Aetna 10-Q 28 Apr 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Entity Information [Line Items]
Entity Registrant Name	AETNA INC /PA/
Entity Central Index Key	1122304
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding	349.2

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Revenue:
Health care premiums	$12,940.10		$11,911.70
Other premiums	538		561.6
Fees and other revenue	1,375	[1]	1,248.80	[1]
Net investment income	232.9		244.2
Net realized capital gains (losses)	8.1		28.5
Total revenue	15,094.10		13,994.80
Benefits and expenses:
Health care costs	10,240.50	[2]	9,576.30	[2]
Current and future benefits	528.1		578.7
Operating expenses:
Selling expenses	414.9		402.8
General and administrative expenses	2,401.80	[3]	2,047.60	[3]
Total operating expenses	2,816.70		2,450.40
Interest expense	79		85.6
Amortization of other acquired intangible assets	63.2		62.2
Loss on early extinguishment of long-term debt	0		91.9
Total benefits and expenses	13,727.50		12,845.10
Income before income taxes	1,366.60		1,149.70
Income taxes:
Current	647		418.5
Deferred	-56.7		61.8
Total income taxes	590.3		480.3
Net Income including non-controlling interests	776.3		669.4
Less: Net income (loss) attributable to non-controlling interests	-1.2		3.9
Net income attributable to Aetna	777.5		665.5
Earnings per common share:
Basic	$2.22		$1.84
Diluted	$2.20		$1.82
Administrative Services Contract Member Co Payments And Plan Sponsor Reimbursements	24.1		21.8
Pharmaceutical And Processing Costs	299.3		275.4
Insured Member Co Payments	$33.40		$30.60
[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 $24.1 million and $21.8 million (net of pharmaceutical and processing costs of $299.3 million and $275.4 million) for the three months ended March 31, 2015 and 2014, respectively.
[2]	Health care costs have been reduced by Insured member co-payments related to our mail order and specialty pharmacy operations of $33.4 million and $30.6 million for the three months ended March 31, 2015 and 2014, respectively.
[3]	The three months ended March 31, 2015 include $45.6 million of transaction and integration-related costs related to the acquisitions of Coventry Health Care, Inc. (“Coventry”), the InterGlobal group (“InterGlobal”) and bSwift LLC (“bswift”). The three months ended March 31, 2014 include $63.7 million of integration-related costs related to the acquisition of Coventry.

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Net Income including non-controlling interests	$776.30		$669.40
Other comprehensive (loss) income	78.2		125.7
Comprehensive Income including non-controlling interests	854.5		795.1
Comprehensive income (loss) attributable to non-controlling interests	-1.2		3.9
Comprehensive Income attributable to Aetna	855.7		791.2
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Net unrealized gains (losses)	-2.2	[1]	1.1	[1]
Less: reclassification of gains (losses) to earnings	1.6	[1]	0.4	[1]
Other comprehensive (loss) income	-3.8	[1]	0.7	[1]
Other Securities [Member]
Net unrealized gains (losses)	77.9		137.2
Less: reclassification of gains (losses) to earnings	-7.2		-3.3
Other comprehensive (loss) income	85.1		140.5
Foreign Currency and Derivative Gain (Loss) [Member]
Net unrealized gains (losses)	-13.9		-12.5
Less: Foreign currency and derivatives reclassification of losses to earnings	-1		10.1
Other comprehensive (loss) income	-12.9		-22.6
Pension and OPEB Plan [Member]
Amortization of net actuarial losses	-10.5		-7.7
Amortization of prior service cost	0.7		0.6
Other comprehensive (loss) income	$9.80		$7.10
[1]	Represents unrealized (losses) gains 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_Statement_of_Comp

Consolidated Statement of Comprehensive Income (Paranthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	($3.40)	[1]	$1.70	[1]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	2.4	[1]	0.6	[1]
Other Securities [Member]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	119.9		211
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	-11		-5
Foreign Currency and Derivative Gain (Loss) [Member]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	-21.4		-19.2
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax	-1.5		15.6
Pension and OPEB Plan [Member]
Amortization of net actuarial losses, before tax	-16.1		-11.9
Amortization of prior service credit, before tax	$1		$1
[1]	Represents unrealized (losses) gains 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_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$1,915.80	$1,420.40
Investments	2,374.10	2,595.20
Premiums receivable, net	2,153.50	1,623
Other receivables, net	2,244	2,065.90
Accrued investment income	224.4	223.9
Collateral received under securities loan agreements	864	826.9
Income taxes receivable	0	372.7
Deferred income taxes	493.1	443
Other current assets	3,122.40	2,193
Total current assets	13,391.30	11,764
Long-term investments	22,587.60	22,193.90
Reinsurance recoverables	755.3	751.4
Goodwill	10,641.50	10,613.20
Other acquired intangible assets, net	1,880.40	1,948.30
Property and equipment, net	662.6	669.8
Other long-term assets	1,188.70	1,130
Separate Account Assets	4,448	4,331.50
Total assets	55,555.40	53,402.10
Current liabilities:
Health care costs payable	6,087.20	5,621.10
Future policy benefits	699.8	705.9
Unpaid claims	744.7	745.3
Unearned premiums	627.6	519.5
Policyholders' funds	2,138.90	1,984.50
Collateral payable under securities loan agreements	864	1,028.60
Short-term debt	297	500
Current portion of long-term debt	0	229.3
Income taxes payable	322.3	0
Accrued expenses and other current liabilities	4,886.40	4,022.30
Total current liabilities	16,667.90	15,356.50
Future policy benefits	6,399.50	6,427.40
Unpaid claims	1,649.70	1,650.60
Policyholders' funds	1,181.10	1,163.20
Long-term debt, less current portion	7,846.10	7,852
Deferred income taxes	914	867.5
Other long-term liabilities	1,330.20	1,201.60
Separate Accounts liabilities	4,448	4,331.50
Total liabilities	40,436.50	38,850.30
Commitments and contingencies (Note 12)
Shareholders' equity:
Common stock ($.01 par value; 2.5 billion shares authorized and 349.2 million shares issued and outstanding in 2015; 2.6 billion shares authorized and 349.8 million shares issued and outstanding in 2014) and additional paid-in capital	4,539.70	4,542.20
Retained earnings	11,546	11,051.70
Accumulated other comprehensive loss	-1,033.10	-1,111.30
Total Aetna shareholders' equity	15,052.60	14,482.60
Non-controlling Interests	66.3	69.2
Total equity	15,118.90	14,551.80
Total liabilities and equity	$55,555.40	$53,402.10

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Paranthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	2,500,000,000	2,600,000,000
Common Stock, Shares, Issued	349,200,000	349,800,000
Common Stock, Shares, Outstanding	349,200,000	349,800,000

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (Unaudited) (USD $)	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]
In Millions, except Share data, unless otherwise specified
Balance at beginning of period at Dec. 31, 2013			$4,382.20	$10,555.40	($912.10)	$14,025.50
Total equity at beginning of period at Dec. 31, 2013	14,078.20
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2013							52.7
Balance at beginning of period (in shares) at Dec. 31, 2013		362,200,000
Comprehensive income:
Net income attributable to Aetna	665.5	0	0	665.5	0	665.5
Net income (loss) attributable to non-controlling interest	3.9						3.9
Net Income including non-controlling interests	669.4
Other increases (decreases) in noncontrolling interests	0.8	0	0	0	0	0	0.8
Other comprehensive (loss) income	125.7	0	0	0	125.7	125.7	0
Common shares issued for benefit plans, including tax benefits, net of employee tax withholdings	32.4		32.4	0	0	32.4	0
Common shares issued for benefit plans, including tax benefits, net of employee tax withholdings (in shares)		1,700,000
Repurchases of common shares	-465		-0.1	-464.9	0	-465	0
Repurchases of common shares (in shares)		-6,500,000
Dividends declared	-80.5	0	0	-80.5	0	-80.5	0
Total equity at end of period at Mar. 31, 2014	14,361
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Mar. 31, 2014							57.4
Balance at end of period at Mar. 31, 2014			4,414.50	10,675.50	-786.4	14,303.60
Balance at end of period (in shares) at Mar. 31, 2014		357,400,000
Balance at beginning of period at Dec. 31, 2014	14,482.60		4,542.20	11,051.70	-1,111.30	14,482.60
Total equity at beginning of period at Dec. 31, 2014	14,551.80
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2014	69.2						69.2
Balance at beginning of period (in shares) at Dec. 31, 2014	349,800,000	349,800,000
Comprehensive income:
Net income attributable to Aetna	777.5	0	0	777.5	0	777.5
Net income (loss) attributable to non-controlling interest	-1.2						-1.2
Net Income including non-controlling interests	776.3
Other increases (decreases) in noncontrolling interests	-1.7	0	0	0	0	0	-1.7
Other comprehensive (loss) income	78.2	0	0	0	78.2	78.2	0
Common shares issued for benefit plans, including tax benefits, net of employee tax withholdings	-2.4		-2.4	0	0	-2.4	0
Common shares issued for benefit plans, including tax benefits, net of employee tax withholdings (in shares)		1,500,000
Repurchases of common shares	-196.3		-0.1	-196.2	0	-196.3	0
Repurchases of common shares (in shares)	-2,100,000	-2,100,000
Dividends declared	-87	0	0	-87	0	-87	0
Total equity at end of period at Mar. 31, 2015	15,118.90
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Mar. 31, 2015	66.3						66.3
Balance at end of period at Mar. 31, 2015	$15,052.60		$4,539.70	$11,546	($1,033.10)	$15,052.60
Balance at end of period (in shares) at Mar. 31, 2015	349,200,000	349,200,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net Income including non-controlling interests	$776.30	$669.40
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized capital (gains) losses	-8.1	-28.5
Depreciation and amortization	164	154.7
Debt fair value amortization	-7.8	-15.1
Equity in earnings of affiliates, net	-9.7	-20.6
Stock-based compensation expense	49.8	38.8
Amortization of net investment premium	22.3	18.3
Loss on early extinguishment of long-term debt	0	91.9
Changes in assets and liabilities:
Accrued investment income	-0.5	-1.5
Premiums due and other receivables	-830.4	-337
Income taxes	629.5	420.3
Other assets and other liabilities	128.7	-70.6
Health care and insurance liabilities	564.5	501.4
Other, net	-5.2	0.7
Net cash provided by operating activities	1,473.40	1,422.20
Cash flows used for investing activities:
Proceeds from sales and maturities of investments	2,608.90	2,143.60
Cost of investments	-2,493.90	-2,303.60
Additions to property, equipment and software	-82.3	-93.8
Cash used for acquisitions, net of cash acquired	-10.9	0
Net cash provided by (used for) investing activities	21.8	-253.8
Cash flows used for financing activities:
Repayment of long-term debt	-228.8	-839.7
Issuance of long-term debt	0	741.9
Net (repayment) issuance of short-term debt	-203	0
Deposits and interest credited for investment contracts	0.9	1.1
Withdrawals of investment contracts	-8.5	-1
Common Shares Issued Under Benefit Plans	-79.9	-17
Stock-based compensation tax benefits	27.7	13.9
(Settlements) proceeds from repurchase agreements	-201.7	156.2
Common shares repurchased	-196.3	-465
Dividends paid to shareholders	-87.1	-81.6
Collateral on interest rate swaps	-21.4	-16.7
(Distributions) contributions, non-controlling interests	-1.7	1.3
Net cash used for financing activities	-999.8	-506.6
Net increase (decrease) in cash and cash equivalents	495.4	661.8
Cash and cash equivalents, beginning of period	1,420.40	1,412.30
Cash and cash equivalents, end of period	1,915.80	2,074.10
Supplemental cash flow information:
Interest paid	47.6	72.9
Income taxes paid		46.2
Income tax refunds	($66.80)

Organization

Organization	3 Months Ended
	Mar. 31, 2015
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 products and services, such as Accountable Care Solutions, that complement and enhance our medical products. Medical products include point-of-service (“POS”), preferred provider organization (“PPO”), health maintenance organization (“HMO”) and indemnity benefit plans. Medical products also include health savings accounts (“HSAs”) and Aetna HealthFund®, consumer-directed health plans that combine traditional POS or PPO and/or dental coverage, subject to a deductible, with an accumulating benefit account (which may be funded by the plan sponsor and/or the member in the case of HSAs). 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 network in select geographies.
	•	Group Insurance primarily includes group life insurance and group disability products. Group life insurance products are offered on an Insured basis, and include basic and supplemental group term life, group universal life, supplemental or voluntary programs and accidental death and dismemberment coverage. Group disability products consist primarily of short-term and long-term disability products (and products which combine both), which are offered to employers on both an Insured and an ASC basis, and absence management services offered to employers, which include short-term and long-term disability administration and leave management. Group Insurance also includes long-term care products that were offered primarily on an Insured basis, which provide benefits covering the cost of care in private home settings, adult day care, assisted living or nursing facilities. 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 15 beginning on page 33 for additional information).

