Aetna 10-Q 2 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information Document shares in Millions	3 Months Ended
	Mar. 31, 2017shares
Entity Information [Line Items]
Entity Registrant Name	AETNA INC /PA/
Entity Central Index Key	1,122,304
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding	331.7

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 3,877	$ 17,996
Investments	3,079	3,046
Premiums receivable, net	2,745	2,356
Other receivables, net	2,367	2,224
Accrued investment income	230	232
Income taxes receivable	75	44
Other current assets	2,645	2,551
Total current assets	15,018	28,449
Long-term investments	21,922	21,833
Reinsurance recoverables	716	727
Goodwill	10,637	10,637
Other acquired intangible assets, net	1,382	1,442
Property and equipment, net	577	587
Deferred income taxes	93	0
Other long-term assets	1,762	1,480
Separate Account assets	4,244	3,991
Total assets	56,351	69,146
Current liabilities:
Health care costs payable	6,432	6,558
Future policy benefits	645	645
Unpaid claims	790	801
Unearned premiums	2,078	556
Policyholders' funds	2,775	2,772
Current portion of long-term debt	1,249	1,634
Accrued expenses and other current liabilities	5,579	5,728
Total current liabilities	19,548	18,694
Future policy benefits	5,908	5,929
Unpaid claims	1,705	1,703
Policyholders' funds	870	812
Long-term debt, less current portion	8,174	19,027
Deferred income taxes	0	4
Other long-term liabilities	1,564	1,043
Separate Accounts liabilities	4,244	3,991
Total liabilities	42,013	51,203
Commitments and contingencies (Note 14)
Shareholders' equity:
Common stock ($.01 par value; 2.5 billion shares authorized and 331.7 million shares issued and outstanding in 2017; 2.5 billion shares authorized and 351.7 million shares issued and outstanding in 2016) and additional paid-in capital	4,006	4,716
Retained earnings	11,531	14,717
Accumulated other comprehensive loss	(1,276)	(1,552)
Total Aetna shareholders' equity	14,261	17,881
Non-controlling interests	77	62
Total equity	14,338	17,943
Total liabilities and equity	$ 56,351	$ 69,146

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Paranthetical) - $ / shares shares in Millions	Mar. 31, 2017	Dec. 31, 2016
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	2,500	2,500
Common Stock, Shares, Issued	331.7	351.7
Common Stock, Shares, Outstanding	331.7	351.7

Consolidated Statements of Inco

Consolidated Statements of Income (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Revenue:
Health care premiums		$ 13,219	$ 13,469
Other premiums		544	540
Fees and other revenue	[1]	1,475	1,467
Net investment income		260	218
Net realized capital gains (losses)		(333)	(1)
Total revenue		15,165	15,693
Benefits and expenses:
Health care costs	[2]	10,916	10,848
Current and future benefits		545	529
Operating expenses:
Selling expenses		421	421
General and administrative expenses		3,432	2,442
Total operating expenses		3,853	2,863
Interest expense		173	102
Amortization of other acquired intangible assets	[3]	60	62
Loss on early extinguishment of long-term debt	[3]	246	0
Total benefits and expenses		15,793	14,404
Income before income taxes	[3]	(628)	1,289
Income taxes:
Current		(7)	560
Deferred		(242)	(9)
Total income taxes		(249)	551
Net Income including non-controlling interests		(379)	738
Less: Net income (loss) attributable to non-controlling interests		2	1
Net income attributable to Aetna		$ (381)	$ 737
Earnings per common share:
Basic		$ (1.11)	$ 2.10
Diluted		$ (1.11)	$ 2.08
Administrative Services Contract Member Co Payments And Plan Sponsor Reimbursements		$ 31	$ 24
Pharmaceutical And Processing Costs		340	308
Insured Member Co Payments		$ 34	$ 34
[1]	Fees and other revenue include administrative services contract member co-payments and plan sponsor reimbursements related to our mail order and specialty pharmacy operations of $31 million and $24 million (net of pharmaceutical and processing costs of $340 million and $308 million) for the three months ended March 31, 2017 and 2016, respectively.
[2]	Health care costs have been reduced by Insured member co-payments related to our mail order and specialty pharmacy operations of $34 million for each of the three month periods ended March 31, 2017 and 2016.
[3]	In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:•In the three months ended March 31, 2017, we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020.•In the three months ended March 31, 2017, we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations.•We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Net Income including non-controlling interests		$ (379)	$ 738
Other comprehensive (loss) income		276	75
Comprehensive Income including non-controlling interests		(103)	813
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest		2	1
Comprehensive Income attributable to Aetna		(105)	812
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Other comprehensive (loss) income	[1]	0	1
Pension and OPEB Plan [Member]
Other comprehensive (loss) income		10	10
Net Unrealized Gains (Losses) All Other Securities [Member]
Other comprehensive (loss) income		44	221
Derivatives [Member]
Other comprehensive (loss) income		$ 222	$ (157)
[1]	Represents specifically identified unrealized gains and losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Parent [Member]	Noncontrolling Interest [Member]
Balance at beginning of period (in shares) at Dec. 31, 2015		349.5
Balance at beginning of period at Dec. 31, 2015			$ 4,647	$ 12,797	$ (1,330)	$ 16,114
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2015							$ 65
Total equity at beginning of period at Dec. 31, 2015	$ 16,179
Comprehensive income:
Net income attributable to Aetna	737	$ 0	0	737	0	737
Net income (loss) attributable to non-controlling interest	1						1
Net Income including non-controlling interests	738
Other increases (decreases) in noncontrolling interests	(1)	0	0	0	0	0	(1)
Other comprehensive (loss) income	75	$ 0	0	0	75	75	0
Common shares issued for benefit plans, net of employee tax withholdings		1.1
Common shares issued for benefit plans, net of employee tax withholdings	(15)		(15)	0	0	(15)	0
Dividends declared	(88)	$ 0	0	(88)	0	(88)	0
Balance at end of period at Mar. 31, 2016			4,632	13,446	(1,255)	16,823
Balance at end of period (in shares) at Mar. 31, 2016		350.6
Total equity at end of period at Mar. 31, 2016	$ 16,888
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Mar. 31, 2016							65
Balance at beginning of period (in shares) at Dec. 31, 2016	351.7	351.7
Balance at beginning of period at Dec. 31, 2016	$ 17,881		4,716	14,717	(1,552)	17,881
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2016	62						62
Total equity at beginning of period at Dec. 31, 2016	17,943
Comprehensive income:
Net income attributable to Aetna	(381)	$ 0	0	(381)	0	(381)
Net income (loss) attributable to non-controlling interest	2						2
Net Income including non-controlling interests	(379)
Other increases (decreases) in noncontrolling interests	13	0	0	0	0	0	13
Other comprehensive (loss) income	276	$ 0	0	0	276	276	0
Common shares issued for benefit plans, net of employee tax withholdings		0.9
Common shares issued for benefit plans, net of employee tax withholdings	(49)		(49)	0	0	(49)	0
Repurchases of common shares (in shares)		(20.9)
Repurchases of common shares	(3,300)		(661)	(2,639)	0	(3,300)	0
Dividends declared	(166)	$ 0	0	(166)	0	(166)	0
Balance at end of period at Mar. 31, 2017	$ 14,261		$ 4,006	$ 11,531	$ (1,276)	$ 14,261
Balance at end of period (in shares) at Mar. 31, 2017	331.7	331.7
Total equity at end of period at Mar. 31, 2017	$ 14,338
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Mar. 31, 2017	$ 77						$ 77

Consolidated Statements of Cash

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 including non-controlling interests		$ (379)	$ 738
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized capital (gains) losses		333	1
Depreciation and amortization		160	169
Debt fair value amortization		(7)	(7)
Equity in earnings of affiliates, net		(38)	15
Stock-based compensation expense		54	54
Amortization of net investment premium		17	21
Loss on early extinguishment of long-term debt	[1]	(246)	0
Changes in assets and liabilities:
Premiums due and other receivables		(477)	(182)
Income taxes		(271)	519
Other assets and other liabilities		(95)	(262)
Health care and insurance liabilities		1,356	725
Net cash provided by operating activities		899	1,791
Cash flows used for investing activities:
Proceeds from sales and maturities of investments		2,738	2,938
Cost of investments		(2,723)	(3,060)
Additions to property, equipment and software		(71)	(55)
Net cash provided by (used for) investing activities		(56)	(177)
Cash flows used for financing activities:
Repayment of long-term debt		(11,484)	0
Common shares issued under benefit plans, net		(103)	(79)
Common shares repurchased		(3,300)	0
Dividends paid to shareholders		(88)	(87)
Net (payment) receipt on interest rate derivatives		0	(206)
(Distributions) contributions, non-controlling interests		13	0
Net cash provided by (used for) financing activities		(14,962)	(372)
Net increase (decrease) in cash and cash equivalents		(14,119)	1,242
Cash and cash equivalents, beginning of period		17,996	2,524
Cash and cash equivalents, end of period		3,877	3,766
Supplemental cash flow information:
Interest paid		130	44
Income taxes paid		$ 22	$ 31
[1]	In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:•In the three months ended March 31, 2017, we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020.•In the three months ended March 31, 2017, we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations.•We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.

Organization

Organization	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization We conduct our operations in three business segments: • Health Care consists of medical, pharmacy benefit management services, dental, behavioral health and vision plans offered on both an Insured basis (where we assume all or a majority of the risk for medical and dental care costs) and an employer-funded basis (where the plan sponsor under an administrative services contract (“ASC”) assumes all or a majority of this risk) and emerging business products and services that complement and enhance our medical products. We also offer Medicare and Medicaid products and services and other medical products, such as medical management and data analytics services, medical stop loss insurance, workers’ compensation administrative services and products that provide access to our provider networks in select geographies. • Group Insurance primarily includes group life insurance and group disability products. Group life insurance products are offered on an Insured basis. Group disability products are offered to employers on both an Insured and an ASC basis. Group Insurance also includes long-term care products that were offered primarily on an Insured basis. We no longer solicit or accept new long-term care customers. • Large Case Pensions manages a variety of retirement products (including pension and annuity products) primarily for tax-qualified pension plans. These products provide a variety of funding and benefit payment distribution options and other services. Large Case Pensions also includes certain discontinued products (refer to Note 16 for additional information).

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for annual financial statements. We have omitted certain footnote disclosures that would substantially duplicate the disclosures in our 2016 Annual Report on Form 10-K (our “2016 Annual Report”), unless the information contained in those disclosures materially changed or is required by GAAP. The accompanying unaudited consolidated financial statements and related condensed notes should be read in conjunction with the consolidated financial statements and related notes presented in our 2016 Annual Report. These interim financial statements necessarily rely on estimates, including assumptions as to annualized tax rates. In the opinion of management, all adjustments necessary for a fair statement of results for the interim periods have been made. All such adjustments are of a normal, recurring nature. The Company has evaluated subsequent events that occurred after March 31, 2017 through the date the financial statements were issued and determined there were no subsequent events to disclose. Reclassifications Certain reclassifications were made to 2016 financial information to conform with the 2017 presentation. New Accounting Standards Simplifying the Test for Goodwill Impairment Effective January 1, 2017, we adopted, on a prospective basis, new accounting guidance which simplifies the accounting for goodwill impairment. The new guidance eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. A goodwill impairment charge would be recognized if the carrying amount of a reporting unit exceeds the estimated fair value of the reporting unit. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results. Classification of Certain Cash Receipts and Cash Payments in the Statement of Cash Flows Effective January 1, 2017, we adopted, on a retrospective basis, new accounting guidance which clarifies the classification of certain cash receipts and cash payments in our Consolidated Statements of Cash Flows. As a result, certain cash distributions received from our equity method investments will now be classified as cash inflows from operating activities. These cash distributions previously were classified as cash inflows from investing activities. There were no material reclassifications in our Consolidated Statements of Cash Flows for the three months ended March 31, 2017 and March 31, 2016 as a result of the adoption of this new guidance. Future Application of Accounting Standards Revenue from Contracts with Customers Effective January 1, 2018, we will adopt new accounting guidance related to revenue recognition from contracts with customers. While industry-specific guidance related to contracts with customers within the scope of Accounting Standards Codification (“ASC”) 944 Financial Services - Insurance remains unchanged, most other industry-specific revenue recognition requirements have been removed. The new guidance requires that an entity recognize revenue for the transfer of goods or services to a customer at an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. The new guidance also requires additional disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. We currently anticipate adopting the new guidance using the modified retrospective approach with a cumulative effect adjustment to retained earnings. While we are still evaluating the impact of this new guidance on our financial statements, we anticipate that any impact will only relate to contracts with customers outside the scope of ASC Topic 944. Adoption of this new guidance could result in reclassifications within our Consolidated Statements of Income; however, we do not anticipate any material changes in the timing of our recognition of revenue or net income. Recognition and Measurement of Financial Assets and Financial Liabilities Effective January 1, 2018, we will adopt new accounting guidance related to the recognition and measurement of financial assets and financial liabilities. Under the new guidance, all equity investments in unconsolidated entities will be measured at fair value with changes in fair value recognized in net income. A reporting entity may elect to report equity investments without a readily determinable fair value at cost. The new guidance also revises certain disclosures regarding financial assets and liabilities. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results. Leases Effective January 1, 2019, we will adopt new accounting guidance related to the recognition, measurement and disclosure requirements for leases. Under the new guidance, lessees will be required to recognize a right-of-use asset and corresponding lease liability on their balance sheets for all leases other than those that meet the definition of a short-term lease. The new guidance also revises certain disclosure requirements regarding leases. While we are still evaluating the impact of adoption of this new guidance, we anticipate that we will be required to record an asset and corresponding liability related to our operating leases (as described in Note 17 in our 2016 Annual Report) on our Consolidated Balance Sheets. Accounting for Interest Associated with the Purchase of Callable Debt Securities Effective January 1, 2019, we will adopt new accounting guidance related to the amortization of purchased callable debt securities held at a premium. Under the new guidance, premiums on callable debt securities are amortized to the earliest call date rather than to the contractual maturity date. Callable debt securities held at a discount will continue to be amortized to the contractual maturity date. We are still assessing the impact of this new guidance on our financial position and operating results. Measurement of Credit Losses on Financial Instruments Effective January 1, 2020, we will adopt new accounting guidance related to the measurement of credit losses on financial assets and certain other instruments. The new guidance requires the use of a new forward-looking expected loss impairment model for trade and other receivables, held-to-maturity debt securities, loans and other instruments. The new guidance also requires impairments and recoveries for available-for-sale debt securities to be recorded through an allowance account and revises certain disclosure requirements. We are still assessing the impact of this new guidance on our financial position and operating results.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Business Combination Disclosure	3. Terminated Acquisition and Terminated Divestiture On July 2, 2015, we entered into a definitive agreement (the "Merger Agreement") to acquire Humana Inc. ("Humana"). On July 21, 2016, the U.S. Department of Justice (the “DOJ”) and certain state attorneys general filed a civil complaint in the U.S. District Court for the District of Columbia (the “District Court”) against us and Humana charging that our acquisition of Humana (the “Humana Transaction”) would violate Section 7 of the Clayton Antitrust Act, and seeking a permanent injunction to prevent Aetna from acquiring Humana. On January 23, 2017, the District Court granted the DOJ’s request to enjoin the Humana Transaction. On February 14, 2017, Aetna and Humana entered into a mutual termination agreement (the “Termination Agreement”) pursuant to which the parties thereto (collectively the “Parties”) agreed to terminate the Merger Agreement, including all schedules and exhibits thereto, and all ancillary agreements contemplated thereby, entered pursuant thereto or entered in connection therewith (other than certain confidentiality agreements) (collectively with the Merger Agreement, the “Transaction Documents”), effective immediately as of February 14, 2017 (the “Termination Date”). Under the Termination Agreement, Aetna agreed to pay Humana the Regulatory Termination Fee (as defined in the Merger Agreement) of $1.0 billion in cash in full satisfaction of any amounts required to be paid by Aetna under the Merger Agreement. The Parties also agreed to release each other from any and all liability, claims, rights, actions, causes of action, suits, liens, obligations, accounts, debts, demands, agreements, promises, liabilities, controversies, costs, charges, damages, expenses and fees, however arising, in connection with, arising out of or related to the Transaction Documents, the transactions contemplated therein or thereby or certain related matters. We paid Humana the Regulatory Termination Fee on February 16, 2017 and recorded the expense in general and administrative expenses. We funded that payment with the proceeds of the 2016 senior notes (as defined below). In June 2016, we issued $13.0 billion of senior notes to partially fund the Humana Transaction (collectively, the “2016 senior notes”). In accordance with the terms of the 2016 senior notes, on February 14, 2017, we issued a notice of redemption for $10.2 billion aggregate principal amount of certain of the 2016 senior notes (collectively, the “Special Mandatory Redemption Notes”) at a redemption price equal to 101% of the aggregate principal amount of those notes plus accrued and unpaid interest. We redeemed the Special Mandatory Redemption Notes on March 16, 2017, and we funded the redemption with the proceeds of the 2016 senior notes. As a result of the redemption of the Special Mandatory Redemption Notes, we recognized certain costs in our net income during the three months ended March 31, 2017. Refer to Note 8 for additional information. In order to address the DOJ’s perceived competitive concerns regarding Medicare Advantage relating to the Humana Transaction, on August 2, 2016, we entered into a definitive agreement (the “Aetna APA”) to sell for cash to Molina Healthcare, Inc. (“Molina”) certain of our Medicare Advantage assets. On February 14, 2017, Aetna and Molina entered into a Termination Agreement (the “APA Termination Agreement”) pursuant to which Aetna terminated the Aetna APA, including all schedules and exhibits thereto, and all ancillary agreements contemplated thereby or entered pursuant thereto. Under the APA Termination Agreement, Aetna agreed to pay Molina in cash (a) a termination fee of $53 million and (b) approximately 70% of Molina’s transaction costs. We paid Molina the termination fee on February 16, 2017 and the applicable transaction costs of $7 million on February 27, 2017 and recorded the expense in general and administrative expenses. The payments were funded with the proceeds of the 2016 senior notes.

