Aetna 10-Q 29 Oct 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information Document	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013
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	30-Sep-13
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding	367.5

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Revenue:
Health care premiums	$11,025.20		$7,246.80		$28,512.30		$21,602.10
Other premiums	525.9		482.1		1,561.50		1,427.20
Group annuity contract conversion premium	54.1		0		54.1		0
Fees and other revenue	1,233.10	[1]	954.9	[1]	3,326.10	[1]	2,881.70	[1]
Net investment income	210		216.2		670.1		681.6
Net realized capital (losses) gains	-12.7		17.3		-12.2		77.6
Total revenue	13,035.60		8,917.30		34,111.90		26,670.20
Benefits and expenses:
Health care costs	9,161.90	[2]	5,847.70	[2]	23,548.30	[2]	17,613.50	[2]
Current and future benefits	557		517.3		1,655.40		1,512.50
Benefit expense on group annuity contract conversion	54.1		0		54.1		0
Operating expenses:
Selling expenses	353.9		272.8		983.3		820.5
General and administrative expenses	1,950.60		1,366.80		5,154.80		4,131.50
Total operating expenses	2,304.50		1,639.60		6,138.10		4,952
Interest expense	86.1		68.5		247.4		192.2
Amortization of other acquired intangible assets	65.3		34.1		149.5		108.9
Reduction of reserve for anticipated future losses on discontinued products	0		0		-86		0
Loss on early extinguishment of long-term debt	0		35.4		0		35.4
Total benefits and expenses	12,228.90		8,142.60		31,706.80		24,414.50
Income before income taxes	806.7		774.7		2,405.10		2,255.70
Income taxes:
Current	283.5		239.6		826		696.1
Deferred	4.2		35.5		36		90.4
Total income taxes	287.7		275.1		862		786.5
Net Income including non-controlling interests	519		499.6		1,543.10		1,469.20
Net (Loss) Income Attributable to Non-controlling Interest	0.4		0.4		-1.6		1.4
Net income	518.6		499.2		1,544.70		1,467.80
Earnings per common share:
Basic	$1.40		$1.49		$4.39		$4.29
Diluted	$1.38		$1.47		$4.35		$4.23
Administrative Services Contract Member Co Payments And Plan Sponsor Reimbursements	21.7		18.8		62.3		58.3
Pharmaceutical And Processing Costs	286.3		295.9		834		875.7
Insured Member Co Payments	$25.90		$29.50		$85		$97.50
[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 $21.7 million and $62.3 million (net of pharmaceutical and processing costs of $286.3 million and $834.0 million) for the three and nine months ended September 30, 2013, respectively, and $18.8 million and $58.3 million (net of pharmaceutical and processing costs of $295.9 million and $875.7 million) for the three and nine months ended September 30, 2012, respectively.
[2]	Health care costs have been reduced by Insured member co-payments related to our mail order and specialty pharmacy operations of $25.9 million and $85.0 million for the three and nine months ended September 30, 2013, respectively, and $29.5 million and $97.5 million for the three and nine months ended September 30, 2012, respectively.

Consolidated_Statement_of_Comp

Consolidated Statement of Comprehensive Income (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Net Income including non-controlling interests	$519		$499.60		$1,543.10		$1,469.20
Other comprehensive (loss) income	18.9		166		-422.7		300.3
Comprehensive Income including non-controlling interests	537.9		665.6		1,120.40		1,769.50
Comprehensive (loss) income attributable to non-controlling interests	0.4		0.4		-1.6		1.4
Comprehensive Income attributable to Aetna	537.5		665.2		1,122		1,768.10
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Net unrealized gains (losses)	-6.3	[1]	3.5	[1]	-40.8	[1]	6.1	[1]
Less: Net unrealized gains (losses) on securities, reclassification of gains to earnings	-2	[1]	0.4	[1]	-20.6	[1]	3.7	[1]
Other comprehensive (loss) income	-4.3	[1]	3.1	[1]	-20.2	[1]	2.4	[1]
Other Securities [Member]
Net unrealized gains (losses)	-7.8		160.9		-481.1		316.6
Less: Net unrealized gains (losses) on securities, reclassification of gains to earnings	-14.1		13.3		-17.2		58.1
Other comprehensive (loss) income	6.3		147.6		-463.9		258.5
Foreign Currency Gain (Loss) [Member]
Net unrealized gains (losses)	4		3		22.9		2.6
Less: Foreign currency and derivatives reclassification of losses to earnings	-0.9		-0.9		-2.6		-2.4
Other comprehensive (loss) income	4.9		3.9		25.5		5
Pension and OPEB Plan [Member]
Amortization of net actuarial losses	12.7		12.1		37.9		36.4
Amortization of prior service cost	-0.7		-0.7		-2		-2
Other comprehensive (loss) income	$12		$11.40		$35.90		$34.40
[1]	Represents unrealized losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.

