Humana (HUM) 10-Q 3 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2017shares
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
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	144,314,925

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 8,425	$ 3,877
Investment securities	8,205	7,595
Receivables, less allowance for doubtful accounts of $113 in 2017 and $118 in 2016:	1,838	1,280
Other current assets	3,849	3,438
Total current assets	22,317	16,190
Property and equipment, net	1,525	1,505
Long-term investment securities	2,424	2,203
Goodwill	3,279	3,272
Other long-term assets	2,167	2,226
Total assets	31,712	25,396
Current liabilities:
Benefits payable	4,761	4,563
Trade accounts payable and accrued expenses	4,675	2,467
Book overdraft	178	212
Unearned revenues	3,420	280
Short-term borrowings	470	300
Total current liabilities	13,504	7,822
Long-term debt	4,780	3,792
Future policy benefits payable	2,827	2,834
Other long-term liabilities	367	263
Total liabilities	21,478	14,711
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $1 par; 10,000,000 shares authorized; none issued	0	0
Common stock, $0.16 2/3 par; 300,000,000 shares authorized; 198,565,891 shares issued at March 31, 2017 and 198,495,007 shares issued at December 31, 2016	33	33
Capital in excess of par value	2,246	2,562
Retained earnings	12,509	11,454
Accumulated other comprehensive loss	(58)	(66)
Treasury stock, at cost, 54,250,966 shares at March 31, 2017 and 49,189,811 shares at December 31, 2016	(4,496)	(3,298)
Total stockholders’ equity	10,234	10,685
Total liabilities and stockholders’ equity	$ 31,712	$ 25,396

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 113	$ 118
Preferred stock, par (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par (in dollars per share)	$ 0.1667	$ 0.1667
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	198,565,891	198,495,007
Treasury stock, shares	54,250,966	49,189,811

Condensed Consolidated Statemen

Condensed Consolidated Statements Of Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Premiums	$ 13,398	$ 13,440
Services	253	260
Investment income	111	100
Total revenues	13,762	13,800
Operating expenses:
Benefits	11,326	11,397
Operating costs	1,553	1,734
Merger termination fee and related costs, net	(947)	34
Depreciation and amortization	92	88
Total operating expenses	12,024	13,253
Income from operations	1,738	547
Interest expense	49	47
Income before income taxes	1,689	500
Provision for income taxes	574	246
Net income	$ 1,115	$ 254
Basic earnings per common share (in dollars per share)	$ 7.54	$ 1.70
Diluted earnings per common share (in dollars per share)	7.49	1.68
Dividends per common share (in dollars per share)	$ 0.40	$ 0.29

Condensed Consolidated Stateme5

Condensed Consolidated Statements Of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 1,115	$ 254
Other comprehensive income:
Change in gross unrealized investment gains/losses	38	48
Effect of income taxes	(14)	(17)
Total change in unrealized investment gains/losses, net of tax	24	31
Reclassification adjustment for net realized gains included in investment income	(26)	(20)
Effect of income taxes	10	7
Total reclassification adjustment, net of tax	(16)	(13)
Other comprehensive income, net of tax	8	18
Comprehensive income	$ 1,123	$ 272

Condensed Consolidated Stateme6

Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities
Net income	$ 1,115	$ 254
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized capital gains	(26)	(20)
Stock-based compensation	26	23
Depreciation	100	94
Other intangible amortization	18	21
Provision for deferred income taxes	29	15
Changes in operating assets and liabilities, net of effect of businesses acquired and dispositions:
Receivables	(558)	(576)
Other assets	(415)	(685)
Benefits payable	198	138
Other liabilities	542	1,210
Unearned revenues	3,140	(4)
Other, net	36	32
Net cash provided by operating activities	4,205	502
Cash flows from investing activities
Acquisitions, net of cash acquired	(7)	0
Purchases of property and equipment	(122)	(125)
Purchases of investment securities	(1,876)	(1,430)
Maturities of investment securities	284	213
Proceeds from sales of investment securities	795	914
Net cash used in investing activities	(926)	(428)
Cash flows from financing activities
Receipts from contract deposits, net	1,730	318
Proceeds from issuance of senior notes, net	991	0
Proceeds from issuance of commercial paper, net	169	0
Change in book overdraft	(34)	(44)
Common stock repurchases	(1,574)	(71)
Dividends paid	(47)	(47)
Proceeds from stock option exercises and other	34	0
Net cash provided by financing activities	1,269	156
Increase in cash and cash equivalents	4,548	230
Cash and cash equivalents at beginning of period	3,877	2,571
Cash and cash equivalents at end of period	8,425	2,801
Supplemental cash flow disclosures:
Interest payments	10	10
Income tax (refunds) payments, net	$ (4)	$ 5

BASIS OF PRESENTATION AND SIGNI

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS	3 Months Ended
	Mar. 31, 2017
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, 2016 , that was filed with the Securities and Exchange Commission, or the SEC, on February 17, 2017 . We refer to the Form 10-K as the “ 2016 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 2016 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. Aetna Merger On July 2, 2015, we entered into an Agreement and Plan of Merger, which we refer to in this report as the Merger Agreement, with Aetna Inc. and certain wholly owned subsidiaries of Aetna Inc., which we refer to collectively as Aetna, which set forth the terms and conditions under which we agreed to merge with, and become a wholly owned subsidiary of Aetna, a transaction we refer to in this report as the Merger. The Merger was subject to customary closing conditions, including, among other things, (i) the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the receipt of necessary approvals under state insurance and healthcare laws and regulations and pursuant to certain licenses of certain of Humana’s subsidiaries, and (ii) the absence of legal restraints and prohibitions on the consummation of the Merger. On July 21, 2016, the U.S. Department of Justice and the attorneys general of certain U.S. jurisdictions filed a civil antitrust complaint in the U.S. District Court for the District of Columbia against us and Aetna, alleging that the Merger would violate Section 7 of the Clayton Antitrust Act and seeking a permanent injunction to prevent the Merger from being completed. On January 23, 2017, the Court ruled in favor of the DOJ and granted a permanent injunction of the proposed transaction. On February 14, 2017, we and Aetna agreed to mutually terminate the Merger Agreement, as our Board determined that an appeal of the Court's ruling would not be in the best interest of our stockholders. On February 16, 2017, under terms of the Merger Agreement, we received a breakup fee of $1 billion from Aetna , which is included in our condensed consolidated statement of income in the line captioned Merger termination fee and related costs, net. Prior period Merger related transaction costs, previously included in operating costs, have been recast to conform to the 2017 presentation. Business Segment Reclassifications During the three months ended March 31, 2017, we realigned certain of our businesses among our reportable segments to correspond with internal management reporting changes and our previously announced planned exit from the individual commercial medical business on January 1, 2018. Additionally, we renamed our Group segment to the Group and Specialty segment, and began presenting the individual commercial business results as a separate segment rather than as part of the Retail segment. Specialty health insurance benefits, including dental, vision, other supplement health, and financial protection products, marketed to individuals are now included in the Group and Specialty segment. Specialty health insurance benefits marketed to employer groups continue to be included in the Group and Specialty segment. As a result of this realignment, our reportable segments now include Retail, Group and Specialty, Healthcare Services, and Individual Commercial. Prior period segment financial information has been recast to conform to the 2017 presentation. See Note 15 for segment financial information.

RECENTLY ISSUED ACCOUNTING PRON

RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS	3 Months Ended
	Mar. 31, 2017
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 2016, are not included in the scope of the new guidance. We are analyzing how we may recognize revenue under the new guidance by reviewing selected sample contracts presently in place. The new guidance is effective for us beginning with annual and interim periods in 2018. While we expect revenue related to our Pharmacy, Provider Services, ASO and other services businesses to remain primarily unchanged, we are still evaluating the impact of the new guidance on the customer arrangements for these businesses. Accordingly, we continue to evaluate the impact of the new standard on our results of operations, financial condition and cash flows. 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, and requires retrospective application to previously issued annual and interim financial statements. We have begun the process of identifying 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, 2019. 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, or 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. 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. 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, 2017
Business Combinations [Abstract]
ACQUISITIONS AND DIVESTITURES	ACQUISITIONS AND DIVESTITURES During 2017 and 2016 , we acquired 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 the first quarter of 2017 and 2016 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, 2017
Investments, Debt and Equity Securities [Abstract]
INVESTMENT SECURITIES	INVESTMENT SECURITIES Investment securities classified as current and long-term were as follows at March 31, 2017 and December 31, 2016 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) March 31, 2017 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 833 $ — $ (12 ) $ 821 Mortgage-backed securities 1,645 4 (31 ) 1,618 Tax-exempt municipal securities 3,408 9 (48 ) 3,369 Mortgage-backed securities: Residential 8 — — 8 Commercial 412 1 (4 ) 409 Asset-backed securities 132 — — 132 Corporate debt securities 4,198 144 (70 ) 4,272 Total debt securities $ 10,636 $ 158 $ (165 ) $ 10,629 December 31, 2016 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 800 $ 1 $ (15 ) $ 786 Mortgage-backed securities 1,662 6 (31 ) 1,637 Tax-exempt municipal securities 3,358 15 (68 ) 3,305 Mortgage-backed securities: Residential 9 — — 9 Commercial 307 1 (4 ) 304 Asset-backed securities 160 — — 160 Corporate debt securities 3,530 145 (78 ) 3,597 Total debt securities $ 9,826 $ 168 $ (196 ) $ 9,798 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, 2017 and December 31, 2016 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) March 31, 2017 U.S. Treasury and other U.S. U.S. Treasury and agency $ 705 $ (12 ) $ 3 $ — $ 708 $ (12 ) Mortgage-backed 1,565 (31 ) 3 — 1,568 (31 ) Tax-exempt municipal 2,493 (47 ) 25 (1 ) 2,518 (48 ) Mortgage-backed securities: Residential — — 4 — 4 — Commercial 190 (3 ) 8 (1 ) 198 (4 ) Asset-backed securities 65 — 52 — 117 — Corporate debt securities 1,710 (65 ) 70 (5 ) 1,780 (70 ) Total debt securities $ 6,728 $ (158 ) $ 165 $ (7 ) $ 6,893 $ (165 ) December 31, 2016 U.S. Treasury and other U.S. U.S. Treasury and agency $ 697 $ (15 ) $ 3 $ — $ 700 $ (15 ) Mortgage-backed 1,528 (31 ) 3 — 1,531 (31 ) Tax-exempt municipal 2,756 (67 ) 43 (1 ) 2,799 (68 ) Mortgage-backed securities: Residential — — 4 — 4 — Commercial 182 (3 ) 24 (1 ) 206 (4 ) Asset-backed securities 51 — 63 — 114 — Corporate debt securities 1,544 (71 ) 69 (7 ) 1,613 (78 ) Total debt securities $ 6,758 $ (187 ) $ 209 $ (9 ) $ 6,967 $ (196 ) Approximately 98% of our debt securities were investment-grade quality, with a weighted average credit rating of AA by S&P at March 31, 2017 . 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 970 positions out of a total of approximately 2,220 positions at March 31, 2017 . All issuers of securities we own that were trading at an unrealized loss at March 31, 2017 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, 2017 , 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, 2017 . 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, 2017 and 2016 : Three months ended 2017 2016 (in millions) Gross realized gains $ 27 $ 31 Gross realized losses (1 ) (11 ) Net realized capital gains $ 26 $ 20 There were no material other-than-temporary impairments for the three months ended March 31, 2017 or 2016 . The contractual maturities of debt securities available for sale at March 31, 2017 , 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 $ 561 $ 562 Due after one year through five years 2,764 2,770 Due after five years through ten years 2,188 2,153 Due after ten years 2,926 2,977 Mortgage and asset-backed securities 2,197 2,167 Total debt securities $ 10,636 $ 10,629