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies
	2	Summary of Significant Accounting Policies
	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 accompanying unaudited consolidated financial statements and related notes should be read in conjunction with the consolidated financial statements and related notes presented in our 2014 Annual Report on Form 10-K (our “2014 Annual Report”).  Certain financial information that is normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), but that is not required for interim reporting purposes, has been condensed or omitted.  We have omitted certain footnote disclosures that would substantially duplicate the disclosures in our 2014 Annual Report, unless the information contained in those disclosures materially changed and is required by GAAP.  We evaluated subsequent events that occurred after March 31, 2015 through the date the financial statements were issued and determined there were no other items to disclose other than as disclosed in Note 10 beginning on page 27.
	Reclassifications
	Certain reclassifications were made to 2014 financial information to conform with the 2015 presentation.
	Principles of Consolidation
	The accompanying unaudited consolidated financial statements have been prepared in accordance with GAAP and include the accounts of Aetna and the subsidiaries we control.  All significant intercompany balances have been eliminated in consolidation.
	Accounting for certain provisions of the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act of 2010 (collectively, “Health Care Reform” or the “ACA”)
	We are participating in certain public health insurance exchanges established pursuant to Health Care Reform (“Public Exchanges”). 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 certain risk management programs as described below.
	We recognize monthly premiums received from Public Exchange members and the Premium Subsidy as premium revenue ratably over the contract period. The Cost Sharing Subsidy offsets health care costs when incurred. We record a liability if the Cost Sharing Subsidy is paid in advance or a receivable if incurred health care costs exceed the Cost Sharing Subsidy received to date.
	Accounting for Health Care Reform’s Reinsurance, Risk Adjustment and Risk Corridor (the “3Rs”)
	Reinsurance
	Health Care Reform established a temporary three-year reinsurance program, under which all issuers of major medical commercial insurance products and self-insured plan sponsors are required to contribute funding in amounts set by HHS. Funds collected will be utilized to reimburse issuers’ high claims costs incurred for qualified individual members. The expense related to this required funding is reflected in general and administrative expenses for all of our insurance products with the exception of products associated with qualified individual members; this expense for qualified individual members is reflected as a reduction of premium revenue. When annual claim costs incurred by our qualified individual members exceed a specified attachment point, we are entitled to certain reimbursements from this program. We record a receivable and offset health care costs to reflect our estimate of these recoveries. As of March 31, 2015 and December 31, 2014, we recorded a receivable under the temporary three-year reinsurance program of approximately $385 million and $338 million, respectively.
	Risk Adjustment
	Health Care Reform established a permanent risk adjustment program to transfer funds from qualified individual and small group insurance plans with below average risk scores to plans with above average risk scores. Based on the risk of our qualified plan members relative to the average risk of members of other qualified plans in comparable markets, we estimate our ultimate risk adjustment receivable or payable and reflect the pro-rata year-to-date impact as an adjustment to our premium revenue. At March 31, 2015 and December 31, 2014, we recorded a net payable of approximately $428 million and $230 million, respectively, under the risk adjustment program.
	Risk Corridor
	Health Care Reform established a temporary three-year risk sharing program for qualified individual and small group insurance plans. Under this program we make (or receive) a payment to (or from) HHS based on the ratio of allowable costs to target costs (as defined by Health Care Reform). We record a risk corridor receivable or payable as an adjustment to premium revenue on a pro-rata year-to-date basis based on our estimate of the ultimate risk sharing amount. At March 31, 2015 and December 31, 2014, we did not record any Health Care Reform risk corridor receivables because payments from HHS under this program are uncertain, and we recorded an immaterial Health Care Reform risk corridor payable at each respective date.
	We expect to perform an annual final reconciliation and settlement with HHS of the Cost Sharing Subsidy and 3Rs in each subsequent year.
	New Accounting Standards
	Accounting for Investments in Qualified Affordable Housing Projects
	Effective January 1, 2015, we were permitted to make an accounting policy election to adopt new accounting guidance relating to the recognition of amortization of investments in qualified affordable housing projects. The guidance sets forth a new method of measurement, referred to as the proportional amortization method, under which income and expense items related to qualified affordable housing projects would be recorded in the income taxes line item. We did not make the accounting policy election to adopt this new accounting guidance.
	Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity
	Effective January 1, 2015, we adopted amended accounting guidance related to when an entity reports a discontinued operation in its financial position and operating results.  The guidance clarifies that a discontinued operation is required to be reported if the disposal represents a significant shift that has (or will have) a major effect on an entity’s operations and financial results when a component of an entity or a group of components of an entity are either classified as held for sale or are disposed of by sale.  The amendments also require additional disclosures about discontinued operations. We had no discontinued operations during the three months ended March 31, 2015.
	Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures
	Effective January 1, 2015, we adopted new accounting guidance related to the accounting for repurchase-to-maturity transactions and repurchase financing arrangements. This guidance aligns the accounting for repurchase-to-maturity transactions and repurchase agreements executed as repurchase financings with other typical repurchase agreements, resulting in these transactions generally being accounted for as secured borrowings. The adoption of this new guidance had no impact on our financial position or operating results. The guidance also requires additional disclosures about repurchase agreements and other similar transactions accounted for as secured borrowings which we will adopt effective April 1, 2015.
	Future Application of Accounting Standards
	Revenue from Contracts with Customers
	Effective January 1, 2017, we will adopt new accounting guidance related to revenue recognition from contracts with customers. This new guidance removes most industry-specific revenue recognition requirements (insurance contracts are not covered by this guidance) and 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 the 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. The new guidance allows an entity to adopt the standard either through a full retrospective approach or a modified retrospective approach with a cumulative effect adjustment to retained earnings. We are still assessing the impact of this standard on our financial position and operating results in addition to evaluating the transition method we will use when we adopt this standard.
	Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Service Period
	Effective January 1, 2016, we will adopt new accounting guidance related to the accounting for share-based payments when the terms of an award provide that a performance target could be achieved after the requisite service period. This guidance clarifies that awards with these provisions should be treated as performance conditions that affect vesting, and do not impact the award’s estimated grant-date fair value. Early adoption of this new guidance is permitted. The adoption of this new guidance will not have an impact on our financial position or operating results.
	Disclosure of Uncertainties About an Entity’s Ability to Continue as a Going Concern
	Effective December 31, 2016, we will adopt amended accounting guidance related to management’s evaluation of whether there is substantial doubt about an entity’s ability to continue as a going concern and the related disclosures. The adoption of this new guidance will not have a material impact on our financial position or operating results.
	Determining Whether the Host Contract in a Hybrid Financial Instrument Issued in the Form of a Share Is More Akin to Debt or to Equity
	Effective December 31, 2015, we will adopt amended accounting guidance related to the approach used in determining whether the host contract in a hybrid financial instrument issued in the form of a share is more akin to debt or equity. Early adoption of this new guidance is permitted. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results.
	Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items
	Effective January 1, 2016, we will adopt amended accounting guidance related to the presentation of extraordinary items. The amendment eliminates the concept of extraordinary items which represent events that are both unusual and infrequent. Presentation and disclosure of items that are unusual or infrequent will be retained, and will be expanded to include items that are both unusual and infrequent. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results.
	Amendments to the Consolidation Analysis
	Effective January 1, 2016, we will adopt amended accounting guidance related to the evaluation of consolidation for certain legal entities. The amendment changes how a reporting entity assesses consolidation, including whether an entity is considered a variable interest entity, determination of the primary beneficiary and how related parties are considered in the analysis. Early adoption of this new guidance is permitted. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results.
	Simplifying the Presentation of Debt Issuance Costs
	Effective January 1, 2016, we will adopt amended accounting guidance related to the financial statement presentation of debt issuance costs. The amendment requires debt issuance costs to be presented as a direct deduction from the carrying amount of our debt liability, consistent with the approach used for debt discounts. Amortization of debt issuance costs will also be reported in the Statements of Income as interest expense, as opposed to general and administrative expenses. Early adoption of this new guidance is permitted. This new guidance must be applied on a full retrospective basis, with all prior periods restated for the new presentation. The adoption of this new guidance will require certain reclassifications in our financial statements and is not expected to have a material impact on our financial position or operating results.
	Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement
	Effective January 1, 2016, we will adopt amended accounting guidance related to the evaluation of fees paid by a customer in a cloud computing arrangement. The amendment provides additional guidance that aids in determining whether a cloud computing arrangement contains a software license. Arrangements that do not contain a software license must be accounted for as a service contract. If a software license is included in the cloud computing arrangement, the license element must be accounted for consistent with the acquisition of a software license. Early adoption of this new guidance is permitted. The adoption of this new guidance is not expected to have a material impact on our financial position or operating results.

Earnings_Per_Common_Share

Earnings Per Common Share	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Common Share
	3	Earnings Per Common Share
	Basic earnings per share (“EPS”) is computed by dividing net 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, 2015 and 2014 are as follows:
	(Millions, except per common share data)	2015			2014
	Net income attributable to Aetna	$	777.5		$	665.5
	Weighted average shares used to compute basic EPS	349.5			361.6
	Dilutive effect of outstanding stock-based compensation awards	3.2			3.4
	Weighted average shares used to compute diluted EPS	352.7			365
	Basic EPS	$	2.22		$	1.84
	Diluted EPS	$	2.2		$	1.82
	The stock-based compensation awards excluded from the calculation of diluted EPS for the three months ended March 31, 2015 and 2014 are as follows:
	(Millions)	2015		2014
	Stock appreciation rights (“SARs”) (1)	1.9		1.3
	Other stock-based compensation awards (2)	1.1		1.3
	(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)	Performance stock units ("PSUs"), certain market stock units ("MSUs") with performance conditions, and performance stock appreciation rights ("PSARs") are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period.
	All outstanding stock options were included in the calculation of diluted EPS for the three months ended March 31, 2014. We no longer have any stock options outstanding as of March 31, 2015.

Operating_Expenses

Operating Expenses	3 Months Ended
	Mar. 31, 2015
Operating Expenses [Abstract]
Operating Expenses	4.     Operating Expenses
	For the three months ended March 31, 2015 and 2014, selling expenses (which include broker commissions, the variable component of our internal sales force compensation and premium taxes) and general and administrative expenses were as follows:
	(Millions)	2015		2014
	Selling expenses	$	414.9	$	402.8
	General and administrative expenses:
	Salaries and related benefits	1,206.60		1,119.50
	Other general and administrative expenses  (1) (2)	1,195.20		928.1
	Total general and administrative expenses (3)	2,401.80		2,047.60
	Total operating expenses	$	2,816.70	$	2,450.40
	(1)	The three months ended March 31, 2015 and 2014 include estimated fees mandated by the ACA comprised primarily of the health insurer fee of $218.7 million and $154.8 million, respectively, and our estimated contribution to the funding of the reinsurance program of $53.6 million and $84.9 million, respectively. Refer to Note 2 beginning on page 6 for additional information on fees mandated by the ACA.
	(2)	In the three months ended December 31, 2012, we recorded a charge of $120.0 million pretax related to the settlement of purported class action litigation regarding Aetna’s payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffs’ counsel and the costs of administering the settlement. In the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $103.0 million pretax in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.
	(3)	The three months ended March 31, 2015 include $45.6 million of transaction and integration-related costs related to the acquisitions of Coventry Health Care, Inc. (“Coventry”), the InterGlobal group (“InterGlobal”) and bSwift LLC (“bswift”). The three months ended March 31, 2014 include $63.7 million of integration-related costs related to the acquisition of Coventry.
	Refer to the reconciliation of operating earnings to net income attributable to Aetna in Note 13 beginning on page 32 for additional information.

Investments

Investments	3 Months Ended
	Mar. 31, 2015
Investments [Abstract]
Investments	5.     Investments
	Total investments at March 31, 2015 and December 31, 2014 were as follows:
		March 31, 2015										December 31, 2014
	(Millions)	Current			Long-term			Total				Current			Long-term		Total
	Debt and equity securities available for sale	$	2,237.30		$	19,346.50		$	21,583.80			$	2,463.80		$	18,977.90	$	21,441.70
	Mortgage loans	127.6			1,387.60			1,515.20				124.2			1,438.00		1,562.20
	Other investments	9.2			1,853.50			1,862.70				7.2			1,778.00		1,785.20
	Total investments	$	2,374.10		$	22,587.60		$	24,961.70			$	2,595.20		$	22,193.90	$	24,789.10
	At March 31, 2015, we did not have any repurchase agreements outstanding. At December 31, 2014, approximately $202 million of investments were pledged as collateral under repurchase agreements. At March 31, 2015 and December 31, 2014, approximately $835 million and $798 million, respectively, of investments were pledged under securities loan agreements.
	Debt and Equity Securities
	Debt and equity securities available for sale at March 31, 2015 and December 31, 2014 were as follows:
	(Millions)	Amortized			Gross			Gross					Fair
		Cost			Unrealized			Unrealized					Value
					Gains			Losses
	March 31, 2015
	Debt securities:
	U.S. government securities	$	1,341.00		$	111.4		$	(1.3	)			$	1,451.10
	States, municipalities and political subdivisions	4,582.40			285.9			(7.8		)			4,860.50
	U.S. corporate securities	7,961.70			670.1			(14.3		)			8,617.50
	Foreign securities	3,252.00			305.2			(10.3		)			3,546.90
	Residential mortgage-backed securities	884.8			32.4			(1.9		)			915.3
	Commercial mortgage-backed securities	1,301.50			50.5			(.5		)	(1)		1,351.50
	Other asset-backed securities	743.6			9.5			(2.8		)	(1)		750.3
	Redeemable preferred securities	55.2			12.9			—					68.1
	Total debt securities	20,122.20			1,477.90			(38.9		)			21,561.20
	Equity securities	24.4			2			(3.8		)			22.6
	Total debt and equity securities (2)	$	20,146.60		$	1,479.90		$	(42.7	)			$	21,583.80
	December 31, 2014
	Debt securities:
	U.S. government securities	$	1,301.20		$	96.3		$	(.6	)			$	1,396.90
	States, municipalities and political subdivisions	4,540.00			277.2			(7.8		)			4,809.40
	U.S. corporate securities	8,033.20			606.8			(33.6		)			8,606.40
	Foreign securities	3,343.60			267			(18.3		)			3,592.30
	Residential mortgage-backed securities	902.7			28.9			(3.9		)			927.7
	Commercial mortgage-backed securities	1,324.60			52.8			(1.6		)	(1)		1,375.80
	Other asset-backed securities	644.7			5.8			(6.5		)	(1)		644
	Redeemable preferred securities	56.8			12.5			—					69.3
	Total debt securities	20,146.80			1,347.30			(72.3		)			21,421.80
	Equity securities	23.3			0.4			(3.8		)			19.9
	Total debt and equity securities (2)	$	20,170.10		$	1,347.70		$	(76.1	)			$	21,441.70
	(1)	At March 31, 2015 and December 31, 2014, we held securities for which we previously recognized $15.6 million and $18.6 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at March 31, 2015 and December 31, 2014 of $3.3 million and $3.6 million, respectively.
	(2)	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 15 beginning on page 33 for additional information on our accounting for discontinued products).  At March 31, 2015, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $428.1 million and gross unrealized capital losses of $9.7 million and, at December 31, 2014, debt and equity securities with a fair value of approximately $3.6 billion, gross unrealized capital gains of $391.3 million and gross unrealized capital losses of $16.7 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, 2015 is shown below by contractual maturity.  Actual maturities may differ from contractual maturities because securities may be restructured, called or prepaid.
	(Millions)	Fair
		Value
	Due to mature:
	Less than one year	$	1,104.50
	One year through five years	5,631.90
	After five years through ten years	5,817.10
	Greater than ten years	5,990.60
	Residential mortgage-backed securities	915.3
	Commercial mortgage-backed securities	1,351.50
	Other asset-backed securities	750.3
	Total	$	21,561.20
	Mortgage-Backed and Other Asset-Backed Securities
	All of our residential mortgage-backed securities at March 31, 2015 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, 2015, our residential mortgage-backed securities had an average credit quality rating of AAA and a weighted average duration of 3.1 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, 2015, these securities had an average credit quality rating of AA+ and a weighted average duration of 2.0 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, 2015, these securities had an average credit quality rating of A+ and a weighted average duration of 1.5 years.
	Unrealized Capital Losses and Net Realized Capital Gains (Losses)
	When a debt or equity security is in an unrealized capital loss position, we monitor the duration and severity of the loss to determine if sufficient market recovery can occur within a reasonable period of time.  We recognize an other-than-temporary impairment (“OTTI”) when we intend to sell a debt security that is in an unrealized capital loss position or if we determine a credit-related loss on a debt or equity security has occurred.
	Summarized below are the debt and equity securities we held at March 31, 2015 and December 31, 2014 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)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
		Value			Losses			Value				Losses			Value		Losses
March 31, 2015
Debt securities:
U.S. government securities	$	64		$	0.9		$	12.9			$	0.4		$	76.9	$	1.3
States, municipalities and political subdivisions	535			4.3			139.3				3.5			674.3		7.8
U.S. corporate securities	567.1			9.6			140				4.7			707.1		14.3
Foreign securities	304.3			7.3			72.8				3			377.1		10.3
Residential mortgage-backed securities	54.7			0.2			106.3				1.7			161		1.9
Commercial mortgage-backed securities	76.1			0.1			34.1				0.4			110.2		0.5
Other asset-backed securities	177.2			2.7			16.1				0.1			193.3		2.8
Redeemable preferred securities	3			—			—				—			3		—
Total debt securities	1,781.40			25.1			521.5				13.8			2,302.90		38.9
Equity securities	—			—			1.4				3.8			1.4		3.8
Total debt and equity securities (1)	$	1,781.40		$	25.1		$	522.9			$	17.6		$	2,304.30	$	42.7
December 31, 2014
Debt securities:
U.S. government securities	$	20.6		$	0.1		$	19.8			$	0.5		$	40.4	$	0.6
States, municipalities and political subdivisions	457.4			2.2			347.4				5.6			804.8		7.8
U.S. corporate securities	1,074.10			19.9			515.2				13.7			1,589.30		33.6
Foreign securities	540			12.8			148				5.5			688		18.3
Residential mortgage-backed securities	3.9			0.1			166.9				3.8			170.8		3.9
Commercial mortgage-backed securities	181.5			0.7			69				0.9			250.5		1.6
Other asset-backed securities	373.1			6.1			21.3				0.4			394.4		6.5
Redeemable preferred securities	3			—			—				—			3		—
Total debt securities	2,653.60			41.9			1,287.60				30.4			3,941.20		72.3
Equity securities	8			—			1.4				3.8			9.4		3.8
Total debt and equity securities (1)	$	2,661.60		$	41.9		$	1,289.00			$	34.2		$	3,950.60	$	76.1
(1)	At March 31, 2015 and December 31, 2014, debt and equity securities in an unrealized capital loss position of $9.7 million and $16.7 million, respectively, and with related fair value of $221.4 million and $402.7 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, 2015, 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, 2015 were as follows:
	Supporting discontinued and						Supporting remaining							Total
	experience-rated products						products
(Millions)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
	Value			Losses			Value				Losses			Value		Losses
Due to mature:
Less than one year	$	—		$	—		$	27.4			$	0.1		$	27.4	$	0.1
One year through five years	5.5			—			505.7				4.6			511.2		4.6
After five years through ten years	112.6			2.3			656.5				11.7			769.1		14
Greater than ten years	91.6			3.6			439.1				11.4			530.7		15
Residential mortgage-backed securities	—			—			161				1.9			161		1.9
Commercial mortgage-backed securities	10.3			—			99.9				0.5			110.2		0.5
Other asset-backed securities	—			—			193.3				2.8			193.3		2.8
Total	$	220		$	5.9		$	2,082.90			$	33		$	2,302.90	$	38.9
Net realized capital gains (losses) for the three months ended March 31, 2015 and 2014, excluding amounts related to experience-rated contract holders and discontinued products, were as follows:
(Millions)	2015			2014
OTTI losses on debt securities recognized in earnings	$	(2.4	)	$	(.2	)
Net realized capital gains, excluding OTTI losses on debt securities	10.5			28.7
Net realized capital gains	$	8.1		$	28.5
The net realized capital gains for the three months ended March 31, 2015 were primarily attributable to gains from the sale of debt securities. The net realized capital gains for the three months ended March 31, 2014 were primarily attributable to the recognition of a gain on the termination of interest rate swaps as well as gains from the sale of debt securities. Refer to Note 9 of Condensed Notes to Consolidated Financial Statements beginning on page 26 for more information on the termination of the outstanding interest rate swaps in the first quarter of 2014.
We had no individually material realized capital losses on debt or equity securities that impacted our operating results during three months ended March 31, 2015 or 2014.
Excluding amounts related to experience-rated and discontinued products, proceeds from the sale of debt securities and the related gross realized capital gains and losses for the three months ended March 31, 2015 and 2014 were as follows:
(Millions)	2015			2014
Proceeds on sales	$	945.9		$	1,092.80
Gross realized capital gains	24.9			24.6
Gross realized capital losses	8.8			13
Mortgage Loans
Our mortgage loans are collateralized by commercial real estate.  During the three months ended March 31, 2015 and 2014 we had the following activity in our mortgage loan portfolio:
(Millions)	2015			2014
New mortgage loans	$	12.7		$	33.9
Mortgage loans fully repaid	39.5			19.8
Mortgage loans foreclosed	9			—
At March 31, 2015 and December 31, 2014, we had no material problem, restructured or potential problem mortgage loans.  We also had no material impairment reserves on these loans at March 31, 2015 or December 31, 2014.
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.  Category 1 represents loans of superior quality, and Categories 6 and 7 represent loans where collections are potentially at risk.  The vast majority of our mortgage loans fall into the Level 2 to 4 ratings.  These ratings represent loans where credit risk is minimal to acceptable; however, these loans may display some susceptibility to economic changes.  Category 5 represents loans where credit risk is not substantial but these loans warrant management’s close attention.  These indicators are based upon several factors, including current loan to value ratios, property condition, market trends, creditworthiness of the borrower and deal structure.  Based upon our most recent assessments at March 31, 2015 and December 31, 2014, our mortgage loans were given the following credit quality indicators:
(In Millions, except credit ratings indicator)	March 31,			December 31,
	2015			2014
1	$	58.7		$	59.7
2 to 4	1,416.20			1,443.40
5	13.3			18.6
6 and 7	27			40.5
Total	$	1,515.20		$	1,562.20
Variable Interest Entities
In determining whether to consolidate a variable interest entity (“VIE”), we consider several factors, including whether we have the power to direct activities, the obligation to absorb losses and the right to receive benefits that could potentially be significant to the VIE.  We have relationships with certain real estate partnerships and one hedge fund partnership that are considered VIEs, but are not consolidated.  We record the amount of our investment in these partnerships as long-term investments on our balance sheets and recognize our share of partnership income or losses in earnings.  Our maximum exposure to loss as a result of our investment in these partnerships is our investment balance at March 31, 2015 and December 31, 2014 of approximately $210 million and $209 million, respectively, and the risk of recapture of tax credits related to the real estate partnerships previously recognized, which we do not consider significant.  We do not have a future obligation to fund losses or debts on behalf of these investments; however, we may voluntarily contribute funds.  The real estate partnerships construct, own and manage low-income housing developments and had total assets of approximately $5.8 billion and $5.7 billion at March 31, 2015 and December 31, 2014, respectively.  The hedge fund partnership had total assets of approximately $6.9 billion and $7.1 billion at March 31, 2015 and December 31, 2014, respectively.
Non-controlling (Minority) Interests
At March 31, 2015 and December 31, 2014, continuing business non-controlling interests were approximately $66 million and $69 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 loss attributable to non-controlling interests was $1.2 million for the three months ended March 31, 2015 and net income attributable to non-controlling interests was $3.9 million for the three months ended March 31, 2014. These non-controlling interests did not have a material impact on our financial position or operating results.
Net Investment Income
Sources of net investment income for the three months ended March 31, 2015 and 2014 were as follows:
(Millions)	2015			2014
Debt securities	$	196.4		$	198.1
Mortgage loans	21.9			23.9
Other investments	23.9			30.1
Gross investment income	242.2			252.1
Investment expenses	(9.3		)	(7.9		)
Net investment income (1)	$	232.9		$	244.2
(1)	Net investment income includes $66.6 million and $80.4 million for the three months ended March 31, 2015 and 2014, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom

Other Comprehensive (Loss) Income	3 Months Ended
	Mar. 31, 2015
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive (Loss) Income	6.    Other Comprehensive (Loss) Income
	Shareholders’ equity included the following activity in accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014:
		Net Unrealized Gains (Losses)														Pension and OPEB Plans										Total
																										Accumulated
																										Other
		Securities									Foreign															Comprehensive
											Currency															(Loss) Income
											and
	(Millions)	Previously					All Other				Derivatives			Unrecognized					Unrecognized
		Impaired (1)												Net Actuarial					Prior Service
														Losses					Credit
	Three months ended March 31, 2015
	Balance at December 31, 2014	$	34.9				$	568			$	(60.9	)			$	(1,670.9	)			$	17.6				$	(1,111.3	)
	Other comprehensive (loss) income
	before reclassifications	(2.2		)			77.9				(13.9		)			—					—					61.8
	Amounts reclassified from accumulated
	other comprehensive income	(1.6		)	(2	)	7.2		(2	)	1			(3	)	10.5			(4	)	(.7		)	(4	)	16.4
	Other comprehensive (loss) income	(3.8		)			85.1				(12.9		)			10.5					(.7		)			78.2
	Balance at March 31, 2015	$	31.1				$	653.1			$	(73.8	)			$	(1,660.4	)			$	16.9				$	(1,033.1	)
	Three months ended March 31, 2014
	Balance at December 31, 2013	$	34.2				$	326.8			$	0.4				$	(1,293.8	)			$	20.3				$	(912.1	)
	Other comprehensive income (loss)
	before reclassifications	1.1					137.2				(12.5		)			—					—					125.8
	Amounts reclassified from accumulated
	other comprehensive income	(.4		)	(2	)	3.3		(2	)	(10.1		)	(3	)	7.7			(4	)	(.6		)	(4	)	(.1		)
	Other comprehensive income (loss)	0.7					140.5				(22.6		)			7.7					(.6		)			125.7
	Balance at March 31, 2014	$	34.9				$	467.3			$	(22.2	)			$	(1,286.1	)			$	19.7				$	(786.4	)
	(1)	Represents unrealized gains 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 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 foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the effective portion of derivatives related to interest rate swaps which are reflected in interest expense and were not material during the three months ended March 31, 2015 or 2014. Refer to Note 9 of Condensed Notes to Consolidated Financial Statements beginning on page 26 for additional information.
	(4)	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 8 of Condensed Notes to Consolidated Financial Statements beginning on page 25 for additional information.
	Refer to the Consolidated Statements of Comprehensive Income on page 2 for additional information regarding reclassifications out of accumulated other comprehensive income on a pretax basis.

Financial_Instruments

Financial Instruments	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Financial Instruments	7.    Financial Instruments
	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 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, 2015 or December 31, 2014.
	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, 2015 or December 31, 2014.  The total fair value of our broker quoted debt securities was approximately $124 million at March 31, 2015 and $126 million at December 31, 2014.  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 held.  Our publicly-traded securities are classified in Level 1 because quoted prices are available for these securities in an active market.  For privately-held 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.
	Financial assets and liabilities measured at fair value on a recurring basis in our balance sheets at March 31, 2015 and December 31, 2014 were as follows:
	(Millions)	Level 1			Level 2				Level 3				Total
	March 31, 2015
	Assets:
	Debt securities:
	U.S. government securities	$	1,253.90		$	197.2			$	—			$	1,451.10
	States, municipalities and political subdivisions	—			4,859.40				1.1				4,860.50
	U.S. corporate securities	—			8,561.40				56.1				8,617.50
	Foreign securities	—			3,515.10				31.8				3,546.90
	Residential mortgage-backed securities	—			915.3				—				915.3
	Commercial mortgage-backed securities	—			1,344.00				7.5				1,351.50
	Other asset-backed securities	—			708.5				41.8				750.3
	Redeemable preferred securities	—			64				4.1				68.1
	Total debt securities	1,253.90			20,164.90				142.4				21,561.20
	Equity securities	1.8			—				20.8				22.6
	Derivatives	—			0.3				—				0.3
	Total	$	1,255.70		$	20,165.20			$	163.2			$	21,584.10
	Liabilities:
	Derivatives	$	—		$	69.5			$	—			$	69.5
	December 31, 2014
	Assets:
	Debt securities:
	U.S. government securities	$	1,198.40		$	198.5			$	—			$	1,396.90
	States, municipalities and political subdivisions	—			4,808.20				1.2				4,809.40
	U.S. corporate securities	—			8,548.20				58.2				8,606.40
	Foreign securities	—			3,560.70				31.6				3,592.30
	Residential mortgage-backed securities	—			927.7				—				927.7
	Commercial mortgage-backed securities	—			1,368.30				7.5				1,375.80
	Other asset-backed securities	—			602.5				41.5				644
	Redeemable preferred securities	—			65.2				4.1				69.3
	Total debt securities	1,198.40			20,079.30				144.1				21,421.80
	Equity securities	1.8			—				18.1				19.9
	Derivatives	—			0.3				—				0.3
	Total	$	1,200.20		$	20,079.60			$	162.2			$	21,442.00
	Liabilities:
	Derivatives	$	—		$	53.4			$	—			$	53.4
	There were no transfers between Levels 1 and 2 during the three months ended March 31, 2015 or 2014. During the three months ended March 31, 2015 and 2014, 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 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 credit worthiness 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 certain of our financial instruments at March 31, 2015 and December 31, 2014 were as follows:
	Carrying			Estimated Fair Value
(Millions)	Value			Level 1			Level 2			Level 3			Total
March 31, 2015
Assets:
Mortgage loans	$	1,515.20		$	—		$	—		$	1,581.60		$	1,581.60
Bank loans	233.5			—			223.2			9.3			232.5
Equity securities (1)	34.9			N/A			N/A			N/A			N/A
Liabilities:
Investment contract liabilities:
With a fixed maturity	8.9			—			—			8.9			8.9
Without a fixed maturity	548.8			—			—			542			542
Long-term debt	7,846.10			—			8,781.80			—			8,781.80
December 31, 2014
Assets:
Mortgage loans	$	1,562.20		$	—		$	—		$	1,621.40		$	1,621.40
Bank loans	231.2			—			217.6			9.4			227
Equity securities (1)	34.9			N/A			N/A			N/A			N/A
Liabilities:
Investment contract liabilities:
With a fixed maturity	16.6			—			—			16.6			16.6
Without a fixed maturity	557.5			—			—			551.5			551.5
Long-term debt	8,081.30			—			8,764.80			—			8,764.80
(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 business 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 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 beginning on page 19.  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, 2015 and December 31, 2014 were as follows:
	March 31, 2015														December 31, 2014
(Millions)	Level 1			Level 2				Level 3				Total			Level 1		Level 2		Level 3		Total
Debt securities	$	698.2		$	2,740.30			$	3.5			$	3,442.00		$	876	$	2,495.00	$	2.9	$	3,373.90
Equity securities	179.9			5.9				—				185.8			173.3		5.7		—		179
Derivatives	—			(1.1		)		—				(1.1		)	—		0.2		—		0.2
Common/collective trusts	—			595.9				—				595.9			—		574		—		574
Total (1)	$	878.1		$	3,341.00			$	3.5			$	4,222.60		$	1,049.30	$	3,074.90	$	2.9	$	4,127.10
(1)	Excludes $225.4 million and $204.4 million of cash and cash equivalents and other receivables at March 31, 2015 and December 31, 2014, respectively.
During the three months ended March 31, 2015 and 2014, 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 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 as of March 31, 2015 and December 31, 2014 were as follows:
	Gross Amounts of		Gross Amounts Not Offset
	Recognized Assets (1)		in the Balance Sheets
			Financial Instruments			Cash Collateral Received
(Millions)									Net Amount
31-Mar-15
Derivatives	$	0.3	$	10.7		$	—		$	11
Total	$	0.3	$	10.7		$	—		$	11
31-Dec-14
Derivatives	$	0.3	$	10.2		$	—		$	10.5
Total	$	0.3	$	10.2		$	—		$	10.5
(1) There were no amounts offset in our balance sheets at March 31, 2015 or December 31, 2014.
Financial liabilities, including derivative liabilities, subject to offsetting and enforceable master netting arrangements as of March 31, 2015 and December 31, 2014 were as follows:
	Gross Amounts of		Gross Amounts Not Offset
	Recognized Liabilities (1)		in the Balance Sheets
			Financial Instruments			Cash Collateral Paid
(Millions)									Net Amount
31-Mar-15
Derivatives	$	69.5	$	1.3		$	(70.4	)	$	0.4
Securities lending	864		(864.0		)	—			—
Total	$	933.5	$	(862.7	)	$	(70.4	)	$	0.4
31-Dec-14
Derivatives	$	53.4	$	0.9		$	(49.0	)	$	5.3
Securities lending	826.9		(826.9		)	—			—
Repurchase agreements	201.7		—			—			201.7
Total	$	1,082.00	$	(826.0	)	$	(49.0	)	$	207
(1) There were no amounts offset in our balance sheets at March 31, 2015 or December 31, 2014.