Consolidated_Statement_of_Comp1

Consolidated Statement of Comprehensive Income (Paranthetical) (Parentheticals) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	($9.70)	[1]	$5.40	[1]	($62.80)	[1]	$9.40	[1]
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	-3.1	[1]	0.6	[1]	-31.7	[1]	5.7	[1]
Other Securities [Member]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	-12		247.6		-740.1		487.1
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, before Tax	-21.6		19.9		-26.4		88.8
Foreign Currency Gain (Loss) [Member]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	6.1		4.6		35.2		4
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax	-1.4		-1.4		-4		-3.7
Pension and OPEB Plan [Member]
Amortization of net actuarial loss, before tax	-19.6		-18.6		-58.3		-56
Amortization of prior service cost, before tax	$1.10		$1		$3		$3
[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 $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Current assets:
Cash and cash equivalents	$2,082.40		$2,579.20
Investments	2,036.40		2,221.90
Premiums receivable, net	1,233.20		804.7
Other receivables, net	2,001.70		808
Accrued investment income	204.3		194.3
Collateral received under securities loan agreements	550.2		47.1
Income taxes receivable	19.8		139.9
Deferred income taxes	546.1		426.5
Other current assets	1,357.80		1,022.80
Total current assets	10,031.90		8,244.40
Long-term investments	20,498.60		19,698.20
Reinsurance recoverables	766.3		876.8
Goodwill	10,205.70	[1]	6,214.40
Other acquired intangible assets, net	2,159.20		818.7
Property and equipment, net	715.6		540
Other long-term assets	942		854.9
Separate Account Assets	3,933.60		4,247.10
Total assets	49,252.90		41,494.50
Current liabilities:
Health care costs payable	4,531.10		2,992.50
Future policy benefits	725.8		739.9
Unpaid claims	669.2		620.7
Unearned premiums	479.2		403.5
Policyholders' funds	1,660.70		1,276.90
Collateral payable under securities loan agreements	550.2		47.1
Current portion of long-term debt	392.2	[2]	0	[2]
Accrued expenses and other current liabilities	3,237.50		2,383.60
Total current liabilities	12,245.90		8,464.20
Future policy benefits	6,701.60		6,853.70
Unpaid claims	1,593.60		1,546.90
Policyholders' funds	1,231.20		1,364
Long-term debt, less current portion	7,874.10		6,481.30
Deferred income taxes	550.4		473.5
Other long-term liabilities	1,453		1,634.60
Separate Accounts liabilities	3,933.60		4,247.10
Total liabilities	35,583.40		31,065.30
Commitments and contingencies (Note 14)
Shareholders' equity:
Common stock ($.01 par value; 2.6 billion shares authorized and 367.5 million shares issued and outstanding in 2013; 2.6 billion shares authorized and 327.6 million shares issued and outstanding in 2012) and additional paid-in capital	4,356.40		1,095.30
Retained earnings	10,717.90		10,343.90
Accumulated other comprehensive loss	-1,456.10		-1,033.40
Total Aetna shareholders' equity	13,618.20		10,405.80
Total equity	13,669.50		10,429.20
Total liabilities and shareholders' equity	49,252.90		41,494.50
Securities Loaned or Sold under Agreements to Repurchase [Member]
Current assets:
Collateral received under securities loan agreements	550.2	[3]	47.1	[3]
Noncontrolling Interest [Member]
Shareholders' equity:
Stockholders' Equity Attributable to Noncontrolling Interest	$51.30		$23.40
[1]	At September 30, 2013, approximately $113 million was assigned to the Group Insurance segment, with the remainder assigned to the Health Care segment.
[2]	At September 30, 2013, our 6.3% senior notes due August 2014 are classified as current in the accompanying consolidated balance sheet.
[3]	There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Paranthetical) (Parentheticals) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Common Stock, Par or Stated Value Per Share	$0.01	$0.01
Common Stock, Shares Authorized	2,600,000,000	2,600,000,000
Common Stock, Shares, Issued	367,500,000	327,600,000
Common Stock, Shares, Outstanding	367,500,000	327,600,000