Investments

Investments	3 Months Ended
	Mar. 31, 2017
Investments [Abstract]
Investments	4. Investments Total investments at March 31, 2017 and December 31, 2016 were as follows: March 31, 2017 December 31, 2016 (Millions) Current Long-term Total Current Long-term Total Debt and equity securities available for sale $ 2,928 $ 18,925 $ 21,853 $ 2,876 $ 18,866 $ 21,742 Mortgage loans 151 1,356 1,507 170 1,341 1,511 Other investments — 1,641 1,641 — 1,626 1,626 Total investments $ 3,079 $ 21,922 $ 25,001 $ 3,046 $ 21,833 $ 24,879 Debt and Equity Securities Debt and equity securities available for sale at March 31, 2017 and December 31, 2016 were as follows: (Millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value March 31, 2017 Debt securities: U.S. government securities $ 1,595 $ 49 $ — $ 1,644 States, municipalities and political subdivisions 4,886 170 (41 ) 5,015 U.S. corporate securities 8,400 394 (44 ) 8,750 Foreign securities 3,004 180 (17 ) 3,167 Residential mortgage-backed securities 760 9 (7 ) 762 Commercial mortgage-backed securities 1,331 3 (36 ) 1,298 Other asset-backed securities 1,108 9 (5 ) 1,112 Redeemable preferred securities 22 5 — 27 Total debt securities 21,106 819 (150 ) 21,775 Equity securities 69 11 (2 ) 78 Total debt and equity securities (1)(2) $ 21,175 $ 830 $ (152 ) $ 21,853 December 31, 2016 Debt securities: U.S. government securities $ 1,643 $ 51 $ — $ 1,694 States, municipalities and political subdivisions 5,047 152 (61 ) 5,138 U.S. corporate securities 8,145 385 (55 ) 8,475 Foreign securities 2,958 163 (33 ) 3,088 Residential mortgage-backed securities 793 11 (9 ) 795 Commercial mortgage-backed securities 1,382 5 (39 ) 1,348 Other asset-backed securities 1,077 7 (9 ) 1,075 Redeemable preferred securities 22 5 — 27 Total debt securities 21,067 779 (206 ) 21,640 Equity securities 84 20 (2 ) 102 Total debt and equity securities (1)(2) $ 21,151 $ 799 $ (208 ) $ 21,742 (1) At both March 31, 2017 and December 31, 2016 , we held securities for which we previously recognized an immaterial amount of non-credit related impairments in accumulated other comprehensive loss. These securities each had an immaterial amount of net unrealized capital gains at both March 31, 2017 and December 31, 2016 . (2) Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 16 for additional information on our accounting for discontinued products). At March 31, 2017 , debt and equity securities with a fair value of approximately $2.8 billion , gross unrealized capital gains of $192 million and gross unrealized capital losses of $29 million and, at December 31, 2016 , debt and equity securities with a fair value of approximately $2.9 billion , gross unrealized capital gains of $195 million and gross unrealized capital losses of $35 million were included in total debt and equity securities, but support our experience-rated and discontinued products. Changes in net unrealized capital gains (losses) on these securities are not reflected in accumulated other comprehensive income. The fair value of debt securities at March 31, 2017 is shown below by contractual maturity. Actual maturities may differ from contractual maturities because securities may be restructured, called or prepaid, or we intend to sell a security prior to maturity. (Millions) Amortized Cost Fair Value Due to mature: Less than one year $ 1,498 $ 1,513 One year through five years 6,948 7,121 After five years through ten years 4,775 4,909 Greater than ten years 4,686 5,060 Residential mortgage-backed securities 760 762 Commercial mortgage-backed securities 1,331 1,298 Other asset-backed securities 1,108 1,112 Total $ 21,106 $ 21,775 Mortgage-Backed and Other Asset-Backed Securities All of our residential mortgage-backed securities at March 31, 2017 were issued by the Government National Mortgage Association, the Federal National Mortgage Association or the Federal Home Loan Mortgage Corporation and carry agency guarantees and explicit or implicit guarantees by the U.S. Government. At March 31, 2017 , our residential mortgage-backed securities had an average credit quality rating of AAA and a weighted average duration of 4.7 years. Our commercial mortgage-backed securities have underlying loans that are dispersed throughout the United States. Significant market observable inputs used to value these securities include loss severity and probability of default. At March 31, 2017 , these securities had an average credit quality rating of AAA and a weighted average duration of 6.9 years. Our other asset-backed securities have a variety of underlying collateral (e.g., automobile loans, credit card receivables, home equity loans and commercial loans). Significant market observable inputs used to value these securities include the unemployment rate, loss severity and probability of default. At March 31, 2017 , these securities had an average credit quality rating of AA- and a weighted average duration of 1.3 years. Summarized below are the debt and equity securities we held at March 31, 2017 and December 31, 2016 that were in an unrealized capital loss position, aggregated by the length of time the investments have been in that position: Less than 12 months Greater than 12 months Total (1) (Millions, except number of securities) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses March 31, 2017 Debt securities: U.S. government securities 32 $ 59 $ — — $ — $ — 32 $ 59 $ — States, municipalities and political subdivisions 530 1,539 38 45 87 3 575 1,626 41 U.S. corporate securities 1,210 1,965 35 79 78 9 1,289 2,043 44 Foreign securities 421 693 15 42 57 2 463 750 17 Residential mortgage-backed securities 194 431 7 102 16 — 296 447 7 Commercial mortgage-backed securities 280 1,025 36 — — — 280 1,025 36 Other asset-backed securities 239 449 3 114 102 2 353 551 5 Total debt securities 2,906 6,161 134 382 340 16 3,288 6,501 150 Equity securities 1 4 — 10 2 2 11 6 2 Total debt and equity securities (1) 2,907 $ 6,165 $ 134 392 $ 342 $ 18 3,299 $ 6,507 $ 152 December 31, 2016 Debt securities: U.S. government securities 26 $ 39 $ — 1 $ 1 $ — 27 $ 40 $ — States, municipalities and political subdivisions 865 2,228 58 37 75 3 902 2,303 61 U.S. corporate securities 1,428 2,277 44 114 101 11 1,542 2,378 55 Foreign securities 649 970 27 62 76 6 711 1,046 33 Residential mortgage-backed securities 188 455 8 104 17 1 292 472 9 Commercial mortgage-backed securities 285 1,038 39 3 3 — 288 1,041 39 Other asset-backed securities 226 403 4 208 177 5 434 580 9 Total debt securities 3,667 7,410 180 529 450 26 4,196 7,860 206 Equity securities 2 3 — 8 3 2 10 6 2 Total debt and equity securities (1) 3,669 $ 7,413 $ 180 537 $ 453 $ 28 4,206 $ 7,866 $ 208 (1) At March 31, 2017 and December 31, 2016 , debt and equity securities in an unrealized capital loss position of $29 million and $35 million , respectively, and with related fair value of $794 million and $890 million , respectively, related to experience-rated and discontinued products. We reviewed the securities in the tables above and concluded that these are performing assets generating investment income to support the needs of our business. In performing this review, we considered factors such as the quality of the investment security based on research performed by our internal credit analysts and external rating agencies and the prospects of realizing the carrying value of the security based on the investment’s current prospects for recovery. At March 31, 2017 , we did not intend to sell these securities, and we did not believe it was more likely than not that we would be required to sell these securities prior to anticipated recovery of their amortized cost basis. The maturity dates for debt securities in an unrealized capital loss position at March 31, 2017 were as follows: Supporting discontinued and experience-rated products Supporting remaining products Total (Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Due to mature: Less than one year $ 7 $ — $ 207 $ — $ 214 $ — One year through five years 47 1 1,612 19 1,659 20 After five years through ten years 252 6 1,095 25 1,347 31 Greater than ten years 261 14 997 37 1,258 51 Residential mortgage-backed securities 17 — 430 7 447 7 Commercial mortgage-backed securities 182 6 843 30 1,025 36 Other asset-backed securities 27 — 524 5 551 5 Total $ 793 $ 27 $ 5,708 $ 123 $ 6,501 $ 150 Mortgage Loans Our mortgage loans are collateralized by commercial real estate. During the three months ended March 31, 2017 and 2016 we had the following activity in our mortgage loan portfolio: Three Months Ended March 31, (Millions) 2017 2016 New mortgage loans $ 54 $ 12 Mortgage loans fully repaid 48 48 We assess our mortgage loans on a regular basis for credit impairments, and annually assign a credit quality indicator to each loan. Our credit quality indicator is internally developed and categorizes our portfolio on a scale from 1 to 7. These indicators are based upon several factors, including current loan to value ratios, property condition, market trends, creditworthiness of the borrower and deal structure. The vast majority of our mortgage loans fall into categories 2 to 4. • Category 1 - Represents loans of superior quality • Category 2 to 4 - Represents loans where credit risk is minimal to acceptable; however, these loans may display some susceptibility to economic changes. • Categories 5 and 6 - Represents loans where credit risk is not substantial, but these loans warrant management’s close attention. • Category 7 - Represents loans where collections are potentially at risk and if necessary, an impairment is recorded. Based upon our most recent assessments at March 31, 2017 and December 31, 2016 , our mortgage loans were given the following credit quality indicators: (In Millions, except credit ratings indicator) March 31, 2017 December 31, 2016 1 $ 44 $ 45 2 to 4 1,446 1,449 5 and 6 17 17 7 — — Total $ 1,507 $ 1,511 Net Investment Income Sources of net investment income for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, (Millions) 2017 2016 Debt securities $ 190 $ 195 Mortgage loans 22 29 Other investments 58 4 Gross investment income 270 228 Investment expenses (10 ) (10 ) Net investment income (1) $ 260 $ 218 (1) Net investment income includes $66 million and $45 million for the three months ended March 31, 2017 and 2016, respectively, related to investments supporting our experience-rated and discontinued products. Realized Capital Gains/Losses Net realized capital losses for the three months ended March 31, 2017 and 2016 , excluding amounts related to experience-rated contract holders and discontinued products, were as follows: Three Months Ended March 31, (Millions) 2017 2016 Other-than-temporary impairment (“OTTI”) losses on debt securities recognized in earnings $ (2 ) $ (9 ) Other net realized capital (losses) gains (331 ) 8 Net realized capital losses $ (333 ) $ (1 ) The net realized capital losses for the three months ended March 31, 2017 were primarily attributable to the recognition into earnings of the entire unamortized effective portion of the related hedge losses upon the mandatory redemption of $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes and the redemption of $750 million aggregate principal amount of senior notes due 2020. The net realized capital losses for the three months ended March 31, 2016 were primarily attributable to yield-related OTTI on debt securities, substantially offset by gains from the sales of other investments. We had no individually material realized capital losses on debt or equity securities that impacted our operating results during three months ended March 31, 2017 or 2016 . Excluding amounts related to experience-rated and discontinued products, proceeds from the sale of available for sale debt and equity securities and the related gross realized capital gains and losses for the three months ended March 31, 2017 and 2016 were as follows (1) : Three Months Ended March 31, (Millions) 2017 2016 Proceeds on sales $ 1,110 $ 1,546 Gross realized capital gains 21 32 Gross realized capital losses 14 31 (1) The proceeds on sales and gross realized capital gains and losses exclude the impact of the sales of short-term debt securities which primarily relate to our investments in mutual funds. These investments were excluded from the disclosed amounts because they represent an immaterial amount of aggregate gross realized capital gains or losses and have a high volume of sales activity. Variable Interest Entities We have investments in certain hedge fund and private equity investments and real estate partnerships that are considered Variable Interest Entities (“VIE’s”). We do not have a future obligation to fund losses or debts on behalf of these investments; however, we may voluntarily contribute funds. In evaluating whether we are the primary beneficiary of a VIE, we considered several factors, including whether we (a) have the power to direct the activities that most significantly impact the VIE’s economic performance and (b) the obligation to absorb losses and the right to receive benefits that could potentially be significant to the VIE. Variable Interest Entities - Primary Beneficiary We have one majority owned hedge fund investment where we are the investment manager and have the power to direct the activities that most significantly impact the VIE’s economic performance, including determining the hedge fund’s investment strategy. Accordingly, we are the primary beneficiary and consolidate the investment in our operating results. The fund invests in additional hedge funds that are VIEs; however, we are not the primary beneficiary of these underlying funds as discussed in further detail below. Substantially all of the assets of the VIE hedge fund are comprised of hedge fund investments reported as long-term investments on our Consolidated Balance Sheets. The VIE hedge fund had no material liabilities at March 31, 2017 or December 31, 2016 . The total amount of the VIE hedge fund’s assets included in long term investments on our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016 were $459 million and $472 million , respectively. Variable Interest Entities - Other Variable Interest Holder Our involvement with VIEs where we are not determined to be the primary beneficiary consists of the following: Hedge fund and private equity investments - We invest in hedge fund and private equity investments in order to generate investment returns for our investment portfolio supporting our businesses. Real estate partnerships - We invest in various real estate partnerships including those that construct, own and manage low-income housing developments. For the low income housing development investments, substantially all of the projected benefits to us are from tax credits and other tax benefits. We are not the primary beneficiary of these investments because the nature of our involvement with the activities of these VIEs does not give us the power to direct the activities that most significantly impact their economic performance. We record the amount of our investment in these VIEs as long-term investments on our Consolidated Balance Sheets and recognize our share of each VIE’s income or losses in earnings. Our maximum exposure to loss from these VIEs is limited to our investment balances as disclosed below and the risk of recapture of tax credits related to the real estate partnerships previously recognized, which we do not consider significant. The total amount of other variable interest holder VIE assets included in long term investments on our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016 were as follows: (Millions) March 31, 2017 December 31, 2016 Hedge fund investments $ 355 $ 384 Private equity investments 497 454 Real estate partnerships 263 278 Total $ 1,115 $ 1,116 The carrying value of the total assets and liabilities of our other variable interest holder VIE investments at March 31, 2017 and December 31, 2016 were as follows: (Millions) March 31, 2017 December 31, 2016 Assets: Hedge fund investments $ 34,203 $ 32,926 Private equity investments 26,819 25,368 Real estate partnerships 6,549 6,743 Total $ 67,571 $ 65,037 Liabilities: Hedge fund investments $ 3,464 $ 2,819 Private equity investments 3,353 2,354 Real estate partnerships 4,727 4,938 Total $ 11,544 $ 10,111 Non-controlling (Minority) Interests At March 31, 2017 and December 31, 2016 , continuing business non-controlling interests were $77 million and $62 million , respectively, primarily related to third party interests in our investment holdings as well as third party interests in certain of our operating entities. The non-controlling entities’ share was included in total equity. Net income attributable to non-controlling interests was $2 million and $1 million for the three months ended March 31, 2017 and 2016 , respectively. These non-controlling interests did not have a material impact on our financial position or operating results.

Fair Value

Fair Value	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Financial Instruments	5. Fair Value The preparation of our consolidated financial statements in accordance with GAAP requires certain of our assets and liabilities to be reflected at their fair value, and others on another basis, such as an adjusted historical cost basis. In this note, we provide details on the fair value of financial assets and liabilities and how we determine those fair values. We present this information for those financial instruments that are measured at fair value for which the change in fair value impacts net income attributable to Aetna or other comprehensive income separately from other financial assets and liabilities. Financial Instruments Measured at Fair Value in our Balance Sheets Certain of our financial instruments are measured at fair value in our Consolidated Balance Sheets. The fair values of these instruments are based on valuations that include inputs that can be classified within one of three levels of a hierarchy established by GAAP. The following are the levels of the hierarchy and a brief description of the type of valuation information (“inputs”) that qualifies a financial asset or liability for each level: ◦ Level 1 – Unadjusted quoted prices for identical assets or liabilities in active markets. ◦ Level 2 – Inputs other than Level 1 that are based on observable market data. These include: quoted prices for similar assets in active markets, quoted prices for identical assets in inactive markets, inputs that are observable that are not prices (such as interest rates and credit risks) and inputs that are derived from or corroborated by observable markets. ◦ Level 3 – Developed from unobservable data, reflecting our own assumptions. Financial assets and liabilities are classified based upon the lowest level of input that is significant to the valuation. When quoted prices in active markets for identical assets and liabilities are available, we use these quoted market prices to determine the fair value of financial assets and liabilities and classify these assets and liabilities in Level 1. In other cases where a quoted market price for identical assets and liabilities in an active market is either not available or not observable, we estimate fair value using valuation methodologies based on available and observable market information or by using a matrix pricing model. These financial assets and liabilities would then be classified in Level 2. If quoted market prices are not available, we determine fair value using broker quotes or an internal analysis of each investment’s financial performance and cash flow projections. Thus, financial assets and liabilities may be classified in Level 3 even though there may be some significant inputs that may be observable. The following is a description of the valuation methodologies used for our financial assets and liabilities that are measured at fair value, including the general classification of such assets and liabilities pursuant to the valuation hierarchy. Debt Securities – Where quoted prices are available in an active market, our debt securities are classified in Level 1 of the fair value hierarchy. Our Level 1 debt securities are comprised primarily of U.S. Treasury securities. The fair values of our Level 2 debt securities are obtained using models such as matrix pricing, which use quoted market prices of debt securities with similar characteristics, or discounted cash flows to estimate fair value. We review these prices to ensure they are based on observable market inputs that include, but are not limited to, quoted prices for similar assets in active markets, quoted prices for identical assets in inactive markets and inputs that are observable but not prices (for example, interest rates and credit risks). We also review the methodologies and the assumptions used to calculate prices from these observable inputs. On a quarterly basis, we select a sample of our Level 2 debt securities’ prices and compare them to prices provided by a secondary source. Variances over a specified threshold are identified and reviewed to confirm the price provided by the primary source represents an appropriate estimate of fair value. In addition, our internal investment team consistently compares the prices obtained for select Level 2 debt securities to the team’s own independent estimates of fair value for those securities. We obtained one price for each of our Level 2 debt securities and did not adjust any of these prices at March 31, 2017 or December 31, 2016 . We also value certain debt securities using Level 3 inputs. For Level 3 debt securities, fair values are determined by outside brokers or, in the case of certain private placement securities, are priced internally. Outside brokers determine the value of these debt securities through a combination of their knowledge of the current pricing environment and market flows. We obtained one non-binding broker quote for each of these Level 3 debt securities and did not adjust any of these quotes at March 31, 2017 or December 31, 2016 . The total fair value of our broker quoted debt securities was $110 million at March 31, 2017 and $80 million at December 31, 2016 . Examples of these broker quoted Level 3 debt securities include certain U.S. and foreign corporate securities and certain of our commercial mortgage-backed securities as well as other asset-backed securities. For some of our private placement securities, our internal staff determines the value of these debt securities by analyzing spreads of corporate and sector indices as well as interest spreads of comparable public bonds. Examples of these private placement Level 3 debt securities include certain U.S. and foreign securities and certain tax-exempt municipal securities. Equity Securities – We currently have two classifications of equity securities: those that are publicly traded and those that are privately placed. Our publicly-traded securities are classified in Level 1 because quoted prices are available for these securities in an active market. For privately-placed equity securities, there is no active market; therefore, we classify these securities in Level 3 because we price these securities through an internal analysis of each investment’s financial statements and cash flow projections. Significant unobservable inputs consist of earnings and revenue multiples, discount for lack of marketability and comparability adjustments. An increase or decrease in any of these unobservable inputs would result in a change in the fair value measurement, which may be significant. Derivatives – Where quoted prices are available in an active market, our derivatives are classified in Level 1. Certain of our derivative instruments are valued using models that primarily use market observable inputs and therefore are classified in Level 2 because they are traded in markets where quoted market prices are not readily available. There were no financial liabilities measured at fair value on a recurring basis in our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016. Financial assets measured at fair value on a recurring basis in our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016 were as follows: (Millions) Level 1 Level 2 Level 3 Total March 31, 2017 Assets: Debt securities: U.S. government securities $ 1,482 $ 162 $ — $ 1,644 States, municipalities and political subdivisions — 5,014 1 5,015 U.S. corporate securities — 8,671 79 8,750 Foreign securities — 3,146 21 3,167 Residential mortgage-backed securities — 762 — 762 Commercial mortgage-backed securities — 1,267 31 1,298 Other asset-backed securities — 1,106 6 1,112 Redeemable preferred securities — 27 — 27 Total debt securities 1,482 20,155 138 21,775 Equity securities 47 — 31 78 Total $ 1,529 $ 20,155 $ 169 $ 21,853 December 31, 2016 Assets: Debt securities: U.S. government securities $ 1,514 $ 180 $ — $ 1,694 States, municipalities and political subdivisions — 5,137 1 5,138 U.S. corporate securities — 8,395 80 8,475 Foreign securities — 3,067 21 3,088 Residential mortgage-backed securities — 795 — 795 Commercial mortgage-backed securities — 1,348 — 1,348 Other asset-backed securities — 1,075 — 1,075 Redeemable preferred securities — 26 1 27 Total debt securities 1,514 20,023 103 21,640 Equity securities 59 — 43 102 Total $ 1,573 $ 20,023 $ 146 $ 21,742 There were no transfers between Levels 1 and 2 during the three months ended March 31, 2017 or 2016 . During the three months ended March 31, 2017 and 2016 , we had an immaterial amount of gross transfers into and out of Level 3 financial assets. Financial Instruments Not Measured at Fair Value in our Balance Sheets The following is a description of the valuation methodologies used for estimating the fair value of our financial assets and liabilities that are carried on our Consolidated Balance Sheets at adjusted cost or contract value. Mortgage loans: Fair values are estimated by discounting expected mortgage loan cash flows at market rates that reflect the rates at which similar loans would be made to similar borrowers. These rates reflect our assessment of the creditworthiness of the borrower and the remaining duration of the loans. The fair value estimates of mortgage loans of lower credit quality, including problem and restructured loans, are based on the estimated fair value of the underlying collateral. Bank loans: Where fair value is determined by quoted market prices of bank loans with similar characteristics, our bank loans are classified in Level 2. For bank loans classified in Level 3, fair value is determined by outside brokers using their internal analyses through a combination of their knowledge of the current pricing environment and market flows. Equity securities: Certain of our equity securities are carried at cost. The fair values of our cost-method investments are not estimated if there are no identified events or changes in circumstances that may have a significant adverse effect on the fair value of the investment. Investment contract liabilities: • With a fixed maturity : Fair value is estimated by discounting cash flows at interest rates currently being offered by, or available to, us for similar contracts. • Without a fixed maturity : Fair value is estimated as the amount payable to the contract holder upon demand. However, we have the right under such contracts to delay payment of withdrawals that may ultimately result in paying an amount different than that determined to be payable on demand. Long-term debt: Fair values are based on quoted market prices for the same or similar issued debt or, if no quoted market prices are available, on the current rates estimated to be available to us for debt of similar terms and remaining maturities. The carrying value and estimated fair value classified by level of fair value hierarchy for our financial instruments carried on our Consolidated Balance Sheets at adjusted cost or contract value at March 31, 2017 and December 31, 2016 were as follows: Carrying Value Estimated Fair Value (Millions) Level 1 Level 2 Level 3 Total March 31, 2017 Assets: Mortgage loans $ 1,507 $ — $ — $ 1,539 $ 1,539 Bank loans 8 — — 8 8 Equity securities (1) 45 N/A N/A N/A N/A Liabilities: Investment contract liabilities: With a fixed maturity 8 — — 8 8 Without a fixed maturity 370 — — 354 354 Long-term debt 9,423 — 10,128 — 10,128 (Millions) December 31, 2016 Assets: Mortgage loans $ 1,511 $ — $ — $ 1,540 $ 1,540 Bank loans 8 — — 8 8 Equity securities (1) 35 N/A N/A N/A N/A Liabilities: Investment contract liabilities: With a fixed maturity 8 — — 8 8 Without a fixed maturity 378 — — 364 364 Long-term debt 20,661 — 21,468 — 21,468 (1) It was not practical to estimate the fair value of these cost-method investments as it represents shares of unlisted companies. Separate Accounts Measured at Fair Value in our Balance Sheets Separate Accounts assets in our Large Case Pensions segment represent funds maintained to meet specific objectives of contract holders. Since contract holders bear the investment risk of these assets, a corresponding Separate Accounts liability has been established equal to the assets. These assets and liabilities are carried at fair value. Net investment income and capital gains and losses accrue directly to such contract holders. The assets of each account are legally segregated and are not subject to claims arising from our other businesses. Deposits, withdrawals, net investment income and realized and unrealized capital gains and losses on Separate Accounts assets are not reflected in our Consolidated Statements of Income, Shareholders’ Equity or Cash Flows. Separate Accounts assets include debt and equity securities and derivative instruments. The valuation methodologies used for these assets are similar to the methodologies described in this Note 5 . Separate Accounts assets also include investments in common/collective trusts that are carried at fair value. Common/collective trusts invest in other investment funds otherwise known as the underlying funds. The Separate Accounts’ interests in the common/collective trust funds are based on the fair values of the investments of the underlying funds and therefore are classified in Level 2. The assets in the underlying funds primarily consist of equity securities. Investments in common/collective trust funds are valued at their respective net asset value per share/unit on the valuation date. Separate Accounts financial assets at March 31, 2017 and December 31, 2016 were as follows: March 31, 2017 December 31, 2016 (Millions) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Debt securities $ 784 $ 2,488 $ 2 $ 3,274 $ 766 $ 2,378 $ — $ 3,144 Equity securities 147 6 — 153 166 6 — 172 Common/collective trusts — 589 — 589 — 582 — 582 Total (1) $ 931 $ 3,083 $ 2 $ 4,016 $ 932 $ 2,966 $ — $ 3,898 (1) Excludes $228 million and $93 million of cash and cash equivalents and other receivables at March 31, 2017 and December 31, 2016 , respectively. During the three months ended March 31, 2017 and 2016 , we had an immaterial amount of Level 3 Separate Accounts financial assets. Offsetting Financial Assets and Liabilities Certain financial assets and liabilities are offset in our Consolidated Balance Sheets or are subject to master netting arrangements or similar agreements with the applicable counterparty. Financial assets, including derivative assets, subject to offsetting and enforceable master netting arrangements at March 31, 2017 and December 31, 2016 were as follows: Gross Amounts of Recognized Assets (1) Gross Amounts Not Offset in the Balance Sheets Financial Instruments Cash Collateral Received (Millions) Net Amount March 31, 2017 Derivatives $ — $ 17 $ — $ 17 Total $ — $ 17 $ — $ 17 December 31, 2016 Derivatives $ — $ 17 $ — $ 17 Total $ — $ 17 $ — $ 17 (1) There were no amounts offset in our Consolidated Balance Sheets at March 31, 2017 or December 31, 2016 . There were no financial liabilities, including derivative liabilities, subject to offsetting and enforceable master netting arrangements at March 31, 2017 and December 31, 2016 .