FAIR VALUE

FAIR VALUE	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE	FAIR VALUE Financial Assets The following table summarizes our fair value measurements at March 31, 2017 and December 31, 2016 , 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, 2017 Cash equivalents $ 8,034 $ 8,034 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 821 — 821 — Mortgage-backed securities 1,618 — 1,618 — Tax-exempt municipal securities 3,369 — 3,366 3 Mortgage-backed securities: Residential 8 — 8 — Commercial 409 — 409 — Asset-backed securities 132 — 132 — Corporate debt securities 4,272 — 4,268 4 Total debt securities 10,629 — 10,622 7 Total invested assets $ 18,663 $ 8,034 $ 10,622 $ 7 December 31, 2016 Cash equivalents $ 3,654 $ 3,654 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 786 — 786 — Mortgage-backed securities 1,637 — 1,637 — Tax-exempt municipal securities 3,305 — 3,302 3 Mortgage-backed securities: Residential 9 — 9 — Commercial 304 — 304 — Asset-backed securities 160 — 160 — Corporate debt securities 3,597 — 3,593 4 Total debt securities 9,798 — 9,791 7 Total invested assets $ 13,452 $ 3,654 $ 9,791 $ 7 There were no material transfers between Level 1 and Level 2 during the three months ended March 31, 2017 or 2016 . Our Level 3 assets had a fair value of $7 million at March 31, 2017 , or 0.04% of our total invested assets. During the three months ended March 31, 2017 and 2016 , the changes in the fair value of the assets measured using significant unobservable inputs (Level 3) were comprised of the following: For the three months ended March 31, 2017 2016 Private Auction Total Private Auction Total (in millions) Beginning balance at January 1 $ 4 $ 3 $ 7 $ 6 $ 5 $ 11 Settlements — — — — (2 ) (2 ) Balance at March 31 $ 4 $ 3 $ 7 $ 6 $ 3 $ 9 Financial Liabilities Our long-term debt is recorded at carrying value in our consolidated balance sheets. The carrying value of our long-term debt outstanding, net of unamortized debt issuance costs, was $4,780 million at March 31, 2017 and $3,792 million at December 31, 2016 . The fair value of our long-term debt was $5,052 million at March 31, 2017 and $4,004 million at December 31, 2016 . 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 $470 million as of March 31, 2017 and $300 million as of December 31, 2016 . Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis As disclosed in Note 3, we completed the acquisition of certain health and wellness related businesses during the first quarter of 2017 and 2016 . 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 the three months ended March 31, 2017 or 2016 .

MEDICARE PART D

MEDICARE PART D	3 Months Ended
	Mar. 31, 2017
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 2016 Form 10-K. The accompanying condensed consolidated balance sheets include the following amounts associated with Medicare Part D at March 31, 2017 and December 31, 2016 . 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, 2017 December 31, 2016 Risk CMS Risk CMS (in millions) Other current assets $ 8 $ 1,044 $ 8 $ 1,001 Trade accounts payable and accrued expenses (126 ) (1,895 ) (158 ) (128 ) Net current (liability) asset (118 ) (851 ) (150 ) 873 Other long-term assets 12 — — — Other long-term liabilities (74 ) — — — Net long-term liability (62 ) — — — Total net (liability) asset $ (180 ) $ (851 ) $ (150 ) $ 873

HEALTH CARE REFORM

HEALTH CARE REFORM	3 Months Ended
	Mar. 31, 2017
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 are applicable to certain of our commercial medical insurance products as further discussed in Note 2 to our 2016 Form 10-K. Operating results for our individual commercial medical business compliant with the Health Care Reform Law have been challenged primarily due to unanticipated modifications in the program subsequent to the passing of the Health Care Reform Law, resulting in higher covered population morbidity and the ensuing enrollment and claims issues causing volatility in claims experience. We took a number of actions in 2015 to improve the profitability of our individual commercial medical business in 2016. These actions were subject to regulatory restrictions in certain geographies and included premium increases for the 2016 coverage year related generally to the first half of 2015 claims experience, the discontinuation of certain products as well as exit of certain markets for 2016, network improvements, enhancements to claims and clinical processes and administrative cost control. Despite these actions, the deterioration in the second half of 2015 claims experience together with 2016 open enrollment results indicating the retention of many high-utilizing members for 2016 resulted in a probable future loss. As a result of our then assessment of the profitability of our individual medical policies compliant with the Health Care Reform Law, in the fourth quarter of 2015, we recorded a provision for probable future losses (premium deficiency reserve, or PDR) for the 2016 coverage year of $176 million in benefits payable in our consolidated balance sheet with a corresponding increase in benefits expense in our consolidated statement of income. In the first quarter of 2016, we applied $13 million current period results to the PDR liability. There is no premium deficiency reserve in 2017. On November 10, 2016, the U.S. Court of Federal Claims ruled in favor of the government in one of a series of cases filed by insurers, unrelated to us, against the U.S. Department of Health and Human Services, or HHS, to collect risk corridor payments, rejecting all of the insurer’s statutory, contract and Constitutional claims for payment. On November 18, 2016, HHS issued a memorandum indicating a significant funding shortfall for the 2015 coverage year, the second consecutive year of significant shortfalls. Given the successful challenge of the risk corridor provisions in court, Congressional inquiries into the funding of the risk corridor program, and significant funding shortfalls under the first two years of the program, during the fourth quarter of 2016 we wrote-off $583 million in risk corridor receivables outstanding as of September 30, 2016, including $415 million associated with the 2014 and 2015 coverage years. From inception of the risk corridor program through March 31, 2017, we collected approximately $37 million from CMS for risk corridor receivables associated with the 2014 coverage year funded by HHS in accordance with previous guidance, utilizing funds HHS collected from us and other carriers under the risk corridor program. On February 14, 2017, we announced we are exiting our individual commercial medical business January 1, 2018. As discussed previously, we have worked over the past several years to address market and programmatic challenges in order to keep coverage options available wherever we could offer a viable product. This has included pursuing business changes, such as modifying networks, restructuring product offerings, reducing the company’s geographic footprint and increasing premiums. All of these actions were taken with the expectation that our individual commercial medical business would stabilize to the point where we could continue to participate in the program. However, based on our analysis of data associated with our healthcare exchange membership following the 2017 open enrollment period, we saw further signs of an unbalanced risk pool. Therefore, we decided that we cannot continue to offer this coverage and plan to exit this business commencing January 1, 2018. The accompanying condensed consolidated balance sheets include the following amounts associated with the 3Rs at March 31, 2017 and December 31, 2016 . Amounts classified as long-term represent settlements that we expect to exceed 12 months at March 31, 2017 . March 31, 2017 December 31, 2016 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Prior Coverage Years Premiums receivable $ 320 $ — $ 307 $ — Other current assets — 207 — 260 Trade accounts payable and (124 ) — (117 ) — Net current asset 196 207 190 260 Other long-term assets — — 6 — Total prior coverage years' net 196 207 196 260 Current Coverage Year Other long-term assets 17 — — — Other long-term liabilities (26 ) — — — Total 2017 coverage year net (9 ) — — — Total net asset $ 187 $ 207 $ 196 $ 260 During the three months ended March 31, 2017 , we received $60 million for reinsurance recoverables and $2 million for risk adjustment settlements, in each case associated with prior coverage years. During the three months ended March 31, 2016 , we received $213 million for reinsurance recoverables and $6 million for risk adjustment and risk corridor settlements associated with prior coverage years. To the extent certain provisions of the Health Care Reform Law are successfully challenged in court or there are changes in legislation or the application of legislation, there can be no guarantee that receivables established under the reinsurance or risk adjustment provisions of the Health Care Reform Law will ultimately be collected. If we fail to effectively implement our operational and strategic initiatives with respect to the implementation of the Health Care Reform Law, our business may be materially adversely affected. Additionally, potential legislative changes, including activities to repeal or replace the Health Care Reform Law, creates uncertainty for our business, and we cannot predict when, or in what form, such legislative changes may occur. The annual health insurance industry fee has been suspended for calendar year 2017, but is scheduled to resume in calendar year 2018. In September 2016, we paid the federal government $916 million f or our portion of the annual health insurance industry fee attributed to calendar year 2016 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, 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 $227 million for the three months ended March 31, 2016 , resulting from the amortization of the 2016 annual health insurance industry fee.