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]	Equity Issued in Business Combination [Member]	Equity Issued in Business Combination [Member]	Equity Issued in Business Combination [Member]	Equity Issued in Business Combination [Member]	Equity Issued in Business Combination [Member]	Equity Issued in Business Combination [Member]
In Millions, except Share data, unless otherwise specified									Common Stock Including Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Parent [Member]	Noncontrolling Interest [Member]
Balance at beginning of period at Dec. 31, 2011			$962.80	$10,346.60	($1,189.20)	$10,120.20
Total equity at beginning of period at Dec. 31, 2011	10,144.60
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2011							24.4
Balance at beginning of period (in shares) at Dec. 31, 2011		349,700,000
Comprehensive income:
Net income	1,467.80	0	0	1,467.80	0	1,467.80
Net (Loss) Income Attributable to Non-controlling Interest	1.4						1.4
Net Income including non-controlling interests	1,469.20
Other increases (decreases) in noncontrolling interests	-2.7	0	0	0	0	0	-2.7
Other comprehensive (loss) income	300.3	0	0	0	300.3	300.3	0
Common shares issued for benefit plans, including tax benefits	110.9		110.9	0	0	110.9	0
Common shares issued for benefit plans, including tax benefits (in shares)	6,000,000
Repurchases of common shares	-924.5		-0.2	-924.3	0	-924.5	0
Repurchases of common shares (in shares)		-21,200,000
Dividends declared	-177.9	0	0	-177.9	0	-177.9	0
Total equity at end of period at Sep. 30, 2012	10,919.90
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Sep. 30, 2012							23.1
Balance at end of period at Sep. 30, 2012			1,073.50	10,712.20	-888.9	10,896.80
Balance at end of period (in shares) at Sep. 30, 2012		334,500,000
Balance at beginning of period at Dec. 31, 2012	10,405.80		1,095.30	10,343.90	-1,033.40	10,405.80
Total equity at beginning of period at Dec. 31, 2012	10,429.20
Stockholders' Equity Attributable to Noncontrolling Interest at beginning of period at Dec. 31, 2012							23.4
Balance at beginning of period (in shares) at Dec. 31, 2012	327,600,000	327,600,000
Comprehensive income:
Net income	1,544.70	0	0	1,544.70	0	1,544.70
Net (Loss) Income Attributable to Non-controlling Interest	-1.6						-1.6
Net Income including non-controlling interests	1,543.10
Other increases (decreases) in noncontrolling interests	29.5	0	0	0	0	0	29.5
Other comprehensive (loss) income	-422.7	0	0	0	-422.7	-422.7	0
Total number of shares issued in a business acquisition	52,200,000							52,200,000
Common shares issued for benefit plans, including tax benefits	196.7		196.7	0	0	196.7	0	3,064.60	3,064.60	0	0	3,064.60	0
Common shares issued for benefit plans, including tax benefits (in shares)		3,900,000
Repurchases of common shares	-957.7		-0.2	-957.5	0	-957.7	0
Repurchases of common shares (in shares)	-16,000,000	-16,200,000
Dividends declared	-213.2	0	0	-213.2	0	-213.2	0
Total equity at end of period at Sep. 30, 2013	13,669.50
Stockholders' Equity Attributable to Noncontrolling Interest at end of period at Sep. 30, 2013							51.3
Balance at end of period at Sep. 30, 2013	$13,618.20		$4,356.40	$10,717.90	($1,456.10)	$13,618.20
Balance at end of period (in shares) at Sep. 30, 2013	367,500,000	367,500,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net Income including non-controlling interests	$1,543.10	$1,469.20
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized capital gains	12.2	-77.6
Depreciation and amortization	406.5	338
Amortization of debt fair value adjustment	-24.2	0
Equity in earnings of affiliates, net	-18.2	-18.1
Stock-based compensation expense	90.6	96.2
Reduction of reserve for anticipated future losses on discontinued products	-86	0
Reversal of allowance and gain on sale of reinsurance recoverable	-49.4	0
Amortization of net investment premium	38.1	15.6
Loss on early extinguishment of long-term debt	0	35.4
Changes in assets and liabilities:
Accrued investment income	9.4	7.6
Premiums due and other receivables	-308.5	-253.7
Income taxes	99.4	232.7
Other assets and other liabilities	-38.1	-589.9
Health care and insurance liabilities	-16.9	20.4
Other, net	-3.4	4.1
Net cash provided by operating activities	1,654.60	1,279.90
Cash flows from investing activities:
Proceeds from sales and maturities of investments	11,117.30	8,236.70
Cost of investments	-10,298.50	-8,444.20
Additions to property, equipment and software	-331.6	-252.5
Cash used for acquisition, net of cash acquired	-1,635.90	-8.6
Other, net	2.5	0
Net cash used for investing activities	-1,146.20	-468.6
Cash flows from financing activities:
Net repayment of long-term debt	0	123.6
Net proceeds from issuance of long-term debt	0	712.9
Net repayment of short-term debt	0	-355.9
Deposits and interest credited for investment contracts	3.4	3.9
Withdrawals of investment contracts	-9.7	-16
Common shares under benefit plans, net	39	-13.9
Stock-based compensation tax benefits	62.9	30
Common shares repurchased	-957.7	-924.5
Dividends paid to shareholders	-205.2	-180.6
Collateral on interest rate swaps	32.6	17.6
Contributions (distributions) from noncontrolling interests	29.5	-2.7
Net cash used for financing activities	-1,005.20	-852.8
Net decrease in cash and cash equivalents	-496.8	-41.5
Cash and cash equivalents, beginning of period	2,579.20	679.7
Cash and cash equivalents, end of period	2,082.40	638.2
Supplemental cash flow information:
Interest paid	229.6	153.1
Income taxes paid	$699.50	$523.80

