
Interest payments	22	10
Income tax payments (refunds), net	$ 4	$ (4)

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS	3 Months Ended
	Mar. 31, 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. Acquisition of a 40% Minority Interest in Kindred’s Homecare Business On December 19, 2017, we announced that we entered into a definitive agreement to acquire a 40% minority interest in the Kindred at Home Division, or Kindred at Home, of Kindred Healthcare, Inc., or Kindred, for estimated cash consideration of approximately $800 million , including our share of transaction and related expenses, to facilitate a complete separation from the Long Term Acute Care and Rehabilitation businesses (the Specialty Hospital company). TPG Capital, or TPG, and Welsh, Carson, Anderson & Stowe, or WCAS, collectively, the Sponsors, along with us are jointly creating 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 will be separated, with the result being that the Specialty Hospital Company will be owned by the Sponsors and Kindred at Home will be owned by a joint venture owned by the Sponsors and us. We will own 40 % of Kindred at Home, with the remaining 60 % owned by a new entity owned by TPG and WCAS. At the closing of the transaction, we will enter a shareholders agreement with the Sponsors that will provide for certain rights and obligations of each party concerning the newly formed joint venture that will own Kindred at Home. 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. Consideration upon exercise of the put option per the agreement would be valued at an exit multiple of 10.5 times the preceding twelve months earnings before interest, income taxes, depreciation and amortization, or EBITDA, subject to certain adjustments. In addition, the multiple is subject to adjustment up to 11.5 times EBITDA based on the achievement of certain pre-defined value-based outcomes tied to clinical metrics. The 11.5 times EBITDA exit multiple is comparable to the valuation of our acquired interest in Kindred at Home. Finally, 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 for cash consideration using the same valuation methodology applicable to the previously discussed put option consideration. The above transactions, which are anticipated to close in the summer of 2018, are subject to customary state and federal regulatory approvals, as well as other customary closing conditions. On April 5, 2018, Kindred's stockholders approved the transaction. We expect to fund the transaction through the use of parent company cash and will account for the minority investment under the equity method. Acquisition of a 40% Minority Interest in Curo Health Services On April 23, 2018, we, along with the same Kindred at Home sponsors, TPG and WCAS, collectively referred to as the "Consortium," entered into a definitive agreement to acquire privately held Curo Health Services, or Curo, one of the nations' leading hospice operators providing care to patients at 245 locations in 22 states. The Consortium is purchasing Curo for approximately $1.4 billion , and at the closing of the transaction, we will have a 40% minority interest. The Curo transaction, which is anticipated to close during the summer of 2018, is subject to customary state and federal regulatory approvals as well as other customary closing conditions . The Curo transaction is not conditioned upon the closing of the Consortium’s separate acquisition of Kindred at Home and is expected to occur after the closing of Kindred at Home. Upon the closing of these transactions, the Consortium intends to merge Curo with the hospice business of Kindred at Home. Sale of Closed Block of Commercial Long-Term Care Insurance Business On November 6, 2017, we entered into a definitive agreement to sell the stock 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 insurance policies . Based on the terms of the definitive agreement we expect to record a net loss associated with the sale of KMG of approximately $350 million . The estimated loss includes a pretax loss of approximately $760 million , offset by the expected tax benefit of approximately $410 million . We will fund the transaction with approximately $203 million of parent company cash contributed into KMG, subject to customary adjustments, in addition to the transfer of approximately $150 million of statutory capital with the sale, which together should be more than offset by the estimated $410 million cash savings associated with the expected tax treatment of the sale. The KMG transaction is anticipated to close by the third quarter of 2018 subject to customary closing conditions, including South Carolina Department of Insurance approval. There can be no assurance we will obtain regulatory approvals needed to sell the business or do so under terms acceptable to us. 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 March 31, 2018 was $94 million and is expected to be 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 March 31, 2018, accounts receivable related to services were $ 162 million . For the three months ended March 31, 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 March 31, 2018. For the three months ended March 31, 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. 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	3 Months Ended
	Mar. 31, 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 98% of our consolidated external revenues for the three months ended March 31, 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 are in the process of reconciling the population of lease agreements and other arrangements that may contain embedded leases for purposes of adopting the new standard. While we expect to record significant leased assets and corresponding lease obligations based on our existing population of individual leases, we continue to evaluate the impact on our results of operations, financial position and 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. 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	3 Months Ended
	Mar. 31, 2018
Business Combinations [Abstract]
ACQUISITIONS AND DIVESTITURES	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. The purchase price allocation is preliminary, subject to completion of valuation analyses, including for example, refining assumptions used to calculate the fair value of intangible assets. On April 10, 2018, we acquired Family Physicians Group, or FPG, for cash considerations of approximately $190 million . FPG is one of the largest at-risk providers serving 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. The acquisition of FPG advances our strategy of helping physicians and clinicians evolve from treating health episodically to managing health holistically. This acquisition is not expected to have a material impact on our results of operations, financial condition, or cash flows. During 2018 and 2017 , we acquired other health and wellness related businesses which, individually or in the aggregate, have not had a material impact on our results of operations, financial condition, or cash flows. The results of operations and financial condition of these businesses have been included in our 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	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
INVESTMENT SECURITIES	INVESTMENT SECURITIES Investment securities classified as current and long-term were as follows at March 31, 2018 and December 31, 2017 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) March 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 505 $ 1 $ (5 ) $ 501 Mortgage-backed securities 2,308 — (56 ) 2,252 Tax-exempt municipal securities 3,549 6 (61 ) 3,494 Mortgage-backed securities: Residential 24 — (1 ) 23 Commercial 580 — (11 ) 569 Asset-backed securities 554 1 (1 ) 554 Corporate debt securities 4,693 131 (114 ) 4,710 Total debt securities $ 12,213 $ 139 $ (249 ) $ 12,103 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 March 31, 2018 and December 31, 2017 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) March 31, 2018 U.S. Treasury and other U.S. U.S. Treasury and agency $ 362 $ (2 ) $ 129 $ (3 ) $ 491 $ (5 ) Mortgage-backed 1,489 (28 ) 638 (28 ) 2,127 (56 ) Tax-exempt municipal 2,409 (41 ) 621 (20 ) 3,030 (61 ) Mortgage-backed securities: Residential 18 — 3 (1 ) 21 (1 ) Commercial 451 (10 ) 28 (1 ) 479 (11 ) Asset-backed securities 162 (1 ) 7 — 169 (1 ) Corporate debt securities 2,431 (60 ) 761 (54 ) 3,192 (114 ) Total debt securities $ 7,322 $ (142 ) $ 2,187 $ (107 ) $ 9,509 $ (249 ) 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 99% 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 March 31, 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 1,410 positions out of a total of approximately 2,230 positions at March 31, 2018 . All issuers of securities we own that were trading at an unrealized loss at March 31, 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 March 31, 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 March 31, 2018 . The detail of realized gains (losses) related to investment securities and included within investment income was as follows for the three months ended March 31, 2018 and 2017 : Three months ended 2018 2017 (in millions) Gross realized gains $ 32 $ 27 Gross realized losses (3 ) (1 ) Net realized capital gains $ 29 $ 26 There were no material other-than-temporary impairments for the three months ended March 31, 2018 or 2017 . The contractual maturities of debt securities available for sale at March 31, 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 $ 856 $ 854 Due after one year through five years 2,846 2,803 Due after five years through ten years 2,317 2,247 Due after ten years 2,728 2,801 Mortgage and asset-backed securities 3,466 3,398 Total debt securities $ 12,213 $ 12,103