GOODWILL AND OTHER INTANGIBLE A

GOODWILL AND OTHER INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLE ASSETS	GOODWILL AND OTHER INTANGIBLE ASSETS The carrying amount of goodwill for our reportable segments has been retrospectively adjusted to conform to the 2017 business segment reclassifications as discussed in Note 1. There was no impairment. Changes in the carrying amount of goodwill for our reportable segments for the three months ended March 31, 2017 were as follows: Retail Group and Specialty Healthcare Total (in millions) Balance at January 1, 2017 $ 1,059 $ 261 $ 1,952 $ 3,272 Acquisitions — — 7 7 Balance at March 31, 2017 $ 1,059 $ 261 $ 1,959 $ 3,279 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, 2017 and December 31, 2016 . March 31, 2017 December 31, 2016 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 9.8 years $ 566 $ 360 $ 206 $ 566 $ 347 $ 219 Trade names and 8.2 years 104 72 32 104 69 35 Provider contracts 14.1 years 51 30 21 51 29 22 Noncompetes and 8.2 years 32 29 3 32 28 4 Total other intangible 9.8 years $ 753 $ 491 $ 262 $ 753 $ 473 $ 280 For the three months ended March 31, 2017 and 2016 , amortization expense for other intangible assets was approximately $18 million and $21 million , respectively. The following table presents our estimate of amortization expense for 2017 and each of the five next succeeding years: (in millions) For the years ending December 31,: 2017 $ 71 2018 63 2019 52 2020 48 2021 14 2022 11

BENEFITS PAYABLE

BENEFITS PAYABLE	3 Months Ended
	Mar. 31, 2017
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, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 4,563 $ 4,976 Less: Premium deficiency reserve — (176 ) Less: Reinsurance recoverables (76 ) (85 ) Balances at January 1, net 4,487 4,715 Incurred related to: Current year 11,580 11,751 Prior years (231 ) (340 ) Total incurred 11,349 11,411 Paid related to: Current year (7,695 ) (7,692 ) Prior years (3,451 ) (3,576 ) Total paid (11,146 ) (11,268 ) Premium deficiency reserve — 189 Reinsurance recoverable 71 67 Ending Balance $ 4,761 $ 5,114 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, 2017 and 2016. March 31, 2017 March 31, 2016 (in millions) Premium deficiency reserve - Individual Commercial $ — $ 13 Military services — 3 Future policy benefits: Individual Commercial (33 ) (40 ) Other Businesses 10 10 Total future policy benefits (23 ) (30 ) Total $ (23 ) $ (14 ) Military services benefits expense for the three months ended March 31, 2016 in the table above reflect expenses associated with our contracts with the Veterans Administration. 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, 2017 and 2016, 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, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 3,507 $ 3,600 Less: Reinsurance recoverables (76 ) (85 ) Balances at January 1, net 3,431 3,515 Incurred related to: Current year 10,255 9,851 Prior years (204 ) (218 ) Total incurred 10,051 9,633 Paid related to: Current year (7,014 ) (6,706 ) Prior years (2,572 ) (2,685 ) Total paid (9,586 ) (9,391 ) Reinsurance recoverable 71 67 Ending Balance $ 3,967 $ 3,824 At March 31, 2017, benefits payable for our Retail segment included IBNR of approximately $2.7 billion , primarily associated with claims incurred in 2017. 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, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 578 $ 616 Incurred related to: Current year 1,306 1,260 Prior years (20 ) (41 ) Total incurred 1,286 1,219 Paid related to: Current year (824 ) (728 ) Prior years (493 ) (502 ) Total paid (1,317 ) (1,230 ) Ending Balance $ 547 $ 605 At March 31, 2017, benefits payable for our Group and Specialty segment included IBNR of approximately $468 million , primarily associated with claims incurred in 2017. Individual Commercial Segment Activity in benefits payable for our Individual Commercial segment was as follows for the three months ended March 31, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 454 $ 740 Less: Premium deficiency reserve — (176 ) Balances at January 1, net 454 564 Incurred related to: Current year 185 826 Prior years (6 ) (80 ) Total incurred 179 746 Paid related to: Current year (49 ) (465 ) Prior years (363 ) (370 ) Total paid (412 ) (835 ) Premium deficiency reserve — 189 Ending Balance $ 221 $ 664 At March 31, 2017, benefits payable for our Individual Commercial segment included IBNR of approximately $169 million , primarily associated with claims incurred in 2017. 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, 2017 Net outstanding liabilities Retail $ 3,896 Group and Specialty 547 Individual Commercial 221 Other Businesses 26 Benefits payable, net of reinsurance 4,690 Reinsurance recoverable on unpaid claims Retail 71 Total reinsurance recoverable on unpaid claims 71 Total benefits payable, gross $ 4,761

EARNINGS PER COMMON SHARE COMPU

EARNINGS PER COMMON SHARE COMPUTATION	3 Months Ended
	Mar. 31, 2017
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, 2017 and 2016 : Three months ended March 31, 2017 2016 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 1,115 $ 254 Weighted average outstanding shares of common stock 147,824 149,161 Dilutive effect of: Employee stock options 199 218 Restricted stock 849 1,517 Shares used to compute diluted earnings per common share 148,872 150,896 Basic earnings per common share $ 7.54 $ 1.70 Diluted earnings per common share $ 7.49 $ 1.68 Number of antidilutive stock options and restricted stock 938 1,285

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Dividends The following table provides details of dividend payments, excluding dividend equivalent rights for unvested stock awards, in 2016 and 2017 under our Board approved quarterly cash dividend policy: Record Payment Amount Total (in millions) 2016 payments 12/30/2015 1/29/2016 $ 0.29 $ 43 3/31/2016 4/29/2016 $ 0.29 $ 43 6/30/2016 7/29/2016 $ 0.29 $ 43 10/13/2016 10/28/2016 $ 0.29 $ 43 2017 payments 1/12/2017 1/27/2017 $ 0.29 $ 43 3/31/2017 4/28/2017 $ 0.40 $ 58 On April 20, 2017 , the Board declared a cash dividend of $0.40 per share payable on July 31, 2017 to stockholders of record on June 30, 2017 . Stock Repurchases On February 14, 2017 our Board of Directors replaced a previous share repurchase authorization of up to $2 billion , of which $1.04 billion remained unused, with a new authorization for repurchases of up to $2.25 billion of our common shares expiring on December 31, 2017 exclusive of shares repurchased in connection with employee stock plans. 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. Our remaining repurchase authorization was $1.05 billion as of May 3, 2017, which includes $300 million of stock held back as part of the accelerated share repurchase agreement as more fully described below. On February 16, 2017 , we entered into an accelerated share repurchase agreement, or ASR Agreement, with Goldman, Sachs & Co. LLC, or Goldman Sachs, to repurchase $1.5 billion of our common stock as part of the $2.25 billion share repurchase program referred to above. Under the ASR Agreement, on February 22, 2017 , we made a payment of $1.5 billion to Goldman Sachs from available cash on hand and received an initial delivery of 5.83 million shares of our common stock from Goldman Sachs based on the then current market price of Humana common stock. The payment to Goldman Sachs was recorded as a reduction to stockholders’ equity, consisting of a $1.2 billion increase in treasury stock, which reflected the value of the initial 5.83 million shares received upon initial settlement, and a $300 million decrease in capital in excess of par value, which reflected the value of stock held back by Goldman Sachs pending final settlement of the ASR Agreement. The final number of shares that we may receive, or be required to remit, under the ASR agreement will be determined based on the daily volume-weighted average share price of our common stock over the term of the ASR agreement. Final settlement under the ASR agreement is expected to occur by the end of the third quarter of 2017. The ASR agreement contains provisions customary for agreements of this type, including provisions for adjustments to the transaction terms upon certain specified events, the circumstances generally under which final settlement of the ASR Agreement may be accelerated or extended or the ASR agreement may be terminated early by Goldman Sachs or Humana, and various acknowledgments and representations made by the parties to each other. At final settlement, under certain circumstances, we may be entitled to receive additional shares of our common stock from Goldman Sachs or we may be required to make a payment. If we are obligated to make payment, we may elect to satisfy such obligation in cash or shares of our common stock. The obligation of Goldman Sachs under the ASR agreement is guaranteed by The Goldman Sachs Group, Inc. In connection with employee stock plans, we acquired 0.35 million common shares for $74 million and 0.43 million common shares for $71 million during the three months ended March 31, 2017 and 2016 , respectively. Treasury Stock Reissuance We reissued 1.13 million shares of treasury stock during the three months ended March 31, 2017 at a cost of $76 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 $4 million at March 31, 2017 and $17 million at December 31, 2016 . In addition, accumulated other comprehensive income included $54 million , net of tax, at March 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. There was $49 million such liability, net of tax, at December 31, 2016 . Refer to Note 18 to the consolidated financial statements in our 2016 Form 10-K for further discussion of our long-term care insurance policies.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The effective income tax rate was 34.0% for the three months ended March 31, 2017 , compared to 49.2% for the three months ended March 31, 2016 primarily due to the 2017 temporary suspension of the non-deductible health insurance industry fee as well as previously non-deductible transaction costs that, as a result of termination of the Merger Agreement, became deductible for tax purposes and were recorded as such in the three months ended March 31, 2017.

DEBT

DEBT	3 Months Ended
	Mar. 31, 2017
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, 2017 and December 31, 2016 : March 31, 2017 December 31, 2016 (in millions) Senior notes: $500 million, 7.20% due June 15, 2018 $ 501 $ 501 $300 million, 6.30% due August 1, 2018 304 304 $400 million, 2.625% due October 1, 2019 398 398 $600 million, 3.15% due December 1, 2022 595 595 $600 million, 3.85% due October 1, 2024 595 595 $600 million, 3.95% due March 15, 2027 594 — $250 million, 8.15% due June 15, 2038 263 264 $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 — Total long-term debt $ 4,780 $ 3,792 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 . We intend to use the net proceeds from these issuances for general corporate purposes. 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 7.20% and 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, each series of our senior notes (other than the 6.30% senior notes) contain a change of control provision that may require us to purchase the notes under certain circumstances. Prior to 2009, we were parties to interest-rate swap agreements that exchanged the fixed interest rate under our senior notes for a variable interest rate based on LIBOR. As a result, the carrying value of the senior notes was adjusted to reflect changes in value caused by an increase or decrease in interest rates. During 2008, we terminated all of our swap agreements. The cumulative adjustment to the carrying value of our senior notes was $103 million as of the termination date which is being amortized as a reduction to interest expense over the remaining term of the senior notes. In October 2014, the redemption of our 6.45% senior notes reduced the unamortized carrying value adjustment by $12 million . The unamortized carrying value adjustment was $22 million as of March 31, 2017 and $23 million as of December 31, 2016 . Credit Agreement Our 5 -year $1.0 billion unsecured revolving credit agreement expires July 2018. 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 basis points, varies depending on our credit ratings ranging from 90.0 to 150.0 basis points. We also pay an annual facility fee regardless of utilization. This facility fee, currently 15 basis points, may fluctuate between 10.0 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, 2017 and a maximum leverage ratio of 3.0:1 . We are in compliance with the financial covenants, with actual net worth of $10.2 billion and an actual leverage ratio of 1.3:1 , as measured in accordance with the credit agreement as of March 31, 2017 . In addition, the credit agreement includes an uncommitted $250 million incremental loan facility. At March 31, 2017 , we had no borrowings and no letters of credit outstanding under the credit agreement . Accordingly, as of March 31, 2017 , we had $1.0 billion of remaining borrowing capacity 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. Amounts available under the program may be borrowed, repaid and re-borrowed from time to time, with the aggregate face or principal amount outstanding under the program at any time not to exceed $1 billion . 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, 2017 was $500 million . There were outstanding borrowings of $470 million at March 31, 2017 and $300 million at December 31, 2016 .