Organization

Organization	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization
	1	Organization
	We conduct our operations in three business segments:
	•	Health Care consists of medical, pharmacy benefit management services, dental, behavioral health and vision plans offered on both an Insured basis (where we assume all or a majority of the risk for medical and dental care costs) and an employer-funded basis (where the plan sponsor under an administrative services contract (“ASC”) assumes all or a majority of this risk) and emerging businesses products and services, such as Accountable Care Solutions (“ACS”), 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 markets.
	•	Group Insurance primarily includes group life insurance and group disability products. Group life 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 insurance (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 17 beginning on page 36 for additional information). We do not actively market Large Case Pensions products, but continue to accept deposits from existing customers and manage the run-off of our existing business.
	On May 7, 2013 we completed the acquisition of Coventry Health Care, Inc. (“Coventry”) in a transaction valued at approximately $8.7 billion, including the fair value of Coventry's outstanding debt (refer to Note 3 beginning on page 7 for additional information).

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
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 2012 Annual Report on Form 10-K (our “2012 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 2012 Annual Report, unless the information contained in those disclosures materially changed and is required by GAAP.  We evaluated subsequent events that occurred after September 30, 2013 through the date the financials were issued and determined there were no other items to disclose.
	Principles of Consolidation
	These 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.
	Reclassifications
	Certain reclassifications were made to 2012 financial information to conform with 2013 presentation.
	New Accounting Standards
	Testing Intangibles for Impairment
	Effective January 1, 2013, we adopted new accounting guidance for testing indefinite-lived intangible assets for impairment. Under this guidance, an entity has the option first to assess qualitative factors to determine whether it is more likely than not that the fair value of an indefinite-lived intangible asset is less than its carrying value. If management determines that an indefinite-lived intangible asset's fair value is likely greater than its carrying value, then no additional analysis is necessary, as the indefinite-lived intangible asset is not impaired. The adoption of this new guidance did not have an impact on our financial position or operating results.
	Future Application of Accounting Standards
	Fees Paid to the Federal Government by Health Insurers
	Effective January 1, 2014, we will adopt new accounting guidance relating to the recognition and income statement reporting of any mandated fees to be paid to the federal government by health insurers. This guidance will apply primarily to new fees enacted in the Patient Protection and Affordable Care Act and the Health Care and Education Reconciliation Act of 2010 (collectively, “Health Care Reform”). The mandated fees are expected to be material, and this new accounting guidance will result in the recognition of this expense on a straight-line basis beginning in 2014.
	Amendments to the Scope, Measurement and Disclosure Requirements of Investment Companies
	Effective January 1, 2014, we will adopt new accounting guidance relating to the approach for determining whether an entity is considered an investment company. This guidance clarifies the characteristics and sets measurement and disclosure requirements for an investment company. The adoption of this new guidance is not expected to have an impact on our financial position or operating results.