Health Care and Other Insurance

Health Care and Other Insurance Liabilities	3 Months Ended
	Mar. 31, 2017
Health Care and Other Insurance Liabilities [Abstract]
Short-Duration Insurance and Deposit Contracts [Text Block]	6. Health Care and Other Insurance Liabilities Health Care Costs Payable The following table shows the components of the change in health care costs payable during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Health care costs payable, beginning of the period $ 6,558 $ 6,306 Less: Reinsurance recoverables 5 4 Health care costs payable, beginning of the period, net 6,553 6,302 Add: Components of incurred health care costs Current year 11,420 11,475 Prior years (614 ) (627 ) Total incurred health care costs (1) 10,806 10,848 Less: Claims paid Current year 6,298 5,929 Prior years 4,742 4,398 Total claims paid 11,040 10,327 Health care costs payable, end of period, net 6,319 6,823 Add: Premium deficiency reserve 110 — Add: Reinsurance recoverables 3 2 Health care costs payable, end of period $ 6,432 $ 6,825 (1) Total incurred health care costs exclude from the table above $110 million related to the premium deficiency reserve recorded during the three months ended March 31, 2017 for the 2017 coverage year on our individual Commercial products. Our estimates of prior years’ health care costs payable decreased by $614 million and $627 million in the three months ended March 31, 2017 and 2016, respectively, resulting from claims settled for amounts less than originally estimated, primarily due to lower health care cost trends as well as the actual claim submission time being faster than we assumed in establishing our health care costs payable in the prior year. This development does not directly correspond to an increase in our current year operating results as these reductions were offset by estimated current period health care costs when we established our estimate of the current year health care costs payable. At March 31, 2017 , total Health Care liabilities for the ultimate cost of medical claims that have been incurred but not yet reported to us and of those which have been reported to us but not yet paid (collectively, “IBNR”) plus expected development on reported claims totaled approximately $5.5 billion . The substantial majority of the total Health Care IBNR liabilities plus expected development on reported claims at March 31, 2017 related to the current year. Long-Term Disability Unpaid Claims The following table shows the components of the change in unpaid long-term disability claims during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Long-term disability unpaid claims beginning of the period $ 1,904 $ 1,819 Less: Reinsurance recoverables 26 27 Long-term disability unpaid claims, beginning of the period, net 1,878 1,792 Add: Components of incurred claims Current year 131 137 Prior years 5 4 Total incurred claims 136 141 Less: Claims paid Current year 1 1 Prior years 134 119 Total claims paid 135 120 Long-term disability unpaid claims, end of period, net 1,879 1,813 Add: Reinsurance recoverables 26 27 Long-term disability unpaid claims, end of period $ 1,905 $ 1,840 Our estimates of prior years’ long-term disability unpaid claims liability were relatively consistent with actual results in each of the three month periods ended March 31, 2017 and 2016. The reconciliation of the long-term disability unpaid claims liability to the total unpaid claims liability in our Consolidated Balance Sheets is as follows at March 31, 2017 and 2016: At March 31, (Millions) 2017 2016 Long-term disability unpaid claims $ 1,905 $ 1,840 Term life unpaid claims 472 485 Other unpaid claims 118 122 Total unpaid claims $ 2,495 $ 2,447

Health Care Reform

Health Care Reform	3 Months Ended
	Mar. 31, 2017
Health Care Reform [Abstract]
Health Care Reform Programs	7. The ACA’s Reinsurance, Risk Adjustment and Risk Corridor (the “3Rs”) We participate in certain public health insurance exchanges (“Public Exchanges”) established pursuant to the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act of 2010 (as amended, collectively, the “ACA”). Under regulations established by the U.S. Department of Health and Human Services (“HHS”), HHS pays us a portion of the premium (“Premium Subsidy”) and a portion of the health care costs (“Cost Sharing Subsidy”) for low-income individual Public Exchange members. In addition, HHS administers the 3Rs risk management programs. The ACA’s temporary Reinsurance and Risk Corridor programs expired at the end of 2016. Our net receivable (payable) related to the 3Rs risk management programs at March 31, 2017 and December 31, 2016 were as follows: At March 31, 2017 At December 31, 2016 (Millions) Reinsurance Risk Adjustment Risk Corridor Reinsurance Risk Adjustment Risk Corridor Current $ 166 $ (696 ) $ 1 $ 202 $ (690 ) $ (10 ) Long-term 12 (38 ) — — — — Total net receivable (payable) $ 178 $ (734 ) $ 1 $ 202 $ (690 ) $ (10 ) At March 31, 2017 , we estimate that we are entitled to receive a total of $529 million from HHS under the three-year ACA risk corridor program for the 2014 through 2016 program years. In November 2016, HHS announced that all 2015 ACA risk corridor collections will be used to pay a portion of the balances on the 2014 ACA risk corridor payments. At March 31, 2017 and December 31, 2016, we did not record any ACA risk corridor receivables related to the 2016 or 2015 program years or any amount in excess of the HHS’s announced pro-rated funding amount for the 2014 program year because payments from HHS are uncertain. We expect to perform an annual final reconciliation and settlement with HHS of the Cost Sharing Subsidy and 3Rs in each subsequent year, except for the final reconciliation and settlement of the 2014 Cost Sharing Subsidy which occurred in 2016. Fees Mandated by the ACA Beginning January 1, 2014, the ACA imposes an annual premium-based health insurer fee (“HIF”) for each calendar year payable in September which is not deductible for tax purposes. In December 2015, the Consolidated Appropriation Act was enacted which included a one year suspension in 2017 of the HIF. Accordingly, there was no expense related to the HIF for the three months ended March 31, 2017 compared with an expense of $214 million for the three months ended March 31, 2016. Beginning January 1, 2014, the ACA established a temporary reinsurance program that expired at the end of 2016. Accordingly, there was no expense related to our estimated contribution for the funding of the ACA’s reinsurance program for the three months ended March 31, 2017 compared with an expense of $29 million for the three months ended March 31, 2016.

Debt

Debt	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Debt	8. Debt Long Term Debt The carrying value of our long-term debt at March 31, 2017 and December 31, 2016 was as follows: (Millions) March 31, December 31, Senior notes, 5.95% due March 2017 (1) $ — $ 386 Senior notes, 1.75% due May 2017 (1) 250 250 Senior notes, 1.5% due November 2017 (1) 499 499 Senior notes, floating rate due December 2017 (1) 499 499 Senior notes, 1.7% due June 2018 998 997 Senior notes, 2.2% due March 2019 374 374 Senior notes, 1.9% due June 2019 — 1,642 Senior notes, 3.95% due September 2020 — 745 Senior notes, 2.4% due June 2021 — 1,839 Senior notes, 5.45% due June 2021 658 661 Senior notes, 4.125% due June 2021 496 495 Senior notes, 2.75% due November 2022 986 986 Senior notes, 2.8% due June 2023 1,290 1,290 Senior notes, 3.5% due November 2024 743 742 Senior notes, 3.2% due June 2026 — 2,771 Senior notes, 4.25% due June 2036 — 1,480 Senior notes, 6.625% due June 2036 765 765 Senior notes, 6.75% due December 2037 527 527 Senior notes, 4.5% due May 2042 478 478 Senior notes, 4.125% due November 2042 489 489 Senior notes, 4.75% due March 2044 371 371 Senior notes, 4.375% due June 2046 — 2,375 Total long-term debt 9,423 20,661 Less current portion of long-term debt 1,249 1,634 Total long-term debt, less current portion $ 8,174 $ 19,027 (1) At March 31, 2017 , our 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and our floating rate senior notes, due December 2017 are each classified as current in our Consolidated Balance Sheet. At December 31, 2016 , our 5.95% senior notes due March 2017, 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and floating rate senior notes due December 2017 are each classified as current in our Consolidated Balance Sheet. 2016 Senior Notes In June 2016, in connection with the Humana Transaction, we issued the 2016 senior notes, which were comprised of: $500 million of floating rate senior notes due December 2017, $1.0 billion of 1.7% senior notes due June 2018, approximately $1.7 billion of 1.9% senior notes due June 2019, approximately $1.9 billion of 2.4% senior notes due June 2021, $1.3 billion of 2.8% senior notes due June 2023, $2.8 billion of 3.2% senior notes due June 2026, $1.5 billion of 4.25% senior notes due June 2036 and $2.4 billion of 4.375% senior notes due June 2046. Early Extinguishment of Long-Term Debt Special Mandatory Redemption Notes As a result of the termination of the Merger Agreement, we redeemed the entire $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes, which were due in 2019, 2021, 2026, 2036 and 2046 at a redemption price equal to 101% of the aggregate principal amount of those notes plus accrued and unpaid interest. We redeemed those notes on March 16, 2017, and we funded the redemption with the proceeds of the 2016 senior notes. As a result of the redemption, we recorded a loss on early extinguishment of long-term debt of $125 million ( $192 million pretax) in the three months ended March 31, 2017 . Prior to issuing the 2016 senior notes, during 2015 and 2016 we entered into various interest rate swaps and treasury rate locks that were designated as cash flow hedges against interest rate exposure related to the forecasted future issuance of fixed-rate debt to be primarily used to finance a portion of the purchase price of the Humana Transaction. In addition, we redesignated existing interest rate swaps with an aggregate notional value of $500 million as cash flow hedges against interest rate exposure related to the forecasted future issuance of fixed rate debt. Prior to issuance of the 2016 senior notes in June 2016, we terminated all outstanding hedges and paid an aggregate of $348 million to the hedge counter parties upon termination. The aggregate effective portion of the hedge loss of $342 million pretax was recorded in accumulated other comprehensive loss, net of tax. Upon the redemption of the Special Mandatory Redemption Notes, the entire remaining unamortized effective portion of the hedge loss of $323 million pretax recorded in accumulated other comprehensive loss was recognized as a realized capital loss in the three months ended March 31, 2017 . 2020 Notes On February 27, 2017, we announced the redemption for cash of the entire $750 million aggregate principal amount outstanding of our 3.95% senior notes due September 1, 2020 (the “2020 Notes”). The redemption of these notes occurred on March 29, 2017 at a redemption price that included a make-whole premium, plus accrued and unpaid interest. We funded the redemption from available cash and short-term debt. As a result of the redemption, we recognized a loss on the early extinguishment of long-term debt of $35 million ( $54 million pretax) in the three months ended March 31, 2017 . Upon redemption of the 2020 Notes, the entire remaining unamortized effective portion of the hedge loss of $13 million related to the issuance of the 2020 Notes recorded in accumulated other comprehensive loss was recognized as a realized capital loss in the three months ended March 31, 2017 . Refer to Note 11 for additional information regarding hedge losses reclassified from accumulated other comprehensive loss to net income during the three months ended March 31, 2017 . Revolving Credit Facility On March 27, 2012, we entered into an unsecured $1.5 billion five-year revolving credit agreement (the “Credit Agreement”) with several financial institutions. On September 24, 2012, and in connection with the acquisition of Coventry Health Care, Inc. (“Coventry”), we entered into a First Amendment (the “First Amendment”) to the Credit Agreement and also entered into an Incremental Commitment Agreement (the “Incremental Commitment Agreement”). On March 2, 2015, we entered into a Second Amendment to the Credit Agreement (the “Second Amendment”). On July 30, 2015, in connection with the Humana Transaction, we entered into a Third Amendment (the “Third Amendment”). On March 17, 2017 we entered into a Fourth Amendment to the Credit Agreement (the “Fourth Amendment,” and together with the First Amendment, the Incremental Commitment Agreement, the Second Amendment, the Third Amendment and the Credit Agreement, resulting in the “Facility”). The Facility is an unsecured $2.0 billion revolving credit agreement that matures on March 27, 2021. The Third Amendment modified the calculation of total debt for purposes of determining compliance prior to the closing date of the Humana Transaction (the “Closing Date”) with certain covenants to exclude debt incurred by us to finance the Humana Transaction, the other financing transactions related to the Humana Transaction and/or the payment of fees and expenses incurred in connection therewith so long as either (A) the net proceeds of such debt were set aside to finance the Humana Transaction, the other financing transactions related to the Humana Transaction and/or the payment of fees and expenses incurred in connection therewith or (B) such debt was subject to mandatory redemption in the event that the Merger Agreement is terminated or expires. Among other things, the Fourth Amendment extended the maturity date of the existing Credit Agreement to March 27, 2021, eliminated the availability of swingline loans, provided us with additional time on each business day to provide notice of borrowings and added customary provisions to reflect European Union “bail-in” directive legislation. In addition, upon our agreement with one or more financial institutions, we may expand the commitments under the Facility by an additional $500 million . The Facility also provides for the issuance of up to $200 million of letters of credit at our request, which count as usage of the available commitments under the Facility. Various interest rate options are available under the Facility. Any revolving borrowings mature on the termination date of the Facility. We pay facility fees on the Facility ranging from .050% to .150% per annum, depending upon our long-term senior unsecured debt rating. The facility fee was .100% at March 31, 2017 . The Facility contains a financial covenant that requires us to maintain a ratio of total debt to consolidated capitalization as of the end of each fiscal quarter at or below 50% . For this purpose, consolidated capitalization equals the sum of total shareholders’ equity, excluding any overfunded or underfunded status of our pension and OPEB plans and any net unrealized capital gains and losses, and total debt (as defined in the Facility). We met this requirement at March 31, 2017 . There were no amounts outstanding under the Facility at any time during the three months ended March 31, 2017 or 2016. Term Loan Agreement On July 30, 2015, in connection with the Humana Transaction, we entered into a senior three-year $3.2 billion term loan credit agreement (the “Term Loan Agreement”) with a group of seventeen lenders. The lenders’ commitments under the Term Loan Agreement terminated on February 14, 2017, as a result of the termination of the Merger Agreement. Commercial Paper At both March 31, 2017 and December 31, 2016, we did not have any commercial paper outstanding. Federal Home Loan Bank of Boston We are a member of the Federal Home Loan Bank of Boston (the “FHLBB”), and as a member we have the ability to obtain cash advances, subject to certain minimum collateral requirements. Our maximum borrowing capacity available from the FHLBB at March 31, 2017 was $801 million . At both March 31, 2017 and December 31, 2016 , we did not have any outstanding borrowings from the FHLBB.

Pension and Other Postretiremen

Pension and Other Postretirement Plans	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Pension and Other Postretirement Plans	9. Pension and Other Postretirement Plans Defined Benefit Retirement Plans Components of the net periodic benefit (income) cost of our defined benefit pension plans and other postretirement employee benefit (“OPEB”) plans for the three months ended March 31, 2017 and 2016 were as follows: Pension Plans OPEB Plans Three Months Ended Three Months Ended March 31, March 31, (Millions) 2017 2016 2017 2016 Amortization of prior service credit $ — $ — $ (1 ) $ (1 ) Interest cost 51 65 2 3 Expected return on plan assets (95 ) (97 ) (1 ) (1 ) Recognized net actuarial losses 16 15 1 1 Net periodic benefit (income) cost $ (28 ) $ (17 ) $ 1 $ 2 Effective as of the beginning of 2017, we changed the approach used to estimate the interest cost component of net periodic benefit cost for pension and OPEB plans that utilize a yield curve approach. Historically, we estimated the interest cost using a single weighted average discount rate derived from the yield curve used to measure the projected benefit obligation. We have now elected to measure interest cost by applying the specific spot rates along that yield curve to the relevant projected cash flows for each component. We believe the new approach provides a more precise estimate of such interest cost. This refinement has no effect on the estimation of our plan obligations. We have accounted for this as a change in accounting estimate and, accordingly, have accounted for it on a prospective basis beginning in 2017. The reduction in net periodic benefit cost associated with this change in the three months ended March 31, 2017 was $6 million ( $10 million pre-tax). We expect this change to result in a reduction in net periodic benefit cost of approximately $26 million ( $41 million pre-tax) for the full year 2017. For our pension benefits, the 2017 weighted-average discount rate for interest costs under the new approach adopted as of the beginning of 2017 is 3.51% . Under the prior methodology, the 2017 weighted-average discount rate would have been 4.22% .