GUARANTEES AND CONTINGENCIES

GUARANTEES AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
GUARANTEES AND CONTINGENCIES	GUARANTEES AND CONTINGENCIES Government Contracts Our Medicare products, which accounted for approximately 78% of our total premiums and services revenue for the three months ended March 31, 2017 , 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 2018 calendar year are due by June 5, 2017. 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. CMS is phasing-in the process of calculating risk scores using diagnoses data from the Risk Adjustment Processing System, or RAPS, to diagnosis 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 2016, 10% of the risk score was calculated from claims data submitted through EDS, increasing to 25% of the risk score calculated from claims data through EDS for 2017. In April 2017 CMS revised the pace of the phase-in. For 2018, 15% of the risk corridor 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 data set). 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. In recent years, the final reconciliation payment has occurred in July of the calendar year following the payment year, although CMS has stated that this year's final payment will occur in October. 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, 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, 2017 , our military services business, which accounted for approximately 1% of our total premiums and services revenue for the three months ended March 31, 2017 , primarily consisted of the TRICARE South Region contract. The current 5 -year South Region contract, which was set to expire on March 31, 2017 , is subject to annual renewals on April 1 of each year during its term at the government’s option, including an option to extend for a sixth year through March 31, 2018. On March 2, 2017, we received notice that the Defense Health Agency, or DHA, had exercised its option to extend the TRICARE South Region contract for that sixth year. On July 21, 2016, we were notified by the DHA that we were awarded the contract for the new TRICARE East Region, which is a consolidation of the former North and South Regions, with delivery of health care services expected to commence on October 1, 2017. On March 30, 2017, we received notice that the DHA is moving the date upon which delivery of health care services is expected to commence under the new TRICARE East Region contract from October 1, 2017, to January 1, 2018. We expect the sixth option period under the current TRICARE South Region contract would be terminated in the event that delivery of health care services under the new TRICARE East Region contract commences prior to March 31, 2018. The next generation East Region and West Region contract awards are currently subject to protests by an unsuccessful bidder in the U.S. Court of Federal Claims and before the DHA. Our state-based Medicaid business accounted for approximately 5% of our total premiums and services revenue for the three months ended March 31, 2017 . 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), in Illinois and Virginia for stand-alone dual eligible demonstration programs serving individuals dually eligible for both the federal Medicare program and the applicable state-based Medicaid program as well as an Integrated Care Program, or ICP, Medicaid contract in Illinois. 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 Florida Matters On January 6, 2012, the Civil Division of the United States Attorney’s Office for the Southern District of Florida advised us that it is seeking documents and information from us and several of our affiliates relating to several matters including the coding of medical claims by one or more South Florida medical providers, and loans to physician practices. On May 1, 2014, the U.S. Attorney's Office filed a Notice of Non-Intervention in connection with a civil qui tam suit related to one of these matters captioned United States of America ex rel. Olivia Graves v. Plaza Medical Centers, et al. , and the Court ordered the complaint unsealed. Subsequently, the individual plaintiff amended the complaint and served the Company, opting to continue to pursue the action. The individual plaintiff has filed a fourth and fifth amended complaint, both of which have been dismissed, and the third amended complaint has been ordered operative by the Court. The Court has ordered trial to commence on November 13, 2017. We continue to cooperate with and respond to information requests from the U.S. Attorney’s office. These matters could result in additional qui tam litigation. As previously disclosed, the Civil Division of the United States Department of Justice had provided us with an information request, separate from but related to the Plaza Medical matter, 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, including the providers identified in the Plaza Medical matter, 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 and the U.S. Attorney’s Office. These matters are expected to result in additional qui tam litigation. Litigation Related to the Merger Shareholder Action In connection with the terminated Merger Agreement with Aetna Inc., which we refer to as the Merger, three putative class action complaints were filed by purported Humana stockholders challenging the Merger, two in the Circuit Court of Jefferson County, Kentucky and one in the Court of Chancery of the State of Delaware. The complaints are captioned Solak v. Broussard et al., Civ. Act. No. 15CI03374 (Kentucky state court), Litwin v. Broussard et al., Civ. Act. No. 15CI04054 (Kentucky state court) and Scott v. Humana Inc. et al., C.A. No. 11323-VCL (Delaware state court). The complaints named as defendants each member of Humana’s board of directors, Aetna, and, in the case of the Delaware complaint, Humana. Following the termination of the merger agreement, each of the stockholder actions was voluntarily dismissed without prejudice by the plaintiffs as moot. 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, failure to disclose network discounts and various other provider arrangements, 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. Penn Treaty is a financially distressed unaffiliated long-term care insurance company. On March 1, 2017, a court ordered the liquidation of Penn Treaty which triggered assessments from state guaranty associations that resulted in our recording a $54 million estimate in operating costs in the three months ended March 31, 2017. 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, 2017
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION During the three months ended March 31, 2017, we realigned certain of our businesses among our reportable segments to correspond with internal management reporting changes and our previously announced planned exit from the individual commercial medical business on January 1, 2018. Additionally, we renamed our Group segment to the Group and Specialty segment, and began presenting the individual commercial business results as a separate segment rather than as part of the Retail segment. Specialty health insurance benefits, including dental, vision, other supplement health, and financial protection products, marketed to individuals are now included in the Group and Specialty segment. Specialty health insurance benefits marketed to employer groups continue to be included in the Group and Specialty segment. As a result of this realignment, our reportable segments now include Retail, Group and Specialty, Healthcare Services, and Individual Commercial. Prior period segment financial information has been recast to conform to the 2017 presentation. 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, collectively 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 South 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, as well as services and capabilities to promote wellness and advance population health. The Individual Commercial segment consists of our individual commercial fully-insured medical health insurance benefits. We report under the category of Other Businesses those businesses which 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 $3.0 billion and $2.9 billion for the three months ended March 31, 2017 and 2016 , 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 $26 million and $27 million for the three months ended March 31, 2017 and 2016 , 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 2016 Form 10-K. Transactions between reportable segments primarily consist of sales of services rendered by our Healthcare Services segment, primarily pharmacy, provider, and clinical care services, to our Retail, Group and Specialty, and Individual Commercial segment customers . Intersegment sales and expenses are recorded at fair value and eliminated in consolidation. Members served by our segments often use the same provider networks, enabling us in some instances to obtain more favorable contract terms with providers. Our segments also share indirect costs and assets. As a result, the profitability of each segment is interdependent. We allocate most operating expenses to our segments. Assets and certain corporate income and expenses are not allocated to the segments, including the portion of investment income not supporting segment operations, interest expense on corporate debt, and certain other corporate expenses. These items are managed at a corporate level. These corporate amounts are reported separately from our reportable segments and are included with intersegment eliminations in the tables presenting segment results below. Our segment results were as follows for the three and three months ended March 31, 2017 and 2016 : 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 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2016 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,027 $ — $ — $ — $ — $ — $ 8,027 Group Medicare Advantage 1,077 — — — — — 1,077 Medicare stand-alone PDP 1,039 — — — — — 1,039 Total Medicare 10,143 — — — — — 10,143 Fully-insured 104 1,337 — 893 — — 2,334 Specialty — 318 — — — — 318 Medicaid and other 630 5 — — 10 — 645 Total premiums 10,877 1,660 — 893 10 — 13,440 Services revenue: Provider — — 71 — — — 71 ASO and other 1 177 1 — 3 — 182 Pharmacy — — 7 — — — 7 Total services revenue 1 177 79 — 3 — 260 Total revenues - external customers 10,878 1,837 79 893 13 — 13,700 Intersegment revenues Services — 6 4,784 — — (4,790 ) — Products — — 1,360 — — (1,360 ) — Total intersegment revenues — 6 6,144 — — (6,150 ) — Investment income 24 6 7 2 15 46 100 Total revenues 10,902 1,849 6,230 895 28 (6,104 ) 13,800 Operating expenses: Benefits 9,633 1,222 — 729 25 (212 ) 11,397 Operating costs 1,082 434 5,942 169 4 (5,897 ) 1,734 Merger termination fee and related costs, net — — — — — 34 34 Depreciation and amortization 46 21 36 9 — (24 ) 88 Total operating expenses 10,761 1,677 5,978 907 29 (6,099 ) 13,253 Income (loss) from operations 141 172 252 (12 ) (1 ) (5 ) 547 Interest expense — — — — — 47 47 Income (loss) before income taxes $ 141 $ 172 $ 252 $ (12 ) $ (1 ) $ (52 ) $ 500

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 and December 31, 2016 , respectively: Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value (in millions) March 31, 2017 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 833 $ — $ (12 ) $ 821 Mortgage-backed securities 1,645 4 (31 ) 1,618 Tax-exempt municipal securities 3,408 9 (48 ) 3,369 Mortgage-backed securities: Residential 8 — — 8 Commercial 412 1 (4 ) 409 Asset-backed securities 132 — — 132 Corporate debt securities 4,198 144 (70 ) 4,272 Total debt securities $ 10,636 $ 158 $ (165 ) $ 10,629 December 31, 2016 U.S. Treasury and other U.S. government U.S. Treasury and agency obligations $ 800 $ 1 $ (15 ) $ 786 Mortgage-backed securities 1,662 6 (31 ) 1,637 Tax-exempt municipal securities 3,358 15 (68 ) 3,305 Mortgage-backed securities: Residential 9 — — 9 Commercial 307 1 (4 ) 304 Asset-backed securities 160 — — 160 Corporate debt securities 3,530 145 (78 ) 3,597 Total debt securities $ 9,826 $ 168 $ (196 ) $ 9,798
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, 2017 and December 31, 2016 , respectively: Less than 12 months 12 months or more Total Fair Gross Fair Gross Fair Gross (in millions) March 31, 2017 U.S. Treasury and other U.S. U.S. Treasury and agency $ 705 $ (12 ) $ 3 $ — $ 708 $ (12 ) Mortgage-backed 1,565 (31 ) 3 — 1,568 (31 ) Tax-exempt municipal 2,493 (47 ) 25 (1 ) 2,518 (48 ) Mortgage-backed securities: Residential — — 4 — 4 — Commercial 190 (3 ) 8 (1 ) 198 (4 ) Asset-backed securities 65 — 52 — 117 — Corporate debt securities 1,710 (65 ) 70 (5 ) 1,780 (70 ) Total debt securities $ 6,728 $ (158 ) $ 165 $ (7 ) $ 6,893 $ (165 ) December 31, 2016 U.S. Treasury and other U.S. U.S. Treasury and agency $ 697 $ (15 ) $ 3 $ — $ 700 $ (15 ) Mortgage-backed 1,528 (31 ) 3 — 1,531 (31 ) Tax-exempt municipal 2,756 (67 ) 43 (1 ) 2,799 (68 ) Mortgage-backed securities: Residential — — 4 — 4 — Commercial 182 (3 ) 24 (1 ) 206 (4 ) Asset-backed securities 51 — 63 — 114 — Corporate debt securities 1,544 (71 ) 69 (7 ) 1,613 (78 ) Total debt securities $ 6,758 $ (187 ) $ 209 $ (9 ) $ 6,967 $ (196 )
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, 2017 and 2016 : Three months ended 2017 2016 (in millions) Gross realized gains $ 27 $ 31 Gross realized losses (1 ) (11 ) Net realized capital gains $ 26 $ 20
Schedule of Contractual Maturity of Debt Securities Available for Sale	The contractual maturities of debt securities available for sale at March 31, 2017 , 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 $ 561 $ 562 Due after one year through five years 2,764 2,770 Due after five years through ten years 2,188 2,153 Due after ten years 2,926 2,977 Mortgage and asset-backed securities 2,197 2,167 Total debt securities $ 10,636 $ 10,629