Completed_Acquisitions_Complet

Completed Acquisitions, Completed Dispositions	9 Months Ended
	Sep. 30, 2013
Business Combinations [Abstract]
Completed Acquisition
	3	Completed Acquisition; Completed Disposition
	Completed Acquisition
	On August 19, 2012, we entered into a definitive agreement (as amended, the “Merger Agreement”) to acquire Coventry. On May 7, 2013 (the “Effective Date”), we completed our acquisition of Coventry in a transaction valued at approximately $8.7 billion, including $1.8 billion fair value of Coventry's outstanding debt. Coventry is a diversified managed health care company that offers a full portfolio of risk and fee-based products, including Medicare Advantage and Medicare Part D programs, Medicaid managed care plans, group and individual health insurance, coverage for specialty services such as workers' compensation administrative services, and network rental services.
	Pursuant to the terms of the Merger Agreement, by and among Aetna, Jaguar Merger Subsidiary, Inc., a wholly-owned subsidiary of Aetna (“Merger Sub”), and Coventry, Merger Sub merged with and into Coventry (the “Merger”), with Coventry continuing as the surviving corporation and a wholly-owned subsidiary of Aetna.
	Under the terms of the Merger Agreement, Coventry stockholders received $27.30 in cash and 0.3885 of an Aetna common share for each share of Coventry common stock (including restricted shares but excluding shares held by Coventry as treasury stock) outstanding at the effective time of the Merger. As a result, on the Effective Date, we issued approximately 52.2 million common shares, with a fair value of approximately $3.1 billion and paid approximately $3.8 billion in cash in exchange for all of the outstanding shares of Coventry common stock and outstanding awards. Substantially all of Coventry's outstanding equity awards vested and were paid out in cash and canceled in connection with the Merger. An insignificant amount of outstanding Coventry equity awards that pursuant to their terms did not become vested at the effective time of the Merger (the “Rollover Units”) were converted into cash-settled Aetna restricted stock units in connection with the Merger. We funded the cash portion of the purchase price through a combination of available cash on hand and proceeds from the issuance of long-term debt and commercial paper.
	The components of consideration transferred for the acquisition of Coventry were as follows:
	(Certain amounts may reflect rounding adjustments)
		Conversion						Form of
	(Millions, except per common share data)	Calculation			Fair Value			Consideration
	Consideration Transferred:
	Number of shares of Coventry common stock outstanding at May 7, 2013:	133.7
	Multiplied by Aetna's share price at May 7, 2013, multiplied by the							Aetna
	exchange ratio ($58.69*0.3885)	$	22.8		$	3,047.40		Common Shares
	Multiplied by the per common share cash consideration	$	27.3		$	3,648.70		Cash
	Number of shares underlying in-the-money Coventry stock options vested and unvested
	outstanding as of May 7, 2013, canceled and exchanged for cash	4.9
	Multiplied by the excess, if any, of (1) the sum of (x) the per
	common share cash consideration plus (y) the Aetna closing share price (1)
	multiplied by the exchange ratio ($57.93*0.3885) over
	(2) the weighted-average exercise price of such
	in-the-money stock options	$	15.94		$	78.1		Cash
	Number of Coventry performance share units and restricted stock
	units outstanding at May 7, 2013, canceled and paid in cash	1.6
	Multiplied by the equity award cash consideration	$	49.8		$	58.5		Cash (2)
	Number of Coventry restricted shares outstanding at May 7, 2013:	1.1
	Less: employee tax withholdings	(.4		)	$	18.8		Cash
	Net restricted shares outstanding at May 7, 2013	0.7
	Multiplied by Aetna's share price at May 7, 2013, multiplied by							Aetna
	the exchange ratio ($58.69*0.3885)	$	22.8		$	17.2		Common Shares
	Multiplied by the per common share cash consideration	$	27.3		$	20.5		Cash
	Other consideration transferred  (3)				6.9
	Total consideration transferred				$	6,896.10
	(1)	Based on the average of the volume weighted averages of the trading prices of Aetna common shares on the New York Stock Exchange for each of the five consecutive trading days ending on the trading day that was two trading days prior to the Effective Date.
	(2)	Pursuant to the terms of certain employment agreements, an aggregate of approximately .5 million performance share units and restricted stock units did not automatically vest upon the change of control of Coventry. In the absence of such automatic vesting upon a change in control, pursuant to GAAP, Aetna estimated the fair value of these awards at the Effective Date and attributed that fair value to pre-Merger and post-Merger services. Accordingly, $6.9 million of the fair value of these awards was attributed to pre-Merger services and is included in the estimated consideration transferred, and approximately $19.0 million will be accounted for in Aetna's post-Merger financial statements as transaction-related costs and reflected as a selling, general and administrative expense in Aetna's statements of income.