FAIR VALUE

FAIR VALUE	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE	FAIR VALUE Financial Assets The following table summarizes our fair value measurements at March 31, 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) March 31, 2018 Cash equivalents $ 4,346 $ 4,346 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 501 — 501 — Mortgage-backed securities 2,252 — 2,252 — Tax-exempt municipal securities 3,494 — 3,494 — Mortgage-backed securities: Residential 23 — 23 — Commercial 569 — 569 — Asset-backed securities 554 — 554 — Corporate debt securities 4,710 — 4,709 1 Total debt securities 12,103 — 12,102 1 Total invested assets $ 16,449 $ 4,346 $ 12,102 $ 1 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 There were no material transfers between Level 1 and Level 2 during the three months ended March 31, 2018 or 2017 . 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 $4,772 million at March 31, 2018 and $4,770 million at December 31, 2017 . The fair value of our senior notes debt was $4,944 million at March 31, 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 March 31, 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 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	3 Months Ended
	Mar. 31, 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 March 31, 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. March 31, 2018 December 31, 2017 Risk CMS Risk CMS (in millions) Other current assets $ 5 $ 79 $ 4 $ 101 Trade accounts payable and accrued expenses (240 ) (2,509 ) (255 ) (1,085 ) Net current liability (235 ) (2,430 ) (251 ) (984 ) Other long-term assets 33 — — — Other long-term liabilities (78 ) — (28 ) — Net long-term liability (45 ) — (28 ) — Total net liability $ (280 ) $ (2,430 ) $ (279 ) $ (984 )

HEALTH CARE REFORM

HEALTH CARE REFORM	3 Months Ended
	Mar. 31, 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. The accompanying condensed consolidated balance sheets include the following amounts associated with the 3Rs at March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Prior Coverage Years Premiums receivable $ 65 $ — $ 62 $ — Other current assets — — — 44 Trade accounts payable and (79 ) — (80 ) — Net current (liability) asset (14 ) — (18 ) 44 Other long-term assets — — 5 — Total prior coverage years' net (liability) asset (14 ) — (13 ) 44 Current Coverage Year Other long-term assets 1 — — — Other long-term liabilities (11 ) — — — Net long-term liability (10 ) — — — Total 2018 coverage year net liability (10 ) — — — Total net (liability) asset $ (24 ) $ — $ (13 ) $ 44 Net collections under the 3R's associated with prior coverage years were $46 million during the three months ended March 31, 2018 and were $62 million during the three months ended March 31, 2017 . In September 2018, we expect to pay the federal government $1.05 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 2017 when the fee was 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 $263 million for the three months ended March 31, 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 suspended for calendar year 2019 .

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 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 three months ended March 31, 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 360 — 119 479 Balance at March 31, 2018 $ 1,419 $ 261 $ 2,080 $ 3,760 The following table presents details of our other intangible assets included in other long-term assets in the accompanying condensed consolidated balance sheets at March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 9.6 years $ 646 $ 414 $ 232 $ 566 $ 401 $ 165 Trade names and 6.5 years 83 78 5 104 84 20 Provider contracts 11.9 years 68 32 36 68 30 38 Noncompetes and 8.1 years 32 29 3 32 29 3 Total other intangible 9.4 years $ 829 $ 553 $ 276 $ 770 $ 544 $ 226 For the three months ended March 31, 2018 and 2017 , amortization expense for other intangible assets was approximately $30 million and $18 million , respectively. Amortization expense for the three months ended March 31, 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 $ 84 2019 63 2020 61 2021 27 2022 24 2023 16

BENEFITS PAYABLE

BENEFITS PAYABLE	3 Months Ended
	Mar. 31, 2018
Insurance [Abstract]
BENEFITS PAYABLE	BENEFITS PAYABLE On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the three months ended March 31, 2018 and 2017 : For the three months ended March 31, 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 11,947 11,580 Prior years (267 ) (231 ) Total incurred 11,680 11,349 Paid related to: Current year (7,775 ) (7,695 ) Prior years (3,619 ) (3,451 ) Total paid (11,394 ) (11,146 ) Reinsurance recoverable 77 71 Balances, end of period $ 4,961 $ 4,761 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 three months ended March 31, 2018 and 2017 . For the three months ended March 31, 2018 2017 (in millions) Future policy benefits: Individual Commercial $ (16 ) $ (33 ) Other Businesses 6 10 Total future policy benefits $ (10 ) $ (23 ) 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 March 31, 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 three months ended March 31, 2018 and 2017 : For the three months ended March 31, 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 10,739 10,255 Prior years (187 ) (204 ) Total incurred 10,552 10,051 Paid related to: Current year (7,119 ) (7,014 ) Prior years (3,082 ) (2,572 ) Total paid (10,201 ) (9,586 ) Reinsurance recoverable 77 71 Balances, end of period $ 4,321 $ 3,967 At March 31, 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 three months ended March 31, 2018 and 2017 : For the three months ended March 31, 2018 2017 (in millions) Balances, beginning of period $ 568 $ 578 Incurred related to: Current year 1,307 1,306 Prior years (34 ) (20 ) Total incurred 1,273 1,286 Paid related to: Current year (802 ) (824 ) Prior years (463 ) (493 ) Total paid (1,265 ) (1,317 ) Balances, end of period $ 576 $ 547 At March 31, 2018 , benefits payable for our Group and Specialty segment included IBNR of approximately $502 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 three months ended March 31, 2018 and 2017 : For the three months ended March 31, 2018 2017 (in millions) Balances, beginning of period $ 101 $ 454 Incurred related to: Current year — 195 Prior years (44 ) (6 ) Total incurred (44 ) 189 Paid related to: Current year — (59 ) Prior years (29 ) (363 ) Total paid (29 ) (422 ) Balance, end of period $ 28 $ 221 At March 31, 2018 , benefits payable for our Individual Commercial segment included IBNR of approximately $19 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 March 31, 2018 Net outstanding liabilities Retail $ 4,244 Group and Specialty 576 Individual Commercial 28 Other Businesses 36 Benefits payable, net of reinsurance 4,884 Reinsurance recoverable on unpaid claims Retail 77 Total reinsurance recoverable on unpaid claims 77 Total benefits payable, gross $ 4,961

EARNINGS PER COMMON SHARE COMPU

EARNINGS PER COMMON SHARE COMPUTATION	3 Months Ended
	Mar. 31, 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 months ended March 31, 2018 and 2017 : Three months ended March 31, 2018 2017 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 491 $ 1,115 Weighted average outstanding shares of common stock 137,903 147,824 Dilutive effect of: Employee stock options 213 199 Restricted stock 714 849 Shares used to compute diluted earnings per common share 138,830 148,872 Basic earnings per common share $ 3.56 $ 7.54 Diluted earnings per common share $ 3.53 $ 7.49 Number of antidilutive stock options and restricted stock 645 938

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 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 On April 19, 2018 , the Board declared a cash dividend of $0.50 per share payable on July 27, 2018 , to stockholders of record on June 29, 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, the December 2017 ASR, with Bank of America, N.A., or BofA, to repurchase $1.0 billion of our common stock as part of the $3.0 billion share repurchase program authorized on December 14, 2017 . On December 22, 2017 , we made a payment of $1.0 billion to BofA from available cash on hand and received an initial delivery of 3.28 million shares of our common stock from BofA based on the then current market price of Humana common stock. The payment to BofA was recorded as a reduction to stockholders’ equity, consisting of an $800 million increase in treasury stock, which 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. Our remaining repurchase authorization was approximately $2 billion as of May 1, 2018. In connection with employee stock plans, we acquired 0.19 million common shares for $51 million and 0.35 million common shares for $74 million during the three months ended March 31, 2018 and 2017 , respectively. Treasury Stock Reissuance We reissued 0.63 million shares of treasury stock during the three months ended March 31, 2018 at a cost of $66 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 $110 million at March 31, 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 $44 million , net of tax, at March 31, 2018 and $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	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The effective income tax rate was 30.7% for the three months ended March 31, 2018 , compared to 34.0% for the three months ended March 31, 2017 primarily due to the tax reform law enacted on December 22, 2017 (the "Tax Reform Law") , partially offset by the impact of the reinstatement of the non-deductible health insurance industry fee in 2018. The income tax rate for the three months ended March 31, 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 three months ended March 31, 2018 by $6.6 million .