Pension_and_Other_Postretireme

Pension and Other Postretirement Plans	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Pension and Other Postretirement Plans	8.    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, 2015 and 2014 were as follows:
		Pension Plans						OPEB Plans
	(Millions)	2015			2014			2015			2014
	Service cost	$	—		$	—		$	—		$	—
	Amortization of prior service credit	(.1		)	(.1		)	(.9		)	(.9		)
	Interest cost	65.2			72.1			2.7			3
	Expected return on plan assets	(104.8		)	(105.6		)	(.8		)	(.8		)
	Recognized net actuarial losses	15.4			11.7			0.7			0.2
	Net periodic benefit (income) cost	$	(24.3	)	$	(21.9	)	$	1.7		$	1.5

Debt

Debt	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt	9.    Debt
	The carrying value of our long-term debt at March 31, 2015 and December 31, 2014 was as follows:
	(Millions)	March 31,		December 31,
		2015		2014
	Senior notes, 6.125%, due 2015 (1)	$	—	$	229.3
	Senior notes, 5.95%, due 2017	414.3		418.3
	Senior notes, 1.75%, due 2017	249.3		249.2
	Senior notes, 1.5%, due 2017	498.8		498.6
	Senior notes, 2.2%, due 2019	374.7		374.7
	Senior notes, 3.95%, due 2020	745.4		745.2
	Senior notes, 5.45%, due 2021	685.2		688.6
	Senior notes, 4.125%, due 2021	495.7		495.5
	Senior notes, 2.75%, due 2022	987.2		986.8
	Senior notes, 3.5%, due 2024	747		746.9
	Senior notes, 6.625%, due 2036	769.8		769.8
	Senior notes, 6.75%, due 2037	530.8		530.7
	Senior notes, 4.5%, due 2042	480.9		480.8
	Senior notes, 4.125%, due 2042	492.9		492.8
	Senior notes, 4.75%, due 2044	374.1		374.1
	Total long-term debt	7,846.10		8,081.30
	Less current portion of long-term debt	—		229.3
	Total long-term debt, less current portion	$	7,846.10	$	7,852.00
	-1	The 6.125% senior notes were repaid in January 2015. These notes were classified as current in the consolidated balance sheet as of December 31, 2014.
	At March 31, 2015, we had approximately $297 million of commercial paper outstanding with a weighted-average interest rate of .42%. At December 31, 2014, we had approximately $500 million of commercial paper outstanding with a weighted-average interest rate of .30%.
	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, 2015 was approximately $850 million. At both March 31, 2015 and December 31, 2014, we did not have any outstanding borrowings from the FHLBB.
	Interest Rate Swaps
	In March 2014, we entered into two interest rate swaps with an aggregate notional value of $500 million. We designated these swaps as cash flow hedges against interest rate exposure related to the forecasted future issuance of fixed-rate debt to be primarily used to refinance long-term debt maturing in 2017. At March 31, 2015, these interest rate swaps had a pretax fair value loss of $69 million, which was reflected net of tax in accumulated other comprehensive loss within shareholders’ equity.
	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, in connection with the acquisition of 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”). On March 2, 2015, we entered into a Second Amendment to the Credit Agreement (together with the First Amendment, the Incremental Commitment and the Credit Agreement, resulting in the “Facility”). The Facility is an unsecured $2.0 billion revolving credit agreement. Upon our agreement with one or more financial institutions, we may expand the aggregate commitments under the Facility to a maximum of $2.5 billion. 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. In both 2013 and 2014, we extended the maturity date of the Facility by one year. On March 2, 2015, we extended the maturity date of the Facility by an additional year to March 27, 2020.
	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, 2015.  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, 2015.  There were no amounts outstanding under the Facility at any time during the three months ended March 31, 2015 or 2014.

Capital_Stock

Capital Stock	3 Months Ended
	Mar. 31, 2015
Class of Stock Disclosures [Abstract]
Capital Stock	10.    Capital Stock
	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.  During the three months ended March 31, 2015, we repurchased approximately 2 million shares of common stock at a cost of approximately $196 million.  At March 31, 2015, we had remaining authorization to repurchase an aggregate of up to approximately $1.2 billion of common stock under the November 21, 2014 and February 28, 2014 programs. 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.
	As described above, from time to time we enter into accelerated share repurchase agreements with unrelated third party financial institutions. The number of shares repurchased under each agreement is based on the volume-weighted average price of our common stock during the purchase period. We completed the following accelerated share repurchase program during the three months ended March 31, 2015:
	Trade Date:	Value of Repurchase Program (Millions)			Repurchase Period	Number of Shares Repurchased (Millions)
	15-Dec-14	$	150		January and February 2015	1.6
	Under the share repurchase program authorized by our Board, we entered into an accelerated share repurchase agreement with an unrelated third party financial institution on March 2, 2015 to repurchase an aggregate of $100 million of our outstanding common stock during April 2015. The final number of shares repurchased under the agreement will be determined based on the volume-weighted average price of our common stock during the purchase period.
	During the three months ended March 31, 2015 our Board declared the following cash dividend:
	Date Declared	Dividend Amount				Stockholders of	Date Paid/	Total Dividends
		Per Share				Record Date	To be Paid	(Millions)
	February 27, 2015		$	0.25		April 9, 2015	April 24, 2015		$	87.3
	Declaration and payment of future dividends is at the discretion of our Board and may be adjusted as business needs or market conditions change.
	On March 2, 2015, approximately .3 million PSUs, 1.1 million restricted stock units (“RSUs”) and 1.9 million 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, 2015 and ends on December 31, 2017.  The vesting period for the PSUs ends on March 2, 2018. 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 $100.50 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 the three months ended March 31, 2015 and 2014 had an estimated fair market value of $32.13 and $22.68 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 three months ended March 31, 2015 and 2014:
		2015				2014
	Expected term (in years)	6.48				5.72
	Volatility	33.4		%		35.8		%
	Risk-free interest rate	1.81		%		1.74		%
	Dividend yield	1.13		%		1.36		%
	Initial price	$	100.5			$	72.26
	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 5-year and 10-year U.S. Treasury rates for each respective period. The dividend yield is based on our historical dividends in the 12 months prior to the grant date.

Dividend_Restrictions_and_Stat

Dividend Restrictions and Statutory Surplus	3 Months Ended
	Mar. 31, 2015
Dividend Restrictions and Statutory Surplus [Abstract]
Dividend Restrictions and Statutory Surplus	11.    Dividend Restrictions and Statutory Surplus
	Under applicable regulatory requirements at March 31, 2015, the amount of dividends that may be paid through the end of 2015 by our insurance and HMO subsidiaries without prior approval by regulatory authorities was approximately $1.6 billion in the aggregate. There are no such regulatory restrictions on distributions from Aetna to its shareholders. During the first quarter of 2015, our insurance and HMO subsidiaries paid approximately $682 million of dividends to the Company.
	The combined statutory capital and surplus of our insurance and HMO subsidiaries was $9.1 billion and $9.4 billion at March 31, 2015 and December 31, 2014, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	12.    Commitments and Contingencies
	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 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 approximately $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. We intend to vigorously defend ourselves against the claims brought by the plaintiffs. 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 $67.0 million ($103.0 million pretax).
	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 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.  During 2013, CMS selected certain of our Medicare Advantage contracts for contract year 2011 for 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 vigorously defend ourselves against the claims brought in these matters.
	Awards to us and others of certain government contracts, particularly in our Medicaid 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 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 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 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.”
	A significant number of states are investigating life insurers’ claims payment and related escheat practices, and 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 $35.7 million ($55.0 million pretax). Given the legal 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 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, 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, 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, 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 a change 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, and it is reasonably possible that their outcome could be material to us.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	13.    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 to our consolidated results.  The Corporate Financing segment includes 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). Non-GAAP financial measures we disclose, such as operating 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 segments for the three months ended March 31, 2015 and 2014 were as follows:
	(Millions)	Health			Group			Large Case		Corporate			Total Company
		Care			Insurance			Pensions		Financing
	Three Months Ended March 31, 2015
	Revenue from external customers	$	14,285.80		$	554.5		$	12.8	$	—		$	14,853.10
	Operating earnings (loss) (1)	835.6			43.9			2.1		(37.3		)	844.3
	Three Months Ended March 31, 2014
	Revenue from external customers	$	13,131.40		$	544.4		$	46.3	$	—		$	13,722.10
	Operating earnings (loss) (1)	719			41.2			4.8		(43.0		)	722
	(1)	Operating 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 operating earnings (1) to net income attributable to Aetna for the three months ended March 31, 2015 and 2014 was as follows:
	(Millions)	2015			2014
	Operating earnings (1)	$	844.3		$	722
	Transaction and integration-related costs, net of tax	(30.7		)	(41.9		)
	Loss on early extinguishment of long-term debt, net of tax	—			(59.7		)
	Release of litigation-related reserve, net of tax	—			67
	Amortization of other acquired intangible assets, net of tax	(41.1		)	(40.4		)
	Net realized capital gains, net of tax	5			18.5
	Net income attributable to Aetna	$	777.5		$	665.5
	(1)	In addition to net realized capital gains and amortization of other acquired intangible assets, the following other items are excluded from operating earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:
	•	We incurred transaction and integration-related costs of $30.7 million ($45.6 million pretax) during the three months ended March 31, 2015, related to the acquisitions of Coventry, InterGlobal and bswift, and integration-related costs of $41.9 million ($63.7 million pretax) during the three months ended March 31, 2014, related to the acquisition of Coventry. Transaction costs include advisory, legal and other professional fees which are not deductible for tax purposes and are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses.
	•	We incurred a loss on the early extinguishment of long-term debt of $59.7 million ($91.9 million pretax) during the three months ended March 31, 2014 related to the redemption of our 6.0% senior notes due 2016.
	•	We recorded a charge of $78.0 million ($120.0 million pretax) during the three months ended December 31, 2012 related to the settlement of purported class action litigation regarding our payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffs’ counsel and the costs of administering the settlement. During the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $67.0 million ($103.0 million pretax) in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.

Reinsurance

Reinsurance	3 Months Ended
	Mar. 31, 2015
Reinsurance Disclosures [Abstract]
Reinsurance	14.     Reinsurance
	In January 2015, we entered into three-year reinsurance agreements with Vitality Re VI Limited, an unrelated insurer. The agreements allow us to reduce our required capital and provide $200 million of collateralized excess of loss reinsurance coverage on a portion of Aetna’s group Commercial Insured Health Care business. The Company’s similar reinsurance agreements with Vitality Re III Limited expired in January 2015.

Discontinued_Products

Discontinued Products	3 Months Ended
	Mar. 31, 2015
Discontinued Products [Abstract]
Discontinued Products
	15	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.
	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 for SPAs); so we established a reserve for anticipated future losses at the time of discontinuance. At both March 31, 2015 and December 31, 2014, our remaining GIC liability was not material. This reserve represents the present value (at the risk-free rate of return at the time of discontinuance, 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, 2015 and December 31, 2014 reflects management’s best estimate of anticipated future losses, and is included in future policy benefits on our balance sheet.
	The activity in the reserve for anticipated future losses on discontinued products for the three months ended March 31, 2015 and 2014 was as follows (pretax):
	(Millions)	2015		2014
	Reserve, beginning of period	$	1,014.70	$	979.5
	Operating income	3.1		5.8
	Net realized capital gains	19		6.3
	Reserve, end of period	$	1,036.80	$	991.6
	During the three months ended March 31, 2015, our discontinued products reflected operating income and net realized capital gains, primarily attributable to gains from the sale of debt securities and investment real estate. During the three months ended March 31, 2014, our discontinued products reflected operating income and net realized capital gains, primarily attributable to gains from the sale of debt securities. We evaluated these results against the expectations of future cash flows assumed in estimating the reserve for anticipated future losses and did not believe that an adjustment to the reserve was required at March 31, 2015 or 2014.
	Assets and liabilities supporting discontinued products at March 31, 2015 and December 31, 2014 were as
	follows: (1)
	(Millions)	2015		2014
	Assets:
	Debt and equity securities available for sale	$	2,384.20	$	2,376.20
	Mortgage loans	349.8		386.8
	Other investments	706.5		662.2
	Total investments	3,440.50		3,425.20
	Other assets	93.1		112.9
	Collateral received under securities loan agreements	201.2		200.7
	Receivable from continuing products (2)	575.2		566.5
	Total assets	$	4,310.00	$	4,305.30
	Liabilities:
	Future policy benefits	$	2,603.30	$	2,645.80
	Reserve for anticipated future losses on discontinued products	1,036.80		1,014.70
	Collateral payable under securities loan agreements	201.2		200.7
	Current and deferred income taxes	24.8		27.9
	Other liabilities (3)	443.9		416.2
	Total liabilities	$	4,310.00	$	4,305.30
	(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 $91 million and $97 million for the three months ended March 31, 2015 and 2014, respectively. There were no participant-directed withdrawals from our discontinued products during the three months ended March 31, 2015 or 2014.  Cash required to fund these distributions was provided by earnings and scheduled payments on, and sales of, invested assets.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Interim Financial Statements	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 accompanying unaudited consolidated financial statements and related notes should be read in conjunction with the consolidated financial statements and related notes presented in our 2014 Annual Report on Form 10-K (our “2014 Annual Report”).  Certain financial information that is normally included in annual financial statements prepared in accordance with U.S. generally accepted accounting principles (“GAAP”), but that is not required for interim reporting purposes, has been condensed or omitted.  We have omitted certain footnote disclosures that would substantially duplicate the disclosures in our 2014 Annual Report, unless the information contained in those disclosures materially changed and is required by GAAP.  We evaluated subsequent events that occurred after March 31, 2015 through the date the financial statements were issued and determined there were no other items to disclose other than as disclosed in Note 10 beginning on page 27.
Reclassifications	Reclassifications
	Certain reclassifications were made to 2014 financial information to conform with the 2015 presentation.
Principles of Consolidation	Principles of Consolidation
	The accompanying unaudited consolidated financial statements have been prepared in accordance with GAAP and include the accounts of Aetna and the subsidiaries we control.  All significant intercompany balances have been eliminated in consolidation.
Health Care Reform	Accounting for certain provisions of the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act of 2010 (collectively, “Health Care Reform” or the “ACA”)
	We are participating in certain public health insurance exchanges established pursuant to Health Care Reform (“Public Exchanges”). 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 certain risk management programs as described below.
	We recognize monthly premiums received from Public Exchange members and the Premium Subsidy as premium revenue ratably over the contract period. The Cost Sharing Subsidy offsets health care costs when incurred. We record a liability if the Cost Sharing Subsidy is paid in advance or a receivable if incurred health care costs exceed the Cost Sharing Subsidy received to date.
	Accounting for Health Care Reform’s Reinsurance, Risk Adjustment and Risk Corridor (the “3Rs”)
	Reinsurance
	Health Care Reform established a temporary three-year reinsurance program, under which all issuers of major medical commercial insurance products and self-insured plan sponsors are required to contribute funding in amounts set by HHS. Funds collected will be utilized to reimburse issuers’ high claims costs incurred for qualified individual members. The expense related to this required funding is reflected in general and administrative expenses for all of our insurance products with the exception of products associated with qualified individual members; this expense for qualified individual members is reflected as a reduction of premium revenue. When annual claim costs incurred by our qualified individual members exceed a specified attachment point, we are entitled to certain reimbursements from this program. We record a receivable and offset health care costs to reflect our estimate of these recoveries. As of March 31, 2015 and December 31, 2014, we recorded a receivable under the temporary three-year reinsurance program of approximately $385 million and $338 million, respectively.
	Risk Adjustment
	Health Care Reform established a permanent risk adjustment program to transfer funds from qualified individual and small group insurance plans with below average risk scores to plans with above average risk scores. Based on the risk of our qualified plan members relative to the average risk of members of other qualified plans in comparable markets, we estimate our ultimate risk adjustment receivable or payable and reflect the pro-rata year-to-date impact as an adjustment to our premium revenue. At March 31, 2015 and December 31, 2014, we recorded a net payable of approximately $428 million and $230 million, respectively, under the risk adjustment program.
	Risk Corridor
	Health Care Reform established a temporary three-year risk sharing program for qualified individual and small group insurance plans. Under this program we make (or receive) a payment to (or from) HHS based on the ratio of allowable costs to target costs (as defined by Health Care Reform). We record a risk corridor receivable or payable as an adjustment to premium revenue on a pro-rata year-to-date basis based on our estimate of the ultimate risk sharing amount. At March 31, 2015 and December 31, 2014, we did not record any Health Care Reform risk corridor receivables because payments from HHS under this program are uncertain, and we recorded an immaterial Health Care Reform risk corridor payable at each respective date.
	We expect to perform an annual final reconciliation and settlement with HHS of the Cost Sharing Subsidy and 3Rs in each subsequent year.

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	The computations of basic and diluted EPS for the three months ended March 31, 2015 and 2014 are as follows:
	(Millions, except per common share data)	2015			2014
	Net income attributable to Aetna	$	777.5		$	665.5
	Weighted average shares used to compute basic EPS	349.5			361.6
	Dilutive effect of outstanding stock-based compensation awards	3.2			3.4
	Weighted average shares used to compute diluted EPS	352.7			365
	Basic EPS	$	2.22		$	1.84
	Diluted EPS	$	2.2		$	1.82
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, 2015 and 2014 are as follows:
	(Millions)	2015		2014
	Stock appreciation rights (“SARs”) (1)	1.9		1.3
	Other stock-based compensation awards (2)	1.1		1.3
	(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)	Performance stock units ("PSUs"), certain market stock units ("MSUs") with performance conditions, and performance stock appreciation rights ("PSARs") are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period.