	(3)	Certain of Coventry's named executive officers received payments pursuant to employment agreements entered into prior to the Coventry acquisition. The total compensation paid in cash pursuant to such agreements in connection with the Merger was $6.5 million. Other consideration transferred also includes the portion of the fair value of the Rollover Units that was attributed to pre-Merger services. The fair value attributable to post-Merger services will be recorded as selling, general and administrative expense in Aetna's post-Merger financial statements.
	The transaction has been accounted for using the acquisition method of accounting which requires, among other things, the assets acquired and liabilities assumed to be recognized at their fair values at the Effective Date. The following table summarizes the estimated fair values of major classes of assets acquired and liabilities assumed as part of the Merger, reconciled to the total consideration transferred:
			At May 7,
	(Millions)		2013
	Cash and cash equivalents		$	2,195.60
	Investments		2,156.40
	Premiums and other receivables, net		1,141.10
	Intangible assets acquired		1,490.00
	Property and equipment		174.8
	Other assets		97.5
	Total assets acquired		7,255.40
	Health care costs payable		1,440.10
	Long-term debt		1,803.80
	Net deferred tax liabilities (1)		257
	Other liabilities		854.9
	Total liabilities assumed		4,355.80
	Total identifiable net assets		2,899.60
	Goodwill acquired		3,996.50
	Total consideration transferred		$	6,896.10
	(1)	Includes $521.5 million of deferred tax liabilities on identifiable intangible assets acquired and $75.8 million of deferred tax assets on the fair value adjustment to Coventry's outstanding debt.
	The estimate of fair value results from a complex series of judgments about future events and uncertainties and relies heavily on estimates and assumptions. The judgments used to determine the estimated fair value assigned to each class of assets acquired and liabilities assumed, as well as intangible asset lives, can materially impact our operating results. We will finalize the Coventry purchase accounting for the various open items as soon as reasonably possible during the measurement period. The finalization of our purchase accounting assessment could result in changes in the valuation of assets and liabilities acquired which could be material.
	As of the Effective Date, the expected fair value of premiums receivable and other receivables approximated their historical cost. The gross contractual receivable for premiums receivable was $485.5 million, of which $12.5 million is not expected to be collectible. The gross contractual receivable for other receivables was $682.2 million, of which $14.1 million is not expected to be collectible.
	In connection with the acquisition of Coventry, all of Coventry's outstanding debt remained outstanding. Debt is required to be measured at fair value under the acquisition method of accounting. As a result of this fair value adjustment, the carrying value of Coventry's debt increased by approximately $217 million; this increase will be amortized as a reduction to interest expense over the remaining life of the debt.
	The fair value and weighted-average useful lives for all intangible assets acquired are as follows:
		Fair Value (Millions)			Useful Life (Years)
	Customer lists	$	810		10
	Provider networks	550			17
	Trademarks/tradenames	100			10
	Technology	30			4
Total	$	1,490.00
Goodwill is calculated as the excess of the consideration transferred over the net assets recognized and represents the future economic benefits arising from other intangible assets acquired that do not qualify for separate recognition. Specifically, the goodwill recognized with the acquisition of Coventry includes expected synergies and other benefits that we believe will result from combining the operations of Coventry with the operations of Aetna, as well as any intangible assets that do not qualify for separate recognition.
We preliminarily recorded goodwill related to this acquisition of approximately $4.0 billion, of which $267 million will be tax deductible. All of the goodwill related to this acquisition has been assigned to our Health Care segment.
The amounts recognized for certain assets acquired and liabilities assumed are preliminary until the initial accounting for the acquisition is complete. The following items, among others, are considered preliminary until we gather sufficient information for the initial accounting to be complete:
•	the nature and amounts recognized for current and deferred income tax assets and liabilities;