Shareholders' Equity

Shareholders' Equity	3 Months Ended
	Mar. 31, 2017
Class of Stock Disclosures [Abstract]
Capital Stock	10. Shareholders’ Equity Share Repurchases On November 21, 2014 and February 28, 2014, our Board of Directors (our “Board”) authorized two separate share repurchase programs of our common stock of up to $1.0 billion each. On February 17, 2017, our Board approved a new share repurchase program that authorized us to repurchase up to $4.0 billion of our common stock. At March 31, 2017 , we had remaining authorization to repurchase an aggregate of up to approximately $1.8 billion of common stock under the February 17, 2017 program. The repurchases are effected from time to time in the open market, through negotiated transactions, including accelerated share repurchase agreements, and through plans designed to comply with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended. On February 22, 2017, we entered into accelerated share repurchase (“ASR”) agreements with two unrelated third party financial institutions to repurchase an aggregate of $3.3 billion of Aetna’s common shares. Under the terms of the ASR agreements, we made an approximately $1.7 billion payment to each unrelated third party financial institution on February 22, 2017 and received from each of them an initial delivery of approximately 10.4 million of our common shares on the same day, which represents approximately 80 percent of the total common shares expected to be repurchased under the ASR agreements based on the closing price of $126.34 per share on the day before we entered into the ASR agreements. The final number of our common shares to be repurchased pursuant to the agreements will be based on the volume-weighted average share price of our common shares during the term of the applicable transaction, less a discount and subject to adjustments pursuant to the terms of the applicable ASR agreement. The final settlement of the transactions under the ASR agreements is expected to occur during or prior to the third quarter of 2017. We recorded the initial delivery of our common shares as a decrease to retained earnings of approximately $2.6 billion , and recorded the remaining approximately $0.7 billion as a decrease to additional paid-in capital on our Consolidated Balance Sheets. We will reclassify the approximately $0.7 billion recorded as a reduction to additional paid-in capital to a reduction of retained earnings upon final settlement of the ASR agreements. The ASR agreements met all of the applicable criteria for equity classification, and therefore were not accounted for as derivative instruments. Dividends During the three months ended March 31, 2017 our Board declared the following cash dividends: Date Declared Dividend Amount Per Share Shareholders of Record Date Date Paid/ To be Paid Total Dividends (Millions) February 17, 2017 $ .50 April 13, 2017 April 28, 2017 $ 166 Declaration and payment of future dividends is at the discretion of our Board and may be adjusted as business needs or market conditions change. Stock-based Employee Incentive Plans On February 17, 2017, 0.3 million performance stock units (“PSUs”), 0.4 million restricted stock units (“RSUs”) and 2.1 million stock appreciation rights (“SARs”) were granted to certain employees. The number of vested PSUs (which could range from zero to 200% of the original number of units granted) is dependent upon the degree to which we achieve certain operating performance goals, as determined by our Board’s Committee on Compensation and Talent Management, during a three-year performance period which began January 1, 2017 and ends on December 31, 2019. The vesting period for the PSUs ends on February 17, 2020. Each vested PSU and RSU represents one share of common stock and will be paid in shares of common stock, net of taxes, at the end of the applicable vesting period. The RSUs generally will become 100% vested approximately three years from the grant date, with one-third vesting each December. The SARs, if exercised by the employee, will be settled in common stock, net of taxes, based on the appreciation of our common stock price over $125.27 per share, the closing price of our common stock on the grant date. SARs will generally become 100% vested approximately three years from the grant date, with one-third vesting on each anniversary of the grant date. The SARs granted to certain employees during first quarters of 2017 and 2016 had an estimated fair market value of $32.30 and $34.33 per unit, respectively. The fair value per unit was calculated on each respective grant date using a modified Black-Scholes option pricing model using the following assumptions during the first quarters of 2017 and 2016 : 2017 2016 Expected term (in years) 7.21 7.11 Volatility 26.52 % 32.9 % Risk-free interest rate 2.22 % 1.52 % Dividend yield 1.71 % 0.91 % Initial price $ 125.27 $ 103.45 The expected term is based on historical equity award activity. Volatility is based on a weighted average of the historical volatility of our stock price and implied volatility from traded options on our stock. The risk-free interest rate is based on a U.S. Treasury rate with a life equal to the expected life of the SARs grant. This rate was calculated by interpolating between the 7-year and 10-year U.S. Treasury rates for both the 2017 and 2016 SARs grants. The dividend yield is based on our expected dividends for the upcoming 12 months subsequent to the grant date. Regulatory Requirements Under applicable regulatory requirements at March 31, 2017 , the amount of dividends that may be paid through the end of 2017 by our insurance and HMO subsidiaries without prior approval by regulatory authorities was $1.4 billion in the aggregate. There are no such regulatory restrictions on distributions from Aetna to its shareholders. During the first quarter of 2017 , our insurance and HMO subsidiaries paid $460 million of dividends to the Company. The aggregate statutory capital and surplus of our insurance and HMO subsidiaries was $10.3 billion and $10.4 billion at March 31, 2017 and December 31, 2016 , respectively.

Other Comprehensive (Loss) Inco

Other Comprehensive (Loss) Income	3 Months Ended
	Mar. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive (Loss) Income	11. Other Comprehensive (Loss) Income Shareholders’ equity included the following activity in accumulated other comprehensive loss for three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Previously impaired debt securities: (1) Beginning of period balance $ 16 $ 19 Net unrealized losses ($(2) and $(4) pretax) (1 ) (3 ) Less: Net reclassification of losses to earnings ($(2) and $(5) pretax) (2) (1 ) (4 ) Other comprehensive income — 1 End of period balance 16 20 All other securities: Beginning of period balance 297 312 Net unrealized gains ($92 and $317 pretax) 60 206 Less: Net reclassification of gains (losses) to earnings ($25 and $(23) pretax) (2) 16 (15 ) Other comprehensive income 44 221 End of period balance 341 533 Derivatives and foreign currency: Beginning of period balance (235 ) (74 ) Net unrealized losses ($(2) and $(246) pretax) (1 ) (160 ) Less: Net reclassification of losses to earnings ($(343) and $(6) pretax) (3) (223 ) (3 ) Other comprehensive income (loss) 222 (157 ) End of period balance (13 ) (231 ) Pension and OPEB plans: Beginning of period balance (1,630 ) (1,587 ) Less: Net amortization of net actuarial losses ($(17) and $(16) pretax) (4) (11 ) (11 ) Less: Net amortization of prior service credit ($2 and $1 pretax) (4) 1 1 Other comprehensive income 10 10 End of period balance (1,620 ) (1,577 ) Total beginning of period accumulated other comprehensive loss (1,552 ) (1,330 ) Total other comprehensive loss 276 75 Total end of period accumulated other comprehensive loss $ (1,276 ) $ (1,255 ) (1) Represents specifically identified unrealized gains and losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security. (2) Reclassifications out of accumulated other comprehensive income for specifically identified previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statements of Income. (3) Reclassifications out of accumulated other comprehensive income for specifically identified foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the specifically identified effective portion of derivatives related to interest rate swaps which are reflected in interest expense. During the three months ended March 31, 2017 , we redeemed the entire $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes and the entire $750 million aggregate principal amount outstanding of the senior notes due 2020 and reclassified out of accumulated other comprehensive income the remaining $336 million pre-tax unrealized hedge losses as a realized capital loss within the Consolidated Statements of Income. Refer to Note 8 for additional information. (4) Reclassifications out of accumulated other comprehensive income for specifically identified pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 9 for additional information.

Earnings Per Common Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Common Share	12. Earnings Per Common Share Basic earnings per common share (“EPS”) is computed by dividing net (loss) income attributable to Aetna by the weighted average number of common shares outstanding during the reporting period. Diluted EPS is computed in a similar manner, except that the weighted average number of common shares outstanding is adjusted for the dilutive effects of our outstanding stock-based compensation awards, but only if the effect is dilutive. The computations of basic and diluted EPS for the three months ended March 31, 2017 and 2016 are as follows: Three Months Ended March 31, (Millions, except per common share data) 2017 2016 Net (loss) income attributable to Aetna $ (381 ) $ 737 Weighted average shares used to compute basic EPS 343.8 350.7 Dilutive effect of outstanding stock-based compensation awards — 3.1 Weighted average shares used to compute diluted EPS 343.8 353.8 Basic EPS $ (1.11 ) $ 2.10 Diluted EPS $ (1.11 ) $ 2.08 The stock-based compensation awards excluded from the calculation of diluted EPS for the three months ended March 31, 2017 and 2016 are as follows: Three Months Ended March 31, (Millions) 2017 2016 SARs (1) — .2 Other stock-based compensation awards (2) .9 .8 In-the-money anti-dilutive stock-based compensation awards (3) 10.6 — (1) SARs are excluded from the calculation of diluted EPS if the exercise price is greater than the average market price of Aetna common shares during the period (i.e., the awards are anti-dilutive). (2) PSUs, certain market stock units with performance conditions, and performance stock appreciation rights are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period. (3) In periods when we report a net loss attributable to Aetna, in-the-money stock-based compensation awards are excluded from our calculation of diluted EPS because their inclusion would have an anti-dilutive effect. Therefore we excluded from our calculation of diluted EPS for the three months ended March 31, 2017 in-the-money stock-based compensation awards which would have increased our weighted-average shares used to compute diluted EPS by 2.4 million shares.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2017
Reinsurance Disclosures [Abstract]
Reinsurance	13. Reinsurance In January 2017, we entered into two four-year reinsurance agreements with an unrelated reinsurer. The agreements allow us to reduce our required capital and provide collateralized excess of loss reinsurance coverage on a portion of our group Commercial Insured Health Care business.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. Commitments and Contingencies Guaranty Fund Assessments, Market Stabilization and Other Non-Voluntary Risk Sharing Pools Under guaranty fund laws existing in all states, insurers doing business in those states can be assessed (in most states up to prescribed limits) for certain obligations of insolvent insurance companies to policyholders and claimants. The life and health insurance guaranty associations in which we participate that operate under these laws respond to insolvencies of long-term care insurers as well as health insurers. Our assessments generally are based on a formula relating to our health care premiums in the state compared to the premiums of other insurers. Certain states allow assessments to be recovered over time as offsets to premium taxes. Some states have similar laws relating to HMOs and/or other payors such as not-for-profit consumer-governed health plans established under the ACA. In 2009, the Pennsylvania Insurance Commissioner (the “Commissioner”) placed long-term care insurer Penn Treaty Network America Insurance Company and one of its subsidiaries (collectively, “Penn Treaty”) in rehabilitation, an intermediate action before insolvency, and subsequently petitioned a state court to convert the rehabilitation into a liquidation. Penn Treaty was placed in liquidation in March 2017. We recorded a discounted estimated liability and expense of $231 million pretax during the three months ended March 31, 2017 for our estimated share of future assessments by applicable life and health guaranty associations which reflects a 3.5% discount rate. The undiscounted estimated liability at March 31, 2017 was $347 million . The expense was recorded in general and administrative expenses in our Consolidated Statements of Income, and the liability was recorded in accrued expenses and other current liabilities in our Consolidated Balance Sheets. We did not record an asset for expected premium tax offsets for our in force business at March 31, 2017 as the amount was not material. It is reasonably possible that in the future we may record a liability and expense relating to other insolvencies which could have a material adverse effect on our operating results, financial position and cash flows. While historically we have ultimately recovered more than half of guaranty fund assessments through statutorily permitted premium tax offsets, significant increases in assessments could lead to legislative and/or regulatory actions that may limit future offsets. HMOs in certain states in which we do business are subject to assessments, including market stabilization and other risk-sharing pools, for which we are assessed charges based on incurred claims, demographic membership mix and other factors. We establish liabilities for these assessments based on applicable laws and regulations. In certain states, the ultimate assessments we pay are dependent upon our experience relative to other entities subject to the assessment, and the ultimate liability is not known at the balance sheet date. While the ultimate amount of the assessment is dependent upon the experience of all pool participants, we believe we have adequate reserves to cover such assessments. Litigation and Regulatory Proceedings Out-of-Network Benefit Proceedings We are named as a defendant in several purported class actions and individual lawsuits arising out of our practices related to the payment of claims for services rendered to our members by health care providers with whom we do not have a contract (“out-of-network providers”). Among other things, these lawsuits allege that we paid too little to our health plan members and/or providers for these services, among other reasons, because of our use of data provided by Ingenix, Inc., a subsidiary of one of our competitors (“Ingenix”). Other major health insurers are the subject of similar litigation or have settled similar litigation. Various plaintiffs who are health care providers or medical associations seek to represent nationwide classes of out-of-network providers who provided services to our members during the period from 2001 to the present. Various plaintiffs who are members in our health plans seek to represent nationwide classes of our members who received services from out-of-network providers during the period from 2001 to the present. Taken together, these lawsuits allege that we violated state law, the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), the Racketeer Influenced and Corrupt Organizations Act (“RICO”) and federal antitrust laws, either acting alone or in concert with our competitors. The purported classes seek reimbursement of all unpaid benefits, recalculation and repayment of deductible and coinsurance amounts, unspecified damages and treble damages, statutory penalties, injunctive and declaratory relief, plus interest, costs and attorneys’ fees, and seek to disqualify us from acting as a fiduciary of any benefit plan that is subject to ERISA. Individual lawsuits that generally contain similar allegations and seek similar relief have been brought by health plan members and out-of-network providers. The first class action case was commenced on July 30, 2007. The federal Judicial Panel on Multi-District Litigation (the “MDL Panel”) has consolidated these class action cases in the U.S. District Court for the District of New Jersey (the “New Jersey District Court”) under the caption In re: Aetna UCR Litigation, MDL No. 2020 (“MDL 2020”). In addition, the MDL Panel has transferred the individual lawsuits to MDL 2020. On May 9, 2011, the New Jersey District Court dismissed the physician plaintiffs from MDL 2020 without prejudice. The New Jersey District Court’s action followed a ruling by the United States District Court for the Southern District of Florida (the “Florida District Court”) that the physician plaintiffs were enjoined from participating in MDL 2020 due to a prior settlement and release. The United States Court of Appeals for the Eleventh Circuit has dismissed the physician plaintiffs’ appeal of the Florida District Court’s ruling. On December 6, 2012, we entered into an agreement to settle MDL 2020. Under the terms of the proposed nationwide settlement, we would have been released from claims relating to our out-of-network reimbursement practices from the beginning of the applicable settlement class period through August 30, 2013. The settlement agreement did not contain an admission of wrongdoing. The medical associations were not parties to the settlement agreement. Under the settlement agreement, we would have paid up to $120 million to fund claims submitted by health plan members and health care providers who were members of the settlement classes. These payments also would have funded the legal fees of plaintiffs’ counsel and the costs of administering the settlement. In connection with the proposed settlement, the Company recorded an after-tax charge to net income attributable to Aetna of $78 million in the fourth quarter of 2012. The settlement agreement provided us the right to terminate the agreement under certain conditions related to settlement class members who opted out of the settlement. Based on a report provided to the parties by the settlement administrator, the conditions permitting us to terminate the settlement agreement were satisfied. On March 13, 2014, we notified the New Jersey District Court and plaintiffs’ counsel that we were terminating the settlement agreement. Various legal and factual developments since the date of the settlement agreement led us to believe terminating the settlement agreement was in our best interests. As a result of this termination, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced first quarter 2014 other general and administrative expenses by $103 million pretax. On June 30, 2015, the New Jersey District Court granted in part our motion to dismiss the proceeding. The New Jersey District Court dismissed with prejudice the plaintiffs’ RICO and federal antitrust claims; their ERISA claims that are based on our disclosures and our purported breach of fiduciary duties; and certain of their state law claims. The New Jersey District Court also dismissed with prejudice all claims asserted by several medical association plaintiffs. The plaintiffs’ remaining claims are for ERISA benefits and breach of contract. We intend to defend ourselves vigorously against the plaintiffs’ remaining claims. We also have received subpoenas and/or requests for documents and other information from, and been investigated by, attorneys general and other state and/or federal regulators, legislators and agencies relating to, and we are involved in other litigation regarding, our out-of-network benefit payment and administration practices. It is reasonably possible that others could initiate additional litigation or additional regulatory action against us with respect to our out-of-network benefit payment and/or administration practices. CMS Actions The Centers for Medicare & Medicaid Services (“CMS”) regularly audits our performance to determine our compliance with CMS’s regulations and our contracts with CMS and to assess the quality of services we provide to Medicare beneficiaries. CMS uses various payment mechanisms to allocate and adjust premium payments to our and other companies’ Medicare plans by considering the applicable health status of Medicare members as supported by information prepared, maintained and provided by health care providers. We collect claim and encounter data from providers and generally rely on providers to appropriately code their submissions to us and document their medical records, including the diagnosis data submitted to us with claims. CMS pays increased premiums to Medicare Advantage plans and prescription drug program plans for members who have certain medical conditions identified with specific diagnosis codes. Federal regulators review and audit the providers’ medical records to determine whether those records support the related diagnosis codes that determine the members’ health status and the resulting risk-adjusted premium payments to us. In that regard, CMS has instituted risk adjustment data validation (“RADV”) audits of various Medicare Advantage plans, including certain of the Company’s plans, to validate coding practices and supporting medical record documentation maintained by health care providers and the resulting risk adjusted premium payments to the plans. CMS may require us to refund premium payments if our risk adjusted premiums are not properly supported by medical record data. The Office of Inspector General (the “OIG”) also is auditing risk adjustment data of other companies, and we expect CMS and the OIG to continue auditing risk adjustment data. CMS revised its audit methodology for RADV audits to determine refunds payable by Medicare Advantage plans for contract year 2011 and forward. Under the revised methodology, among other things, CMS will project the error rate identified in the audit sample of approximately 200 members to all risk adjusted premium payments made under the contract being audited. Historically, CMS did not project sample error rates to the entire contract. As a result, the revised methodology may increase our exposure to premium refunds to CMS based on incomplete medical records maintained by providers. Since 2013, CMS has selected certain of our Medicare Advantage contracts for various contract years for RADV audit. We are currently unable to predict which of our Medicare Advantage contracts will be selected for future audit, the amounts of any retroactive refunds of, or prospective adjustments to, Medicare Advantage premium payments made to us, the effect of any such refunds or adjustments on the actuarial soundness of our Medicare Advantage bids, or whether any RADV audit findings would cause a change to our method of estimating future premium revenue in future bid submissions to CMS or compromise premium assumptions made in our bids for prior contract years or the current contract year. Any premium or fee refunds or adjustments resulting from regulatory audits, whether as a result of RADV, Public Exchange related or other audits by CMS, the OIG, HHS or otherwise, including audits of our minimum medical loss ratio rebates, methodology and/or reports, could be material and could adversely affect our operating results, financial position and cash flows. Other Litigation and Regulatory Proceedings We are involved in numerous other lawsuits arising, for the most part, in the ordinary course of our business operations, including claims of or relating to bad faith, medical malpractice, non-compliance with state and federal regulatory regimes, marketing misconduct, failure to timely or appropriately pay or administer claims and benefits in our Health Care and Group Insurance businesses (including our post-payment audit and collection practices and reductions in payments to providers due to sequestration), provider network structure (including the use of performance-based networks and termination of provider contracts), provider directory accuracy, rescission of insurance coverage, improper disclosure of personal information, anticompetitive practices, patent infringement and other intellectual property litigation, other legal proceedings in our Health Care and Group Insurance businesses and employment litigation. Some of these other lawsuits are or are purported to be class actions. We intend to defend ourselves vigorously against the claims brought in these matters. Awards to us and others of certain government contracts, particularly Medicaid contracts and contracts with government customers in our Commercial business, are subject to increasingly frequent protests by unsuccessful bidders. These protests may result in awards to us being reversed, delayed or modified. The loss or delay in implementation of any government contract could adversely affect our operating results. We will continue to defend vigorously contract awards we receive. In addition, our operations, current and past business practices, current and past contracts, and accounts and other books and records are subject to routine, regular and special investigations, audits, examinations and reviews by, and from time to time we receive subpoenas and other requests for information from, CMS, the U.S. Department of Health and Human Services, various state insurance and health care regulatory authorities, state attorneys general, treasurers and offices of inspector general, the Center for Consumer Information and Insurance Oversight, OIG, the Office of Personnel Management, the U.S. Department of Labor, the U.S. Department of the Treasury, the U.S. Food and Drug Administration, committees, subcommittees and members of the U.S. Congress, the U.S. Department of Justice (the “DOJ”), the Federal Trade Commission, U.S. attorneys and other state, federal and international governmental authorities. These government actions include inquiries by, and testimony before, certain members, committees and subcommittees of the U.S. Congress regarding our withdrawal from certain states’ Public Exchanges for 2017, certain of our current and past business practices, including our overall claims processing and payment practices, our business practices with respect to our small group products, student health products or individual customers (such as market withdrawals, rating information, premium increases and medical benefit ratios), executive compensation matters and travel and entertainment expenses, as well as the investigations by, and subpoenas and requests from, attorneys general and others described above under “Out-of-Network Benefit Proceedings.” We also have produced documents and information to the Civil Division of the DOJ in cooperation with a current investigation of our patient chart review processes in connection with risk adjustment data submissions under Parts C and D of the Medicare program. A significant number of states are investigating life insurers’ claims payment and related escheat practices. These investigations have resulted in significant charges to earnings by other life insurers in connection with related settlements. We have received requests for information from a number of states, and certain of our subsidiaries are being audited, with respect to our life insurance claim payment and related escheat practices. In the fourth quarter of 2013, we made changes to our life insurance claim payment practices (including related escheatment practices) based on evolving industry practices and regulatory expectations and interpretations, including expanding our existing use of the Social Security Administration’s Death Master File to identify additional potentially unclaimed death benefits and locate applicable beneficiaries. As a result of these changes, in the fourth quarter of 2013, we increased our estimated liability for unpaid life insurance claims with respect to insureds who passed away on or before December 31, 2013, and recorded in current and future benefits a charge of $36 million ( $55 million pretax). Given the judicial, legislative and regulatory uncertainty with respect to life insurance claim payment and related escheat practices, it is reasonably possible that we may incur additional liability related to those practices, whether as a result of further changes in our business practices, litigation, government actions or otherwise, which could adversely affect our operating results and cash flows. There also continues to be a heightened level of review and/or audit by regulatory authorities of, and increased litigation regarding, our and the rest of the health care and related benefits industry’s business and reporting practices, including premium rate increases, utilization management, development and application of medical policies, complaint, grievance and appeal processing, information privacy, provider network structure (including provider network adequacy, the use of performance-based networks and termination of provider contracts), provider directory accuracy, calculation of minimum medical loss ratios and/or payment of related rebates, delegated arrangements, rescission of insurance coverage, limited benefit health products, student health products, pharmacy benefit management practices (including the use of narrow networks and the placement of drugs in formulary tiers), sales practices, customer service practices, vendor oversight and claim payment practices (including payments to out-of-network providers and payments on life insurance policies). As a leading national health and related benefits company, we regularly are the subject of government actions of the types described above. These government actions may prevent or delay us from implementing planned premium rate increases and may result, and have resulted, in restrictions on our business, changes to or clarifications of our business practices, retroactive adjustments to premiums, refunds or other payments to members, beneficiaries, states or the federal government, withholding of premium payments to us by government agencies, assessments of damages, civil or criminal fines or penalties, or other sanctions, including the possible suspension or loss of licensure and/or suspension or exclusion from participation in government programs. Estimating the probable losses or a range of probable losses resulting from litigation, government actions and other legal proceedings is inherently difficult and requires an extensive degree of judgment, particularly where the matters involve indeterminate claims for monetary damages, involve claims for injunctive relief, may involve fines, penalties or punitive damages that are discretionary in amount, involve a large number of claimants or regulatory authorities, represent a change in regulatory policy, present novel legal theories, are in the early stages of the proceedings, are subject to appeal or could result in changes in business practices. In addition, because most legal proceedings are resolved over long periods of time, potential losses are subject to change due to, among other things, new developments, changes in litigation strategy, the outcome of intermediate procedural and substantive rulings and other parties’ settlement posture and their evaluation of the strength or weakness of their case against us. Except as specifically noted above under “Other Litigation and Regulatory Proceedings,” we are currently unable to predict the ultimate outcome of, or reasonably estimate the losses or a range of losses resulting from, the matters described above under “Litigation and Regulatory Proceedings”, and it is reasonably possible that their outcome could be material to us.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Segment Information	15. Segment Information Our operations are conducted in three business segments: Health Care, Group Insurance and Large Case Pensions. Our Corporate Financing segment is not a business segment. It is added to our business segments to reconcile our segment reporting to our consolidated results. The Corporate Financing segment includes transaction and integration-related costs, income taxes, interest expense on our outstanding debt and the financing components of our pension and OPEB plan expense (the service cost and prior service cost components of this expense are allocated to our business segments). Effective March 31, 2017, to more clearly differentiate between the GAAP and non-GAAP financial measures used in this Quarterly Report on Form 10-Q and our other disclosures, we changed the naming convention for our non-GAAP financial measures from "operating" measures to "adjusted" measures. The underlying calculations of our consolidated non-GAAP financial measures did not change. Prior to March 31, 2017, operating earnings was the measure reported to the chief executive officer for purposes of assessing financial performance and making operating decisions, such as the allocation of resources among our business segments. Effective March 31, 2017, the chief executive officer assesses our consolidated results based on adjusted earnings and assesses business segment results based on pre-tax adjusted earnings because income taxes are recorded in our Corporate Financing segment and are not allocated to our business segments. Also effective March 31, 2017, transaction and integration-related costs were reclassified to our Corporate Financing segment because they do not reflect our underlying business performance. The prior period has been restated to reflect this presentation. Non-GAAP financial measures we disclose, such as adjusted earnings and pre-tax adjusted earnings, should not be considered a substitute for, or superior to, financial measures determined or calculated in accordance with GAAP. Summarized financial information of our segment operations for the three months ended March 31, 2017 and 2016 were as follows: (Millions) Health Care Group Insurance Large Case Pensions Corporate Financing Total Company Three Months Ended March 31, 2017 Revenue from external customers $ 14,667 $ 556 $ 15 $ — $ 15,238 Pre-tax adjusted earnings (loss) (1) 1,476 33 4 (62 ) 1,451 Three Months Ended March 31, 2016 Revenue from external customers $ 14,908 $ 551 $ 17 $ — $ 15,476 Pre-tax adjusted earnings (loss) (1) 1,456 25 1 (65 ) 1,417 (1) Pre-tax adjusted earnings (loss) excludes net realized capital gains or losses, amortization of other acquired intangible assets and the other items described in the reconciliation below. A reconciliation of (loss) income before income taxes to pre-tax adjusted earnings (1) for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, (Millions) 2017 2016 (Loss) income before income taxes (GAAP measure) $ (628 ) $ 1,289 Less: Income before income taxes attributable to non-controlling interests (GAAP measure) 3 1 (Loss) income before income taxes attributable to Aetna (GAAP measure) (631 ) 1,288 Loss on early extinguishment of long-term debt 246 — Penn Treaty-related guaranty fund assessments 231 — Transaction and integration-related costs 1,212 66 Amortization of other acquired intangible assets 60 62 Net realized capital losses 333 1 Pre-tax adjusted earnings (1) $ 1,451 $ 1,417 (1) In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance: • In the three months ended March 31, 2017 , we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020. • In the three months ended March 31, 2017 , we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations. • We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.