DEBT

DEBT	3 Months Ended
	Mar. 31, 2018
Debt Disclosure [Abstract]
DEBT	DEBT The carrying value of long-term debt outstanding, net of unamortized debt issuance costs, was as follows at March 31, 2018 and December 31, 2017 : March 31, 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 397 397 $400 million, 2.90% due December 15, 2022 396 396 $600 million, 3.15% due December 1, 2022 596 595 $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 $ 4,772 $ 4,770 Senior Notes 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 In May 2017 we amended and restated our previous 5 -year $1.0 billion unsecured revolving credit agreement expiring July 2018 with a 5 -year $2.0 billion unsecured revolving credit agreement which 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, including a customary material adverse effect clause which could limit our ability to borrow additional funds. In addition, the credit agreement contains customary restrictive and financial covenants as well as customary events of default, including financial covenants regarding the maintenance of a minimum level of net worth of $9.5 billion at March 31, 2018 and a maximum leverage ratio of 3.0 :1 . We are in compliance with the financial covenants, with actual net worth of $10.1 billion and an actual leverage ratio of 1.4 :1 as measured in accordance with the credit agreement as of March 31, 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 March 31, 2018 , we had no borrowings and no letters of credit outstanding under the credit agreement . Accordingly, as of March 31, 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 We previously entered into a commercial paper program pursuant to which we may issue short-term, unsecured commercial paper notes privately placed on a discount basis through certain broker dealers. On June 15, 2017, we increased the size of the commercial paper program to permit the issuance of the commercial notes with the aggregate face or principal amount outstanding under the program 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 three months ended March 31, 2018 was $442 million . There were outstanding borrowings of $398 million at March 31, 2018 and $150 million at December 31, 2017 .

GUARANTEES AND CONTINGENCIES

GUARANTEES AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
GUARANTEES AND CONTINGENCIES	GUARANTEES AND CONTINGENCIES Government Contracts Our Medicare products, which accounted for approximately 81% of our total premiums and services revenue for the three months ended March 31, 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. Our bids for the 2019 calendar year are due by June 4, 2018. 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 claims 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 provides that, in calculating the economic impact of audit results for an MA contract, if any, the results of the RADV audit sample will 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. 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 released. 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. However, as indicated, we are awaiting additional guidance from CMS regarding the FFS Adjuster. Accordingly, we cannot determine whether such RADV audits will 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, CMS' comments in formalized guidance regarding “overpayments” to MA plans appear to be inconsistent with CMS' prior RADV audit guidance. These 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, appear to equate each Medicare Advantage risk adjustment data error with an “overpayment” without reconciliation to the principles underlying the FFS Adjuster referenced above. 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 March 31, 2018 , our military services business, which accounted for approximately 1% of our total premiums and services revenue for the three months ended March 31, 2018 , primarily consisted of the T2017 TRICARE 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 six million TRICARE beneficiaries, under which delivery of health care services commenced on January 1, 2018. The T2017 East Region contract is a 5-year contract set to expire on December 31, 2022 and is subject to renewals on January 1 of each year during its term at the government's option. Our state-based Medicaid business accounted for approximately 4% of our total premiums and services revenue for the three months ended March 31, 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 by comparison of our Medicare Advantage profitability to our non-Medicare Advantage business profitability and a requirement 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. 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 March 31, 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 lawsuit is unsealed, and 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	3 Months Ended
	Mar. 31, 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 and voluntary insurance benefits and financial protection products, 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. 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. 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 $2.9 billion and $3.0 billion for the three months ended March 31, 2018 and 2017 , 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 $39 million and $26 million for the three months ended March 31, 2018 and 2017 , 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 months ended March 31, 2018 and 2017 : Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2018 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,970 $ — $ — $ — $ — $ — $ 8,970 Group Medicare Advantage 1,524 — — — — — 1,524 Medicare stand-alone PDP 896 — — — — — 896 Total Medicare 11,390 — — — — — 11,390 Fully-insured 125 1,392 — (5 ) — — 1,512 Specialty — 347 — — — — 347 Medicaid and other 553 — — — 9 — 562 Total premiums 12,068 1,739 — (5 ) 9 — 13,811 Services revenue: Provider — — 65 — — — 65 ASO and other 2 219 — — 2 — 223 Pharmacy — — 39 — — — 39 Total services revenue 2 219 104 — 2 — 327 Total revenues - external customers 12,070 1,958 104 (5 ) 11 — 14,138 Intersegment revenues Services — 5 4,018 — — (4,023 ) — Products — — 1,535 — — (1,535 ) — Total intersegment revenues — 5 5,553 — — (5,558 ) — Investment income 37 7 6 — 35 56 141 Total revenues 12,107 1,970 5,663 (5 ) 46 (5,502 ) 14,279 Operating expenses: Benefits 10,552 1,273 — (60 ) 26 (121 ) 11,670 Operating costs 1,222 463 5,441 2 2 (5,381 ) 1,749 Depreciation and amortization 66 23 49 — — (38 ) 100 Total operating expenses 11,840 1,759 5,490 (58 ) 28 (5,540 ) 13,519 Income from operations 267 211 173 53 18 38 760 Interest expense — — — — — 53 53 Income (loss) before income taxes $ 267 $ 211 $ 173 $ 53 $ 18 $ (15 ) $ 707 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2017 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,376 $ — $ — $ — $ — $ — $ 8,376 Group Medicare Advantage 1,318 — — — — — 1,318 Medicare stand-alone PDP 941 — — — — — 941 Total Medicare 10,635 — — — — — 10,635 Fully-insured 118 1,378 — 283 — — 1,779 Specialty — 322 — — — — 322 Medicaid and other 653 — — — 9 — 662 Total premiums 11,406 1,700 — 283 9 — 13,398 Services revenue: Provider — — 70 — — — 70 ASO and other 2 161 — — 2 — 165 Pharmacy — — 18 — — — 18 Total services revenue 2 161 88 — 2 — 253 Total revenues - external customers 11,408 1,861 88 283 11 — 13,651 Intersegment revenues Services — 5 4,310 — — (4,315 ) — Products — — 1,552 — — (1,552 ) — Total intersegment revenues — 5 5,862 — — (5,867 ) — Investment income 25 11 8 1 21 45 111 Total revenues 11,433 1,877 5,958 284 32 (5,822 ) 13,762 Operating expenses: Benefits 10,051 1,286 — 156 29 (196 ) 11,326 Operating costs 954 399 5,680 62 4 (5,546 ) 1,553 Merger termination fee and related costs, net — — — — — (947 ) (947 ) Depreciation and amortization 58 21 34 3 — (24 ) 92 Total operating expenses 11,063 1,706 5,714 221 33 (6,713 ) 12,024 Income (loss) from operations 370 171 244 63 (1 ) 891 1,738 Interest expense — — — — — 49 49 Income (loss) before income taxes $ 370 $ 171 $ 244 $ 63 $ (1 ) $ 842 $ 1,689