Operating_Expenses_Tables

Operating Expenses (Tables)	3 Months Ended
	Mar. 31, 2015
Operating Expenses [Abstract]
Operating Expenses	For the three months ended March 31, 2015 and 2014, selling expenses (which include broker commissions, the variable component of our internal sales force compensation and premium taxes) and general and administrative expenses were as follows:
	(Millions)	2015		2014
	Selling expenses	$	414.9	$	402.8
	General and administrative expenses:
	Salaries and related benefits	1,206.60		1,119.50
	Other general and administrative expenses  (1) (2)	1,195.20		928.1
	Total general and administrative expenses (3)	2,401.80		2,047.60
	Total operating expenses	$	2,816.70	$	2,450.40
	(1)	The three months ended March 31, 2015 and 2014 include estimated fees mandated by the ACA comprised primarily of the health insurer fee of $218.7 million and $154.8 million, respectively, and our estimated contribution to the funding of the reinsurance program of $53.6 million and $84.9 million, respectively. Refer to Note 2 beginning on page 6 for additional information on fees mandated by the ACA.
	(2)	In the three months ended December 31, 2012, we recorded a charge of $120.0 million pretax related to the settlement of purported class action litigation regarding Aetna’s payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffs’ counsel and the costs of administering the settlement. In the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $103.0 million pretax in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.
	(3)	The three months ended March 31, 2015 include $45.6 million of transaction and integration-related costs related to the acquisitions of Coventry Health Care, Inc. (“Coventry”), the InterGlobal group (“InterGlobal”) and bSwift LLC (“bswift”). The three months ended March 31, 2014 include $63.7 million of integration-related costs related to the acquisition of Coventry.

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments [Abstract]
Total investments	Total investments at March 31, 2015 and December 31, 2014 were as follows:
		March 31, 2015										December 31, 2014
	(Millions)	Current			Long-term			Total				Current			Long-term		Total
	Debt and equity securities available for sale	$	2,237.30		$	19,346.50		$	21,583.80			$	2,463.80		$	18,977.90	$	21,441.70
	Mortgage loans	127.6			1,387.60			1,515.20				124.2			1,438.00		1,562.20
	Other investments	9.2			1,853.50			1,862.70				7.2			1,778.00		1,785.20
	Total investments	$	2,374.10		$	22,587.60		$	24,961.70			$	2,595.20		$	22,193.90	$	24,789.10
Debt and equity securities available for sale	Debt and equity securities available for sale at March 31, 2015 and December 31, 2014 were as follows:
	(Millions)	Amortized			Gross			Gross					Fair
		Cost			Unrealized			Unrealized					Value
					Gains			Losses
	March 31, 2015
	Debt securities:
	U.S. government securities	$	1,341.00		$	111.4		$	(1.3	)			$	1,451.10
	States, municipalities and political subdivisions	4,582.40			285.9			(7.8		)			4,860.50
	U.S. corporate securities	7,961.70			670.1			(14.3		)			8,617.50
	Foreign securities	3,252.00			305.2			(10.3		)			3,546.90
	Residential mortgage-backed securities	884.8			32.4			(1.9		)			915.3
	Commercial mortgage-backed securities	1,301.50			50.5			(.5		)	(1)		1,351.50
	Other asset-backed securities	743.6			9.5			(2.8		)	(1)		750.3
	Redeemable preferred securities	55.2			12.9			—					68.1
	Total debt securities	20,122.20			1,477.90			(38.9		)			21,561.20
	Equity securities	24.4			2			(3.8		)			22.6
	Total debt and equity securities (2)	$	20,146.60		$	1,479.90		$	(42.7	)			$	21,583.80
	December 31, 2014
	Debt securities:
	U.S. government securities	$	1,301.20		$	96.3		$	(.6	)			$	1,396.90
	States, municipalities and political subdivisions	4,540.00			277.2			(7.8		)			4,809.40
	U.S. corporate securities	8,033.20			606.8			(33.6		)			8,606.40
	Foreign securities	3,343.60			267			(18.3		)			3,592.30
	Residential mortgage-backed securities	902.7			28.9			(3.9		)			927.7
	Commercial mortgage-backed securities	1,324.60			52.8			(1.6		)	(1)		1,375.80
	Other asset-backed securities	644.7			5.8			(6.5		)	(1)		644
	Redeemable preferred securities	56.8			12.5			—					69.3
	Total debt securities	20,146.80			1,347.30			(72.3		)			21,421.80
	Equity securities	23.3			0.4			(3.8		)			19.9
	Total debt and equity securities (2)	$	20,170.10		$	1,347.70		$	(76.1	)			$	21,441.70
	(1)	At March 31, 2015 and December 31, 2014, we held securities for which we previously recognized $15.6 million and $18.6 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at March 31, 2015 and December 31, 2014 of $3.3 million and $3.6 million, respectively.
	(2)	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 15 beginning on page 33 for additional information on our accounting for discontinued products).  At March 31, 2015, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $428.1 million and gross unrealized capital losses of $9.7 million and, at December 31, 2014, debt and equity securities with a fair value of approximately $3.6 billion, gross unrealized capital gains of $391.3 million and gross unrealized capital losses of $16.7 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, 2015 is shown below by contractual maturity.  Actual maturities may differ from contractual maturities because securities may be restructured, called or prepaid.
	(Millions)	Fair
		Value
	Due to mature:
	Less than one year	$	1,104.50
	One year through five years	5,631.90
	After five years through ten years	5,817.10
	Greater than ten years	5,990.60
	Residential mortgage-backed securities	915.3
	Commercial mortgage-backed securities	1,351.50
	Other asset-backed securities	750.3
	Total	$	21,561.20
Debt and Equity Securities in an Unrealized Capital Loss Position	Summarized below are the debt and equity securities we held at March 31, 2015 and December 31, 2014 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)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
		Value			Losses			Value				Losses			Value		Losses
	March 31, 2015
	Debt securities:
	U.S. government securities	$	64		$	0.9		$	12.9			$	0.4		$	76.9	$	1.3
	States, municipalities and political subdivisions	535			4.3			139.3				3.5			674.3		7.8
	U.S. corporate securities	567.1			9.6			140				4.7			707.1		14.3
	Foreign securities	304.3			7.3			72.8				3			377.1		10.3
	Residential mortgage-backed securities	54.7			0.2			106.3				1.7			161		1.9
	Commercial mortgage-backed securities	76.1			0.1			34.1				0.4			110.2		0.5
	Other asset-backed securities	177.2			2.7			16.1				0.1			193.3		2.8
	Redeemable preferred securities	3			—			—				—			3		—
	Total debt securities	1,781.40			25.1			521.5				13.8			2,302.90		38.9
	Equity securities	—			—			1.4				3.8			1.4		3.8
	Total debt and equity securities (1)	$	1,781.40		$	25.1		$	522.9			$	17.6		$	2,304.30	$	42.7
	December 31, 2014
	Debt securities:
	U.S. government securities	$	20.6		$	0.1		$	19.8			$	0.5		$	40.4	$	0.6
	States, municipalities and political subdivisions	457.4			2.2			347.4				5.6			804.8		7.8
	U.S. corporate securities	1,074.10			19.9			515.2				13.7			1,589.30		33.6
	Foreign securities	540			12.8			148				5.5			688		18.3
	Residential mortgage-backed securities	3.9			0.1			166.9				3.8			170.8		3.9
	Commercial mortgage-backed securities	181.5			0.7			69				0.9			250.5		1.6
	Other asset-backed securities	373.1			6.1			21.3				0.4			394.4		6.5
	Redeemable preferred securities	3			—			—				—			3		—
	Total debt securities	2,653.60			41.9			1,287.60				30.4			3,941.20		72.3
	Equity securities	8			—			1.4				3.8			9.4		3.8
	Total debt and equity securities (1)	$	2,661.60		$	41.9		$	1,289.00			$	34.2		$	3,950.60	$	76.1
	(1)	At March 31, 2015 and December 31, 2014, debt and equity securities in an unrealized capital loss position of $9.7 million and $16.7 million, respectively, and with related fair value of $221.4 million and $402.7 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, 2015 were as follows:
		Supporting discontinued and						Supporting remaining							Total
		experience-rated products						products
	(Millions)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
		Value			Losses			Value				Losses			Value		Losses
	Due to mature:
	Less than one year	$	—		$	—		$	27.4			$	0.1		$	27.4	$	0.1
	One year through five years	5.5			—			505.7				4.6			511.2		4.6
	After five years through ten years	112.6			2.3			656.5				11.7			769.1		14
	Greater than ten years	91.6			3.6			439.1				11.4			530.7		15
	Residential mortgage-backed securities	—			—			161				1.9			161		1.9
	Commercial mortgage-backed securities	10.3			—			99.9				0.5			110.2		0.5
	Other asset-backed securities	—			—			193.3				2.8			193.3		2.8
	Total	$	220		$	5.9		$	2,082.90			$	33		$	2,302.90	$	38.9
Net realized capital gains (losses)	Net realized capital gains (losses) for the three months ended March 31, 2015 and 2014, excluding amounts related to experience-rated contract holders and discontinued products, were as follows:
	(Millions)	2015			2014
	OTTI losses on debt securities recognized in earnings	$	(2.4	)	$	(.2	)
	Net realized capital gains, excluding OTTI losses on debt securities	10.5			28.7
	Net realized capital gains	$	8.1		$	28.5
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 debt securities and the related gross realized capital gains and losses for the three months ended March 31, 2015 and 2014 were as follows:
	(Millions)	2015			2014
	Proceeds on sales	$	945.9		$	1,092.80
	Gross realized capital gains	24.9			24.6
	Gross realized capital losses	8.8			13
Activity in mortgage loan portfolio	During the three months ended March 31, 2015 and 2014 we had the following activity in our mortgage loan portfolio:
	(Millions)	2015			2014
	New mortgage loans	$	12.7		$	33.9
	Mortgage loans fully repaid	39.5			19.8
	Mortgage loans foreclosed	9			—
Mortgage loan internal credit rating	Based upon our most recent assessments at March 31, 2015 and December 31, 2014, our mortgage loans were given the following credit quality indicators:
	(In Millions, except credit ratings indicator)	March 31,			December 31,
		2015			2014
	1	$	58.7		$	59.7
	2 to 4	1,416.20			1,443.40
	5	13.3			18.6
	6 and 7	27			40.5
	Total	$	1,515.20		$	1,562.20
Net Investment Income	Sources of net investment income for the three months ended March 31, 2015 and 2014 were as follows:
	(Millions)	2015			2014
	Debt securities	$	196.4		$	198.1
	Mortgage loans	21.9			23.9
	Other investments	23.9			30.1
	Gross investment income	242.2			252.1
	Investment expenses	(9.3		)	(7.9		)
	Net investment income (1)	$	232.9		$	244.2
	(1)	Net investment income includes $66.6 million and $80.4 million for the three months ended March 31, 2015 and 2014, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom1

Other Comprehensive (Loss) Income (Tables)	3 Months Ended
	Mar. 31, 2015
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	Shareholders’ equity included the following activity in accumulated other comprehensive loss for the three months ended March 31, 2015 and 2014:
		Net Unrealized Gains (Losses)														Pension and OPEB Plans										Total
																										Accumulated
																										Other
		Securities									Foreign															Comprehensive
											Currency															(Loss) Income
											and
	(Millions)	Previously					All Other				Derivatives			Unrecognized					Unrecognized
		Impaired (1)												Net Actuarial					Prior Service
														Losses					Credit
	Three months ended March 31, 2015
	Balance at December 31, 2014	$	34.9				$	568			$	(60.9	)			$	(1,670.9	)			$	17.6				$	(1,111.3	)
	Other comprehensive (loss) income
	before reclassifications	(2.2		)			77.9				(13.9		)			—					—					61.8
	Amounts reclassified from accumulated
	other comprehensive income	(1.6		)	(2	)	7.2		(2	)	1			(3	)	10.5			(4	)	(.7		)	(4	)	16.4
	Other comprehensive (loss) income	(3.8		)			85.1				(12.9		)			10.5					(.7		)			78.2
	Balance at March 31, 2015	$	31.1				$	653.1			$	(73.8	)			$	(1,660.4	)			$	16.9				$	(1,033.1	)
	Three months ended March 31, 2014
	Balance at December 31, 2013	$	34.2				$	326.8			$	0.4				$	(1,293.8	)			$	20.3				$	(912.1	)
	Other comprehensive income (loss)
	before reclassifications	1.1					137.2				(12.5		)			—					—					125.8
	Amounts reclassified from accumulated
	other comprehensive income	(.4		)	(2	)	3.3		(2	)	(10.1		)	(3	)	7.7			(4	)	(.6		)	(4	)	(.1		)
	Other comprehensive income (loss)	0.7					140.5				(22.6		)			7.7					(.6		)			125.7
	Balance at March 31, 2014	$	34.9				$	467.3			$	(22.2	)			$	(1,286.1	)			$	19.7				$	(786.4	)
	(1)	Represents unrealized gains 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 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 foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the effective portion of derivatives related to interest rate swaps which are reflected in interest expense and were not material during the three months ended March 31, 2015 or 2014. Refer to Note 9 of Condensed Notes to Consolidated Financial Statements beginning on page 26 for additional information.
	(4)	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 8 of Condensed Notes to Consolidated Financial Statements beginning on page 25 for additional information.