Discontinued Products

Discontinued Products	3 Months Ended
	Mar. 31, 2017
Discontinued Products [Abstract]
Discontinued Products	16. Discontinued Products Prior to 1993, we sold single-premium annuities (“SPAs”) and guaranteed investment contracts (“GICs”), primarily to employer sponsored pension plans. In 1993, we discontinued selling these products to Large Case Pensions customers, and now we refer to these products as discontinued products. In November 2016, the last outstanding GIC matured. We discontinued selling these products because they were generating losses for us, and we projected that they would continue to generate losses over their life (which is currently greater than 30 years); so we established a reserve for anticipated future losses at the time of discontinuance. This reserve represents the present value (at the risk-free rate of return consistent with the duration of the liabilities) of the difference between the expected cash flows from the assets supporting these products and the cash flows expected to be required to meet the obligations of the outstanding contracts. Key assumptions in setting the reserve for anticipated future losses include future investment results, payments to retirees, mortality and retirement rates and the cost of asset management and customer service. In 2014, we modified the mortality tables used in order to reflect the more up-to-date 2014 Retired Pensioner’s Mortality table. The mortality tables were previously modified in 2012, in order to reflect the more up-to-date 2000 Retired Pensioner’s Mortality table, and in 1995, in order to reflect the more up-to-date 1994 Uninsured Pensioner’s Mortality table. In 1997, we began the use of a bond default assumption to reflect historical default experience. Other than these changes, since 1993 there have been no significant changes to the assumptions underlying the reserve. We review the adequacy of this reserve quarterly based on actual experience. As long as our expected future losses remain consistent with prior projections, the results of the discontinued products are applied against the reserve and do not impact net income attributable to Aetna. If actual or expected future losses are greater than we currently estimate, we may increase the reserve, which could adversely impact net income attributable to Aetna. If actual or expected future losses are less than we currently estimate, we may decrease the reserve, which could favorably impact net income attributable to Aetna. The reserve at each of March 31, 2017 and December 31, 2016 reflects management’s best estimate of anticipated future losses, and is included in future policy benefits on our Consolidated Balance Sheets. The activity in the reserve for anticipated future losses on discontinued products for the three months ended March 31, 2017 and 2016 was as follows (pretax): (Millions) 2017 2016 Reserve, beginning of period $ 962 $ 1,067 Operating income (loss) 16 (13 ) Net realized capital gains 14 12 Reserve, end of period $ 992 $ 1,066 During the three months ended March 31, 2017 , our discontinued products reflected operating income and net realized capital gains, primarily attributable to gains from the sale of investment real estate and debt securities. During the three months ended March 31, 2016 , our discontinued products reflected an operating loss and net realized capital gains, primarily attributable to gains from the sale of debt securities and investment real estate. Assets and liabilities supporting discontinued products (1) at March 31, 2017 and December 31, 2016 were as follows: (Millions) 2017 2016 Assets: Debt and equity securities available for sale $ 1,872 $ 1,913 Mortgage loans 369 370 Other investments 615 646 Total investments 2,856 2,929 Other assets 109 104 Receivable from continuing products (2) 562 554 Total assets $ 3,527 $ 3,587 Liabilities: Future policy benefits $ 2,282 $ 2,326 Reserve for anticipated future losses on discontinued products 992 962 Current and deferred income taxes 38 42 Other liabilities (3) 215 257 Total liabilities $ 3,527 $ 3,587 (1) Assets supporting the discontinued products are distinguished from assets supporting continuing products. (2) At the time of discontinuance, a receivable from Large Case Pensions’ continuing products was established on the discontinued products Balance Sheet. This receivable represented the net present value of anticipated cash shortfalls in the discontinued products, which will be funded from continuing products. Interest on the receivable is accrued at the discount rate that was used to calculate the reserve. The offsetting payable, on which interest is similarly accrued, is reflected in continuing products. Interest on the payable generally offsets investment income on the assets available to fund the shortfall. These amounts are eliminated in consolidation. (3) Net unrealized capital gains on the available-for-sale debt securities are included in other liabilities and are not reflected in consolidated shareholders’ equity. The distributions on our discontinued products consisted of scheduled contract maturities, settlements and benefit payments of $84 million and $94 million for the three months ended March 31, 2017 , and 2016, respectively. Participant-directed withdrawals from our discontinued products were not significant during the three months ended March 31, 2017 or 2016 . Cash required to fund these distributions was provided by earnings and scheduled payments on, and sales of, invested assets.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Interim Financial Statements	These interim financial statements necessarily rely on estimates, including assumptions as to annualized tax rates. In the opinion of management, all adjustments necessary for a fair statement of results for the interim periods have been made. All such adjustments are of a normal, recurring nature. The Company has evaluated subsequent events that occurred after March 31, 2017 through the date the financial statements were issued and determined there were no subsequent events to disclose.
Reclassifications	Reclassifications Certain reclassifications were made to 2016 financial information to conform with the 2017 presentation.
Principles of Consolidation	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial reporting. Accordingly, they do not include all of the information and footnotes required by GAAP for annual financial statements. We have omitted certain footnote disclosures that would substantially duplicate the disclosures in our 2016 Annual Report on Form 10-K (our “2016 Annual Report”), unless the information contained in those disclosures materially changed or is required by GAAP. The accompanying unaudited consolidated financial statements and related condensed notes should be read in conjunction with the consolidated financial statements and related notes presented in our 2016 Annual Report.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2017
Investments [Abstract]
Total investments	Total investments at March 31, 2017 and December 31, 2016 were as follows: March 31, 2017 December 31, 2016 (Millions) Current Long-term Total Current Long-term Total Debt and equity securities available for sale $ 2,928 $ 18,925 $ 21,853 $ 2,876 $ 18,866 $ 21,742 Mortgage loans 151 1,356 1,507 170 1,341 1,511 Other investments — 1,641 1,641 — 1,626 1,626 Total investments $ 3,079 $ 21,922 $ 25,001 $ 3,046 $ 21,833 $ 24,879
Debt and equity securities available for sale	Debt and equity securities available for sale at March 31, 2017 and December 31, 2016 were as follows: (Millions) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value March 31, 2017 Debt securities: U.S. government securities $ 1,595 $ 49 $ — $ 1,644 States, municipalities and political subdivisions 4,886 170 (41 ) 5,015 U.S. corporate securities 8,400 394 (44 ) 8,750 Foreign securities 3,004 180 (17 ) 3,167 Residential mortgage-backed securities 760 9 (7 ) 762 Commercial mortgage-backed securities 1,331 3 (36 ) 1,298 Other asset-backed securities 1,108 9 (5 ) 1,112 Redeemable preferred securities 22 5 — 27 Total debt securities 21,106 819 (150 ) 21,775 Equity securities 69 11 (2 ) 78 Total debt and equity securities (1)(2) $ 21,175 $ 830 $ (152 ) $ 21,853 December 31, 2016 Debt securities: U.S. government securities $ 1,643 $ 51 $ — $ 1,694 States, municipalities and political subdivisions 5,047 152 (61 ) 5,138 U.S. corporate securities 8,145 385 (55 ) 8,475 Foreign securities 2,958 163 (33 ) 3,088 Residential mortgage-backed securities 793 11 (9 ) 795 Commercial mortgage-backed securities 1,382 5 (39 ) 1,348 Other asset-backed securities 1,077 7 (9 ) 1,075 Redeemable preferred securities 22 5 — 27 Total debt securities 21,067 779 (206 ) 21,640 Equity securities 84 20 (2 ) 102 Total debt and equity securities (1)(2) $ 21,151 $ 799 $ (208 ) $ 21,742 (1) At both March 31, 2017 and December 31, 2016 , we held securities for which we previously recognized an immaterial amount of non-credit related impairments in accumulated other comprehensive loss. These securities each had an immaterial amount of net unrealized capital gains at both March 31, 2017 and December 31, 2016 . (2) Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 16 for additional information on our accounting for discontinued products). At March 31, 2017 , debt and equity securities with a fair value of approximately $2.8 billion , gross unrealized capital gains of $192 million and gross unrealized capital losses of $29 million and, at December 31, 2016 , debt and equity securities with a fair value of approximately $2.9 billion , gross unrealized capital gains of $195 million and gross unrealized capital losses of $35 million were included in total debt and equity securities, but support our experience-rated and discontinued products. Changes in net unrealized capital gains (losses) on these securities are not reflected in accumulated other comprehensive income.
Fair value of debt securities by contractual maturity	The fair value of debt securities at March 31, 2017 is shown below by contractual maturity. Actual maturities may differ from contractual maturities because securities may be restructured, called or prepaid, or we intend to sell a security prior to maturity. (Millions) Amortized Cost Fair Value Due to mature: Less than one year $ 1,498 $ 1,513 One year through five years 6,948 7,121 After five years through ten years 4,775 4,909 Greater than ten years 4,686 5,060 Residential mortgage-backed securities 760 762 Commercial mortgage-backed securities 1,331 1,298 Other asset-backed securities 1,108 1,112 Total $ 21,106 $ 21,775
Debt and Equity Securities in an Unrealized Capital Loss Position	Summarized below are the debt and equity securities we held at March 31, 2017 and December 31, 2016 that were in an unrealized capital loss position, aggregated by the length of time the investments have been in that position: Less than 12 months Greater than 12 months Total (1) (Millions, except number of securities) Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses Number of Securities Fair Value Unrealized Losses March 31, 2017 Debt securities: U.S. government securities 32 $ 59 $ — — $ — $ — 32 $ 59 $ — States, municipalities and political subdivisions 530 1,539 38 45 87 3 575 1,626 41 U.S. corporate securities 1,210 1,965 35 79 78 9 1,289 2,043 44 Foreign securities 421 693 15 42 57 2 463 750 17 Residential mortgage-backed securities 194 431 7 102 16 — 296 447 7 Commercial mortgage-backed securities 280 1,025 36 — — — 280 1,025 36 Other asset-backed securities 239 449 3 114 102 2 353 551 5 Total debt securities 2,906 6,161 134 382 340 16 3,288 6,501 150 Equity securities 1 4 — 10 2 2 11 6 2 Total debt and equity securities (1) 2,907 $ 6,165 $ 134 392 $ 342 $ 18 3,299 $ 6,507 $ 152 December 31, 2016 Debt securities: U.S. government securities 26 $ 39 $ — 1 $ 1 $ — 27 $ 40 $ — States, municipalities and political subdivisions 865 2,228 58 37 75 3 902 2,303 61 U.S. corporate securities 1,428 2,277 44 114 101 11 1,542 2,378 55 Foreign securities 649 970 27 62 76 6 711 1,046 33 Residential mortgage-backed securities 188 455 8 104 17 1 292 472 9 Commercial mortgage-backed securities 285 1,038 39 3 3 — 288 1,041 39 Other asset-backed securities 226 403 4 208 177 5 434 580 9 Total debt securities 3,667 7,410 180 529 450 26 4,196 7,860 206 Equity securities 2 3 — 8 3 2 10 6 2 Total debt and equity securities (1) 3,669 $ 7,413 $ 180 537 $ 453 $ 28 4,206 $ 7,866 $ 208 (1) At March 31, 2017 and December 31, 2016 , debt and equity securities in an unrealized capital loss position of $29 million and $35 million , respectively, and with related fair value of $794 million and $890 million , respectively, related to experience-rated and discontinued products.
Maturity dates for debt securities	The maturity dates for debt securities in an unrealized capital loss position at March 31, 2017 were as follows: Supporting discontinued and experience-rated products Supporting remaining products Total (Millions) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Due to mature: Less than one year $ 7 $ — $ 207 $ — $ 214 $ — One year through five years 47 1 1,612 19 1,659 20 After five years through ten years 252 6 1,095 25 1,347 31 Greater than ten years 261 14 997 37 1,258 51 Residential mortgage-backed securities 17 — 430 7 447 7 Commercial mortgage-backed securities 182 6 843 30 1,025 36 Other asset-backed securities 27 — 524 5 551 5 Total $ 793 $ 27 $ 5,708 $ 123 $ 6,501 $ 150
Activity in mortgage loan portfolio	During the three months ended March 31, 2017 and 2016 we had the following activity in our mortgage loan portfolio: Three Months Ended March 31, (Millions) 2017 2016 New mortgage loans $ 54 $ 12 Mortgage loans fully repaid 48 48
Mortgage loan internal credit rating	Based upon our most recent assessments at March 31, 2017 and December 31, 2016 , our mortgage loans were given the following credit quality indicators: (In Millions, except credit ratings indicator) March 31, 2017 December 31, 2016 1 $ 44 $ 45 2 to 4 1,446 1,449 5 and 6 17 17 7 — — Total $ 1,507 $ 1,511
Net Investment Income	Sources of net investment income for the three months ended March 31, 2017 and 2016 were as follows: Three Months Ended March 31, (Millions) 2017 2016 Debt securities $ 190 $ 195 Mortgage loans 22 29 Other investments 58 4 Gross investment income 270 228 Investment expenses (10 ) (10 ) Net investment income (1) $ 260 $ 218 (1) Net investment income includes $66 million and $45 million for the three months ended March 31, 2017 and 2016, respectively, related to investments supporting our experience-rated and discontinued products.
Net realized capital gains (losses)	Net realized capital losses for the three months ended March 31, 2017 and 2016 , excluding amounts related to experience-rated contract holders and discontinued products, were as follows: Three Months Ended March 31, (Millions) 2017 2016 Other-than-temporary impairment (“OTTI”) losses on debt securities recognized in earnings $ (2 ) $ (9 ) Other net realized capital (losses) gains (331 ) 8 Net realized capital losses $ (333 ) $ (1 )
Proceeds and related gross realized capital gains and losses from the sale of debt securities	Excluding amounts related to experience-rated and discontinued products, proceeds from the sale of available for sale debt and equity securities and the related gross realized capital gains and losses for the three months ended March 31, 2017 and 2016 were as follows (1) : Three Months Ended March 31, (Millions) 2017 2016 Proceeds on sales $ 1,110 $ 1,546 Gross realized capital gains 21 32 Gross realized capital losses 14 31 (1) The proceeds on sales and gross realized capital gains and losses exclude the impact of the sales of short-term debt securities which primarily relate to our investments in mutual funds. These investments were excluded from the disclosed amounts because they represent an immaterial amount of aggregate gross realized capital gains or losses and have a high volume of sales activity.
Schedule of Variable Interest Entities	The carrying value of the total assets and liabilities of our other variable interest holder VIE investments at March 31, 2017 and December 31, 2016 were as follows: (Millions) March 31, 2017 December 31, 2016 Assets: Hedge fund investments $ 34,203 $ 32,926 Private equity investments 26,819 25,368 Real estate partnerships 6,549 6,743 Total $ 67,571 $ 65,037 Liabilities: Hedge fund investments $ 3,464 $ 2,819 Private equity investments 3,353 2,354 Real estate partnerships 4,727 4,938 Total $ 11,544 $ 10,111 The total amount of other variable interest holder VIE assets included in long term investments on our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016 were as follows: (Millions) March 31, 2017 December 31, 2016 Hedge fund investments $ 355 $ 384 Private equity investments 497 454 Real estate partnerships 263 278 Total $ 1,115 $ 1,116