FAIR VALUE (Tables)

FAIR VALUE (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Financial Assets Measured at Fair Value on Recurring Basis	The following table summarizes our fair value measurements at March 31, 2017 and December 31, 2016 , 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, 2017 Cash equivalents $ 8,034 $ 8,034 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 821 — 821 — Mortgage-backed securities 1,618 — 1,618 — Tax-exempt municipal securities 3,369 — 3,366 3 Mortgage-backed securities: Residential 8 — 8 — Commercial 409 — 409 — Asset-backed securities 132 — 132 — Corporate debt securities 4,272 — 4,268 4 Total debt securities 10,629 — 10,622 7 Total invested assets $ 18,663 $ 8,034 $ 10,622 $ 7 December 31, 2016 Cash equivalents $ 3,654 $ 3,654 $ — $ — Debt securities: U.S. Treasury and other U.S. government U.S. Treasury and agency obligations 786 — 786 — Mortgage-backed securities 1,637 — 1,637 — Tax-exempt municipal securities 3,305 — 3,302 3 Mortgage-backed securities: Residential 9 — 9 — Commercial 304 — 304 — Asset-backed securities 160 — 160 — Corporate debt securities 3,597 — 3,593 4 Total debt securities 9,798 — 9,791 7 Total invested assets $ 13,452 $ 3,654 $ 9,791 $ 7
Changes in Fair Value of Assets Measured Using Significant Unobservable Inputs	During the three months ended March 31, 2017 and 2016 , the changes in the fair value of the assets measured using significant unobservable inputs (Level 3) were comprised of the following: For the three months ended March 31, 2017 2016 Private Auction Total Private Auction Total (in millions) Beginning balance at January 1 $ 4 $ 3 $ 7 $ 6 $ 5 $ 11 Settlements — — — — (2 ) (2 ) Balance at March 31 $ 4 $ 3 $ 7 $ 6 $ 3 $ 9

MEDICARE PART D (Tables)

MEDICARE PART D (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 and December 31, 2016 . 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, 2017 December 31, 2016 Risk CMS Risk CMS (in millions) Other current assets $ 8 $ 1,044 $ 8 $ 1,001 Trade accounts payable and accrued expenses (126 ) (1,895 ) (158 ) (128 ) Net current (liability) asset (118 ) (851 ) (150 ) 873 Other long-term assets 12 — — — Other long-term liabilities (74 ) — — — Net long-term liability (62 ) — — — Total net (liability) asset $ (180 ) $ (851 ) $ (150 ) $ 873

HEALTH CARE REFORM (Tables)

HEALTH CARE REFORM (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 and December 31, 2016 . Amounts classified as long-term represent settlements that we expect to exceed 12 months at March 31, 2017 . March 31, 2017 December 31, 2016 Risk Adjustment Reinsurance Risk Adjustment Reinsurance (in millions) Prior Coverage Years Premiums receivable $ 320 $ — $ 307 $ — Other current assets — 207 — 260 Trade accounts payable and (124 ) — (117 ) — Net current asset 196 207 190 260 Other long-term assets — — 6 — Total prior coverage years' net 196 207 196 260 Current Coverage Year Other long-term assets 17 — — — Other long-term liabilities (26 ) — — — Total 2017 coverage year net (9 ) — — — Total net asset $ 187 $ 207 $ 196 $ 260

GOODWILL AND OTHER INTANGIBLE26

GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 were as follows: Retail Group and Specialty Healthcare Total (in millions) Balance at January 1, 2017 $ 1,059 $ 261 $ 1,952 $ 3,272 Acquisitions — — 7 7 Balance at March 31, 2017 $ 1,059 $ 261 $ 1,959 $ 3,279
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, 2017 and December 31, 2016 . March 31, 2017 December 31, 2016 Weighted Cost Accumulated Net Cost Accumulated Net ($ in millions) Other intangible assets: Customer contracts/ 9.8 years $ 566 $ 360 $ 206 $ 566 $ 347 $ 219 Trade names and 8.2 years 104 72 32 104 69 35 Provider contracts 14.1 years 51 30 21 51 29 22 Noncompetes and 8.2 years 32 29 3 32 28 4 Total other intangible 9.8 years $ 753 $ 491 $ 262 $ 753 $ 473 $ 280
Schedule of Estimated Amortization Expense	The following table presents our estimate of amortization expense for 2017 and each of the five next succeeding years: (in millions) For the years ending December 31,: 2017 $ 71 2018 63 2019 52 2020 48 2021 14 2022 11

BENEFITS PAYABLE (Tables)

BENEFITS PAYABLE (Tables)	3 Months Ended
	Mar. 31, 2017
Insurance [Abstract]
Activity in Benefits Payable	Activity in benefits payable for our Retail segment was as follows for the three months ended March 31, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 3,507 $ 3,600 Less: Reinsurance recoverables (76 ) (85 ) Balances at January 1, net 3,431 3,515 Incurred related to: Current year 10,255 9,851 Prior years (204 ) (218 ) Total incurred 10,051 9,633 Paid related to: Current year (7,014 ) (6,706 ) Prior years (2,572 ) (2,685 ) Total paid (9,586 ) (9,391 ) Reinsurance recoverable 71 67 Ending Balance $ 3,967 $ 3,824 Activity in benefits payable for our Individual Commercial segment was as follows for the three months ended March 31, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 454 $ 740 Less: Premium deficiency reserve — (176 ) Balances at January 1, net 454 564 Incurred related to: Current year 185 826 Prior years (6 ) (80 ) Total incurred 179 746 Paid related to: Current year (49 ) (465 ) Prior years (363 ) (370 ) Total paid (412 ) (835 ) Premium deficiency reserve — 189 Ending Balance $ 221 $ 664 Activity in benefits payable for our Group and Specialty segment, excluding military services, was as follows for the three months ended March 31, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 578 $ 616 Incurred related to: Current year 1,306 1,260 Prior years (20 ) (41 ) Total incurred 1,286 1,219 Paid related to: Current year (824 ) (728 ) Prior years (493 ) (502 ) Total paid (1,317 ) (1,230 ) Ending Balance $ 547 $ 605 On a consolidated basis, activity in benefits payable, excluding military services, was as follows for the three months ended March 31, 2017 and 2016: For the three months ended March 31, 2017 2016 (in millions) Balances at January 1 $ 4,563 $ 4,976 Less: Premium deficiency reserve — (176 ) Less: Reinsurance recoverables (76 ) (85 ) Balances at January 1, net 4,487 4,715 Incurred related to: Current year 11,580 11,751 Prior years (231 ) (340 ) Total incurred 11,349 11,411 Paid related to: Current year (7,695 ) (7,692 ) Prior years (3,451 ) (3,576 ) Total paid (11,146 ) (11,268 ) Premium deficiency reserve — 189 Reinsurance recoverable 71 67 Ending Balance $ 4,761 $ 5,114
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, 2017 and 2016. March 31, 2017 March 31, 2016 (in millions) Premium deficiency reserve - Individual Commercial $ — $ 13 Military services — 3 Future policy benefits: Individual Commercial (33 ) (40 ) Other Businesses 10 10 Total future policy benefits (23 ) (30 ) Total $ (23 ) $ (14 )
Schedule Of Benefits Expense	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, 2017 Net outstanding liabilities Retail $ 3,896 Group and Specialty 547 Individual Commercial 221 Other Businesses 26 Benefits payable, net of reinsurance 4,690 Reinsurance recoverable on unpaid claims Retail 71 Total reinsurance recoverable on unpaid claims 71 Total benefits payable, gross $ 4,761

EARNINGS PER COMMON SHARE COM28

EARNINGS PER COMMON SHARE COMPUTATION (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 and 2016 : Three months ended March 31, 2017 2016 (dollars in millions, except per common share results; number of shares in thousands) Net income available for common stockholders $ 1,115 $ 254 Weighted average outstanding shares of common stock 147,824 149,161 Dilutive effect of: Employee stock options 199 218 Restricted stock 849 1,517 Shares used to compute diluted earnings per common share 148,872 150,896 Basic earnings per common share $ 7.54 $ 1.70 Diluted earnings per common share $ 7.49 $ 1.68 Number of antidilutive stock options and restricted stock 938 1,285

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2017
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 2016 and 2017 under our Board approved quarterly cash dividend policy: Record Payment Amount Total (in millions) 2016 payments 12/30/2015 1/29/2016 $ 0.29 $ 43 3/31/2016 4/29/2016 $ 0.29 $ 43 6/30/2016 7/29/2016 $ 0.29 $ 43 10/13/2016 10/28/2016 $ 0.29 $ 43 2017 payments 1/12/2017 1/27/2017 $ 0.29 $ 43 3/31/2017 4/28/2017 $ 0.40 $ 58

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 and December 31, 2016 : March 31, 2017 December 31, 2016 (in millions) Senior notes: $500 million, 7.20% due June 15, 2018 $ 501 $ 501 $300 million, 6.30% due August 1, 2018 304 304 $400 million, 2.625% due October 1, 2019 398 398 $600 million, 3.15% due December 1, 2022 595 595 $600 million, 3.85% due October 1, 2024 595 595 $600 million, 3.95% due March 15, 2027 594 — $250 million, 8.15% due June 15, 2038 263 264 $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 — Total long-term debt $ 4,780 $ 3,792