Financial_Instruments_Tables

Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets	Financial assets and liabilities measured at fair value on a recurring basis in our balance sheets at March 31, 2015 and December 31, 2014 were as follows:
	(Millions)	Level 1			Level 2				Level 3				Total
	March 31, 2015
	Assets:
	Debt securities:
	U.S. government securities	$	1,253.90		$	197.2			$	—			$	1,451.10
	States, municipalities and political subdivisions	—			4,859.40				1.1				4,860.50
	U.S. corporate securities	—			8,561.40				56.1				8,617.50
	Foreign securities	—			3,515.10				31.8				3,546.90
	Residential mortgage-backed securities	—			915.3				—				915.3
	Commercial mortgage-backed securities	—			1,344.00				7.5				1,351.50
	Other asset-backed securities	—			708.5				41.8				750.3
	Redeemable preferred securities	—			64				4.1				68.1
	Total debt securities	1,253.90			20,164.90				142.4				21,561.20
	Equity securities	1.8			—				20.8				22.6
	Derivatives	—			0.3				—				0.3
	Total	$	1,255.70		$	20,165.20			$	163.2			$	21,584.10
	Liabilities:
	Derivatives	$	—		$	69.5			$	—			$	69.5
	December 31, 2014
	Assets:
	Debt securities:
	U.S. government securities	$	1,198.40		$	198.5			$	—			$	1,396.90
	States, municipalities and political subdivisions	—			4,808.20				1.2				4,809.40
	U.S. corporate securities	—			8,548.20				58.2				8,606.40
	Foreign securities	—			3,560.70				31.6				3,592.30
	Residential mortgage-backed securities	—			927.7				—				927.7
	Commercial mortgage-backed securities	—			1,368.30				7.5				1,375.80
	Other asset-backed securities	—			602.5				41.5				644
	Redeemable preferred securities	—			65.2				4.1				69.3
	Total debt securities	1,198.40			20,079.30				144.1				21,421.80
	Equity securities	1.8			—				18.1				19.9
	Derivatives	—			0.3				—				0.3
	Total	$	1,200.20		$	20,079.60			$	162.2			$	21,442.00
	Liabilities:
	Derivatives	$	—		$	53.4			$	—			$	53.4
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 certain of our financial instruments at March 31, 2015 and December 31, 2014 were as follows:
		Carrying			Estimated Fair Value
	(Millions)	Value			Level 1			Level 2			Level 3			Total
	March 31, 2015
	Assets:
	Mortgage loans	$	1,515.20		$	—		$	—		$	1,581.60		$	1,581.60
	Bank loans	233.5			—			223.2			9.3			232.5
	Equity securities (1)	34.9			N/A			N/A			N/A			N/A
	Liabilities:
	Investment contract liabilities:
	With a fixed maturity	8.9			—			—			8.9			8.9
	Without a fixed maturity	548.8			—			—			542			542
	Long-term debt	7,846.10			—			8,781.80			—			8,781.80
	December 31, 2014
	Assets:
	Mortgage loans	$	1,562.20		$	—		$	—		$	1,621.40		$	1,621.40
	Bank loans	231.2			—			217.6			9.4			227
	Equity securities (1)	34.9			N/A			N/A			N/A			N/A
	Liabilities:
	Investment contract liabilities:
	With a fixed maturity	16.6			—			—			16.6			16.6
	Without a fixed maturity	557.5			—			—			551.5			551.5
	Long-term debt	8,081.30			—			8,764.80			—			8,764.80
	(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, 2015 and December 31, 2014 were as follows:
		March 31, 2015														December 31, 2014
	(Millions)	Level 1			Level 2				Level 3				Total			Level 1		Level 2		Level 3		Total
	Debt securities	$	698.2		$	2,740.30			$	3.5			$	3,442.00		$	876	$	2,495.00	$	2.9	$	3,373.90
	Equity securities	179.9			5.9				—				185.8			173.3		5.7		—		179
	Derivatives	—			(1.1		)		—				(1.1		)	—		0.2		—		0.2
	Common/collective trusts	—			595.9				—				595.9			—		574		—		574
	Total (1)	$	878.1		$	3,341.00			$	3.5			$	4,222.60		$	1,049.30	$	3,074.90	$	2.9	$	4,127.10
	(1)	Excludes $225.4 million and $204.4 million of cash and cash equivalents and other receivables at March 31, 2015 and December 31, 2014, respectively.
Balance Sheet Offsetting Assets	Financial assets, including derivative assets, subject to offsetting and enforceable master netting arrangements as of March 31, 2015 and December 31, 2014 were as follows:
		Gross Amounts of		Gross Amounts Not Offset
		Recognized Assets (1)		in the Balance Sheets
				Financial Instruments			Cash Collateral Received
	(Millions)									Net Amount
	31-Mar-15
	Derivatives	$	0.3	$	10.7		$	—		$	11
	Total	$	0.3	$	10.7		$	—		$	11
	31-Dec-14
	Derivatives	$	0.3	$	10.2		$	—		$	10.5
	Total	$	0.3	$	10.2		$	—		$	10.5
	(1) There were no amounts offset in our balance sheets at March 31, 2015 or December 31, 2014.
Balance Sheet Offsetting Liabilities	Financial liabilities, including derivative liabilities, subject to offsetting and enforceable master netting arrangements as of March 31, 2015 and December 31, 2014 were as follows:
		Gross Amounts of		Gross Amounts Not Offset
		Recognized Liabilities (1)		in the Balance Sheets
				Financial Instruments			Cash Collateral Paid
	(Millions)									Net Amount
	31-Mar-15
	Derivatives	$	69.5	$	1.3		$	(70.4	)	$	0.4
	Securities lending	864		(864.0		)	—			—
	Total	$	933.5	$	(862.7	)	$	(70.4	)	$	0.4
	31-Dec-14
	Derivatives	$	53.4	$	0.9		$	(49.0	)	$	5.3
	Securities lending	826.9		(826.9		)	—			—
	Repurchase agreements	201.7		—			—			201.7
	Total	$	1,082.00	$	(826.0	)	$	(49.0	)	$	207
	(1) There were no amounts offset in our balance sheets at March 31, 2015 or December 31, 2014.

Pension_and_Other_Postretireme1

Pension and Other Postretirement Plans (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014 were as follows:
		Pension Plans						OPEB Plans
	(Millions)	2015			2014			2015			2014
	Service cost	$	—		$	—		$	—		$	—
	Amortization of prior service credit	(.1		)	(.1		)	(.9		)	(.9		)
	Interest cost	65.2			72.1			2.7			3
	Expected return on plan assets	(104.8		)	(105.6		)	(.8		)	(.8		)
	Recognized net actuarial losses	15.4			11.7			0.7			0.2
	Net periodic benefit (income) cost	$	(24.3	)	$	(21.9	)	$	1.7		$	1.5

Debt_Tables

Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Carrying Value of Long-Term Debt	The carrying value of our long-term debt at March 31, 2015 and December 31, 2014 was as follows:
	(Millions)	March 31,		December 31,
		2015		2014
	Senior notes, 6.125%, due 2015 (1)	$	—	$	229.3
	Senior notes, 5.95%, due 2017	414.3		418.3
	Senior notes, 1.75%, due 2017	249.3		249.2
	Senior notes, 1.5%, due 2017	498.8		498.6
	Senior notes, 2.2%, due 2019	374.7		374.7
	Senior notes, 3.95%, due 2020	745.4		745.2
	Senior notes, 5.45%, due 2021	685.2		688.6
	Senior notes, 4.125%, due 2021	495.7		495.5
	Senior notes, 2.75%, due 2022	987.2		986.8
	Senior notes, 3.5%, due 2024	747		746.9
	Senior notes, 6.625%, due 2036	769.8		769.8
	Senior notes, 6.75%, due 2037	530.8		530.7
	Senior notes, 4.5%, due 2042	480.9		480.8
	Senior notes, 4.125%, due 2042	492.9		492.8
	Senior notes, 4.75%, due 2044	374.1		374.1
	Total long-term debt	7,846.10		8,081.30
	Less current portion of long-term debt	—		229.3
	Total long-term debt, less current portion	$	7,846.10	$	7,852.00
	-1	The 6.125% senior notes were repaid in January 2015. These notes were classified as current in the consolidated balance sheet as of December 31, 2014.

Capital_Stock_Tables

Capital Stock (Tables)	3 Months Ended
	Mar. 31, 2015
Class of Stock Disclosures [Abstract]
Accelerated Share Repurchases	We completed the following accelerated share repurchase program during the three months ended March 31, 2015:
	Trade Date:	Value of Repurchase Program (Millions)			Repurchase Period	Number of Shares Repurchased (Millions)
	15-Dec-14	$	150		January and February 2015	1.6
Dividends declared	During the three months ended March 31, 2015 our Board declared the following cash dividend:
	Date Declared	Dividend Amount				Stockholders of	Date Paid/	Total Dividends
		Per Share				Record Date	To be Paid	(Millions)
	February 27, 2015		$	0.25		April 9, 2015	April 24, 2015		$	87.3
Black Scholes option pricing model	The SARs granted to certain employees during the three months ended March 31, 2015 and 2014 had an estimated fair market value of $32.13 and $22.68 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 three months ended March 31, 2015 and 2014:
		2015				2014
	Expected term (in years)	6.48				5.72
	Volatility	33.4		%		35.8		%
	Risk-free interest rate	1.81		%		1.74		%
	Dividend yield	1.13		%		1.36		%
	Initial price	$	100.5			$	72.26

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Summarized financial information of segments	Summarized financial information of our segments for the three months ended March 31, 2015 and 2014 were as follows:
	(Millions)	Health			Group			Large Case		Corporate			Total Company
		Care			Insurance			Pensions		Financing
	Three Months Ended March 31, 2015
	Revenue from external customers	$	14,285.80		$	554.5		$	12.8	$	—		$	14,853.10
	Operating earnings (loss) (1)	835.6			43.9			2.1		(37.3		)	844.3
	Three Months Ended March 31, 2014
	Revenue from external customers	$	13,131.40		$	544.4		$	46.3	$	—		$	13,722.10
	Operating earnings (loss) (1)	719			41.2			4.8		(43.0		)	722
	(1)	Operating 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 operating earnings (1) to net income attributable to Aetna for the three months ended March 31, 2015 and 2014 was as follows:
	(Millions)	2015			2014
	Operating earnings (1)	$	844.3		$	722
	Transaction and integration-related costs, net of tax	(30.7		)	(41.9		)
	Loss on early extinguishment of long-term debt, net of tax	—			(59.7		)
	Release of litigation-related reserve, net of tax	—			67
	Amortization of other acquired intangible assets, net of tax	(41.1		)	(40.4		)
	Net realized capital gains, net of tax	5			18.5
	Net income attributable to Aetna	$	777.5		$	665.5
	(1)	In addition to net realized capital gains and amortization of other acquired intangible assets, the following other items are excluded from operating earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:
	•	We incurred transaction and integration-related costs of $30.7 million ($45.6 million pretax) during the three months ended March 31, 2015, related to the acquisitions of Coventry, InterGlobal and bswift, and integration-related costs of $41.9 million ($63.7 million pretax) during the three months ended March 31, 2014, related to the acquisition of Coventry. Transaction costs include advisory, legal and other professional fees which are not deductible for tax purposes and are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses.
	•	We incurred a loss on the early extinguishment of long-term debt of $59.7 million ($91.9 million pretax) during the three months ended March 31, 2014 related to the redemption of our 6.0% senior notes due 2016.
	•	We recorded a charge of $78.0 million ($120.0 million pretax) during the three months ended December 31, 2012 related to the settlement of purported class action litigation regarding our payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffs’ counsel and the costs of administering the settlement. During the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $67.0 million ($103.0 million pretax) in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.

Discontinued_Products_Tables

Discontinued Products (Tables)	3 Months Ended
	Mar. 31, 2015
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, 2015 and 2014 was as follows (pretax):
	(Millions)	2015		2014
	Reserve, beginning of period	$	1,014.70	$	979.5
	Operating income	3.1		5.8
	Net realized capital gains	19		6.3
	Reserve, end of period	$	1,036.80	$	991.6
Assets and Liabilities Supporting Discontinued Products	Assets and liabilities supporting discontinued products at March 31, 2015 and December 31, 2014 were as
	follows: (1)
	(Millions)	2015		2014
	Assets:
	Debt and equity securities available for sale	$	2,384.20	$	2,376.20
	Mortgage loans	349.8		386.8
	Other investments	706.5		662.2
	Total investments	3,440.50		3,425.20
	Other assets	93.1		112.9
	Collateral received under securities loan agreements	201.2		200.7
	Receivable from continuing products (2)	575.2		566.5
	Total assets	$	4,310.00	$	4,305.30
	Liabilities:
	Future policy benefits	$	2,603.30	$	2,645.80
	Reserve for anticipated future losses on discontinued products	1,036.80		1,014.70
	Collateral payable under securities loan agreements	201.2		200.7
	Current and deferred income taxes	24.8		27.9
	Other liabilities (3)	443.9		416.2
	Total liabilities	$	4,310.00	$	4,305.30
	(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.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Accounting Changes and Error Corrections [Abstract]
Health care reform risk corridor receivable	$0	$0
Reinsurance Recoverable Under Health Care Reform	385	338
Net health care reform risk adjustment payable (receivable)	$428	$230

Earnings_Per_Common_Share_Deta

Earnings Per Common Share (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income attributable to Aetna	$777.50		$665.50
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares used to compute basic EPS (in shares)	349.5		361.6
Dilutive effect of outstanding stock-based compensation awards (in shares)	3.2		3.4
Weighted average shares used to compute diluted EPS (in shares)	352.7		365
Basic EPS (in dollars per share)	$2.22		$1.84
Diluted EPS (in dollars per share)	$2.20		$1.82
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)	1.9	[1]	1.3	[1]
Other Securities [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	1.1	[2]	1.3	[2]
[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]	Performance stock units ("PSUs"), certain market stock units ("MSUs") with performance conditions, and performance stock appreciation rights ("PSARs") are excluded from the calculation of diluted EPS if all necessary performance conditions have not been satisfied at the end of the reporting period.

Operating_Expenses_Details

Operating Expenses (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2012
Selling expenses	$414.90		$402.80
General and administrative expenses:
Salaries and related benefits	1,206.60		1,119.50
Other general and administrative expenses	1,195.20	[1],[2]	928.1	[1],[2]
Total general and administrative expenses	2,401.80	[3]	2,047.60	[3]
Total operating expenses	2,816.70		2,450.40
Health Insurer Fee	218.7		154.8
Contribution to ACA Reinsurance Program	53.6		84.9
Litigation Settlement, Expense					120
Release of litigation-related reserve, pre-tax			103
General and administrative transaction and integration-related costs	$45.60		$63.70
[1]	In the three months ended December 31, 2012, we recorded a charge of $120.0 million pretax related to the settlement of purported class action litigation regarding Aetnabs payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffsb counsel and the costs of administering the settlement. In the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $103.0 million pretax in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.
[2]	The three months ended MarchB 31, 2015 and 2014 include estimated fees mandated by the ACA comprised primarily of the health insurer fee of $218.7 million and $154.8 million, respectively, and our estimated contribution to the funding of the reinsurance program of $53.6 million and $84.9 million, respectively. Refer to Note 2 beginning on page 6 for additional information on fees mandated by the ACA.
[3]	The three months ended MarchB 31, 2015 include $45.6 million of transaction and integration-related costs related to the acquisitions of Coventry Health Care, Inc. (bCoventryb), the InterGlobal group (bInterGlobalb) and bSwift LLC (bbswiftb). The three months ended MarchB 31, 2014 include $63.7 million of integration-related costs related to the acquisition of Coventry.

Investments_Details

Investments (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Total Investments [Line Items]
Current	$2,374.10	$2,595.20
Long-term investments	22,587.60	22,193.90
Total investments	24,961.70	24,789.10
Available-for-sale Securities Pledged as Collateral	0	202
Debt And Equity Securities Available For Sale [Member]
Total Investments [Line Items]
Current	2,237.30	2,463.80
Long-term investments	19,346.50	18,977.90
Total investments	21,583.80	21,441.70
Mortgage Loans [Member]
Total Investments [Line Items]
Current	127.6	124.2
Long-term investments	1,387.60	1,438
Total investments	1,515.20	1,562.20
Other Investments [Member]
Total Investments [Line Items]
Current	9.2	7.2
Long-term investments	1,853.50	1,778
Total investments	1,862.70	1,785.20
Securities loaned agreements [Member]
Total Investments [Line Items]
Securities Loaned, Asset	$835	$798

Investments_Debt_and_Equity_Se

Investments - Debt and Equity Securities (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Non-credit related impairments previously recognized in other comprehensive income	$15.60		$18.60
Available-for-sale Securities, Amortized Cost Basis	20,146.60	[1]	20,170.10	[1]
Available-for-sale Securities, Gross Unrealized Gains	1,479.90	[1]	1,347.70	[1]
Available-for-sale Securities, Gross Unrealized Losses	-42.7	[1]	-76.1	[1]
Available-for-sale Securities, Fair Value Disclosure	21,583.80	[1]	21,441.70	[1]
Net Unrealized Capital (Loss) Gains	3.3		3.6
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gains	428.1		391.3
Available-for-sale Securities, Gross Unrealized Losses	-9.7		-16.7
Available-for-sale Securities, Fair Value Disclosure	3,700		3,600
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	20,122.20		20,146.80
Available-for-sale Securities, Gross Unrealized Gains	1,477.90		1,347.30
Available-for-sale Securities, Gross Unrealized Losses	-38.9		-72.3
Available-for-sale Securities, Fair Value Disclosure	21,561.20		21,421.80
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,341		1,301.20
Available-for-sale Securities, Gross Unrealized Gains	111.4		96.3
Available-for-sale Securities, Gross Unrealized Losses	-1.3		-0.6
Available-for-sale Securities, Fair Value Disclosure	1,451.10		1,396.90
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	4,582.40		4,540
Available-for-sale Securities, Gross Unrealized Gains	285.9		277.2
Available-for-sale Securities, Gross Unrealized Losses	-7.8		-7.8
Available-for-sale Securities, Fair Value Disclosure	4,860.50		4,809.40
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	7,961.70		8,033.20
Available-for-sale Securities, Gross Unrealized Gains	670.1		606.8
Available-for-sale Securities, Gross Unrealized Losses	-14.3		-33.6
Available-for-sale Securities, Fair Value Disclosure	8,617.50		8,606.40
Foreign Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,252		3,343.60
Available-for-sale Securities, Gross Unrealized Gains	305.2		267
Available-for-sale Securities, Gross Unrealized Losses	-10.3		-18.3
Available-for-sale Securities, Fair Value Disclosure	3,546.90		3,592.30
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	884.8		902.7
Available-for-sale Securities, Gross Unrealized Gains	32.4		28.9
Available-for-sale Securities, Gross Unrealized Losses	-1.9		-3.9
Available-for-sale Securities, Fair Value Disclosure	915.3		927.7
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,301.50		1,324.60
Available-for-sale Securities, Gross Unrealized Gains	50.5		52.8
Available-for-sale Securities, Gross Unrealized Losses	-0.5	[2]	-1.6	[2]
Available-for-sale Securities, Fair Value Disclosure	1,351.50		1,375.80
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	743.6		644.7
Available-for-sale Securities, Gross Unrealized Gains	9.5		5.8
Available-for-sale Securities, Gross Unrealized Losses	-2.8	[2]	-6.5	[2]
Available-for-sale Securities, Fair Value Disclosure	750.3		644
Redeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	55.2		56.8
Available-for-sale Securities, Gross Unrealized Gains	12.9		12.5
Available-for-sale Securities, Gross Unrealized Losses	0		0
Available-for-sale Securities, Fair Value Disclosure	68.1		69.3
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	24.4		23.3
Available-for-sale Securities, Gross Unrealized Gains	2		0.4
Available-for-sale Securities, Gross Unrealized Losses	-3.8		-3.8
Available-for-sale Securities, Fair Value Disclosure	$22.60		$19.90
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 15 beginning on page 33 for additional information on our accounting for discontinued products). At MarchB 31, 2015, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $428.1 million and gross unrealized capital losses of $9.7 million and, at DecemberB 31, 2014, debt and equity securities with a fair value of approximately $3.6 billion, gross unrealized capital gains of $391.3 million and gross unrealized capital losses of $16.7 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.
[2]	At MarchB 31, 2015 and DecemberB 31, 2014, we held securities for which we previously recognized $15.6 million and $18.6 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at MarchB 31, 2015 and DecemberB 31, 2014 of $3.3 million and $3.6 million, respectively.