Fair Value (Tables)

Fair Value (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	Financial assets measured at fair value on a recurring basis in our Consolidated Balance Sheets at March 31, 2017 and December 31, 2016 were as follows: (Millions) Level 1 Level 2 Level 3 Total March 31, 2017 Assets: Debt securities: U.S. government securities $ 1,482 $ 162 $ — $ 1,644 States, municipalities and political subdivisions — 5,014 1 5,015 U.S. corporate securities — 8,671 79 8,750 Foreign securities — 3,146 21 3,167 Residential mortgage-backed securities — 762 — 762 Commercial mortgage-backed securities — 1,267 31 1,298 Other asset-backed securities — 1,106 6 1,112 Redeemable preferred securities — 27 — 27 Total debt securities 1,482 20,155 138 21,775 Equity securities 47 — 31 78 Total $ 1,529 $ 20,155 $ 169 $ 21,853 December 31, 2016 Assets: Debt securities: U.S. government securities $ 1,514 $ 180 $ — $ 1,694 States, municipalities and political subdivisions — 5,137 1 5,138 U.S. corporate securities — 8,395 80 8,475 Foreign securities — 3,067 21 3,088 Residential mortgage-backed securities — 795 — 795 Commercial mortgage-backed securities — 1,348 — 1,348 Other asset-backed securities — 1,075 — 1,075 Redeemable preferred securities — 26 1 27 Total debt securities 1,514 20,023 103 21,640 Equity securities 59 — 43 102 Total $ 1,573 $ 20,023 $ 146 $ 21,742
Carrying Value and Estimated Fair Value of Certain Financial Instruments	The carrying value and estimated fair value classified by level of fair value hierarchy for our financial instruments carried on our Consolidated Balance Sheets at adjusted cost or contract value at March 31, 2017 and December 31, 2016 were as follows: Carrying Value Estimated Fair Value (Millions) Level 1 Level 2 Level 3 Total March 31, 2017 Assets: Mortgage loans $ 1,507 $ — $ — $ 1,539 $ 1,539 Bank loans 8 — — 8 8 Equity securities (1) 45 N/A N/A N/A N/A Liabilities: Investment contract liabilities: With a fixed maturity 8 — — 8 8 Without a fixed maturity 370 — — 354 354 Long-term debt 9,423 — 10,128 — 10,128 (Millions) December 31, 2016 Assets: Mortgage loans $ 1,511 $ — $ — $ 1,540 $ 1,540 Bank loans 8 — — 8 8 Equity securities (1) 35 N/A N/A N/A N/A Liabilities: Investment contract liabilities: With a fixed maturity 8 — — 8 8 Without a fixed maturity 378 — — 364 364 Long-term debt 20,661 — 21,468 — 21,468 (1) It was not practical to estimate the fair value of these cost-method investments as it represents shares of unlisted companies.
Separate Account Financial Assets	Separate Accounts financial assets at March 31, 2017 and December 31, 2016 were as follows: March 31, 2017 December 31, 2016 (Millions) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Debt securities $ 784 $ 2,488 $ 2 $ 3,274 $ 766 $ 2,378 $ — $ 3,144 Equity securities 147 6 — 153 166 6 — 172 Common/collective trusts — 589 — 589 — 582 — 582 Total (1) $ 931 $ 3,083 $ 2 $ 4,016 $ 932 $ 2,966 $ — $ 3,898 (1) Excludes $228 million and $93 million of cash and cash equivalents and other receivables at March 31, 2017 and December 31, 2016 , respectively.
Balance Sheet Offsetting Assets	Financial assets, including derivative assets, subject to offsetting and enforceable master netting arrangements at March 31, 2017 and December 31, 2016 were as follows: Gross Amounts of Recognized Assets (1) Gross Amounts Not Offset in the Balance Sheets Financial Instruments Cash Collateral Received (Millions) Net Amount March 31, 2017 Derivatives $ — $ 17 $ — $ 17 Total $ — $ 17 $ — $ 17 December 31, 2016 Derivatives $ — $ 17 $ — $ 17 Total $ — $ 17 $ — $ 17 (1) There were no amounts offset in our Consolidated Balance Sheets at March 31, 2017 or December 31, 2016 .

Health Care and Other Insuran27

Health Care and Other Insurance Liabilities (Tables)	3 Months Ended
	Mar. 31, 2017
Health Care [Member]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	The following table shows the components of the change in health care costs payable during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Health care costs payable, beginning of the period $ 6,558 $ 6,306 Less: Reinsurance recoverables 5 4 Health care costs payable, beginning of the period, net 6,553 6,302 Add: Components of incurred health care costs Current year 11,420 11,475 Prior years (614 ) (627 ) Total incurred health care costs (1) 10,806 10,848 Less: Claims paid Current year 6,298 5,929 Prior years 4,742 4,398 Total claims paid 11,040 10,327 Health care costs payable, end of period, net 6,319 6,823 Add: Premium deficiency reserve 110 — Add: Reinsurance recoverables 3 2 Health care costs payable, end of period $ 6,432 $ 6,825 (1) Total incurred health care costs exclude from the table above $110 million related to the premium deficiency reserve recorded during the three months ended March 31, 2017 for the 2017 coverage year on our individual Commercial products.
Group Insurance [Member]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block]	The following table shows the components of the change in unpaid long-term disability claims during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Long-term disability unpaid claims beginning of the period $ 1,904 $ 1,819 Less: Reinsurance recoverables 26 27 Long-term disability unpaid claims, beginning of the period, net 1,878 1,792 Add: Components of incurred claims Current year 131 137 Prior years 5 4 Total incurred claims 136 141 Less: Claims paid Current year 1 1 Prior years 134 119 Total claims paid 135 120 Long-term disability unpaid claims, end of period, net 1,879 1,813 Add: Reinsurance recoverables 26 27 Long-term disability unpaid claims, end of period $ 1,905 $ 1,840
Reconciliation to Total Unpaid Claims Liability [Table Text Block]	The reconciliation of the long-term disability unpaid claims liability to the total unpaid claims liability in our Consolidated Balance Sheets is as follows at March 31, 2017 and 2016: At March 31, (Millions) 2017 2016 Long-term disability unpaid claims $ 1,905 $ 1,840 Term life unpaid claims 472 485 Other unpaid claims 118 122 Total unpaid claims $ 2,495 $ 2,447

Health Care Reform (Tables)

Health Care Reform (Tables)	3 Months Ended
	Mar. 31, 2017
Health Care Reform [Abstract]
Health Care Reform Programs	Our net receivable (payable) related to the 3Rs risk management programs at March 31, 2017 and December 31, 2016 were as follows: At March 31, 2017 At December 31, 2016 (Millions) Reinsurance Risk Adjustment Risk Corridor Reinsurance Risk Adjustment Risk Corridor Current $ 166 $ (696 ) $ 1 $ 202 $ (690 ) $ (10 ) Long-term 12 (38 ) — — — — Total net receivable (payable) $ 178 $ (734 ) $ 1 $ 202 $ (690 ) $ (10 )

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Carrying Value of Long-Term Debt	The carrying value of our long-term debt at March 31, 2017 and December 31, 2016 was as follows: (Millions) March 31, December 31, Senior notes, 5.95% due March 2017 (1) $ — $ 386 Senior notes, 1.75% due May 2017 (1) 250 250 Senior notes, 1.5% due November 2017 (1) 499 499 Senior notes, floating rate due December 2017 (1) 499 499 Senior notes, 1.7% due June 2018 998 997 Senior notes, 2.2% due March 2019 374 374 Senior notes, 1.9% due June 2019 — 1,642 Senior notes, 3.95% due September 2020 — 745 Senior notes, 2.4% due June 2021 — 1,839 Senior notes, 5.45% due June 2021 658 661 Senior notes, 4.125% due June 2021 496 495 Senior notes, 2.75% due November 2022 986 986 Senior notes, 2.8% due June 2023 1,290 1,290 Senior notes, 3.5% due November 2024 743 742 Senior notes, 3.2% due June 2026 — 2,771 Senior notes, 4.25% due June 2036 — 1,480 Senior notes, 6.625% due June 2036 765 765 Senior notes, 6.75% due December 2037 527 527 Senior notes, 4.5% due May 2042 478 478 Senior notes, 4.125% due November 2042 489 489 Senior notes, 4.75% due March 2044 371 371 Senior notes, 4.375% due June 2046 — 2,375 Total long-term debt 9,423 20,661 Less current portion of long-term debt 1,249 1,634 Total long-term debt, less current portion $ 8,174 $ 19,027 (1) At March 31, 2017 , our 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and our floating rate senior notes, due December 2017 are each classified as current in our Consolidated Balance Sheet. At December 31, 2016 , our 5.95% senior notes due March 2017, 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and floating rate senior notes due December 2017 are each classified as current in our Consolidated Balance Sheet.

Pension and Other Postretirem30

Pension and Other Postretirement Plans (Tables)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Components of net periodic benefit cost	Components of the net periodic benefit (income) cost of our defined benefit pension plans and other postretirement employee benefit (“OPEB”) plans for the three months ended March 31, 2017 and 2016 were as follows: Pension Plans OPEB Plans Three Months Ended Three Months Ended March 31, March 31, (Millions) 2017 2016 2017 2016 Amortization of prior service credit $ — $ — $ (1 ) $ (1 ) Interest cost 51 65 2 3 Expected return on plan assets (95 ) (97 ) (1 ) (1 ) Recognized net actuarial losses 16 15 1 1 Net periodic benefit (income) cost $ (28 ) $ (17 ) $ 1 $ 2

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Class of Stock Disclosures [Abstract]
Dividends declared	During the three months ended March 31, 2017 our Board declared the following cash dividends: Date Declared Dividend Amount Per Share Shareholders of Record Date Date Paid/ To be Paid Total Dividends (Millions) February 17, 2017 $ .50 April 13, 2017 April 28, 2017 $ 166
Black Scholes option pricing model	The SARs granted to certain employees during first quarters of 2017 and 2016 had an estimated fair market value of $32.30 and $34.33 per unit, respectively. The fair value per unit was calculated on each respective grant date using a modified Black-Scholes option pricing model using the following assumptions during the first quarters of 2017 and 2016 : 2017 2016 Expected term (in years) 7.21 7.11 Volatility 26.52 % 32.9 % Risk-free interest rate 2.22 % 1.52 % Dividend yield 1.71 % 0.91 % Initial price $ 125.27 $ 103.45

Other Comprehensive (Loss) In32

Other Comprehensive (Loss) Income (Tables)	3 Months Ended
	Mar. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	Shareholders’ equity included the following activity in accumulated other comprehensive loss for three months ended March 31, 2017 and 2016 : Three Months Ended March 31, (Millions) 2017 2016 Previously impaired debt securities: (1) Beginning of period balance $ 16 $ 19 Net unrealized losses ($(2) and $(4) pretax) (1 ) (3 ) Less: Net reclassification of losses to earnings ($(2) and $(5) pretax) (2) (1 ) (4 ) Other comprehensive income — 1 End of period balance 16 20 All other securities: Beginning of period balance 297 312 Net unrealized gains ($92 and $317 pretax) 60 206 Less: Net reclassification of gains (losses) to earnings ($25 and $(23) pretax) (2) 16 (15 ) Other comprehensive income 44 221 End of period balance 341 533 Derivatives and foreign currency: Beginning of period balance (235 ) (74 ) Net unrealized losses ($(2) and $(246) pretax) (1 ) (160 ) Less: Net reclassification of losses to earnings ($(343) and $(6) pretax) (3) (223 ) (3 ) Other comprehensive income (loss) 222 (157 ) End of period balance (13 ) (231 ) Pension and OPEB plans: Beginning of period balance (1,630 ) (1,587 ) Less: Net amortization of net actuarial losses ($(17) and $(16) pretax) (4) (11 ) (11 ) Less: Net amortization of prior service credit ($2 and $1 pretax) (4) 1 1 Other comprehensive income 10 10 End of period balance (1,620 ) (1,577 ) Total beginning of period accumulated other comprehensive loss (1,552 ) (1,330 ) Total other comprehensive loss 276 75 Total end of period accumulated other comprehensive loss $ (1,276 ) $ (1,255 ) (1) Represents specifically identified unrealized gains and losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security. (2) Reclassifications out of accumulated other comprehensive income for specifically identified previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statements of Income. (3) Reclassifications out of accumulated other comprehensive income for specifically identified foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the specifically identified effective portion of derivatives related to interest rate swaps which are reflected in interest expense. During the three months ended March 31, 2017 , we redeemed the entire $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes and the entire $750 million aggregate principal amount outstanding of the senior notes due 2020 and reclassified out of accumulated other comprehensive income the remaining $336 million pre-tax unrealized hedge losses as a realized capital loss within the Consolidated Statements of Income. Refer to Note 8 for additional information. (4) Reclassifications out of accumulated other comprehensive income for specifically identified pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 9 for additional information.

Earnings Per Common Share (Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	The computations of basic and diluted EPS for the three months ended March 31, 2017 and 2016 are as follows: Three Months Ended March 31, (Millions, except per common share data) 2017 2016 Net (loss) income attributable to Aetna $ (381 ) $ 737 Weighted average shares used to compute basic EPS 343.8 350.7 Dilutive effect of outstanding stock-based compensation awards — 3.1 Weighted average shares used to compute diluted EPS 343.8 353.8 Basic EPS $ (1.11 ) $ 2.10 Diluted EPS $ (1.11 ) $ 2.08
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The stock-based compensation awards excluded from the calculation of diluted EPS for the three months ended March 31, 2017 and 2016 are as follows: Three Months Ended March 31, (Millions) 2017 2016 SARs (1) — .2 Other stock-based compensation awards (2) .9 .8 In-the-money anti-dilutive stock-based compensation awards (3) 10.6 — (1) SARs are excluded from the calculation of diluted EPS if the exercise price is greater than the average market price of Aetna common shares during the period (i.e., the awards are anti-dilutive). (2) PSUs, certain market stock units with performance conditions, and performance stock appreciation rights are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period. (3) In periods when we report a net loss attributable to Aetna, in-the-money stock-based compensation awards are excluded from our calculation of diluted EPS because their inclusion would have an anti-dilutive effect. Therefore we excluded from our calculation of diluted EPS for the three months ended March 31, 2017 in-the-money stock-based compensation awards which would have increased our weighted-average shares used to compute diluted EPS by 2.4 million shares.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Summarized financial information of segments	Summarized financial information of our segment operations for the three months ended March 31, 2017 and 2016 were as follows: (Millions) Health Care Group Insurance Large Case Pensions Corporate Financing Total Company Three Months Ended March 31, 2017 Revenue from external customers $ 14,667 $ 556 $ 15 $ — $ 15,238 Pre-tax adjusted earnings (loss) (1) 1,476 33 4 (62 ) 1,451 Three Months Ended March 31, 2016 Revenue from external customers $ 14,908 $ 551 $ 17 $ — $ 15,476 Pre-tax adjusted earnings (loss) (1) 1,456 25 1 (65 ) 1,417 (1) Pre-tax adjusted earnings (loss) excludes net realized capital gains or losses, amortization of other acquired intangible assets and the other items described in the reconciliation below.
Reconciliation of Operating Earnings to Net Income	A reconciliation of (loss) income before income taxes to pre-tax adjusted earnings (1) for the three months ended March 31, 2017 and 2016 was as follows: Three Months Ended March 31, (Millions) 2017 2016 (Loss) income before income taxes (GAAP measure) $ (628 ) $ 1,289 Less: Income before income taxes attributable to non-controlling interests (GAAP measure) 3 1 (Loss) income before income taxes attributable to Aetna (GAAP measure) (631 ) 1,288 Loss on early extinguishment of long-term debt 246 — Penn Treaty-related guaranty fund assessments 231 — Transaction and integration-related costs 1,212 66 Amortization of other acquired intangible assets 60 62 Net realized capital losses 333 1 Pre-tax adjusted earnings (1) $ 1,451 $ 1,417 (1) In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance: • In the three months ended March 31, 2017 , we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020. • In the three months ended March 31, 2017 , we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations. • We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.

Discontinued Products (Tables)

Discontinued Products (Tables)	3 Months Ended
	Mar. 31, 2017
Discontinued Products [Abstract]
Activity in the Reserve for Anticipated Future Losses	The activity in the reserve for anticipated future losses on discontinued products for the three months ended March 31, 2017 and 2016 was as follows (pretax): (Millions) 2017 2016 Reserve, beginning of period $ 962 $ 1,067 Operating income (loss) 16 (13 ) Net realized capital gains 14 12 Reserve, end of period $ 992 $ 1,066
Assets and Liabilities Supporting Discontinued Products	Assets and liabilities supporting discontinued products (1) at March 31, 2017 and December 31, 2016 were as follows: (Millions) 2017 2016 Assets: Debt and equity securities available for sale $ 1,872 $ 1,913 Mortgage loans 369 370 Other investments 615 646 Total investments 2,856 2,929 Other assets 109 104 Receivable from continuing products (2) 562 554 Total assets $ 3,527 $ 3,587 Liabilities: Future policy benefits $ 2,282 $ 2,326 Reserve for anticipated future losses on discontinued products 992 962 Current and deferred income taxes 38 42 Other liabilities (3) 215 257 Total liabilities $ 3,527 $ 3,587 (1) Assets supporting the discontinued products are distinguished from assets supporting continuing products. (2) At the time of discontinuance, a receivable from Large Case Pensions’ continuing products was established on the discontinued products Balance Sheet. This receivable represented the net present value of anticipated cash shortfalls in the discontinued products, which will be funded from continuing products. Interest on the receivable is accrued at the discount rate that was used to calculate the reserve. The offsetting payable, on which interest is similarly accrued, is reflected in continuing products. Interest on the payable generally offsets investment income on the assets available to fund the shortfall. These amounts are eliminated in consolidation. (3) Net unrealized capital gains on the available-for-sale debt securities are included in other liabilities and are not reflected in consolidated shareholders’ equity.