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) March 31, 2018 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 505 $ 1 $ (5 ) $ 501 Mortgage-backed securities 2,308 — (56 ) 2,252 Tax-exempt municipal securities 3,549 6 (61 ) 3,494 Mortgage-backed securities: Residential 24 — (1 ) 23 Commercial 580 — (11 ) 569 Asset-backed securities 554 1 (1 ) 554 Corporate debt securities 4,693 131 (114 ) 4,710 Total debt securities $ 12,213 $ 139 $ (249 ) $ 12,103 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 March 31, 2018 and December 31, 2017 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) March 31, 2018 U.S. Treasury and other U.S. U.S. Treasury and agency $ 362 $ (2 ) $ 129 $ (3 ) $ 491 $ (5 ) Mortgage-backed 1,489 (28 ) 638 (28 ) 2,127 (56 ) Tax-exempt municipal 2,409 (41 ) 621 (20 ) 3,030 (61 ) Mortgage-backed securities: Residential 18 — 3 (1 ) 21 (1 ) Commercial 451 (10 ) 28 (1 ) 479 (11 ) Asset-backed securities 162 (1 ) 7 — 169 (1 ) Corporate debt securities 2,431 (60 ) 761 (54 ) 3,192 (114 ) Total debt securities $ 7,322 $ (142 ) $ 2,187 $ (107 ) $ 9,509 $ (249 ) 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 months ended March 31, 2018 and 2017 : Three months ended 2018 2017 (in millions) Gross realized gains $ 32 $ 27 Gross realized losses (3 ) (1 ) Net realized capital gains $ 29 $ 26
Schedule of Contractual Maturity of Debt Securities Available for Sale	The contractual maturities of debt securities available for sale at March 31, 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 $ 856 $ 854 Due after one year through five years 2,846 2,803 Due after five years through ten years 2,317 2,247 Due after ten years 2,728 2,801 Mortgage and asset-backed securities 3,466 3,398 Total debt securities $ 12,213 $ 12,103

FAIR VALUE (Tables)

FAIR VALUE (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Financial Assets Measured at Fair Value on Recurring Basis	The following table summarizes our fair value measurements at March 31, 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) March 31, 2018 Cash equivalents $ 4,346 $ 4,346 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 501 — 501 — Mortgage-backed securities 2,252 — 2,252 — Tax-exempt municipal securities 3,494 — 3,494 — Mortgage-backed securities: Residential 23 — 23 — Commercial 569 — 569 — Asset-backed securities 554 — 554 — Corporate debt securities 4,710 — 4,709 1 Total debt securities 12,103 — 12,102 1 Total invested assets $ 16,449 $ 4,346 $ 12,102 $ 1 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)	3 Months Ended
	Mar. 31, 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 March 31, 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. March 31, 2018 December 31, 2017 Risk CMS Risk CMS (in millions) Other current assets $ 5 $ 79 $ 4 $ 101 Trade accounts payable and accrued expenses (240 ) (2,509 ) (255 ) (1,085 ) Net current liability (235 ) (2,430 ) (251 ) (984 ) Other long-term assets 33 — — — Other long-term liabilities (78 ) — (28 ) — Net long-term liability (45 ) — (28 ) — Total net liability $ (280 ) $ (2,430 ) $ (279 ) $ (984 )

HEALTH CARE REFORM (Tables)

HEALTH CARE REFORM (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Prior Coverage Years Premiums receivable $ 65 $ — $ 62 $ — Other current assets — — — 44 Trade accounts payable and (79 ) — (80 ) — Net current (liability) asset (14 ) — (18 ) 44 Other long-term assets — — 5 — Total prior coverage years' net (liability) asset (14 ) — (13 ) 44 Current Coverage Year Other long-term assets 1 — — — Other long-term liabilities (11 ) — — — Net long-term liability (10 ) — — — Total 2018 coverage year net liability (10 ) — — — Total net (liability) asset $ (24 ) $ — $ (13 ) $ 44

GOODWILL AND OTHER INTANGIBLE26

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 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 three months ended March 31, 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 360 — 119 479 Balance at March 31, 2018 $ 1,419 $ 261 $ 2,080 $ 3,760
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 March 31, 2018 and December 31, 2017 . March 31, 2018 December 31, 2017 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 9.6 years $ 646 $ 414 $ 232 $ 566 $ 401 $ 165 Trade names and 6.5 years 83 78 5 104 84 20 Provider contracts 11.9 years 68 32 36 68 30 38 Noncompetes and 8.1 years 32 29 3 32 29 3 Total other intangible 9.4 years $ 829 $ 553 $ 276 $ 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 $ 84 2019 63 2020 61 2021 27 2022 24 2023 16

BENEFITS PAYABLE (Tables)

BENEFITS PAYABLE (Tables)	3 Months Ended
	Mar. 31, 2018
Insurance [Abstract]
Activity in Benefits Payable	Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the three months ended March 31, 2018 and 2017 : For the three months ended March 31, 2018 2017 (in millions) Balances, beginning of period $ 568 $ 578 Incurred related to: Current year 1,307 1,306 Prior years (34 ) (20 ) Total incurred 1,273 1,286 Paid related to: Current year (802 ) (824 ) Prior years (463 ) (493 ) Total paid (1,265 ) (1,317 ) Balances, end of period $ 576 $ 547 On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the three months ended March 31, 2018 and 2017 : For the three months ended March 31, 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 11,947 11,580 Prior years (267 ) (231 ) Total incurred 11,680 11,349 Paid related to: Current year (7,775 ) (7,695 ) Prior years (3,619 ) (3,451 ) Total paid (11,394 ) (11,146 ) Reinsurance recoverable 77 71 Balances, end of period $ 4,961 $ 4,761 Activity in benefits payable for our Retail segment was as follows for the three months ended March 31, 2018 and 2017 : For the three months ended March 31, 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 10,739 10,255 Prior years (187 ) (204 ) Total incurred 10,552 10,051 Paid related to: Current year (7,119 ) (7,014 ) Prior years (3,082 ) (2,572 ) Total paid (10,201 ) (9,586 ) Reinsurance recoverable 77 71 Balances, end of period $ 4,321 $ 3,967 Activity in benefits payable for our Individual Commercial segment was as follows for the three months ended March 31, 2018 and 2017 : For the three months ended March 31, 2018 2017 (in millions) Balances, beginning of period $ 101 $ 454 Incurred related to: Current year — 195 Prior years (44 ) (6 ) Total incurred (44 ) 189 Paid related to: Current year — (59 ) Prior years (29 ) (363 ) Total paid (29 ) (422 ) Balance, end of period $ 28 $ 221
Benefit Expenses Excluded From Activity in Benefits Payable	Benefits expense excluded from the previous table was as follows for the three months ended March 31, 2018 and 2017 . For the three months ended March 31, 2018 2017 (in millions) Future policy benefits: Individual Commercial $ (16 ) $ (33 ) Other Businesses 6 10 Total future policy benefits $ (10 ) $ (23 )
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 March 31, 2018 Net outstanding liabilities Retail $ 4,244 Group and Specialty 576 Individual Commercial 28 Other Businesses 36 Benefits payable, net of reinsurance 4,884 Reinsurance recoverable on unpaid claims Retail 77 Total reinsurance recoverable on unpaid claims 77 Total benefits payable, gross $ 4,961

EARNINGS PER COMMON SHARE COM28

EARNINGS PER COMMON SHARE COMPUTATION (Tables)	3 Months Ended
	Mar. 31, 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 months ended March 31, 2018 and 2017 : Three months ended March 31, 2018 2017 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 491 $ 1,115 Weighted average outstanding shares of common stock 137,903 147,824 Dilutive effect of: Employee stock options 213 199 Restricted stock 714 849 Shares used to compute diluted earnings per common share 138,830 148,872 Basic earnings per common share $ 3.56 $ 7.54 Diluted earnings per common share $ 3.53 $ 7.49 Number of antidilutive stock options and restricted stock 645 938

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 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

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 2018 and December 31, 2017 : March 31, 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 397 397 $400 million, 2.90% due December 15, 2022 396 396 $600 million, 3.15% due December 1, 2022 596 595 $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 $ 4,772 $ 4,770