Investments_Debt_Securities_by

Investments - Debt Securities by Maturity (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	$21,583.80	[1]	$21,441.70	[1]
Debt Securities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	21,561.20		21,421.80
Available-for-sale Securities With Established Maturities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Due To Mature Less Than One Year	1,104.50
Due to mature one year through five years	5,631.90
Due to mature after five years through ten years	5,817.10
Due to mature greater than ten years	5,990.60
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	3 years 0 months 22 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	915.3		927.7
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	1 year 0 months 361 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,351.50		1,375.80
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	1 year 0 months 165 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	$750.30		$644
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 15 beginning on page 33 for additional information on our accounting for discontinued products). At MarchB 31, 2015, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $428.1 million and gross unrealized capital losses of $9.7 million and, at DecemberB 31, 2014, debt and equity securities with a fair value of approximately $3.6 billion, gross unrealized capital gains of $391.3 million and gross unrealized capital losses of $16.7 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_Po

Investments - Unrealized Loss Position (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$1,781.40	[1]	$2,661.60	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	25.1	[1]	41.9	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	522.9	[1]	1,289	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	17.6	[1]	34.2	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,304.30	[1]	3,950.60	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	42.7	[1]	76.1	[1]
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	221.4		402.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	9.7		16.7
Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,781.40		2,653.60
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	25.1		41.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	521.5		1,287.60
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	13.8		30.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,302.90	[1]	3,941.20	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	38.9	[1]	72.3	[1]
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	220
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	5.9
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	2,082.90
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	33
US Government Agencies Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	64		20.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0.9		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	12.9		19.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0.4		0.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	76.9	[1]	40.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1.3	[1]	0.6	[1]
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	535		457.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	4.3		2.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	139.3		347.4
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	3.5		5.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	674.3	[1]	804.8	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	7.8	[1]	7.8	[1]
Domestic Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	567.1		1,074.10
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	9.6		19.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	140		515.2
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	4.7		13.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	707.1	[1]	1,589.30	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	14.3	[1]	33.6	[1]
Foreign Corporate Debt Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	304.3		540
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	7.3		12.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	72.8		148
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	3		5.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	377.1	[1]	688	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	10.3	[1]	18.3	[1]
Residential Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	54.7		3.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0.2		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	106.3		166.9
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	1.7		3.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	161	[1]	170.8	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1.9	[1]	3.9	[1]
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	76.1		181.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0.1		0.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	34.1		69
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0.4		0.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	110.2	[1]	250.5	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0.5	[1]	1.6	[1]
Other Asset-Backed Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	177.2		373.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	2.7		6.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16.1		21.3
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0.1		0.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	193.3	[1]	394.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	2.8	[1]	6.5	[1]
Redeemable Preferred Stock [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	3		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3	[1]	3	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0	[1]	0	[1]
Equity Securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0		8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1.4		1.4
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	3.8		3.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1.4	[1]	9.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$3.80	[1]	$3.80	[1]
[1]	At MarchB 31, 2015 and DecemberB 31, 2014, debt and equity securities in an unrealized capital loss position of $9.7 million and $16.7 million, respectively, and with related fair value of $221.4 million and $402.7 million, respectively, related to experience-rated and discontinued products.

Investments_Unrealized_Loss_Po1

Investments - Unrealized Loss Position Maturities (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$42.70	[1]	$76.10	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,304.30	[1]	3,950.60	[1]
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	38.9	[1]	72.3	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,302.90	[1]	3,941.20	[1]
Supporting Remaining Products [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	33
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,082.90
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	9.7		16.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	221.4		402.7
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, Aggregate Losses	5.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	220
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, Aggregate Losses	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	27.4
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, Aggregate Losses	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	27.4
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, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	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, Aggregate Losses	4.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	511.2
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, Aggregate Losses	4.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	505.7
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, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5.5
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, Aggregate Losses	14
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	769.1
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, Aggregate Losses	11.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	656.5
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, Aggregate Losses	2.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	112.6
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, Aggregate Losses	15
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	530.7
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, Aggregate Losses	11.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	439.1
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, Aggregate Losses	3.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	91.6
Residential Mortgage Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	161
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, Aggregate Losses	1.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	161
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, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0
Commercial Mortgage Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	110.2
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, Aggregate Losses	0.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	99.9
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, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10.3
Other Asset-Backed Securities [Member] | Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	2.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	193.3
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, Aggregate Losses	2.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	193.3
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, Aggregate Losses	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$0
[1]	At MarchB 31, 2015 and DecemberB 31, 2014, debt and equity securities in an unrealized capital loss position of $9.7 million and $16.7 million, respectively, and with related fair value of $221.4 million and $402.7 million, respectively, related to experience-rated and discontinued products.

Investments_Realized_Gains_Det

Investments - Realized Gains (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
OTTI losses on debt securities recognized in earnings	($2.40)	($0.20)
Net realized capital gains (losses), excluding OTTI losses on securities	10.5	28.7
Net realized capital gains (losses)	8.1	28.5
Debt Securities [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Proceeds On Sales	945.9	1,092.80
Gross Realized Capital Gains	24.9	24.6
Gross Realized Capital Losses	$8.80	$13

Investments_Mortgage_Loans_Det

Investments - Mortgage Loans (Details) (Commercial Real Estate [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Movement in Mortgage Loans on Real Estate [Roll Forward]
New Mortgage Loans	$12.70	$33.90
Mortgage loans fully repaid	39.5	19.8
Mortgage Loans on Real Estate	1,515.20		1,562.20
Mortgage Loans on Real Estate, Foreclosures	9	0
Category 1 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	58.7		59.7
Category 2 to 4 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	1,416.20		1,443.40
Category 5 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	13.3		18.6
Categories 6 and 7 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	$27		$40.50

Investments_Variable_Interest_

Investments - Variable Interest Entities and Noncontrolling Interests (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	$22,587,600,000		$22,193,900,000
Stockholders' Equity Attributable to Noncontrolling Interest	66,300,000		69,200,000
Noncontrolling Interest [Abstract]
Net income (loss) attributable to non-controlling interest	-1,200,000	3,900,000
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Long-term investments	210,000,000		209,000,000
Real Estate Partnerships [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity Assets	5,800,000,000		5,700,000,000
Hedge Fund Partnerships [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Variable Interest Entity Assets	6,900,000,000		7,100,000,000
Noncontrolling Interest [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Stockholders' Equity Attributable to Noncontrolling Interest	66,300,000	57,400,000	69,200,000	52,700,000
Noncontrolling Interest [Abstract]
Net income (loss) attributable to non-controlling interest	($1,200,000)	$3,900,000

Investments_Investment_Income_

Investments - Investment Income (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$242.20		$252.10
Investment expenses	-9.3		-7.9
Net Investment Income	232.9	[1]	244.2	[1]
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net Investment Income	66.6		80.4
Debt Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	196.4		198.1
Mortgage Loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	21.9		23.9
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$23.90		$30.10
[1]	Net investment income includes $66.6 million and $80.4 million for the three months ended MarchB 31, 2015 and 2014, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom2

Other Comprehensive (Loss) Income (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	($1,111.30)
Other comprehensive (loss) income	78.2		125.7
Balance at end of period	-1,033.10
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)	-2.2	[1]	1.1	[1]
Net unrealized gains (losses) on securities, reclassification of gains to earnings	-1.6	[1],[2]	-0.4	[1],[2]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	34.9	[1]	34.2	[1]
Other comprehensive (loss) income	-3.8	[1]	0.7	[1]
Balance at end of period	31.1	[1]	34.9	[1]
Net Unrealized Gains (Losses) All Other Securities [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)	77.9		137.2
Net unrealized gains (losses) on securities, reclassification of gains to earnings	7.2	[2]	3.3	[2]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	568		326.8
Other comprehensive (loss) income	85.1		140.5
Balance at end of period	653.1		467.3
Net Unrealized Gains (Losses) Foreign Currency And Derivatives [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)	-13.9		-12.5
Foreign currency and derivatives reclassification of losses to earnings	1	[3]	-10.1	[3]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	-60.9		0.4
Other comprehensive (loss) income	-12.9		-22.6
Balance at end of period	-73.8		-22.2
Pension And OPEB Plans Unrecognized Net Actuarial (Losses) [Member]
Comprehensive Income Loss [Line Items]
Other comprehensive income, Pensions and Other Post Retirement Employee Benefit Plans, net of tax	0		0
Amortization of net actuarial losses	10.5	[4]	7.7	[4]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	-1,670.90		-1,293.80
Other comprehensive (loss) income	10.5		7.7
Balance at end of period	-1,660.40		-1,286.10
Pension And OPEB Plans Unrecognized Prior Service Cost [Member]
Comprehensive Income Loss [Line Items]
Other comprehensive income, Pensions and Other Post Retirement Employee Benefit Plans, net of tax	0		0
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax	-0.7	[4]	-0.6	[4]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	17.6		20.3
Other comprehensive (loss) income	-0.7		-0.6
Balance at end of period	16.9		19.7
Accumulated Other Comprehensive Loss [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	61.8		125.8
Other Comprehensive Income Loss Net Of Tax Reclassification To Earnings	16.4		-0.1
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	-1,111.30		-912.1
Other comprehensive (loss) income	78.2		125.7
Balance at end of period	($1,033.10)		($786.40)
[1]	Represents unrealized gains 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 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 foreign currency gains (losses) and derivatives are reflected in net realized capital gains (losses) within the Consolidated Statements of Income, except for the effective portion of derivatives related to interest rate swaps which are reflected in interest expense and were not material during the three months ended MarchB 31, 2015 or 2014. Refer to Note 9 of Condensed Notes to Consolidated Financial Statements beginning on page 26 for additional information.
[4]	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statements of Income. Refer to Note 8 of Condensed Notes to Consolidated Financial Statements beginning on pageB 25 for additional information.

Financial_Instruments_Fair_Val

Financial Instruments - Fair Value Measurements (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross Transfers Into Level 3	$0		$0
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	21,583,800,000	[1]		21,441,700,000	[1]
Gross transfers out of level 3	0		0
Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	21,561,200,000			21,421,800,000
US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,451,100,000			1,396,900,000
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	4,860,500,000			4,809,400,000
Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	8,617,500,000			8,606,400,000
Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	3,546,900,000			3,592,300,000
Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	915,300,000			927,700,000
Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,351,500,000			1,375,800,000
Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	750,300,000			644,000,000
Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	68,100,000			69,300,000
Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	22,600,000			19,900,000
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0			0
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	0			0
Assets, Fair Value Disclosure	1,255,700,000			1,200,200,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	69,500,000			53,400,000
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	300,000			300,000
Assets, Fair Value Disclosure	20,165,200,000			20,079,600,000
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	0			0
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	0			0
Assets, Fair Value Disclosure	163,200,000			162,200,000
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Level 1 and Level 2	0		0
Derivative Liabilities	69,500,000			53,400,000
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	300,000			300,000
Assets, Fair Value Disclosure	21,584,100,000			21,442,000,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,253,900,000			1,198,400,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	20,164,900,000			20,079,300,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	142,400,000			144,100,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	21,561,200,000			21,421,800,000
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,253,900,000			1,198,400,000
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	197,200,000			198,500,000
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,451,100,000			1,396,900,000
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	4,859,400,000			4,808,200,000
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,100,000			1,200,000
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	4,860,500,000			4,809,400,000
Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	8,561,400,000			8,548,200,000
Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	56,100,000			58,200,000
Fair Value, Measurements, Recurring [Member] | Domestic Corporate Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	8,617,500,000			8,606,400,000
Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	3,515,100,000			3,560,700,000
Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	31,800,000			31,600,000
Fair Value, Measurements, Recurring [Member] | Foreign Corporate Debt Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	3,546,900,000			3,592,300,000
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	915,300,000			927,700,000
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Residential Mortgage Backed Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	915,300,000			927,700,000
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,344,000,000			1,368,300,000
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	7,500,000			7,500,000
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,351,500,000			1,375,800,000
Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	708,500,000			602,500,000
Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	41,800,000			41,500,000
Fair Value, Measurements, Recurring [Member] | Other Asset-Backed Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	750,300,000			644,000,000
Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	64,000,000			65,200,000
Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	4,100,000			4,100,000
Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stock [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	68,100,000			69,300,000
Fair Value, Measurements, Recurring [Member] | Brokered Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	124,000,000			126,000,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,800,000			1,800,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	0			0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	20,800,000			18,100,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	22,600,000			19,900,000
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [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, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	0			0
Bank loans	223,200,000			217,600,000
Investment contracts with a fixed maturity	0			0
Investment contracts without a fixed maturity	0			0
Long-term debt	8,781,800,000			8,764,800,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	1,581,600,000			1,621,400,000
Bank loans	9,300,000			9,400,000
Investment contracts with a fixed maturity	8,900,000			16,600,000
Investment contracts without a fixed maturity	542,000,000			551,500,000
Long-term debt	0			0
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	1,581,600,000			1,621,400,000
Bank loans	232,500,000			227,000,000
Investment contracts with a fixed maturity	8,900,000			16,600,000
Investment contracts without a fixed maturity	542,000,000			551,500,000
Long-term debt	8,781,800,000			8,764,800,000
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	1,515,200,000			1,562,200,000
Bank loans	233,500,000			231,200,000
Equity Securities (Cost Method)	34,900,000	[2]		34,900,000	[2]
Investment contracts with a fixed maturity	8,900,000			16,600,000
Investment contracts without a fixed maturity	548,800,000			557,500,000
Long-term debt	$7,846,100,000			$8,081,300,000
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 15 beginning on page 33 for additional information on our accounting for discontinued products). At MarchB 31, 2015, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $428.1 million and gross unrealized capital losses of $9.7 million and, at DecemberB 31, 2014, debt and equity securities with a fair value of approximately $3.6 billion, gross unrealized capital gains of $391.3 million and gross unrealized capital losses of $16.7 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.
[2]	It was not practical to estimate the fair value of these cost-method investments as it represents shares of unlisted companies.