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Long-term Debt	$ 9,423	$ 20,661
Loss on Contract Termination	$ 53
Loss on Contract Termination, Percent of Total Costs	70.00%
Debt Issued for Humana Acquisition [Domain]
Business Acquisition [Line Items]
Debt Instrument, Face Amount	$ 13,000
Long-term Debt	$ 10,200
Debt Instrument, Redemption Price, Percentage	101.00%
Humana [Member]
Business Acquisition [Line Items]
Loss on Contract Termination	$ 1,000
Molina Divestiture [Member]
Business Acquisition [Line Items]
Loss on Contract Termination	$ 7

Investments (Details)

Investments (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Total Investments [Line Items]
Current	$ 3,079	$ 3,046
Long-term investments	21,922	21,833
Total investments	25,001	24,879
Debt And Equity Securities Available For Sale [Member]
Total Investments [Line Items]
Current	2,928	2,876
Long-term investments	18,925	18,866
Total investments	21,853	21,742
Mortgage Loans [Member]
Total Investments [Line Items]
Current	151	170
Long-term investments	1,356	1,341
Total investments	1,507	1,511
Other Investments [Member]
Total Investments [Line Items]
Current	0	0
Long-term investments	1,641	1,626
Total investments	$ 1,641	$ 1,626

Investments - Debt and Equity S

Investments - Debt and Equity Securities (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	[1],[2]	$ 21,175	$ 21,151
Available-for-sale Securities, Gross Unrealized Gains	[1],[2]	830	799
Available-for-sale Securities, Gross Unrealized Losses	[1],[2]	(152)	(208)
Available-for-sale Securities, Fair Value Disclosure	[1],[2]	21,853	21,742
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gains		192	195
Available-for-sale Securities, Gross Unrealized Losses		(29)	(35)
Available-for-sale Securities, Fair Value Disclosure		2,800	2,900
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		21,106	21,067
Available-for-sale Securities, Gross Unrealized Gains		819	779
Available-for-sale Securities, Gross Unrealized Losses		(150)	(206)
Available-for-sale Securities, Fair Value Disclosure		21,775	21,640
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		1,595	1,643
Available-for-sale Securities, Gross Unrealized Gains		49	51
Available-for-sale Securities, Gross Unrealized Losses		0	0
Available-for-sale Securities, Fair Value Disclosure		1,644	1,694
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		4,886	5,047
Available-for-sale Securities, Gross Unrealized Gains		170	152
Available-for-sale Securities, Gross Unrealized Losses		(41)	(61)
Available-for-sale Securities, Fair Value Disclosure		5,015	5,138
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		8,400	8,145
Available-for-sale Securities, Gross Unrealized Gains		394	385
Available-for-sale Securities, Gross Unrealized Losses		(44)	(55)
Available-for-sale Securities, Fair Value Disclosure		8,750	8,475
Foreign Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		3,004	2,958
Available-for-sale Securities, Gross Unrealized Gains		180	163
Available-for-sale Securities, Gross Unrealized Losses		(17)	(33)
Available-for-sale Securities, Fair Value Disclosure		3,167	3,088
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		760	793
Available-for-sale Securities, Gross Unrealized Gains		9	11
Available-for-sale Securities, Gross Unrealized Losses		(7)	(9)
Available-for-sale Securities, Fair Value Disclosure		762	795
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		1,331	1,382
Available-for-sale Securities, Gross Unrealized Gains		3	5
Available-for-sale Securities, Gross Unrealized Losses		(36)	(39)
Available-for-sale Securities, Fair Value Disclosure		1,298	1,348
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		1,108	1,077
Available-for-sale Securities, Gross Unrealized Gains		9	7
Available-for-sale Securities, Gross Unrealized Losses		(5)	(9)
Available-for-sale Securities, Fair Value Disclosure		1,112	1,075
Redeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		22	22
Available-for-sale Securities, Gross Unrealized Gains		5	5
Available-for-sale Securities, Gross Unrealized Losses		0	0
Available-for-sale Securities, Fair Value Disclosure		27	27
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis		69	84
Available-for-sale Securities, Gross Unrealized Gains		11	20
Available-for-sale Securities, Gross Unrealized Losses		(2)	(2)
Available-for-sale Securities, Fair Value Disclosure		$ 78	$ 102
[1]	At both March 31, 2017 and December 31, 2016, we held securities for which we previously recognized an immaterial amount of non-credit related impairments in accumulated other comprehensive loss. These securities each had an immaterial amount of net unrealized capital gains at both March 31, 2017 and December 31, 2016.
[2]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 16 for additional information on our accounting for discontinued products). At March 31, 2017, debt and equity securities with a fair value of approximately $2.8 billion, gross unrealized capital gains of $192 million and gross unrealized capital losses of $29 million and, at December 31, 2016, debt and equity securities with a fair value of approximately $2.9 billion, gross unrealized capital gains of $195 million and gross unrealized capital losses of $35 million were included in total debt and equity securities, but support our experience-rated and discontinued products. Changes in net unrealized capital gains (losses) on these securities are not reflected in accumulated other comprehensive income.

Investments - Debt Securities b

Investments - Debt Securities by Maturity (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis		$ 1,498
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Amortized Cost Basis		6,948
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Amortized Cost Basis		4,775
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis		4,686
Available-for-sale Securities, Fair Value Disclosure	[1],[2]	21,853	$ 21,742
Available-for-sale Debt Securities, Amortized Cost Basis		21,106
Debt Securities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure		21,775	21,640
Available-for-sale Securities With Established Maturities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Due To Mature Less Than One Year		1,513
Due to mature one year through five years		7,121
Due to mature after five years through ten years		4,909
Due to mature greater than ten years		$ 5,060
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities		4 years 256 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis		$ 760
Available-for-sale Securities, Fair Value Disclosure		$ 762	795
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities		6 years 329 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis		$ 1,331
Available-for-sale Securities, Fair Value Disclosure		$ 1,298	1,348
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities		1 year 110 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis		$ 1,108
Available-for-sale Securities, Fair Value Disclosure		$ 1,112	$ 1,075
[1]	At both March 31, 2017 and December 31, 2016, we held securities for which we previously recognized an immaterial amount of non-credit related impairments in accumulated other comprehensive loss. These securities each had an immaterial amount of net unrealized capital gains at both March 31, 2017 and December 31, 2016.
[2]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 16 for additional information on our accounting for discontinued products). At March 31, 2017, debt and equity securities with a fair value of approximately $2.8 billion, gross unrealized capital gains of $192 million and gross unrealized capital losses of $29 million and, at December 31, 2016, debt and equity securities with a fair value of approximately $2.9 billion, gross unrealized capital gains of $195 million and gross unrealized capital losses of $35 million were included in total debt and equity securities, but support our experience-rated and discontinued products. Changes in net unrealized capital gains (losses) on these securities are not reflected in accumulated other comprehensive income.

Investments - Unrealized Loss P

Investments - Unrealized Loss Position (Details) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2017USD ($)		Dec. 31, 2016USD ($)
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year	[1]	2,907		3,669
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	[1]	$ 6,165		$ 7,413
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	[1]	$ 134		$ 180
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year	[1]	392		537
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	[1]	$ 342		$ 453
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	[1]	$ 18		$ 28
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	[1]	3,299		4,206
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 6,507	[1]	$ 7,866
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		152	[1]	208
Supporting Discontinued And Experience Rated Products [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		794		890
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 29		$ 35
Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		2,906		3,667
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 6,161		$ 7,410
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 134		$ 180
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		382		529
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 340		$ 450
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 16		$ 26
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		3,288		4,196
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 6,501	[1]	$ 7,860
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		150	[1]	$ 206
Debt Securities [Member] | Supporting Discontinued And Experience Rated Products [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		793
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		27
Debt Securities [Member] | Supporting Remaining Products [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		5,708
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 123
US Government Agencies Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		32		26
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 59		$ 39
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 0		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		0		1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 0		$ 1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 0		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		32		27
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 59	[1]	$ 40
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 0	[1]	$ 0
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		530		865
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 1,539		$ 2,228
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 38		$ 58
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		45		37
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 87		$ 75
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 3		$ 3
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		575		902
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 1,626	[1]	$ 2,303
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 41	[1]	$ 61
Domestic Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		1,210		1,428
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 1,965		$ 2,277
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 35		$ 44
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		79		114
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 78		$ 101
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 9		$ 11
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1,289		1,542
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 2,043	[1]	$ 2,378
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 44	[1]	$ 55
Foreign Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		421		649
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 693		$ 970
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 15		$ 27
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		42		62
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 57		$ 76
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 2		$ 6
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		463		711
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 750	[1]	$ 1,046
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 17	[1]	$ 33
Residential Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		194		188
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 431		$ 455
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 7		$ 8
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		102		104
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 16		$ 17
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 0		$ 1
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		296		292
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 447	[1]	$ 472
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 7	[1]	$ 9
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		280		285
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 1,025		$ 1,038
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 36		$ 39
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		0		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 0		$ 3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 0		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		280		288
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 1,025	[1]	$ 1,041
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 36	[1]	$ 39
Other Asset-Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		239		226
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 449		$ 403
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 3		$ 4
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		114		208
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 102		$ 177
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 2		$ 5
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		353		434
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 551	[1]	$ 580
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 5	[1]	$ 9
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year		1		2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 4		$ 3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses		$ 0		$ 0
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year		10		8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		$ 2		$ 3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses		$ 2		$ 2
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		11		10
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 6	[1]	$ 6
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses		$ 2	[1]	$ 2
[1]	At March 31, 2017 and December 31, 2016, debt and equity securities in an unrealized capital loss position of $29 million and $35 million, respectively, and with related fair value of $794 million and $890 million, respectively, related to experience-rated and discontinued products.

Investments - Unrealized Loss41

Investments - Unrealized Loss Position Maturities (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017		Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 6,507	[1]	$ 7,866
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	152	[1]	208
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6,501	[1]	7,860
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	150	[1]	206
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	794		890
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	29		$ 35
Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	793
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	27
Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,708
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	123
Maturing in Less than one Year [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	214
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Maturing in Less than one Year [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Maturing in Less than one Year [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	207
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Maturing in One Through Five Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,659
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	20
Maturing in One Through Five Years [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	47
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1
Maturing in One Through Five Years [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,612
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	19
Maturing After Five Years Through Ten Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,347
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	31
Maturing After Five Years Through Ten Years [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	252
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	6
Maturing After Five Years Through Ten Years [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,095
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	25
Maturing in Greater Than Ten Years [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,258
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	51
Maturing in Greater Than Ten Years [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	261
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	14
Maturing in Greater Than Ten Years [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	997
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	37
Residential Mortgage Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	447
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	7
Residential Mortgage Backed Securities [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	17
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Residential Mortgage Backed Securities [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	430
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	7
Commercial Mortgage Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,025
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	36
Commercial Mortgage Backed Securities [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	182
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	6
Commercial Mortgage Backed Securities [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	843
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	30
Other Asset-Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	551
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	5
Other Asset-Backed Securities [Member] | Supporting Discontinued And Experience Rated Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	27
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0
Other Asset-Backed Securities [Member] | Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	524
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$ 5
[1]	At March 31, 2017 and December 31, 2016, debt and equity securities in an unrealized capital loss position of $29 million and $35 million, respectively, and with related fair value of $794 million and $890 million, respectively, related to experience-rated and discontinued products.

Investments - Mortgage Loans (D

Investments - Mortgage Loans (Details) - Commercial Real Estate [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Movement in Mortgage Loans on Real Estate [Roll Forward]
New Mortgage Loans	$ 54	$ 12
Mortgage loans fully repaid	48	$ 48
Mortgage Loans on Real Estate	1,507		$ 1,511
Category 1 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	44		45
Category 2 to 4 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	1,446		1,449
Categories 5 and 6 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	17		17
Category 7 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	$ 0		$ 0

Investments - Investment Income

Investments - Investment Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income		$ 270	$ 228
Investment expenses		(10)	(10)
Net Investment Income	[1]	260	218
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net Investment Income		66	45
Debt Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income		190	195
Mortgage Loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income		22	29
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income		$ 58	$ 4
[1]	Net investment income includes $66 million and $45 million for the three months ended March 31, 2017 and 2016, respectively, related to investments supporting our experience-rated and discontinued products.

Investments - Realized Gains (D

Investments - Realized Gains (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Long-term Debt		$ 9,423		$ 20,661
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities		2	$ 9
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments		(331)	8
Realized Investment Gains (Losses)		(333)	(1)
Early Repayment of Senior Debt		750
Debt Securities [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Proceeds On Sales	[1]	1,110	1,546
Gross Realized Capital Gains	[1]	21	32
Gross Realized Capital Losses	[1]	14	$ 31
Debt Issued for Humana Acquisition [Domain]
Schedule of Available-for-sale Securities [Line Items]
Long-term Debt		$ 10,200
[1]	The proceeds on sales and gross realized capital gains and losses exclude the impact of the sales of short-term debt securities which primarily relate to our investments in mutual funds. These investments were excluded from the disclosed amounts because they represent an immaterial amount of aggregate gross realized capital gains or losses and have a high volume of sales activity.

Investments - Variable Interest

Investments - Variable Interest Entities and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	$ 21,922		$ 21,833
Variable Interest Entity Assets	67,571		65,037
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	11,544		10,111
Noncontrolling Interest [Abstract]
Stockholders' Equity Attributable to Noncontrolling Interest	77		62
Net income (loss) attributable to non-controlling interest	2	$ 1
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	459		472
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	1,115		1,116
Variable Interest Entity, Not Primary Beneficiary [Member] | Hedge Funds [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	355		384
Variable Interest Entity, Not Primary Beneficiary [Member] | Private Equity Funds [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	497		454
Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Partnerships [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	263		278
Hedge Funds [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity Assets	34,203		32,926
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	3,464		2,819
Private Equity Funds [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity Assets	26,819		25,368
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	3,353		2,354
Real Estate Partnerships [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity Assets	6,549		6,743
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	$ 4,727		$ 4,938

Fair Value - Fair Value Measure

Fair Value - Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	[1],[2]	$ 21,853		$ 21,742
Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		21,775		21,640
US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,644		1,694
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		5,015		5,138
Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		8,750		8,475
Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		3,167		3,088
Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		762		795
Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,298		1,348
Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,112		1,075
Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		27		27
Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		78		102
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 and Level 2		0	$ 0
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure		21,853		21,742
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		21,775		21,640
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,644		1,694
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		5,015		5,138
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		8,750		8,475
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		3,167		3,088
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		762		795
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,298		1,348
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,112		1,075
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		27		27
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		78		102
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans		1,539		1,540
Bank loans		8		8
Investment contracts with a fixed maturity		8		8
Investment contracts without a fixed maturity		354		364
Long-term debt		10,128		21,468
Carrying (Reported) Amount, Fair Value Disclosure [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans		1,507		1,511
Bank loans		8		8
Equity Securities (Cost Method)	[3]	45		35
Investment contracts with a fixed maturity		8		8
Investment contracts without a fixed maturity		370		378
Long-term debt		9,423		20,661
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure		1,529		1,573
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,482		1,514
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,482		1,514
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		47		59
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans		0		0
Bank loans		0		0
Investment contracts with a fixed maturity		0		0
Investment contracts without a fixed maturity		0		0
Long-term debt		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure		20,155		20,023
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		20,155		20,023
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		162		180
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		5,014		5,137
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		8,671		8,395
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		3,146		3,067
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		762		795
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,267		1,348
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1,106		1,075
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		27		26
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans		0		0
Bank loans		0		0
Investment contracts with a fixed maturity		0		0
Investment contracts without a fixed maturity		0		0
Long-term debt		10,128		21,468
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value Disclosure		169		146
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		138		103
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		1		1
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		79		80
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		21		21
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		31		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		6		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		0		1
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Brokered Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		110		80
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure		31		43
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans		1,539		1,540
Bank loans		8		8
Investment contracts with a fixed maturity		8		8
Investment contracts without a fixed maturity		354		364
Long-term debt		$ 0		$ 0
[1]	At both March 31, 2017 and December 31, 2016, we held securities for which we previously recognized an immaterial amount of non-credit related impairments in accumulated other comprehensive loss. These securities each had an immaterial amount of net unrealized capital gains at both March 31, 2017 and December 31, 2016.
[2]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 16 for additional information on our accounting for discontinued products). At March 31, 2017, debt and equity securities with a fair value of approximately $2.8 billion, gross unrealized capital gains of $192 million and gross unrealized capital losses of $29 million and, at December 31, 2016, debt and equity securities with a fair value of approximately $2.9 billion, gross unrealized capital gains of $195 million and gross unrealized capital losses of $35 million were included in total debt and equity securities, but support our experience-rated and discontinued products. Changes in net unrealized capital gains (losses) on these securities are not reflected in accumulated other comprehensive income.
[3]	It was not practical to estimate the fair value of these cost-method investments as it represents shares of unlisted companies.

Fair Value - Separate Accounts

Fair Value - Separate Accounts Fair Value (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		$ 4,244	$ 3,991
Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets	[1]	4,016	3,898
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets	[1]	931	932
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets	[1]	3,083	2,966
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets	[1]	2	0
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		3,274	3,144
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		784	766
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		2,488	2,378
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		2	0
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		153	172
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		147	166
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		6	6
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		0	0
Common/Collective Trusts [Member] | Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		589	582
Common/Collective Trusts [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		0	0
Common/Collective Trusts [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		589	582
Common/Collective Trusts [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		0	0
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account assets		$ 228	$ 93
[1]	Excludes $228 million and $93 million of cash and cash equivalents and other receivables at March 31, 2017 and December 31, 2016, respectively.

Fair Value - Balance Sheet Offs

Fair Value - Balance Sheet Offsetting (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	[1]	$ 0	$ 0
Derivative, Collateral, Obligation to Return Securities		17	17
Derivative, Collateral, Obligation to Return Cash		0	0
Derivative Asset, Fair Value, Amount Offset Against Collateral		17	17
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Gross	[1]	0	0
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Securities		17	17
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Collateral, Obligation to Return Cash		0	0
Derivative Asset, Securities Purchased under Agreements to Resell, Securities Borrowed, Amount Offset Against Collateral		$ 17	$ 17
[1]	There were no amounts offset in our Consolidated Balance Sheets at March 31, 2017 or December 31, 2016.

Health Care and Other Insuran49

Health Care and Other Insurance Liabilities - Health Care Costs Payable (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Health care costs payable		$ 6,432		$ 6,558
Add Components Of Incurred Health Care Costs [Abstract]
Policyholder Benefits and Claims Incurred, Net, Health	[1]	10,916	$ 10,848
Health Care [Member]
Health care costs payable		6,432	6,825	6,558	$ 6,306
Reinsurance Recoverables on Unpaid Losses, Gross		3	2	5	4
Premium Deficiency Reserves		110	0
Short-Duration Liability for Unpaid Claims, Health Care		6,319	6,823	$ 6,553	$ 6,302
Add Components Of Incurred Health Care Costs [Abstract]
Current Year Claims and Claims Adjustment Expense		11,420	11,475
Prior Year Claims and Claims Adjustment Expense		(614)	(627)
Policyholder Benefits and Claims Incurred, Net, Health	[2]	10,806	10,848
Less Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year		6,298	5,929
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years		4,742	4,398
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid		11,040	$ 10,327
Premium Deficiency Reserve		110
Short-duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net		$ 5,500
[1]	Health care costs have been reduced by Insured member co-payments related to our mail order and specialty pharmacy operations of $34 million for each of the three month periods ended March 31, 2017 and 2016.
[2]	Total incurred health care costs exclude from the table above $110 million related to the premium deficiency reserve recorded during the three months ended March 31, 2017 for the 2017 coverage year on our individual Commercial products.