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, By Segment	Our segment results were as follows for the three months ended March 31, 2018 and 2017 : Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2018 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,970 $ — $ — $ — $ — $ — $ 8,970 Group Medicare Advantage 1,524 — — — — — 1,524 Medicare stand-alone PDP 896 — — — — — 896 Total Medicare 11,390 — — — — — 11,390 Fully-insured 125 1,392 — (5 ) — — 1,512 Specialty — 347 — — — — 347 Medicaid and other 553 — — — 9 — 562 Total premiums 12,068 1,739 — (5 ) 9 — 13,811 Services revenue: Provider — — 65 — — — 65 ASO and other 2 219 — — 2 — 223 Pharmacy — — 39 — — — 39 Total services revenue 2 219 104 — 2 — 327 Total revenues - external customers 12,070 1,958 104 (5 ) 11 — 14,138 Intersegment revenues Services — 5 4,018 — — (4,023 ) — Products — — 1,535 — — (1,535 ) — Total intersegment revenues — 5 5,553 — — (5,558 ) — Investment income 37 7 6 — 35 56 141 Total revenues 12,107 1,970 5,663 (5 ) 46 (5,502 ) 14,279 Operating expenses: Benefits 10,552 1,273 — (60 ) 26 (121 ) 11,670 Operating costs 1,222 463 5,441 2 2 (5,381 ) 1,749 Depreciation and amortization 66 23 49 — — (38 ) 100 Total operating expenses 11,840 1,759 5,490 (58 ) 28 (5,540 ) 13,519 Income from operations 267 211 173 53 18 38 760 Interest expense — — — — — 53 53 Income (loss) before income taxes $ 267 $ 211 $ 173 $ 53 $ 18 $ (15 ) $ 707 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2017 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,376 $ — $ — $ — $ — $ — $ 8,376 Group Medicare Advantage 1,318 — — — — — 1,318 Medicare stand-alone PDP 941 — — — — — 941 Total Medicare 10,635 — — — — — 10,635 Fully-insured 118 1,378 — 283 — — 1,779 Specialty — 322 — — — — 322 Medicaid and other 653 — — — 9 — 662 Total premiums 11,406 1,700 — 283 9 — 13,398 Services revenue: Provider — — 70 — — — 70 ASO and other 2 161 — — 2 — 165 Pharmacy — — 18 — — — 18 Total services revenue 2 161 88 — 2 — 253 Total revenues - external customers 11,408 1,861 88 283 11 — 13,651 Intersegment revenues Services — 5 4,310 — — (4,315 ) — Products — — 1,552 — — (1,552 ) — Total intersegment revenues — 5 5,862 — — (5,867 ) — Investment income 25 11 8 1 21 45 111 Total revenues 11,433 1,877 5,958 284 32 (5,822 ) 13,762 Operating expenses: Benefits 10,051 1,286 — 156 29 (196 ) 11,326 Operating costs 954 399 5,680 62 4 (5,546 ) 1,553 Merger termination fee and related costs, net — — — — — (947 ) (947 ) Depreciation and amortization 58 21 34 3 — (24 ) 92 Total operating expenses 11,063 1,706 5,714 221 33 (6,713 ) 12,024 Income (loss) from operations 370 171 244 63 (1 ) 891 1,738 Interest expense — — — — — 49 49 Income (loss) before income taxes $ 370 $ 171 $ 244 $ 63 $ (1 ) $ 842 $ 1,689

BASIS OF PRESENTATION AND SIG32

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS - Acquisition of a Minority Interest (Details) - Forecast $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)locationState
Consortium
Noncontrolling Interest [Line Items]
Payments to acquire equity method investments	$ 1,400
TPG Capital and Welsh, Carson, Anderson and Stowe
Noncontrolling Interest [Line Items]
Noncontrolling interest ownership percentage by parent	60.00%
Kindred’s Homecare Business
Noncontrolling Interest [Line Items]
Equity method investment, ownership percentage	40.00%
Payments to acquire equity method investments	$ 800
Consideration upon exercise of put option, EBITDA multiple	10.5
Consideration adjustment upon exercise of put option, EBITDA multiple (up to)	11.5
Curo Health Services
Noncontrolling Interest [Line Items]
Equity method investment, ownership percentage	40.00%
Equity method investment, number of locations | location	245
Equity method investment, number of states | State	22

BASIS OF PRESENTATION AND SIG33

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS - Sale of Closed Block of Commercial Long-Term Care Insurance Business (Details) - KMG America Corporation - Disposed of by Sale - Forecast $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Estimated net loss on sale of subsidiary	$ 350
Estimated pretax loss on sale of subsidiary	760
Expected tax benefit on sale of subsidiary	410
Parent company cash contributed to sale of subsidiary	203
Transfer of statutory capital with sale of subsidiary	$ 150

BASIS OF PRESENTATION AND SIG34

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS - Workforce Optimization, Aetna Merger, and Revenue Recognition (Details) $ / shares in Units, $ in Millions	Feb. 16, 2017USD ($)	Mar. 31, 2018USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)employee$ / shares
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		$ 94		$ 140
Break up fee received	$ 1,000	0	$ (947)
Accounts receivable		1,276		$ 854
Services Accounts Receivable
Business Acquisition [Line Items]
Accounts receivable		$ 162

RECENTLY ISSUED ACCOUNTING PR35

RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (Details)	3 Months Ended
	Mar. 31, 2018
Revenue From Premiums and Investment Income | Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage	98.00%

ACQUISITIONS AND DIVESTITURES -

ACQUISITIONS AND DIVESTITURES - Narrative (Details) - USD ($) $ in Millions	Apr. 10, 2018	Mar. 01, 2018	Mar. 31, 2018
Business Acquisition [Line Items]
Goodwill, acquired during period			$ 479
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
MCCI
Business Acquisition [Line Items]
Notes receivable and revolving note, related party		$ 383
Subsequent Event | FPG
Business Acquisition [Line Items]
Payments to acquire business	$ 190

INVESTMENT SECURITIES - Securit

INVESTMENT SECURITIES - Securities Classified as Current and Long-Term (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Amortized Cost	$ 12,213	$ 12,104
Gross Unrealized Gains	139	286
Gross Unrealized Losses	(249)	(88)
Fair Value	12,103	12,302
Debt Securities | Tax-exempt municipal securities
Investment [Line Items]
Amortized Cost	3,549	3,884
Gross Unrealized Gains	6	33
Gross Unrealized Losses	(61)	(28)
Fair Value	3,494	3,889
Debt Securities | Residential Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	24	26
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Fair Value	23	26
Debt Securities | Commercial Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	580	455
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(11)	(2)
Fair Value	569	456
Debt Securities | Asset-backed securities
Investment [Line Items]
Amortized Cost	554	407
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(1)	0
Fair Value	554	408
Debt Securities | Corporate debt securities
Investment [Line Items]
Amortized Cost	4,693	5,175
Gross Unrealized Gains	131	244
Gross Unrealized Losses	(114)	(37)
Fair Value	4,710	5,382
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Investment [Line Items]
Amortized Cost	505	532
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(5)	(2)
Fair Value	501	531
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Investment [Line Items]
Amortized Cost	2,308	1,625
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(56)	(19)
Fair Value	$ 2,252	$ 1,610