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, By Segment	Intersegment sales and expenses are recorded at fair value and eliminated in consolidation. Members served by our segments often use the same provider networks, enabling us in some instances to obtain more favorable contract terms with providers. Our segments also share indirect costs and assets. As a result, the profitability of each segment is interdependent. We allocate most operating expenses to our segments. Assets and certain corporate income and expenses are not allocated to the segments, including the portion of investment income not supporting segment operations, interest expense on corporate debt, and certain other corporate expenses. These items are managed at a corporate level. These corporate amounts are reported separately from our reportable segments and are included with intersegment eliminations in the tables presenting segment results below. Our segment results were as follows for the three and three months ended March 31, 2017 and 2016 : 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 Retail Group and Specialty Healthcare Individual Commercial Other Eliminations/ Consolidated (in millions) Three months ended March 31, 2016 Revenues - external customers Premiums: Individual Medicare Advantage $ 8,027 $ — $ — $ — $ — $ — $ 8,027 Group Medicare Advantage 1,077 — — — — — 1,077 Medicare stand-alone PDP 1,039 — — — — — 1,039 Total Medicare 10,143 — — — — — 10,143 Fully-insured 104 1,337 — 893 — — 2,334 Specialty — 318 — — — — 318 Medicaid and other 630 5 — — 10 — 645 Total premiums 10,877 1,660 — 893 10 — 13,440 Services revenue: Provider — — 71 — — — 71 ASO and other 1 177 1 — 3 — 182 Pharmacy — — 7 — — — 7 Total services revenue 1 177 79 — 3 — 260 Total revenues - external customers 10,878 1,837 79 893 13 — 13,700 Intersegment revenues Services — 6 4,784 — — (4,790 ) — Products — — 1,360 — — (1,360 ) — Total intersegment revenues — 6 6,144 — — (6,150 ) — Investment income 24 6 7 2 15 46 100 Total revenues 10,902 1,849 6,230 895 28 (6,104 ) 13,800 Operating expenses: Benefits 9,633 1,222 — 729 25 (212 ) 11,397 Operating costs 1,082 434 5,942 169 4 (5,897 ) 1,734 Merger termination fee and related costs, net — — — — — 34 34 Depreciation and amortization 46 21 36 9 — (24 ) 88 Total operating expenses 10,761 1,677 5,978 907 29 (6,099 ) 13,253 Income (loss) from operations 141 172 252 (12 ) (1 ) (5 ) 547 Interest expense — — — — — 47 47 Income (loss) before income taxes $ 141 $ 172 $ 252 $ (12 ) $ (1 ) $ (52 ) $ 500

BASIS OF PRESENTATION AND SIG32

BASIS OF PRESENTATION AND SIGNIFICANT EVENTS (Details) $ in Billions	Feb. 14, 2017USD ($)
Settled litigation | U.S. Department Of Justice vs. Humana and Aetna
Business Acquisition [Line Items]
Break up fee to be received	$ 1

RECENTLY ISSUED ACCOUNTING PR33

RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (Details)	12 Months Ended
	Dec. 31, 2016
Revenue From Premiums and Investment Income | Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk, percentage	98.00%

INVESTMENT SECURITIES - Additio

INVESTMENT SECURITIES - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017USD ($)position	Mar. 31, 2016USD ($)	Dec. 31, 2016position
Investment [Line Items]
Percentage of debt securities considered to be of investment-grade	98.00%
Maximum percentage of any general obligation bonds in one state	9.00%
Percentage of tax exempt securities	2.00%
Securities in unrealized loss positions, number of positions	970
Number of positions			2,220
Other-than-temporary impairments | $	$ 0	$ 0

INVESTMENT SECURITIES - Securit

INVESTMENT SECURITIES - Securities Classified as Current and Long-Term (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Amortized Cost	$ 10,636	$ 9,826
Gross Unrealized Gains	158	168
Gross Unrealized Losses	(165)	(196)
Fair Value	10,629	9,798
Debt Securities | Tax-exempt municipal securities
Investment [Line Items]
Amortized Cost	3,408	3,358
Gross Unrealized Gains	9	15
Gross Unrealized Losses	(48)	(68)
Fair Value	3,369	3,305
Debt Securities | Residential Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	8	9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	8	9
Debt Securities | Commercial Mortgage-Backed Securities
Investment [Line Items]
Amortized Cost	412	307
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(4)	(4)
Fair Value	409	304
Debt Securities | Asset-backed securities
Investment [Line Items]
Amortized Cost	132	160
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	132	160
Debt Securities | Corporate debt securities
Investment [Line Items]
Amortized Cost	4,198	3,530
Gross Unrealized Gains	144	145
Gross Unrealized Losses	(70)	(78)
Fair Value	4,272	3,597
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Investment [Line Items]
Amortized Cost	833	800
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(12)	(15)
Fair Value	821	786
Debt Securities | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Investment [Line Items]
Amortized Cost	1,645	1,662
Gross Unrealized Gains	4	6
Gross Unrealized Losses	(31)	(31)
Fair Value	$ 1,618	$ 1,637

INVESTMENT SECURITIES - Gross U

INVESTMENT SECURITIES - Gross Unrealized Losses and Fair Values of Securities (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Investment [Line Items]
Less than 12 months, Fair Value	$ 6,728	$ 6,758
Less than 12 months, Gross Unrealized Losses	(158)	(187)
12 months or more, Fair Value	165	209
12 months or more, Gross Unrealized Losses	(7)	(9)
Total, Fair Value	6,893	6,967
Total, Gross Unrealized Losses	(165)	(196)
Debt Securities | Tax-exempt municipal securities
Investment [Line Items]
Less than 12 months, Fair Value	2,493	2,756
Less than 12 months, Gross Unrealized Losses	(47)	(67)
12 months or more, Fair Value	25	43
12 months or more, Gross Unrealized Losses	(1)	(1)
Total, Fair Value	2,518	2,799
Total, Gross Unrealized Losses	(48)	(68)
Debt Securities | Residential Mortgage-Backed Securities
Investment [Line Items]
Less than 12 months, Fair Value	0	0
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	4	4
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	4	4
Total, Gross Unrealized Losses	0	0
Debt Securities | Commercial Mortgage-Backed Securities
Investment [Line Items]
Less than 12 months, Fair Value	190	182
Less than 12 months, Gross Unrealized Losses	(3)	(3)
12 months or more, Fair Value	8	24
12 months or more, Gross Unrealized Losses	(1)	(1)
Total, Fair Value	198	206
Total, Gross Unrealized Losses	(4)	(4)
Debt Securities | Asset-backed securities
Investment [Line Items]
Less than 12 months, Fair Value	65	51
Less than 12 months, Gross Unrealized Losses	0	0
12 months or more, Fair Value	52	63
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	117	114
Total, Gross Unrealized Losses	0	0
Debt Securities | Corporate debt securities
Investment [Line Items]
Less than 12 months, Fair Value	1,710	1,544
Less than 12 months, Gross Unrealized Losses	(65)	(71)
12 months or more, Fair Value	70	69
12 months or more, Gross Unrealized Losses	(5)	(7)
Total, Fair Value	1,780	1,613
Total, Gross Unrealized Losses	(70)	(78)
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	705	697
Less than 12 months, Gross Unrealized Losses	(12)	(15)
12 months or more, Fair Value	3	3
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	708	700
Total, Gross Unrealized Losses	(12)	(15)
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	1,565	1,528
Less than 12 months, Gross Unrealized Losses	(31)	(31)
12 months or more, Fair Value	3	3
12 months or more, Gross Unrealized Losses	0	0
Total, Fair Value	1,568	1,531
Total, Gross Unrealized Losses	$ (31)	$ (31)

INVESTMENT SECURITIES - Realize

INVESTMENT SECURITIES - Realized Gains (Losses) Within Investment Income (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 27	$ 31
Gross realized losses	(1)	(11)
Net realized capital gains	$ 26	$ 20

INVESTMENT SECURITIES - Contrac

INVESTMENT SECURITIES - Contractual Maturities, Available for Sale (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Amortized Cost
Due within one year	$ 561
Due after one year through five years	2,764
Due after five years through ten years	2,188
Due after ten years	2,926
Mortgage and asset-backed securities	2,197
Amortized Cost	10,636	$ 9,826
Fair Value
Due within one year	562
Due after one year through five years	2,770
Due after five years through ten years	2,153
Due after ten years	2,977
Mortgage and asset-backed securities	2,167
Fair Value	$ 10,629	$ 9,798

FAIR VALUE - Additional Informa

FAIR VALUE - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Upper limit percentage of Level 3 assets to total invested assets	0.04%
Short-term borrowings	$ 470	$ 300
Commercial Paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	470	300
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	4,780	3,792
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	5,052	4,004
Measured On Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	18,663	13,452
Unobservable Inputs (Level 3) | Measured On Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value	$ 7	$ 7

FAIR VALUE - Financial Assets M

FAIR VALUE - Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	$ 10,629	$ 9,798
Measured On Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	8,034	3,654
Debt securities	10,629	9,798
Total invested assets	18,663	13,452
Measured On Recurring Basis | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	3,369	3,305
Measured On Recurring Basis | Residential Mortgage-Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	8	9
Measured On Recurring Basis | Commercial Mortgage-Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	409	304
Measured On Recurring Basis | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	132	160
Measured On Recurring Basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	4,272	3,597
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	821	786
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	1,618	1,637
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	8,034	3,654
Debt securities	0	0
Total invested assets	8,034	3,654
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | Tax-exempt municipal securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | Residential Mortgage-Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | Commercial Mortgage-Backed Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | U.S. Treasury and other U.S. government corporations and agencies | U.S. Treasury and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Quoted Prices in Active Markets (Level 1) | U.S. Treasury and other U.S. government corporations and agencies | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities	0	0
Measured On Recurring Basis | Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Debt securities	10,622	9,791
Total invested assets	10,622	9,791
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	3,366	3,302
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	8	9
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	409	304
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	132	160
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	4,268	3,593
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	821	786
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	1,618	1,637
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	7	7
Total invested assets	7	7
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	3	3
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	4	4
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 - Changes in Level 3

FAIR VALUE - Changes in Level 3 Assets (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 7	$ 11
Settlements	0	(2)
Ending Balance	7	9
Private Placements
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4	6
Settlements	0	0
Ending Balance	4	6
Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3	5
Settlements	0	(2)
Ending Balance	$ 3	$ 3

MEDICARE PART D (Detail)

MEDICARE PART D (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Other current assets	$ 3,849	$ 3,438
Trade accounts payable and accrued expenses	(4,675)	(2,467)
Other long-term assets	2,167	2,226
Other long-term liabilities	(367)	(263)
Risk Corridor Settlement
Segment Reporting Information [Line Items]
Other current assets	8	8
Trade accounts payable and accrued expenses	(126)	(158)
Net current (liability) asset	(118)	(150)
Other long-term assets	12	0
Other long-term liabilities	(74)	0
Net long-term asset	(62)	0
Total net (liability) asset	(180)	(150)
CMS Subsidies/ Discounts
Segment Reporting Information [Line Items]
Other current assets	1,044	1,001
Trade accounts payable and accrued expenses	(1,895)	(128)
Net current (liability) asset	(851)	873
Other long-term assets	0	0
Other long-term liabilities	0	0
Net long-term asset	0	0
Total net (liability) asset	$ (851)	$ 873

HEALTH CARE REFORM (Details)