•	the nature, amounts recognized and measurement basis of certain liabilities, including liabilities arising from contingencies recognized at acquisition (refer to Note 14 beginning on page 30 for additional information); and
•	quantitative information related to goodwill recorded at acquisition.
Actual and Pro Forma Impact of Acquisition
The results of Coventry have been included in our results from the Effective Date through September 30, 2013. The following table presents revenue and net income of Coventry included in our results for the three and nine months ended September 30, 2013:
	Three Months Ended				Nine Months Ended
(Millions)	30-Sep-13				30-Sep-13
Revenue	$	3,531.30			$	5,599.80
Net Income	112.8				169
The following table presents supplemental pro forma information as if the Merger had occurred on January 1, 2012 for the nine months ended September 30, 2013 and for the three and nine months ended September 30, 2012. The pro forma consolidated results are not necessarily indicative of what our consolidated results would have been had the Merger been completed on January 1, 2012. In addition, the pro forma consolidated results do not purport to project the future results of the combined company nor do they reflect the expected realization of any cost savings associated with the Merger.
	Three Months Ended				Nine Months Ended September 30,
(Millions, except per common share data)	30-Sep-12				2013			2012
Total revenue	$	12,253.30			$	38,906.60		$	37,031.80
Net income	600				1,775.30			1,810.10
Earnings per share:
Basic	$	1.55			$	4.73		$	4.59
Diluted	1.54				4.68			4.53
We incurred transaction and integration-related costs related to the acquisition of Coventry of $34.6 million ($51.2 million pretax) and $140.6 million ($189.6 million pretax) during the three and nine months ended September 30, 2013, respectively, and $12.5 million ($13.8 million pretax) during the three and nine months ended September 30, 2012. Transaction costs include advisory, legal and other professional fees and transaction-related payments that are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses, as well as the cost of the bridge credit agreement that was in effect prior to the Coventry acquisition, which is reflected in the GAAP Consolidated Statements of Income in interest expense. Transaction costs also include transaction-related payments as well as expenses related to the negative cost of carry associated with the permanent financing that we obtained in November 2012 for the acquisition of Coventry. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense, net investment income, and general and administrative expenses. Integration-related costs are reflected in our GAAP Consolidated Statements of Income in general and administrative expenses.
The unaudited pro forma consolidated results for the three months ended September 30, 2012 and the nine months ended September 30, 2013 and 2012 reflect the following pro forma adjustments:
•	Elimination of intercompany transactions between Aetna and Coventry, primarily related to network rental fees.
•	Foregone interest income associated with cash and cash equivalents and investments assumed to have been used to partially fund the Merger.
•	Foregone interest income associated with adjusting the amortized cost of Coventry's investment portfolio to fair value as of the completion of the Merger.
•	Elimination of historical Coventry intangible asset amortization expense and capitalized internal-use software amortization expense and addition of intangible asset amortization expense relating to intangibles valued as part of the acquisition.
•	Additional interest expense from the long-term debt Aetna issued in November 2012 as well as the interest expense on short-term debt Aetna issued in March and April 2013. Interest expense was also reduced for the amortization of the fair value adjustment to long-term debt.
•	Elimination of transaction-related costs incurred by Aetna and/or Coventry during 2013 and 2012.
•	Adjustment of the modifications above for the applicable tax impact.
•	Conforming adjustments to align Coventry's presentation to Aetna's accounting policies. At this time, we are not aware of any accounting policy differences that would have a material impact on the combined company's financial statements, however, as we complete our review of Coventry's accounting policies, it is possible that other policy differences may be identified that, when conformed, could have a material impact on the combined company financial statements.
•	Elimination of revenue and directly identifiable costs related to the sale of Aetna's Missouri Medicaid business, Missouri Care, Incorporated (“Missouri Care”), to WellCare Health Plans, Inc. on March 31, 2013.
Completed Disposition
In connection with the acquisition of Coventry, on March 31, 2013, we completed the sale of Missouri Care to WellCare Health Plans, Inc. The sale price was not material and did not have a material impact on our financial position or operating results.