INVESTMENT SECURITIES - Gross U

INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Less than 12 months, Fair Value	$ 7,322	$ 3,999
Less than 12 months, Gross Unrealized Losses	(142)	(30)
12 months or more, Fair Value	2,187	2,308
12 months or more, Gross Unrealized Losses	(107)	(58)
Total, Fair Value	9,509	6,307
Total, Gross Unrealized Losses	(249)	(88)
Debt Securities | Tax-exempt municipal securities
Investment [Line Items]
Less than 12 months, Fair Value	2,409	1,590
Less than 12 months, Gross Unrealized Losses	(41)	(16)
12 months or more, Fair Value	621	661
12 months or more, Gross Unrealized Losses	(20)	(12)
Total, Fair Value	3,030	2,251
Total, Gross Unrealized Losses	(61)	(28)
Debt Securities | Residential Mortgage-Backed Securities
Investment [Line Items]
Less than 12 months, Fair Value	18	20
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	3	3
12 months or more, Gross Unrealized Losses	(1)	0
Total, Fair Value	21	23
Total, Gross Unrealized Losses	(1)	0
Debt Securities | Commercial Mortgage-Backed Securities
Investment [Line Items]
Less than 12 months, Fair Value	451	131
Less than 12 months, Gross Unrealized Losses	(10)	(1)
12 months or more, Fair Value	28	28
12 months or more, Gross Unrealized Losses	(1)	(1)
Total, Fair Value	479	159
Total, Gross Unrealized Losses	(11)	(2)
Debt Securities | Asset-backed securities
Investment [Line Items]
Less than 12 months, Fair Value	162	107
Less than 12 months, Gross Unrealized Losses	(1)	0
12 months or more, Fair Value	7	10
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	169	117
Total, Gross Unrealized Losses	(1)	0
Debt Securities | Corporate debt securities
Investment [Line Items]
Less than 12 months, Fair Value	2,431	1,297
Less than 12 months, Gross Unrealized Losses	(60)	(10)
12 months or more, Fair Value	761	804
12 months or more, Gross Unrealized Losses	(54)	(27)
Total, Fair Value	3,192	2,101
Total, Gross Unrealized Losses	(114)	(37)
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Investment [Line Items]
Less than 12 months, Fair Value	362	273
Less than 12 months, Gross Unrealized Losses	(2)	(1)
12 months or more, Fair Value	129	130
12 months or more, Gross Unrealized Losses	(3)	(1)
Total, Fair Value	491	403
Total, Gross Unrealized Losses	(5)	(2)
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Investment [Line Items]
Less than 12 months, Fair Value	1,489	581
Less than 12 months, Gross Unrealized Losses	(28)	(2)
12 months or more, Fair Value	638	672
12 months or more, Gross Unrealized Losses	(28)	(17)
Total, Fair Value	2,127	1,253
Total, Gross Unrealized Losses	$ (56)	$ (19)

INVESTMENT SECURITIES - Additio

INVESTMENT SECURITIES - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)position	Mar. 31, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Percentage of debt securities considered to be of investment-grade	99.00%
Maximum percentage of any general obligation bonds in one state	9.00%
Percent of tax exempt securities insured	2.00%
Securities in unrealized loss positions, number of positions	1,410
Number of positions	2,230
Other-than-temporary impairments | $	$ 0	$ 0

INVESTMENT SECURITIES - Realize

INVESTMENT SECURITIES - Realized Gains (Losses) Within Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 32	$ 27
Gross realized losses	(3)	(1)
Net realized capital gains	$ 29	$ 26

INVESTMENT SECURITIES - Contrac

INVESTMENT SECURITIES - Contractual Maturities, Available for Sale (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Due within one year	$ 856
Due after one year through five years	2,846
Due after five years through ten years	2,317
Due after ten years	2,728
Mortgage and asset-backed securities	3,466
Amortized Cost	12,213	$ 12,104
Fair Value
Due within one year	854
Due after one year through five years	2,803
Due after five years through ten years	2,247
Due after ten years	2,801
Mortgage and asset-backed securities	3,398
Fair Value	$ 12,103	$ 12,302

FAIR VALUE - Financial Assets M

FAIR VALUE - Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 12,103	$ 12,302
Measured On Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	4,346	4,564
Debt securities	12,103	12,302
Total invested assets	16,449	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	3,494	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	23	26
Measured On Recurring Basis | Commercial Mortgage-Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	569	456
Measured On Recurring Basis | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	554	408
Measured On Recurring Basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	4,710	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	501	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	2,252	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	4,346	4,564
Debt securities	0	0
Total invested assets	4,346	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	12,102	12,301
Total invested assets	12,102	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	3,494	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	23	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	569	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	554	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	4,709	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	501	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	2,252	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	1	1
Total invested assets	1	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	1	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	Mar. 31, 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	4,772	4,770
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Carrying value of debt outstanding	$ 4,944	$ 5,191

MEDICARE PART D (Detail)

MEDICARE PART D (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Other current assets	$ 4,059	$ 2,949
Trade accounts payable and accrued expenses	(6,266)	(4,069)
Other long-term assets	1,805	2,166
Other long-term liabilities	(303)	(237)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	5	4
Trade accounts payable and accrued expenses	(240)	(255)
Net current (liability) asset	(235)	(251)
Other long-term assets	33	0
Other long-term liabilities	(78)	(28)
Net long-term liability	(45)	(28)
Total net (liability) asset	(280)	(279)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	79	101
Trade accounts payable and accrued expenses	(2,509)	(1,085)
Net current (liability) asset	(2,430)	(984)
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term liability	0	0
Total net (liability) asset	$ (2,430)	$ (984)

HEALTH CARE REFORM (Details)

HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Sep. 30, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Nov. 02, 2017
Supplementary Insurance Information, by Segment [Line Items]
Litigation recoveries sought					$ 611
Other current assets		$ 4,059		$ 2,949
Trade accounts payable and accrued expenses		(6,266)		(4,069)
Other long-term assets		1,805		2,166
Other long-term liabilities		(303)		(237)
Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		(24)		(13)
Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		0		44
Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Amortization of deferred charges		263
Prior Coverage Years
Supplementary Insurance Information, by Segment [Line Items]
Proceeds from risk corridor settlements		46	$ 62
Prior Coverage Years | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		65		62
Other current assets		0		0
Trade accounts payable and accrued expenses		(79)		(80)
Net current (liability) asset		(14)		(18)
Other long-term assets		0		5
Total net (liability) asset		(14)		(13)
Prior Coverage Years | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0		0
Other current assets		0		44
Trade accounts payable and accrued expenses		0		0
Net current (liability) asset		0		44
Other long-term assets		0		0
Total net (liability) asset		0		44
Current Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Other long-term assets		1		0
Other long-term liabilities		(11)		0
Net long-term liability		(10)		0
Total net (liability) asset		(10)		0
Current Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Other long-term assets		0		0
Other long-term liabilities		0		0
Net long-term liability		0		0
Total net (liability) asset		$ 0		$ 0
Forecast | Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Payment of annual health insurance industry fee	$ 1,050

GOODWILL AND OTHER INTANGIBLE46

GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill by Segments (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 3,281
Acquisitions	479
Ending balance	3,760
Retail
Goodwill [Roll Forward]
Beginning balance	1,059
Acquisitions	360
Ending balance	1,419
Group and Specialty
Goodwill [Roll Forward]
Beginning balance	261
Acquisitions	0
Ending balance	261
Healthcare Services
Goodwill [Roll Forward]
Beginning balance	1,961
Acquisitions	119
Ending balance	$ 2,080

GOODWILL AND OTHER INTANGIBLE47

GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 5 months
Cost	$ 829	$ 770
Accumulated Amortization	553	544
Net	$ 276	226
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 7 months
Cost	$ 646	566
Accumulated Amortization	414	401
Net	$ 232	165
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	6 years 6 months
Cost	$ 83	104
Accumulated Amortization	78	84
Net	$ 5	20
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	11 years 11 months
Cost	$ 68	68
Accumulated Amortization	32	30
Net	$ 36	38
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 1 month
Cost	$ 32	32
Accumulated Amortization	29	29
Net	$ 3	$ 3

GOODWILL AND OTHER INTANGIBLE48

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Estimated Amortization Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for other intangible assets	$ 30	$ 18
Amortization expense, trade name write-off	12
2,018	84
2,019	63
2,020	61
2,021	27
2,022	24
2,023	$ 16