HEALTH CARE REFORM (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended			12 Months Ended
	Sep. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
Premium deficiency reserve		$ 0				$ 176
Premium deficiency reserve, change in estimate				$ 13
Write off of risk corridor receivables			$ 583
Other current assets		3,849	3,438		$ 3,438
Trade accounts payable and accrued expenses		(4,675)	(2,467)		(2,467)
Other long-term assets		2,167	2,226		2,226
Other long-term liabilities		(367)	(263)		(263)
Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		187	196		196
Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Total net (liability) asset		207	260		260
Health Care Reform
Supplementary Insurance Information, by Segment [Line Items]
Payment of annual health insurance industry fee	$ 916
Amortization of deferred charges				227
2014 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Increase (decrease) in premiums receivable					(37)
2015 Coverage Year
Supplementary Insurance Information, by Segment [Line Items]
Proceeds from reinsurance recoverable		60		213
Proceeds from risk adjustment settlements		2		$ 6
2014 and 2015 ACA Products
Supplementary Insurance Information, by Segment [Line Items]
Write off of risk corridor receivables			415
2016 Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		320	307		307
Other current assets		0	0		0
Trade accounts payable and accrued expenses		(124)	(117)		(117)
Net current asset		196	190		190
Other long-term assets		0	6		6
Total net (liability) asset		196	196		196
2016 Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Premiums receivable		0	0		0
Other current assets		207	260		260
Trade accounts payable and accrued expenses		0	0		0
Net current asset		207	260		260
Other long-term assets		0	0		0
Total net (liability) asset		207	260		260
Current Coverage Year | Risk Adjustment Settlement
Supplementary Insurance Information, by Segment [Line Items]
Other long-term assets		17	0		0
Other long-term liabilities		(26)	0		0
Total net (liability) asset		(9)	0		0
Current Coverage Year | Reinsurance Recoverables
Supplementary Insurance Information, by Segment [Line Items]
Other long-term assets		0	0		0
Other long-term liabilities		0	0		0
Total net (liability) asset		$ 0	$ 0		$ 0

GOODWILL AND OTHER INTANGIBLE44

GOODWILL AND OTHER INTANGIBLE ASSETS - Goodwill by Segments (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 3,272
Acquisitions	7
Ending balance	3,279
Retail
Goodwill [Roll Forward]
Beginning balance	1,059
Acquisitions	0
Ending balance	1,059
Group and Specialty
Goodwill [Roll Forward]
Beginning balance	261
Acquisitions	0
Ending balance	261
Healthcare Services
Goodwill [Roll Forward]
Beginning balance	1,952
Acquisitions	7
Ending balance	$ 1,959

GOODWILL AND OTHER INTANGIBLE45

GOODWILL AND OTHER INTANGIBLE ASSETS - Details of Intangible Assets Included in Other Long-Term Assets (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 9 months 18 days
Cost	$ 753	$ 753
Accumulated Amortization	491	473
Net	$ 262	280
Customer contracts/ relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	9 years 9 months 18 days
Cost	$ 566	566
Accumulated Amortization	360	347
Net	$ 206	219
Trade names and technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 2 months 12 days
Cost	$ 104	104
Accumulated Amortization	72	69
Net	$ 32	35
Provider contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	14 years 1 month 6 days
Cost	$ 51	51
Accumulated Amortization	30	29
Net	$ 21	22
Noncompetes and other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Life	8 years 2 months 12 days
Cost	$ 32	32
Accumulated Amortization	29	28
Net	$ 3	$ 4

GOODWILL AND OTHER INTANGIBLE46

GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Estimated Amortization Expense (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense for other intangible assets	$ 18	$ 21
2,017	71
2,018	63
2,019	52
2,020	48
2,021	14
2,022	$ 11

BENEFITS PAYABLE - Activity in

BENEFITS PAYABLE - Activity in Benefits Payable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	$ 4,563	$ 4,976
Less: Premium deficiency reserve	0	(176)
Less: Reinsurance recoverables	(76)	(85)
Balance			$ 4,487	$ 4,715
Incurred related to:
Current year	11,580	11,751
Prior years	(231)	(340)
Total incurred	11,349	11,411
Paid related to:
Current year	(7,695)	(7,692)
Prior years	(3,451)	(3,576)
Total paid	(11,146)	(11,268)
Premium deficiency reserve	0	(189)
Reinsurance recoverable	(71)	(67)
Ending balance	4,761	5,114
Retail
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	3,507	3,600
Less: Reinsurance recoverables	(76)	(85)
Balance			3,431	3,515
Incurred related to:
Current year	10,255	9,851
Prior years	(204)	(218)
Total incurred	10,051	9,633
Paid related to:
Current year	(7,014)	(6,706)
Prior years	(2,572)	(2,685)
Total paid	(9,586)	(9,391)
Reinsurance recoverable	(71)	(67)
Ending balance	3,967	3,824
Total IBNR	2,700
Group and Specialty
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	578	616
Incurred related to:
Current year	1,306	1,260
Prior years	(20)	(41)
Total incurred	1,286	1,219
Paid related to:
Current year	(824)	(728)
Prior years	(493)	(502)
Total paid	(1,317)	(1,230)
Ending balance	547	605
Total IBNR	468
Individual Commercial
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance	454	740
Less: Premium deficiency reserve	0	(176)
Balance			$ 454	$ 564
Incurred related to:
Current year	185	826
Prior years	(6)	(80)
Total incurred	179	746
Paid related to:
Current year	(49)	(465)
Prior years	(363)	(370)
Total paid	(412)	(835)
Premium deficiency reserve	0	(189)
Ending balance	221	$ 664
Total IBNR	$ 169

BENEFITS PAYABLE - Benefit Expe

BENEFITS PAYABLE - Benefit Expenses Excluded From Activity in Benefits Payable (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Premium deficiency reserve - Individual Commercial	$ 0	$ 13
Military services	0	3
Individual Commercial	(23)	(30)
Total	(23)	(14)
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Individual Commercial	(33)	(40)
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Individual Commercial	$ 10	$ 10

BENEFITS PAYABLE - Reconciliati

BENEFITS PAYABLE - Reconciliation to Consolidated (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 4,690
Reinsurance recoverable on unpaid claims	71	$ 76	$ 67	$ 85
Benefits payable	4,761	4,563	5,114	4,976
Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Reinsurance recoverable on unpaid claims	71	76	67	85
Benefits payable	3,967	3,507	3,824	3,600
Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	547	578	605	616
Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable	221	$ 454	$ 664	$ 740
Operating Segments | Retail
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	3,896
Operating Segments | Group and Specialty
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	547
Operating Segments | Individual Commercial
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	221
Other Businesses
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefits payable, net of reinsurance	$ 26

EARNINGS PER COMMON SHARE COM50

EARNINGS PER COMMON SHARE COMPUTATION (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income available for common stockholders	$ 1,115	$ 254
Weighted average outstanding shares of common stock used to compute basic earnings per common share (in shares)	147,824	149,161
Shares used to compute diluted earnings per common share (in shares)	148,872	150,896
Basic earnings per common share (in dollars per share)	$ 7.54	$ 1.70
Diluted earnings per common share (in dollars per share)	$ 7.49	$ 1.68
Number of antidilutive stock options and restricted stock excluded from computation (in shares)	938	1,285
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)	199	218
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)	849	1,517

STOCKHOLDERS' EQUITY - Schedule

STOCKHOLDERS' EQUITY - Schedule of Details of Dividend Payments (Detail) - USD ($) $ / shares in Units, $ in Millions	Apr. 20, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Subsequent Event [Line Items]
Record Date			Jan. 12, 2017	Oct. 13, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 30, 2015
Payment Date			Jan. 27, 2017	Oct. 28, 2016	Jul. 29, 2016	Apr. 29, 2016	Jan. 29, 2016
Amount per Share (in dollars per share)			$ 0.29	$ 0.29	$ 0.29	$ 0.29	$ 0.29
Total Amount			$ 43	$ 43	$ 43	$ 43	$ 43
Dividends per common share (in dollars per share)			$ 0.40				$ 0.29
Subsequent Event
Subsequent Event [Line Items]
Record Date		Mar. 31, 2017
Payment Date		Apr. 28, 2017
Amount per Share (in dollars per share)		$ 0.40
Total Amount		$ 58
Dividends per common share (in dollars per share)	$ 0.40

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Detail) - USD ($) shares in Thousands	Feb. 22, 2017	Feb. 16, 2017	Mar. 31, 2017	Mar. 31, 2016	May 03, 2017	Feb. 14, 2017	Dec. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Share repurchase authorization						$ 2,250,000,000	$ 2,000,000,000
Remaining authorized amount							1,040,000,000
Common shares acquired in connection with employee stock plans, shares			350	430
Common shares acquired in connection with employee stock plans, amount			$ 74,000,000	$ 71,000,000
Treasury stock reissued (shares)			1,130
Treasury stock reissued			$ 76,000,000
Accumulated other comprehensive loss			(58,000,000)				(66,000,000)
Net unrealized gains on our investment securities
Equity, Class of Treasury Stock [Line Items]
Accumulated other comprehensive loss			(4,000,000)				(17,000,000)
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 loss			$ 54,000,000				$ 49,000,000
Accelerated Share Repurchase Agreement
Equity, Class of Treasury Stock [Line Items]
Share repurchase payment	$ 1,500,000,000
Value of shares repurchased	$ 1,200,000,000	$ 1,500,000,000
Shares repurchased in open market	5,830
Decrease in capital in excess of par value	$ 300,000,000
Subsequent Event | September 2014 Share Repurchase Authorization
Equity, Class of Treasury Stock [Line Items]
Remaining authorized amount					$ 1,050,000,000

INCOME TAXES (Detail)

INCOME TAXES (Detail)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Effective income tax rate	34.00%	49.20%

DEBT - Senior Notes (Details)

DEBT - Senior Notes (Details) - Senior Notes - USD ($)	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Oct. 31, 2014	Dec. 31, 2008
Debt Instrument [Line Items]
Total long-term debt	$ 4,780,000,000	$ 4,780,000,000	$ 3,792,000,000
Proceeds from debt, net of discounts and offering expenses	$ 991,000,000
Redemption price, percentage		100.00%
Unamortized discount (premium)					$ 103,000,000
$500 million, 7.20% due June 15, 2018
Debt Instrument [Line Items]
Stated interest rate	7.20%	7.20%
Face amount	$ 500,000,000	$ 500,000,000
Total long-term debt	$ 501,000,000	$ 501,000,000	501,000,000
$300 million, 6.30% due August 1, 2018
Debt Instrument [Line Items]
Stated interest rate	6.30%	6.30%
Face amount	$ 300,000,000	$ 300,000,000
Total long-term debt	$ 304,000,000	$ 304,000,000	304,000,000
$400 million, 2.625% due October 1, 2019
Debt Instrument [Line Items]
Stated interest rate	2.625%	2.625%
Face amount	$ 400,000,000	$ 400,000,000
Total long-term debt	$ 398,000,000	$ 398,000,000	398,000,000
$600 million, 3.15% due December 1, 2022
Debt Instrument [Line Items]
Stated interest rate	3.15%	3.15%
Face amount	$ 600,000,000	$ 600,000,000
Total long-term debt	$ 595,000,000	$ 595,000,000	595,000,000
$600 million, 3.85% due October 1, 2024
Debt Instrument [Line Items]
Stated interest rate	3.85%	3.85%
Face amount	$ 600,000,000	$ 600,000,000
Total long-term debt	$ 595,000,000	$ 595,000,000	595,000,000
$600 million, 3.95% due March 15, 2027
Debt Instrument [Line Items]
Stated interest rate	3.95%	3.95%
Face amount	$ 600,000,000	$ 600,000,000
Total long-term debt	$ 594,000,000	$ 594,000,000	0
$250 million, 8.15% due June 15, 2038
Debt Instrument [Line Items]
Stated interest rate	8.15%	8.15%
Face amount	$ 250,000,000	$ 250,000,000
Total long-term debt	$ 263,000,000	$ 263,000,000	264,000,000
$400 million, 4.625% due December 1, 2042
Debt Instrument [Line Items]
Stated interest rate	4.625%	4.625%
Face amount	$ 400,000,000	$ 400,000,000
Total long-term debt	$ 396,000,000	$ 396,000,000	396,000,000
$750 million, 4.95% due October 1, 2044
Debt Instrument [Line Items]
Stated interest rate	4.95%	4.95%
Face amount	$ 750,000,000	$ 750,000,000
Total long-term debt	$ 739,000,000	$ 739,000,000	739,000,000
$400 million, 4.80% due March 15, 2047
Debt Instrument [Line Items]
Stated interest rate	4.80%	4.80%
Face amount	$ 400,000,000	$ 400,000,000
Total long-term debt	$ 395,000,000	$ 395,000,000	0
6.45% Senior Notes due June 2016
Debt Instrument [Line Items]
Stated interest rate	6.45%	6.45%
Unamortized discount (premium)	$ 22,000,000	$ 22,000,000	$ 23,000,000	$ 12,000,000