Financial_Instruments_Separate

Financial Instruments - Separate Accounts Fair Value (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	$4,448		$4,331.50
Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	4,222.60	[1]	4,127.10	[1]
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	878.1	[1]	1,049.30	[1]
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	3,341	[1]	3,074.90	[1]
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	3.5	[1]	2.9	[1]
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	698.2		876
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	2,740.30		2,495
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	3.5		2.9
Debt Securities [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	3,442		3,373.90
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	179.9		173.3
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	5.9		5.7
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
Equity Securities [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	185.8		179
Derivatives [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
Derivatives [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	-1.1		0.2
Derivatives [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
Derivatives [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	-1.1		0.2
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	595.9		574
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
Common/Collective Trusts [Member] | Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	595.9		574
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	$225.40		$204.40
[1]	Excludes $225.4 million and $204.4 million of cash and cash equivalents and other receivables at MarchB 31, 2015 and DecemberB 31, 2014, respectively.

Financial_Instruments_Balance_

Financial Instruments - Balance Sheet Offsetting (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]
Collateral received under securities loan agreements	$864		$826.90
Net amount subject to offsetting (Liabilities)	0.4		207
Total Gross Liabilities Recognized Subject to Offsetting	933.5	[1]	1,082	[1]
Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.3	[1]	0.3	[1]
Derivative Assets (including collateral)	11		10.5
Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value (Assets)	10.7		10.2
Collateral Already Posted, Aggregate Fair Value (Liabilities)	-862.7		-826
Cash [Member]
Derivatives, Fair Value [Line Items]
Cash collateral received (Assets)	0		0
Collateral Already Posted, Aggregate Fair Value (Liabilities)	-70.4		-49
Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities (including collateral)	0.4		5.3
Derivative Liability, Fair Value, Gross Liability	69.5	[1]	53.4	[1]
Derivative [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0.3	[1]	0.3	[1]
Derivative Assets (including collateral)	11		10.5
Derivative [Member] | Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value (Assets)	10.7		10.2
Collateral Already Posted, Aggregate Fair Value (Liabilities)	1.3		0.9
Derivative [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Cash collateral received (Assets)	0		0
Collateral Already Posted, Aggregate Fair Value (Liabilities)	-70.4		-49
Securities loaned agreements [Member]
Derivatives, Fair Value [Line Items]
Collateral received under securities loan agreements	864	[1]	826.9	[1]
Securities loaned agreements, net amount	0		0
Securities loaned agreements [Member] | Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Payable Under Securities Loan Agreements (Liabilities)	-864		-826.9
Securities loaned agreements [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value (Liabilities)	0		0
Repurchase Agreements [Member]
Derivatives, Fair Value [Line Items]
Collateral payable under repurchase agreements			201.7
Repurchase agreement liability, net			201.7
Repurchase Agreements [Member] | Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral payable under repurchase agreements			0
Repurchase Agreements [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Collateral payable under repurchase agreements			$0
[1]	There were no amounts offset in our balance sheets at MarchB 31, 2015 or DecemberB 31, 2014.

Pension_and_Other_Postretireme2

Pension and Other Postretirement Plans (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$0	$0
Amortization of prior service credit	-0.1	-0.1
Interest cost	65.2	72.1
Expected Return on Plan Assets	-104.8	-105.6
Amortization of net actuarial losses	15.4	11.7
Net periodic benefit (income) cost	-24.3	-21.9
OPEB Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0
Amortization of prior service credit	-0.9	-0.9
Interest cost	2.7	3
Expected Return on Plan Assets	-0.8	-0.8
Amortization of net actuarial losses	0.7	0.2
Net periodic benefit (income) cost	$1.70	$1.50

Debt_Details

Debt (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Federal Home Loan Bank, Maximum Amount Available	$850
Federal Home Loan Bank, Amount Outstanding	0			0
Long-term Debt	7,846.10			8,081.30
Current portion of long-term debt	0			229.3
Long-term debt, less current portion	7,846.10			7,852
Line of Credit Facility, Maximum Amount Outstanding During Period	0		0
Senior Notes, 6.125%, Due 2015 [Member]
Debt Instrument [Line Items]
Current portion of long-term debt	0	[1]		229.3	[1]
Debt Instrument, Interest Rate, Stated Percentage	6.13%			6.13%
Senior Notes, 6.0%, Due 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Senior Notes, 5.95%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	414.3			418.3
Debt Instrument, Interest Rate, Stated Percentage	5.95%			5.95%
Senior Notes, 1.75%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	249.3			249.2
Debt Instrument, Interest Rate, Stated Percentage	1.75%			1.75%
Senior Notes, 1.5%, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term Debt	498.8			498.6
Debt Instrument, Interest Rate, Stated Percentage	1.50%			1.50%
Senior Notes, 2.2%, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt	374.7			374.7
Debt Instrument, Interest Rate, Stated Percentage	2.20%			2.20%
Senior Notes, 3.95%, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt	745.4			745.2
Debt Instrument, Interest Rate, Stated Percentage	3.95%			3.95%
Senior Notes, 5.45%, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt	685.2			688.6
Debt Instrument, Interest Rate, Stated Percentage	5.45%			5.45%
Senior Notes, 4.125%, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt	495.7			495.5
Debt Instrument, Interest Rate, Stated Percentage	4.13%			4.13%
Senior Notes, 2.75%, Due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt	987.2			986.8
Debt Instrument, Interest Rate, Stated Percentage	2.75%			2.75%
Senior notes, 3.5%, due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt	747			746.9
Debt Instrument, Interest Rate, Stated Percentage	3.50%			3.50%
Senior Notes, 6.625%, Due 2036 [Member]
Debt Instrument [Line Items]
Long-term Debt	769.8			769.8
Debt Instrument, Interest Rate, Stated Percentage	6.63%			6.63%
Senior Notes, 6.75%, Due 2037 [Member]
Debt Instrument [Line Items]
Long-term Debt	530.8			530.7
Debt Instrument, Interest Rate, Stated Percentage	6.75%			6.75%
Senior Notes, 4.5%, Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt	480.9			480.8
Debt Instrument, Interest Rate, Stated Percentage	4.50%			4.50%
Senior Notes, 4.125%, Due 2042 [Member]
Debt Instrument [Line Items]
Long-term Debt	492.9			492.8
Debt Instrument, Interest Rate, Stated Percentage	4.13%			4.13%
Senior Notes, 4.75%, Due 2044 [Member]
Debt Instrument [Line Items]
Long-term Debt	374.1			374.1
Debt Instrument, Interest Rate, Stated Percentage	4.75%			4.75%
March 2014 Cash Flow Hedge [Domain]
Debt Instrument [Line Items]
Derivative, Notional Amount	500
Interest Rate Cash Flow Hedge Liability at Fair Value	$69
[1]	The 6.125% senior notes were repaid in January 2015. These notes were classified as current in the consolidated balance sheet as of December 31, 2014.

Debt_Shortterm_Debt_Details

Debt - Short-term Debt (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Short-term Debt [Line Items]
Commercial Paper	$297	$500
Commercial Paper, Weighted Average Interest Rate	0.42%	0.30%

Debt_Line_of_Credit_Details

Debt - Line of Credit (Details) (USD $)	3 Months Ended
	Mar. 31, 2015
Line of Credit Facility [Line Items]
Unsecured revolving credit agreement	$1,500,000,000
Debt Instrument, Unused Borrowing Capacity, Amount	2,000,000,000
Maximum Amount Of Letters Of Credit Issuable	200,000,000
Facility fee (in hundredths)	0.10%
Minimum [Member]
Line of Credit Facility [Line Items]
Level the debt to capitalization must be below under the facility agreement	0.5
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]
Unsecured revolving credit agreement	$2,500,000,000

Capital_Stock_Repurchases_Deta

Capital Stock - Repurchases (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount		$1,000	$1,000
Stock Repurchased During Period, Shares	2.1
Stock Repurchased During Period, Value	196.3	465
Stock Repurchase Program, Remaining Authorized Repurchase Amount	1,200
Treasury Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value	196
January/February Accelerated Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Shares	1.6
Accelerated Share Repurchases, Settlement (Payment) or Receipt	150
April Accelerated Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$100

Capital_Stock_Dividends_Detail

Capital Stock - Dividends (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015
Class of Stock Disclosures [Abstract]
Dividends Amount Per Share	$0.25
Dividends	$87.30

Capital_Stock_Stock_Units_Deta

Capital Stock - Stock Units (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum Vesting Percentage During Performance Period For Performance Stock Units	0.00%
Maximum Vesting Percentage During Performance Period For Performance Stock Units	200.00%
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
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	1.1
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	1.9
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	100.00%
Estimated Fair Market Value (per unit)	$32.13	$22.68
Expected Term (in years)	6 years 175 days	5 years 263 days
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Volatility Rate	33.40%	35.80%
Risk Free Interest Rate	1.81%	1.74%
Dividend Yield	1.13%	1.36%
Initial Price	$100.50	$72.26

Dividend_Restrictions_and_Stat1

Dividend Restrictions and Statutory Surplus (Details) (Insurance and HMO [Member], USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Insurance and HMO [Member]
Dividend Restrictions and Statutory Surplus [Line Items]
Dividends available	$1,600,000,000
Proceeds from dividends received	682,000,000
Statutory capital and surplus	$9,100,000,000	$9,400,000,000

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2012	Dec. 31, 2013
Loss Contingencies [Line Items]
Litigation Settlement, Expense		$120
Settlement of class action litigation, after-tax		78
Release of litigation-related reserve, after-tax	67
Release of litigation-related reserve, pre-tax	103
Charges for changes in our life claim payments practices, net of tax			35.7
Charge for changes in our life claim payment practices			$55

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	$14,853.10		$13,722.10
Operating Earnings	844.3	[1],[2]	722	[1],[2]
Health Care [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	14,285.80		13,131.40
Operating Earnings	835.6	[2]	719	[2]
Group Insurance [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	554.5		544.4
Operating Earnings	43.9	[2]	41.2	[2]
Large Case Pension [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	12.8		46.3
Operating Earnings	2.1	[2]	4.8	[2]
Corporate Financing [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	0		0
Operating Earnings	($37.30)	[2]	($43)	[2]
[1]	In addition to net realized capital gains and amortization of other acquired intangible assets, the following other items are excluded from operating earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:b"We incurred transaction and integration-related costs of $30.7 million ($45.6 million pretax) during the three months ended MarchB 31, 2015, related to the acquisitions of Coventry, InterGlobal and bswift, and integration-related costs of $41.9 million ($63.7 million pretax) during the three months ended MarchB 31, 2014, related to the acquisition of Coventry. Transaction costs include advisory, legal and other professional fees which are not deductible for tax purposes and are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. b"We incurred a loss on the early extinguishment of long-term debt of $59.7 million ($91.9 million pretax) during the three months ended March 31, 2014 related to the redemption of our 6.0% senior notes due 2016. b"We recorded a charge of $78.0 million ($120.0 million pretax) during the three months ended December 31, 2012 related to the settlement of purported class action litigation regarding our payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffsb counsel and the costs of administering the settlement. During the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $67.0 million ($103.0 million pretax) in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.
[2]	Operating 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_Reconcilia

Segment Information - Reconciliation of Operating Earnings (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2012
Segment Reconciliation [Abstract]
Operating Earnings	$844.30	[1],[2]	$722	[1],[2]
Transaction and integration-related costs, after-tax	-30.7		-41.9
Transaction and integration-related costs, net of tax	45.6		63.7
Loss on early extinguishment of debt, net of tax	0		-59.7
Release of litigation-related reserve, net of tax	0		67
Amortization of other acquired intangible assets, net of tax	-41.1		-40.4
Net realized capital gains (losses), net of tax	5		18.5
Net income attributable to Aetna	777.5		665.5
Loss on early extinguishment of long-term debt	0		91.9
Settlement of class action litigation, after-tax					78
Litigation Settlement, Expense					120
Release of litigation-related reserve, after-tax			67
Release of litigation-related reserve, pre-tax			$103
Senior Notes, 6.0%, Due 2016 [Member]
Segment Reconciliation [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	6.00%
[1]	In addition to net realized capital gains and amortization of other acquired intangible assets, the following other items are excluded from operating earnings because we believe they neither relate to the ordinary course of our business nor reflect our underlying business performance:b"We incurred transaction and integration-related costs of $30.7 million ($45.6 million pretax) during the three months ended MarchB 31, 2015, related to the acquisitions of Coventry, InterGlobal and bswift, and integration-related costs of $41.9 million ($63.7 million pretax) during the three months ended MarchB 31, 2014, related to the acquisition of Coventry. Transaction costs include advisory, legal and other professional fees which are not deductible for tax purposes and are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses. b"We incurred a loss on the early extinguishment of long-term debt of $59.7 million ($91.9 million pretax) during the three months ended March 31, 2014 related to the redemption of our 6.0% senior notes due 2016. b"We recorded a charge of $78.0 million ($120.0 million pretax) during the three months ended December 31, 2012 related to the settlement of purported class action litigation regarding our payment practices related to out-of-network health care providers. That charge included the estimated cost of legal fees of plaintiffsb counsel and the costs of administering the settlement. During the three months ended March 31, 2014, we exercised our right to terminate the settlement agreement. As a result, we released the reserve established in connection with the settlement agreement, net of amounts due to the settlement administrator, which reduced other general and administrative expenses by $67.0 million ($103.0 million pretax) in the three months ended March 31, 2014. Refer to Note 12 beginning on page 28 for additional information on the termination of the settlement agreement.
[2]	Operating earnings (loss) excludes net realized capital gains or losses, amortization of other acquired intangible assets and the other items described in the reconciliation below.

Reinsurance_Details

Reinsurance (Details) (USD $)	Jan. 31, 2015
In Millions, unless otherwise specified
Reinsurance Disclosures [Abstract]
Collateralized excess of loss on resinsurance coverage	$200

Discontinued_Products_Details

Discontinued Products (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Assets:
Investments	$24,961.70			$24,789.10
Collateral received under securities loan agreements	864			826.9
Total assets	55,555.40			53,402.10
Liabilities:
Policyholders' funds	1,181.10			1,163.20
Total liabilities	40,436.50			38,850.30
Discontinued Products [Member]
Reserve For Discontinued Products [Roll Forward]
Reserve, beginning of period	1,014.70	[1]	979.5
Operating income (loss)	3.1		5.8
Net realized capital gains	19		6.3
Reserve, end of period	1,036.80	[1]	991.6
Assets:
Investments	3,440.50	[1]		3,425.20	[1]
Other Assets	93.1	[1]		112.9	[1]
Collateral received under securities loan agreements	201.2	[1]		200.7	[1]
Receivable from continuing products	575.2	[1],[2]		566.5	[1],[2]
Total assets	4,310	[1]		4,305.30	[1]
Liabilities:
Future Policy Benefits	2,603.30	[1]		2,645.80	[1]
Reserve for anticipated future losses on discontinued products	1,036.80	[1]	991.6
Collateral payable under securities loan agreements	201.2	[1]		200.7	[1]
Deferred Tax Liabilities, Net	24.8	[1]		27.9	[1]
Other Liabilities	443.9	[1],[3]		416.2	[1],[3]
Total liabilities	4,310	[1]		4,305.30	[1]
Scheduled Contract Maturities, Settlements And Benefit Payments	91		97
Debt And Equity Securities Available For Sale [Member]
Assets:
Investments	21,583.80			21,441.70
Debt And Equity Securities Available For Sale [Member] | Discontinued Products [Member]
Assets:
Investments	2,384.20	[1]		2,376.20	[1]
Mortgage Loans [Member]
Assets:
Investments	1,515.20			1,562.20
Mortgage Loans [Member] | Discontinued Products [Member]
Assets:
Investments	349.8	[1]		386.8	[1]
Other Investments [Member]
Assets:
Investments	1,862.70			1,785.20
Other Investments [Member] | Discontinued Products [Member]
Assets:
Investments	$706.50	[1]		$662.20	[1]
[1]	Assets supporting the discontinued products are distinguished from assets supporting continuing products.
[2]	At the time of discontinuance, a receivable from Large Case Pensionsb 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 shareholdersb equity.