Health Care and Other Insuran50

Health Care and Other Insurance Liabilities - Other Liabilities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Add Claims Incurred for Other Liabilities [Abstract]
Policyholder Benefits and Claims Incurred, Net, Other	$ 545	$ 529
Group Insurance [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,905	1,840	$ 1,904	$ 1,819
Reinsurance Recoverables on Unpaid Losses, Gross	26	27	26	27
Short-Duration Liability for Unpaid Claims, Other Insurance	1,879	1,813	$ 1,878	$ 1,792
Add Claims Incurred for Other Liabilities [Abstract]
Current Year Claims and Claims Adjustment Expense	131	137
Prior Year Claims and Claims Adjustment Expense	5	4
Policyholder Benefits and Claims Incurred, Net, Other	136	141
Less Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	1	1
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	134	119
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	$ 135	$ 120

Health Care and Other Insuran51

Health Care and Other Insurance Liabilities - Reconciliation of Unpaid Claims (Details) - Group Insurance [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 1,905	$ 1,904	$ 1,840	$ 1,819
Term Life Unpaid Claims	472		485
Other Unpaid Claims Liabilities	118		122
Total Liability for Unpaid Claims	$ 2,495		$ 2,447

Health Care Reform (Details)

Health Care Reform (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Reinsurance Recoverable Under Health Care Reform	$ 178		$ 202
Net health care reform risk adjustment payable (receivable)	(734)		(690)
Health care reform risk corridor net	1		(10)
Health Insurer Fee	0	$ 214
Reinsurance contribution under Health Care Reform	0	$ 29
Current [Member]
Reinsurance Recoverable Under Health Care Reform	166		202
Net health care reform risk adjustment payable (receivable)	(696)		(690)
Health care reform risk corridor net	1		(10)
Long-term [Member]
Reinsurance Recoverable Under Health Care Reform	12		0
Net health care reform risk adjustment payable (receivable)	(38)		0
Health care reform risk corridor net	0		$ 0
Maximum [Member]
Health care reform risk corridor net	$ 529

Debt (Details)

Debt (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Federal Home Loan Bank, Maximum Amount Available		$ 801
Federal Home Loan Bank, Amount Outstanding		0		$ 0
Derivative, Notional Amount		500
Long-term Debt		9,423		20,661
Current portion of long-term debt		1,249		1,634
Long-term debt, less current portion		8,174		19,027
Loss on early extinguishment of long-term debt	[1]	(246)	$ 0
Early Repayment of Senior Debt		750
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		336
Senior Notes, 5.95%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	[2]	$ 0		$ 386
Debt Instrument, Interest Rate, Stated Percentage		5.95%		5.95%
Senior Notes, 1.75%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	[2]	$ 250		$ 250
Debt Instrument, Interest Rate, Stated Percentage		1.75%		1.75%
Senior Notes, 1.5%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	[2]	$ 499		$ 499
Debt Instrument, Interest Rate, Stated Percentage		1.50%		1.50%
Variable Rate [Domain]
Debt Instrument [Line Items]
Long-term Debt	[2]	$ 499		$ 499
Debt Instrument, Face Amount		500
Senior Notes, 1.7%, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 998		$ 997
Debt Instrument, Interest Rate, Stated Percentage		1.70%		1.70%
Debt Instrument, Face Amount		$ 1,000
Senior Notes, 1.9%, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 1,642
Debt Instrument, Interest Rate, Stated Percentage		1.90%		1.90%
Debt Instrument, Face Amount		$ 1,700
Senior Notes, 2.2%, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 374		$ 374
Debt Instrument, Interest Rate, Stated Percentage		2.20%		2.20%
Senior Notes, 3.95%, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 745
Debt Instrument, Interest Rate, Stated Percentage		3.95%		3.95%
Loss on early extinguishment of debt (after tax)		$ 35
Loss on early extinguishment of long-term debt		54
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		13
Senior Notes, 2.4%, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 1,839
Debt Instrument, Interest Rate, Stated Percentage		2.40%		2.40%
Debt Instrument, Face Amount		$ 1,900
Senior Notes, 5.45%, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 658		$ 661
Debt Instrument, Interest Rate, Stated Percentage		5.45%		5.45%
Senior Notes, 4.125%, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 496		$ 495
Debt Instrument, Interest Rate, Stated Percentage		4.125%		4.125%
Senior Notes, 2.75%, Due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 986		$ 986
Debt Instrument, Interest Rate, Stated Percentage		2.75%		2.75%
Senior Notes, 2.8%, Due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 1,290		$ 1,290
Debt Instrument, Interest Rate, Stated Percentage		2.80%		2.80%
Debt Instrument, Face Amount		$ 1,300
Senior notes, 3.5%, due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 743		$ 742
Debt Instrument, Interest Rate, Stated Percentage		3.50%		3.50%
Senior notes, 3.2%, due 2026 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 2,771
Debt Instrument, Interest Rate, Stated Percentage		3.20%		3.20%
Debt Instrument, Face Amount		$ 2,800
Senior notes, 4.25%, due 2036 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 1,480
Debt Instrument, Interest Rate, Stated Percentage		4.25%		4.25%
Debt Instrument, Face Amount		$ 1,500
Senior Notes, 6.625%, Due 2036 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 765		$ 765
Debt Instrument, Interest Rate, Stated Percentage		6.625%		6.625%
Senior Notes, 6.75%, Due 2037 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 527		$ 527
Debt Instrument, Interest Rate, Stated Percentage		6.75%		6.75%
Senior Notes, 4.5%, Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 478		$ 478
Debt Instrument, Interest Rate, Stated Percentage		4.50%		4.50%
Senior Notes, 4.125%, Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 489		$ 489
Debt Instrument, Interest Rate, Stated Percentage		4.125%		4.125%
Senior Notes, 4.75%, Due 2044 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 371		$ 371
Debt Instrument, Interest Rate, Stated Percentage		4.75%		4.75%
Senior Notes, 4.375%, Due 2046 [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 0		$ 2,375
Debt Instrument, Interest Rate, Stated Percentage		4.375%		4.375%
Debt Instrument, Face Amount		$ 2,400
Debt Issued for Humana Acquisition [Domain]
Debt Instrument [Line Items]
Long-term Debt		10,200
Debt Instrument, Face Amount		$ 13,000
Debt Instrument, Redemption Price, Percentage		101.00%
Debt Subject to Mandatory Redemption [Domain]
Debt Instrument [Line Items]
Loss on early extinguishment of debt (after tax)		$ 125
Loss on early extinguishment of long-term debt		192
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		323
Terminated Swaps [Domain]
Debt Instrument [Line Items]
Derivative, Counterparty Payment		348
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		342
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period		$ 0	$ 0
[1]	In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:•In the three months ended March 31, 2017, we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020.•In the three months ended March 31, 2017, we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations.•We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.
[2]	At March 31, 2017, our 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and our floating rate senior notes, due December 2017 are each classified as current in our Consolidated Balance Sheet. At December 31, 2016, our 5.95% senior notes due March 2017, 1.75% senior notes due May 2017, 1.5% senior notes due November 2017 and floating rate senior notes due December 2017 are each classified as current in our Consolidated Balance Sheet.

Debt - Short-term Debt (Details

Debt - Short-term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Derivative, Notional Amount	$ 500
Senior Notes, 5.95%, Due 2017 [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.95%	5.95%
Senior Notes, 2.2%, Due 2019 [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.20%	2.20%
Senior Notes, 1.75%, Due 2017 [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%	1.75%
Senior Notes, 1.5%, Due 2017 [Member]
Short-term Debt [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.50%	1.50%

Debt - Line of Credit (Details)

Debt - Line of Credit (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Line of Credit Facility [Line Items]
Debt Instrument, Unused Borrowing Capacity, Amount	$ 2,000
Additional Credit Facility	500
Maximum Amount Of Letters Of Credit Issuable	$ 200
Facility fee (in hundredths)	0.10%
Term Loan Principal	$ 3,200
Minimum [Member]
Line of Credit Facility [Line Items]
Level the debt to capitalization must be below under the facility agreement	50.00%
Minimum [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Facility fee (in hundredths)	0.05%
Maximum [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Facility fee (in hundredths)	0.15%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period	$ 0	$ 0
Unsecured revolving credit agreement	1,500
Bridge Loan [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period	0
Term Loan [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period	$ 0

Pension and Other Postretirem56

Pension and Other Postretirement Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Amortization of prior service credit	$ 0	$ 0
Interest cost	51	65
Expected Return on Plan Assets	(95)	(97)
Amortization of net actuarial losses	16	15
Net periodic benefit (income) cost	(28)	(17)
OPEB Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Amortization of prior service credit	(1)	(1)
Interest cost	2	3
Expected Return on Plan Assets	(1)	(1)
Amortization of net actuarial losses	1	1
Net periodic benefit (income) cost	$ 1	$ 2
2017 Pension New Methodology [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	3.51%
2017 Pension Original Methodology [Domain] [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	4.22%
After Income Tax Expense (Benefit) [Member] | 2017 Pension Estimated Three Month Impact [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit (income) cost	$ 6
After Income Tax Expense (Benefit) [Member] | 2017 Pension Estimated Full Year Impact [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit (income) cost	26
Before Income Tax Expense (Benefit) [Member] | 2017 Pension Estimated Three Month Impact [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit (income) cost	10
Before Income Tax Expense (Benefit) [Member] | 2017 Pension Estimated Full Year Impact [Domain]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit (income) cost	$ 41

Shareholders' Equity - Repurcha

Shareholders' Equity - Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2014	Jun. 30, 2014
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount	$ 4,000	$ 1,000	$ 1,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	1,800
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 3,300
Accelerated Share Repurcase (Percent Initially Delivered)	80.00%
Accelerated Share Repurchases, Initial Price Paid Per Share	$ 126.34
Stock Repurchased During Period, Value	$ 3,300
Third Party - One [Domain]
Equity, Class of Treasury Stock [Line Items]
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 1,700
Repurchases of common shares (in shares)	10.4
Third Party - Two [Domain]
Equity, Class of Treasury Stock [Line Items]
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 1,700
Repurchases of common shares (in shares)	10.4
Retained Earnings [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value	$ 2,639
Common Stock Including Additional Paid in Capital [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value	661
Amount to reclassify to retained earnings [Domain]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value	$ 700

Shareholders' Equity - Dividend

Shareholders' Equity - Dividends (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)$ / shares
Class of Stock Disclosures [Abstract]
Dividends Amount Per Share | $ / shares	$ 0.50
Dividends | $	$ 166

Shareholders' Equity - Stock Un

Shareholders' Equity - Stock Units (Details) - $ / shares shares in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0.3
Minimum Vesting Percentage During Performance Period For Performance Stock Units	0.00%
Maximum Vesting Percentage During Performance Period For Performance Stock Units	200.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	0.4
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	2.1
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%
Estimated Fair Market Value (per unit)	$ 32.30	$ 34.33
Expected Term (in years)	7 years 77 days	7 years 40 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate	26.52%	32.90%
Risk Free Interest Rate	2.22%	1.52%
Dividend Yield	1.71%	0.91%
Initial Price	$ 125.27	$ 103.45

Shareholders' Equity - Statutor

Shareholders' Equity - Statutory Accounting Practices (Details) - Insurance and HMO [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval	$ 1,400
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	460
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 10,300	$ 10,400

Other Comprehensive (Loss) In61

Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		$ (1,552)
Other comprehensive (loss) income		276	$ 75
Balance at end of period		(1,276)
Long-term Debt		9,423		$ 20,661
Early Repayment of Senior Debt		750
Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net		336
Accumulated Other Comprehensive Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		(1,552)	(1,330)
Balance at end of period		(1,276)	(1,255)
Debt Issued for Humana Acquisition [Domain]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Long-term Debt		10,200
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax		(2)	(4)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax		(2)	(5)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[1]	16	19
Net unrealized gains (losses)	[1]	(1)	(3)
Net unrealized gains (losses) on securities, reclassification of gains to earnings	[1],[2]	(1)	(4)
Other comprehensive (loss) income	[1]	0	1
Balance at end of period	[1]	16	20
Other Securities [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax		92	317
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax		25	(23)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		297	312
Net unrealized gains (losses)		60	206
Net unrealized gains (losses) on securities, reclassification of gains to earnings	[2]	16	(15)
Other comprehensive (loss) income			221
Balance at end of period		341	533
Foreign Currency and Derivative Gain (Loss) [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax		(2)	(246)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax		(343)	(6)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		(235)	(74)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax		(1)	(160)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	[3]	(223)	(3)
Other comprehensive (loss) income			(157)
Balance at end of period		(13)	(231)
Pension and OPEB Plan [Member]
Comprehensive Income Loss [Line Items]
Amortization of net actuarial losses, before tax		(17)	(16)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, before Tax		(2)	(1)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		(1,630)	(1,587)
Less: amortization of net actuarial losses	[4]	(11)	(11)
Less: Amortization of prior service cost	[4]	1	1
Other comprehensive (loss) income		10	10
Balance at end of period		$ (1,620)	$ (1,577)
[1]	Represents specifically identified unrealized gains and losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.
[2]	Reclassifications out of accumulated other comprehensive income for specifically identified previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statements of Income.
[3]	Reclassifications out of accumulated other comprehensive income for specifically identified foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the specifically identified effective portion of derivatives related to interest rate swaps which are reflected in interest expense. During the three months ended March 31, 2017, we redeemed the entire $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes and the entire $750 million aggregate principal amount outstanding of the senior notes due 2020 and reclassified out of accumulated other comprehensive income the remaining $336 million pre-tax unrealized hedge losses as a realized capital loss within the Consolidated Statements of Income. Refer to Note 8 for additional information.
[4]	Reclassifications out of accumulated other comprehensive income for specifically identified pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 9 for additional information.

Earnings Per Common Share (Deta

Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to Aetna		$ (381)	$ 737
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares used to compute basic EPS (in shares)		343.8	350.7
Dilutive effect of outstanding stock-based compensation awards (in shares)		0	3.1
Weighted average shares used to compute diluted EPS (in shares)		343.8	353.8
Basic EPS (in dollars per share)		$ (1.11)	$ 2.10
Diluted EPS (in dollars per share)		$ (1.11)	$ 2.08
Stock Appreciation Rights (SARs) [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	[1]	0	0.2
Other Securities [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	[2]	0.9	0.8
In-the-money anti-dilutive stock based compensation [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Dilutive effect of outstanding stock-based compensation awards (in shares)		2.4
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	[3]	10.6	0
[1]	SARs are excluded from the calculation of diluted EPS if the exercise price is greater than the average market price of Aetna common shares during the period (i.e., the awards are anti-dilutive).
[2]	PSUs, certain market stock units with performance conditions, and performance stock appreciation rights are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period.
[3]	In periods when we report a net loss attributable to Aetna, in-the-money stock-based compensation awards are excluded from our calculation of diluted EPS because their inclusion would have an anti-dilutive effect. Therefore we excluded from our calculation of diluted EPS for the three months ended March 31, 2017 in-the-money stock-based compensation awards which would have increased our weighted-average shares used to compute diluted EPS by 2.4 million shares.

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 31, 2017	Jun. 30, 2014	Dec. 31, 2013	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Loss Contingency, Discounted Amount of Insurance-related Assessment Liability	$ 231
Loss Contingency Accrual, Insurance-related Assessment, Discount Rate	3.50%
Loss Contingency, Undiscounted Amount of Insurance-related Assessment Liability	$ 347
Litigation Settlement, Expense				$ 120
Settlement of class action litigation, after-tax				$ 78
Release of litigation-related reserve, pre-tax		$ 103
Charges for changes in our life claim payments practices, net of tax			$ 36
Charge for changes in our life claim payment practices			$ 55

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers		$ 15,238	$ 15,476
Pre-tax adjusted earnings	[1],[2]	1,451	1,417
Health Care [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers		14,667	14,908
Pre-tax adjusted earnings	[2]	1,476	1,456
Group Insurance [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers		556	551
Pre-tax adjusted earnings	[2]	33	25
Large Case Pension [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers		15	17
Pre-tax adjusted earnings	[2]	4	1
Corporate Financing [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers		0	0
Pre-tax adjusted earnings	[2]	$ (62)	$ (65)
[1]	In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:•In the three months ended March 31, 2017, we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020.•In the three months ended March 31, 2017, we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations.•We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.
[2]	Pre-tax adjusted earnings (loss) excludes net realized capital gains or losses, amortization of other acquired intangible assets and the other items described in the reconciliation below.

Segment Information - Reconcili

Segment Information - Reconciliation of Pre-tax Adjusted Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reconciliation [Abstract]
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	[1]	$ (628)	$ 1,289
Income (Loss) Attributable to Noncontrolling Interest	[1]	3	1
Income Before Income Tax	[1]	(631)	1,288
Loss on early extinguishment of long-term debt	[1]	246	0
Loss Contingency, Insurance-related Assessment	[1]	231	0
Transaction and integration-related costs	[1]	1,212	66
Amortization of Intangible Assets	[1]	60	62
Net Realized Capital Gains (Losses)	[1]	333	1
Pre-tax adjusted earnings	[1],[2]	1,451	$ 1,417
Long-term Debt		9,423		$ 20,661
Early Repayment of Senior Debt		750
Debt Issued for Humana Acquisition [Domain]
Segment Reconciliation [Abstract]
Long-term Debt		10,200
Other 2016 Senior Notes [Domain]
Segment Reconciliation [Abstract]
Long-term Debt		$ 2,800
[1]	In addition to net realized capital losses and gains and amortization of other acquired intangible assets, the following other items are excluded from adjusted earnings and pre-tax adjusted earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:•In the three months ended March 31, 2017, we incurred losses on the early extinguishment of long-term debt due to (a) the mandatory redemption of the $10.2 billion aggregate principal amount of the Special Mandatory Redemption Notes following the termination of the Merger Agreement and (b) the early redemption of $750 million aggregate principal amount of our outstanding senior notes due 2020.•In the three months ended March 31, 2017, we recorded an expense for estimated future guaranty fund assessments related to Penn Treaty, which was placed in rehabilitation in 2009 and placed in liquidation in March 2017. This expense does not directly relate to the underwriting or servicing of products for customers and is not directly related to the core performance of our business operations.•We incurred transaction and integration-related costs during the three months ended March 31, 2017 and 2016 primarily related to the Humana Transaction. Transaction costs include costs associated with the termination of the Merger Agreement, the termination of our agreement to sell certain assets to Molina Healthcare, Inc. and advisory, legal and other professional fees which are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. Transaction costs also include the negative cost of carry associated with the debt financing that we obtained in June 2016 for the Humana Transaction. Prior to the mandatory redemption of the Special Mandatory Redemption Notes, the negative cost of carry associated with these senior notes was excluded from adjusted earnings and pre-tax adjusted earnings. The negative cost of carry associated with the $2.8 billion aggregate principal amount of our senior notes issued in June 2016 that are not subject to mandatory redemption (the “Other 2016 Senior Notes”) was excluded from adjusted earnings and pre-tax adjusted earnings through the date of the termination of the Merger Agreement. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense and net investment income. Subsequent to the termination of the Merger Agreement, the interest expense and net investment income associated with the Other 2016 Senior Notes were no longer excluded from adjusted earnings and pre-tax adjusted earnings.
[2]	Pre-tax adjusted earnings (loss) excludes net realized capital gains or losses, amortization of other acquired intangible assets and the other items described in the reconciliation below.

Discontinued Products (Details)

Discontinued Products (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016	Mar. 31, 2017		Dec. 31, 2016
Assets:
Investments					$ 25,001		$ 24,879
Total assets					56,351		69,146
Liabilities:
Future policy benefits					5,908		5,929
Total liabilities					42,013		51,203
Discontinued Products [Member]
Reserve For Discontinued Products [Roll Forward]
Reserve, beginning of period		$ 962	[1]	$ 1,067
Operating income (loss)		16		(13)
Net realized capital gains		14		12
Reserve, end of period		992	[1]	1,066
Assets:
Investments	[1]				2,856		2,929
Other Assets	[1]				109		104
Receivable from continuing products	[1],[2]				562		554
Total assets	[1]				3,527		3,587
Liabilities:
Future policy benefits	[1]				2,282		2,326
Reserve for anticipated future losses on discontinued products		962	[1]	1,067	992	[1]	962	[1]
Current And Deferred Income Tax Liabilities	[1]				38		42
Other Liabilities	[1],[3]				215		257
Total liabilities	[1]				3,527		3,587
Scheduled Contract Maturities, Settlements And Benefit Payments		$ 84		$ 94
Debt And Equity Securities Available For Sale [Member]
Assets:
Investments					21,853		21,742
Debt And Equity Securities Available For Sale [Member] | Discontinued Products [Member]
Assets:
Investments	[1]				1,872		1,913
Mortgage Loans [Member]
Assets:
Investments					1,507		1,511
Mortgage Loans [Member] | Discontinued Products [Member]
Assets:
Investments	[1]				369		370
Other Investments [Member]
Assets:
Investments					1,641		1,626
Other Investments [Member] | Discontinued Products [Member]
Assets:
Investments	[1]				$ 615		$ 646
[1]	Assets supporting the discontinued products are distinguished from assets supporting continuing products.
[2]	At the time of discontinuance, a receivable from Large Case Pensions’ continuing products was established on the discontinued products Balance Sheet. This receivable represented the net present value of anticipated cash shortfalls in the discontinued products, which will be funded from continuing products. Interest on the receivable is accrued at the discount rate that was used to calculate the reserve. The offsetting payable, on which interest is similarly accrued, is reflected in continuing products. Interest on the payable generally offsets investment income on the assets available to fund the shortfall. These amounts are eliminated in consolidation.
[3]	Net unrealized capital gains on the available-for-sale debt securities are included in other liabilities and are not reflected in consolidated shareholders’ equity.