DEBT - Credit Agreement (Detail

DEBT - Credit Agreement (Details)	3 Months Ended
	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Actual net worth	$ 10,234,000,000	$ 10,685,000,000
Credit Agreement | Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Term	5 years
Maximum borrowing capacity	$ 1,000,000,000
Minimum level of net worth required	9,500,000,000
Actual net worth	$ 10,200,000,000
Required maximum leverage ratio	3
Actual leverage ratio	1.3
Uncommitted incremental loan facility	$ 250,000,000
Line of credit, outstanding borrowings	0
Remaining borrowing capacity	1,000,000,000
Credit Agreement | Line of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 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	0.90%
Facility fee (percentage)	0.10%
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%

DEBT - Commercial Paper (Detail

DEBT - Commercial Paper (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Oct. 31, 2014
Short-term Debt [Line Items]
Outstanding borrowings	$ 470,000,000	$ 300,000,000
Commercial Paper
Short-term Debt [Line Items]
Maximum borrowing capacity			$ 1,000,000,000
Maximum amount outstanding during period	500,000,000
Outstanding borrowings	$ 470,000,000	$ 300,000,000

GUARANTEES AND CONTINGENCIES (D

GUARANTEES AND CONTINGENCIES (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)complaint	May 01, 2014matter	Jan. 06, 2012provider
Loss Contingencies [Line Items]
Number of medical providers questioned (one or more) | provider			1
Number of matters related to a Notice of Non-Intervention | matter		1
TRICARE Contract
Loss Contingencies [Line Items]
Contract term, years	5 years
Total Medicare
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	78.00%
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	5.00%
Penn Treaty Insolvency | Insurance-related Assessments
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss | $	$ 54
Pending Litigation | Solak v. Broussard et al., Litwin v. Broussard et al., Scott v. Humana Inc. et al.
Loss Contingencies [Line Items]
Number of pending claims	3
Pending Litigation | Solak v. Broussard et al., Litwin v. Broussard et al., Scott v. Humana Inc. et al. | KENTUCKY
Loss Contingencies [Line Items]
Number of pending claims	2
Pending Litigation | Solak v. Broussard et al., Litwin v. Broussard et al., Scott v. Humana Inc. et al. | DELAWARE
Loss Contingencies [Line Items]
Number of pending claims	1

SEGMENT INFORMATION - Additiona

SEGMENT INFORMATION - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)Segment	Mar. 31, 2016USD ($)
Segment Reporting [Abstract]
Number of reportable segments | Segment	4
Member co-share amounts and government subsidies	$ 3,000	$ 2,900
Depreciation and amortization classified as benefit expense	$ 26	$ 27

SEGMENT INFORMATION - Reconcili

SEGMENT INFORMATION - Reconciliation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Premiums	$ 13,398	$ 13,440
Services	253	260
Revenues	13,651	13,700
Investment income	111	100
Total revenues	13,762	13,800
Benefits	11,326	11,397
Operating costs	1,553	1,734
Merger termination fee and related costs, net	(947)	34
Depreciation and amortization	92	88
Total operating expenses	12,024	13,253
Interest expense	1,738	547
Interest expense	49	47
Income (loss) before income taxes	1,689	500
Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	8,376	8,027
Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	1,318	1,077
Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	941	1,039
Total Medicare
Segment Reporting Information [Line Items]
Premiums	10,635	10,143
Fully-insured
Segment Reporting Information [Line Items]
Premiums	1,779	2,334
Specialty
Segment Reporting Information [Line Items]
Premiums	322	318
Medicaid and other
Segment Reporting Information [Line Items]
Premiums	662	645
Provider
Segment Reporting Information [Line Items]
Services	70	71
ASO and other
Segment Reporting Information [Line Items]
Services	165	182
Pharmacy
Segment Reporting Information [Line Items]
Services	18	7
Intersegment revenues
Segment Reporting Information [Line Items]
Revenues	(5,867)	(6,150)
Intersegment revenues | Retail
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Group and Specialty
Segment Reporting Information [Line Items]
Revenues	5	6
Intersegment revenues | Healthcare Services
Segment Reporting Information [Line Items]
Revenues	5,862	6,144
Intersegment revenues | Individual Commercial
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Services
Segment Reporting Information [Line Items]
Revenues	(4,315)	(4,790)
Intersegment revenues | Services | Retail
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Services | Group and Specialty
Segment Reporting Information [Line Items]
Revenues	5	6
Intersegment revenues | Services | Healthcare Services
Segment Reporting Information [Line Items]
Revenues	4,310	4,784
Intersegment revenues | Services | Individual Commercial
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Products
Segment Reporting Information [Line Items]
Revenues	(1,552)	(1,360)
Intersegment revenues | Products | Retail
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Products | Group and Specialty
Segment Reporting Information [Line Items]
Revenues	0	0
Intersegment revenues | Products | Healthcare Services
Segment Reporting Information [Line Items]
Revenues	1,552	1,360
Intersegment revenues | Products | Individual Commercial
Segment Reporting Information [Line Items]
Revenues	0	0
Operating Segments | Retail
Segment Reporting Information [Line Items]
Premiums	11,406	10,877
Services	2	1
Revenues	11,408	10,878
Investment income	25	24
Total revenues	11,433	10,902
Benefits	10,051	9,633
Operating costs	954	1,082
Depreciation and amortization	58	46
Total operating expenses	11,063	10,761
Interest expense	370	141
Interest expense	0	0
Income (loss) before income taxes	370	141
Operating Segments | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	1,700	1,660
Services	161	177
Revenues	1,861	1,837
Investment income	11	6
Total revenues	1,877	1,849
Benefits	1,286	1,222
Operating costs	399	434
Depreciation and amortization	21	21
Total operating expenses	1,706	1,677
Interest expense	171	172
Interest expense	0	0
Income (loss) before income taxes	171	172
Operating Segments | Healthcare Services
Segment Reporting Information [Line Items]
Premiums	0	0
Services	88	79
Revenues	88	79
Investment income	8	7
Total revenues	5,958	6,230
Benefits	0	0
Operating costs	5,680	5,942
Depreciation and amortization	34	36
Total operating expenses	5,714	5,978
Interest expense	244	252
Interest expense	0	0
Income (loss) before income taxes	244	252
Operating Segments | Individual Commercial
Segment Reporting Information [Line Items]
Premiums	283	893
Services	0	0
Revenues	283	893
Investment income	1	2
Total revenues	284	895
Benefits	156	729
Operating costs	62	169
Depreciation and amortization	3	9
Total operating expenses	221	907
Interest expense	63	(12)
Interest expense	0	0
Income (loss) before income taxes	63	(12)
Operating Segments | Individual Medicare Advantage | Retail
Segment Reporting Information [Line Items]
Premiums	8,376	8,027
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	1,318	1,077
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	941	1,039
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	10,635	10,143
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	118	104
Operating Segments | Fully-insured | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	1,378	1,337
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	283	893
Operating Segments | Specialty | Retail
Segment Reporting Information [Line Items]
Premiums	0	0
Operating Segments | Specialty | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	322	318
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	653	630
Operating Segments | Medicaid and other | Group and Specialty
Segment Reporting Information [Line Items]
Premiums	0	5
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	70	71
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	1
Operating Segments | ASO and other | Group and Specialty
Segment Reporting Information [Line Items]
Services	161	177
Operating Segments | ASO and other | Healthcare Services
Segment Reporting Information [Line Items]
Services	0	1
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	18	7
Operating Segments | Pharmacy | Individual Commercial
Segment Reporting Information [Line Items]
Services	0	0
Other Businesses
Segment Reporting Information [Line Items]
Premiums	9	10
Services	2	3
Revenues	11	13
Investment income	21	15
Total revenues	32	28
Benefits	29	25
Operating costs	4	4
Depreciation and amortization	0	0
Total operating expenses	33	29
Interest expense	(1)	(1)
Interest expense	0	0
Income (loss) before income taxes	(1)	(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	10
Other Businesses | Provider
Segment Reporting Information [Line Items]
Services	0	0
Other Businesses | ASO and other
Segment Reporting Information [Line Items]
Services	2	3
Other Businesses | Pharmacy
Segment Reporting Information [Line Items]
Services	0	0
Eliminations/ Corporate
Segment Reporting Information [Line Items]
Premiums	0	0
Services	0	0
Revenues	0	0
Investment income	45	46
Total revenues	(5,822)	(6,104)
Benefits	(196)	(212)
Operating costs	(5,546)	(5,897)
Merger termination fee and related costs, net	(947)	34
Depreciation and amortization	(24)	(24)
Total operating expenses	(6,713)	(6,099)
Interest expense	891	(5)
Interest expense	49	47
Income (loss) before income taxes	842	(52)
Eliminations/ Corporate | Individual Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Group Medicare Advantage
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Medicare stand-alone PDP
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Total Medicare
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Fully-insured
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Specialty
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Medicaid and other
Segment Reporting Information [Line Items]
Premiums	0	0
Eliminations/ Corporate | Provider
Segment Reporting Information [Line Items]
Services	0	0
Eliminations/ Corporate | ASO and other
Segment Reporting Information [Line Items]
Services	0	0
Eliminations/ Corporate | Pharmacy
Segment Reporting Information [Line Items]
Services	$ 0	$ 0