BENEFITS PAYABLE - Activity in

BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 4,668	$ 4,563
Less: Reinsurance recoverables	(70)	(76)
Balances, beginning of period, net			$ 4,598	$ 4,487
Incurred related to:
Current year	11,947	11,580
Prior years	(267)	(231)
Total incurred	11,680	11,349
Paid related to:
Current year	(7,775)	(7,695)
Prior years	(3,619)	(3,451)
Total paid	(11,394)	(11,146)
Reinsurance recoverable	77	71
Ending balance	4,961	4,761
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	3,963	3,507
Less: Reinsurance recoverables	(70)	(76)
Balances, beginning of period, net			$ 3,893	$ 3,431
Incurred related to:
Current year	10,739	10,255
Prior years	(187)	(204)
Total incurred	10,552	10,051
Paid related to:
Current year	(7,119)	(7,014)
Prior years	(3,082)	(2,572)
Total paid	(10,201)	(9,586)
Reinsurance recoverable	77	71
Ending balance	4,321	3,967
Total IBNR	2,800
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	568	578
Incurred related to:
Current year	1,307	1,306
Prior years	(34)	(20)
Total incurred	1,273	1,286
Paid related to:
Current year	(802)	(824)
Prior years	(463)	(493)
Total paid	(1,265)	(1,317)
Ending balance	576	547
Total IBNR	502
Individual Commercial
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	101	454
Incurred related to:
Current year	0	195
Prior years	(44)	(6)
Total incurred	(44)	189
Paid related to:
Current year	0	(59)
Prior years	(29)	(363)
Total paid	(29)	(422)
Ending balance	28	$ 221
Total IBNR	$ 19

BENEFITS PAYABLE - Benefit Expe

BENEFITS PAYABLE - Benefit Expenses Excluded From Activity in Benefits Payable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	$ (10)	$ (23)
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	(16)	(33)
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total future policy benefits	$ 6	$ 10

BENEFITS PAYABLE - Reconciliati

BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 4,884
Reinsurance recoverable on unpaid claims	77	$ 70	$ 71	$ 76
Benefits payable	4,961	4,668	4,761	4,563
Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reinsurance recoverable on unpaid claims	77	70	71	76
Benefits payable	4,321	3,963	3,967	3,507
Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	576	568	547	578
Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	28	$ 101	$ 221	$ 454
Operating Segments | Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	4,244
Operating Segments | Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	576
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	28
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 36

EARNINGS PER COMMON SHARE COM52

EARNINGS PER COMMON SHARE COMPUTATION (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 491	$ 1,115
Weighted average outstanding shares of common stock used to compute basic earnings per common share (in shares)	137,903	147,824
Shares used to compute diluted earnings per common share (in shares)	138,830	148,872
Basic earnings per common share (in dollars per share)	$ 3.56	$ 7.54
Diluted earnings per common share (in dollars per share)	$ 3.53	$ 7.49
Number of antidilutive stock options and restricted stock excluded from computation (in shares)	645	938
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)	213	199
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)	714	849

STOCKHOLDERS' EQUITY - Schedule

STOCKHOLDERS' EQUITY - Schedule of Details of Dividend Payments (Detail) - USD ($) $ / shares in Units, $ in Millions	Apr. 19, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Subsequent Event [Line Items]
Record Date			Dec. 29, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Jan. 12, 2017
Payment Date			Jan. 26, 2018	Oct. 27, 2017	Jul. 31, 2017	Apr. 28, 2017	Jan. 27, 2017
Amount per Share (in dollars per share)			$ 0.40	$ 0.40	$ 0.40	$ 0.40	$ 0.29
Total Amount			$ 55	$ 57	$ 58	$ 58	$ 43
Dividend declared per common share (in dollars per share)			$ 0.5				$ 0.40
Subsequent Event
Subsequent Event [Line Items]
Record Date		Mar. 30, 2018
Payment Date		Apr. 27, 2018
Amount per Share (in dollars per share)		$ 0.50
Total Amount		$ 69
Dividend declared per common share (in dollars per share)	$ 0.50

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands	Mar. 26, 2018	Dec. 22, 2017	Mar. 31, 2018	Mar. 26, 2018	Mar. 31, 2017	May 01, 2018	Dec. 31, 2017	Dec. 21, 2017	Dec. 14, 2017
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization									$ 3,000,000,000
Common shares acquired in connection with employee stock plans (in shares)			190		350
Common shares acquired in connection with employee stock plans, amount			$ 51,000,000		$ 74,000,000
Treasury stock reissued (in shares)			630
Treasury stock reissued			$ 66,000,000
Accumulated other comprehensive gain (loss)			(154,000,000)				$ 19,000,000
Net unrealized (losses) gains on investment securities
Equity, Class of Treasury Stock [Line Items]
Accumulated other comprehensive gain (loss)			(110,000,000)				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)			$ 44,000,000				$ 106,000,000
December 2017 ASR
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization								$ 1,000,000,000
Share repurchase payment		$ 1,000,000,000
Shares repurchased (in shares)	460	3,280		3,740
Value of shares repurchased	$ 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
Subsequent Event
Equity, Class of Treasury Stock [Line Items]
Remaining authorized amount						$ 2,000,000,000

INCOME TAXES (Detail)

INCOME TAXES (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate	30.70%	34.00%
Provisional income tax benefit, Tax Reform Law	$ 6.6

DEBT - Senior Notes (Details)

DEBT - Senior Notes (Details) - Senior Notes - USD ($)	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt		$ 4,772,000,000	$ 4,770,000,000
Proceeds from debt, net of discounts and offering expenses	$ 991,000,000
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	397,000,000
Face amount		$ 400,000,000
Stated interest rate		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
Stated interest rate		2.90%
$600 million, 3.15% due December 1, 2022
Debt Instrument [Line Items]
Long-term debt		$ 596,000,000	595,000,000
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		$ 596,000,000	595,000,000
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		$ 595,000,000	594,000,000
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		$ 395,000,000	$ 396,000,000
Face amount	$ 400,000,000	$ 400,000,000
Stated interest rate	4.80%	4.80%

DEBT - Credit Agreement (Detail

DEBT - Credit Agreement (Details)	3 Months Ended
	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	May 31, 2017USD ($)
Line of Credit Facility [Line Items]
Actual net worth	$ 10,081,000,000	$ 9,842,000,000
Credit Agreement | Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Term	5 years
Maximum borrowing capacity	$ 2,500,000,000		$ 1,000,000,000
Minimum level of net worth required	9,500,000,000
Actual net worth	$ 10,100,000,000
Required maximum leverage ratio	3
Actual leverage ratio	1.4
Uncommitted incremental loan facility	$ 500,000,000
Line of credit, outstanding borrowings	0
Credit Agreement | Line of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Line of credit, outstanding borrowings	$ 0
Credit Agreement | London Interbank Offered Rate (LIBOR) | Line of Credit | 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) | Line of Credit | 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) | Line of Credit | 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 | Line of Credit | 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 ($)	3 Months Ended
	Mar. 31, 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	3 Months Ended
	Mar. 31, 2018	Nov. 02, 2017
Loss Contingencies [Line Items]
Litigation recoveries sought		$ 611
Total Medicare
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	81.00%
Military services
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	1.00%
Medicaid
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	4.00%

SEGMENT INFORMATION - Additiona

SEGMENT INFORMATION - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)Segment	Mar. 31, 2017USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment	4
Member co-share amounts and government subsidies	$ 2,900	$ 3,000
Depreciation and amortization classified as benefit expense	$ 39	$ 26

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation (Detail) - USD ($) $ in Millions	Feb. 16, 2017	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Premiums		$ 13,811	$ 13,398
Services		327	253
Total revenues - external customers		14,138	13,651
Investment income		141	111
Total revenues		14,279	13,762
Benefits		11,670	11,326
Operating costs		1,749	1,553
Merger termination fee and related costs, net	$ 1,000	0	(947)
Depreciation and amortization		100	92
Total operating expenses		13,519	12,024
Income (loss) from operations		760	1,738
Interest expense		53	49
Income (loss) before income taxes		707	1,689
Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums		8,970	8,376
Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums		1,524	1,318
Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums		896	941
Total Medicare
Segment Reporting Information [Line Items]
Premiums		11,390	10,635
Fully-insured
Segment Reporting Information [Line Items]
Premiums		1,512	1,779
Specialty
Segment Reporting Information [Line Items]
Premiums		347	322
Medicaid and other
Segment Reporting Information [Line Items]
Premiums		562	662
Provider
Segment Reporting Information [Line Items]
Services		65	70
ASO and other
Segment Reporting Information [Line Items]
Services		223	165
Pharmacy
Segment Reporting Information [Line Items]
Services		39	18
Intersegment revenues
Segment Reporting Information [Line Items]
Total revenues		(5,558)	(5,867)
Intersegment revenues | Retail
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Group and Specialty
Segment Reporting Information [Line Items]
Total revenues		5	5
Intersegment revenues | Healthcare Services
Segment Reporting Information [Line Items]
Total revenues		5,553	5,862
Intersegment revenues | Individual Commercial
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Services
Segment Reporting Information [Line Items]
Total revenues		(4,023)	(4,315)
Intersegment revenues | Services | Retail
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Services | Group and Specialty
Segment Reporting Information [Line Items]
Total revenues		5	5
Intersegment revenues | Services | Healthcare Services
Segment Reporting Information [Line Items]
Total revenues		4,018	4,310
Intersegment revenues | Services | Individual Commercial
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Products
Segment Reporting Information [Line Items]
Total revenues		(1,535)	(1,552)
Intersegment revenues | Products | Retail
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Products | Group and Specialty
Segment Reporting Information [Line Items]
Total revenues		0	0
Intersegment revenues | Products | Healthcare Services
Segment Reporting Information [Line Items]
Total revenues		1,535	1,552
Intersegment revenues | Products | Individual Commercial
Segment Reporting Information [Line Items]
Total revenues		0	0
Operating Segments | Retail
Segment Reporting Information [Line Items]
Premiums		12,068	11,406
Services		2	2
Total revenues - external customers		12,070	11,408
Investment income		37	25
Total revenues		12,107	11,433
Benefits		10,552	10,051
Operating costs		1,222	954
Merger termination fee and related costs, net			0
Depreciation and amortization		66	58
Total operating expenses		11,840	11,063
Income (loss) from operations		267	370
Interest expense		0	0
Income (loss) before income taxes		267	370
Operating Segments | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		1,739	1,700
Services		219	161
Total revenues - external customers		1,958	1,861
Investment income		7	11
Total revenues		1,970	1,877
Benefits		1,273	1,286
Operating costs		463	399
Merger termination fee and related costs, net			0
Depreciation and amortization		23	21
Total operating expenses		1,759	1,706
Income (loss) from operations		211	171
Interest expense		0	0
Income (loss) before income taxes		211	171
Operating Segments | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Services		104	88
Total revenues - external customers		104	88
Investment income		6	8
Total revenues		5,663	5,958
Benefits		0	0
Operating costs		5,441	5,680
Merger termination fee and related costs, net			0
Depreciation and amortization		49	34
Total operating expenses		5,490	5,714
Income (loss) from operations		173	244
Interest expense		0	0
Income (loss) before income taxes		173	244
Operating Segments | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		(5)	283
Services		0	0
Total revenues - external customers		(5)	283
Investment income		0	1
Total revenues		(5)	284
Benefits		(60)	156
Operating costs		2	62
Merger termination fee and related costs, net			0
Depreciation and amortization		0	3
Total operating expenses		(58)	221
Income (loss) from operations		53	63
Interest expense		0	0
Income (loss) before income taxes		53	63
Operating Segments | Individual Medicare Advantage | Retail
Segment Reporting Information [Line Items]
Premiums		8,970	8,376
Operating Segments | Individual Medicare Advantage | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Individual Medicare Advantage | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Individual Medicare Advantage | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Group Medicare Advantage | Retail
Segment Reporting Information [Line Items]
Premiums		1,524	1,318
Operating Segments | Group Medicare Advantage | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Group Medicare Advantage | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Group Medicare Advantage | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicare stand-alone PDP | Retail
Segment Reporting Information [Line Items]
Premiums		896	941
Operating Segments | Medicare stand-alone PDP | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicare stand-alone PDP | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicare stand-alone PDP | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Total Medicare | Retail
Segment Reporting Information [Line Items]
Premiums		11,390	10,635
Operating Segments | Total Medicare | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Total Medicare | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Total Medicare | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Fully-insured | Retail
Segment Reporting Information [Line Items]
Premiums		125	118
Operating Segments | Fully-insured | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		1,392	1,378
Operating Segments | Fully-insured | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Fully-insured | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		(5)	283
Operating Segments | Specialty | Retail
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Specialty | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		347	322
Operating Segments | Specialty | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Specialty | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicaid and other | Retail
Segment Reporting Information [Line Items]
Premiums		553	653
Operating Segments | Medicaid and other | Group and Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicaid and other | Healthcare Services
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Medicaid and other | Individual Commercial
Segment Reporting Information [Line Items]
Premiums		0	0
Operating Segments | Provider | Retail
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | Provider | Group and Specialty
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | Provider | Healthcare Services
Segment Reporting Information [Line Items]
Services		65	70
Operating Segments | Provider | Individual Commercial
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | ASO and other | Retail
Segment Reporting Information [Line Items]
Services		2	2
Operating Segments | ASO and other | Group and Specialty
Segment Reporting Information [Line Items]
Services		219	161
Operating Segments | ASO and other | Healthcare Services
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | ASO and other | Individual Commercial
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | Pharmacy | Retail
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | Pharmacy | Group and Specialty
Segment Reporting Information [Line Items]
Services		0	0
Operating Segments | Pharmacy | Healthcare Services
Segment Reporting Information [Line Items]
Services		39	18
Operating Segments | Pharmacy | Individual Commercial
Segment Reporting Information [Line Items]
Services		0	0
Other Businesses
Segment Reporting Information [Line Items]
Premiums		9	9
Services		2	2
Total revenues - external customers		11	11
Investment income		35	21
Total revenues		46	32
Benefits		26	29
Operating costs		2	4
Merger termination fee and related costs, net			0
Depreciation and amortization		0	0
Total operating expenses		28	33
Income (loss) from operations		18	(1)
Interest expense		0	0
Income (loss) before income taxes		18	(1)
Other Businesses | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Total Medicare
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Fully-insured
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Specialty
Segment Reporting Information [Line Items]
Premiums		0	0
Other Businesses | Medicaid and other
Segment Reporting Information [Line Items]
Premiums		9	9
Other Businesses | Provider
Segment Reporting Information [Line Items]
Services		0	0
Other Businesses | ASO and other
Segment Reporting Information [Line Items]
Services		2	2
Other Businesses | Pharmacy
Segment Reporting Information [Line Items]
Services		0	0
Eliminations/ Corporate
Segment Reporting Information [Line Items]
Investment income		56	45
Total revenues		(5,502)	(5,822)
Benefits		(121)	(196)
Operating costs		(5,381)	(5,546)
Merger termination fee and related costs, net			(947)
Depreciation and amortization		(38)	(24)
Total operating expenses		(5,540)	(6,713)
Income (loss) from operations		38	891
Interest expense		53	49
Income (loss) before income taxes		$ (15)	$ 842