Earnings_Per_Common_Share

Earnings Per Common Share	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Common Share
	4	Earnings Per Common Share
	Basic earnings per share (“EPS”) is computed by dividing net income 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 and nine months ended September 30, 2013 and 2012 were as follows:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(Millions, except per common share data)	2013		2012		2013		2012
	Net income attributable to Aetna	$	518.6	$	499.2	$	1,544.70	$	1,467.80
	Weighted average shares used to compute basic EPS	371.1		334.8		351.8		342.2
	Dilutive effect of outstanding stock-based compensation awards (1)	4.1		3.8		3.7		5
	Weighted average shares used to compute diluted EPS	375.2		338.6		355.5		347.2
	Basic EPS	$	1.4	$	1.49	$	4.39	$	4.29
	Diluted EPS	$	1.38	$	1.47	$	4.35	$	4.23
	(1)	Stock-based compensation awards are not included in 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).  Approximately 2.2 million stock appreciation rights were not included in the calculation of diluted EPS for the nine months ended September 30, 2013 and 11.0 million and 8.6 million stock appreciation rights were not included in the calculation of diluted EPS for the three and nine months ended September 30, 2012, respectively, because they were anti-dilutive. All stock options were included in the calculation of diluted EPS for the three and nine months ended September 30, 2013 and 2012.
	In connection with the May 7, 2013 acquisition of Coventry, we issued approximately 52.2 million Aetna common shares in exchange for all the outstanding shares of Coventry common stock. Those Aetna common shares were outstanding and included in the calculation of weighted average shares used to compute basic EPS for the period from the Effective Date through September 30, 2013. In future periods, those Aetna common shares will be outstanding for the full reporting period and will be weighted accordingly.

Operating_Expenses

Operating Expenses	9 Months Ended
	Sep. 30, 2013
Operating Expenses [Abstract]
Operating Expenses	5.     Operating Expenses
	For the three and nine months ended September 30, 2013 and 2012, 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:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(Millions)	2013		2012		2013		2012
	Selling expenses	$	353.9	$	272.8	$	983.3	$	820.5
	General and administrative expenses:
	Salaries and related benefits	1,119.40		780.4		2,914.50		2,336.70
	Other general and administrative expenses  (1) (2)	831.2		586.4		2,240.30		1,794.80
	Total general and administrative expenses	1,950.60		1,366.80		5,154.80		4,131.50
	Total operating expenses	$	2,304.50	$	1,639.60	$	6,138.10	$	4,952.00
	(1)	Includes $51.2 million and $171.4 million of transaction and integration-related costs related to the acquisition of Coventry, including advisory, legal and other professional services fees and transaction-related payments as well as integration costs incurred in the three and nine months ended September 30, 2013, respectively and $10.0 million during the three and nine months ended September 30, 2012.
	(2)	In 2008, as a result of the liquidation proceedings of Lehman Re Ltd. (“Lehman Re”), a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re. This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $42.2 million pretax.
	Refer to the reconciliation of operating earnings to net income attributable to Aetna in Note 15 beginning on page 34 for additional information.

Goodwill_and_Other_Acquired_In

Goodwill and Other Acquired Intangible Assets (Notes)	9 Months Ended
	Sep. 30, 2013
Goodwill and Other Acquired Intangible Assets [Abstract]
Goodwill and Intangible Assets Disclosure [Text Block]
	6	Goodwill and Other Acquired Intangible Assets
	The change in goodwill for the nine months ended September 30, 2013 was as follows:
	(Millions)	2013
	Balance, beginning of the period	$	6,214.40
	Goodwill acquired:
	Coventry (1)	3,996.50
	Other	(5.2		)
	Balance, end of the period (2)	$	10,205.70
	(1)	Goodwill related to the acquisition of Coventry is considered preliminary, pending the final allocation of the applicable purchase price.
	(2)	At September 30, 2013, approximately $113 million was assigned to the Group Insurance segment, with the remainder assigned to the Health Care segment.
	Other acquired intangible assets at September 30, 2013 and December 31, 2012 were comprised of the following:
	(Millions)	Cost			Accumulated			Net Balance		Amortization
					Amortization					Period (Years)
	30-Sep-13
	Provider networks	$	1,253.20			$	493.4	$	759.8		25-Dec	(1)
	Customer lists	1,347.00				326.7		1,020.30			14-May	(1)
	Value of business acquired (“VOBA”)	149.2				43.7		105.5			20	(2)
	Technology	146.6				43.4		103.2			10-Apr
	Other	6.7				1.8		4.9			15-Feb
	Definite-lived trademarks	165				21.8		143.2			20-Sep
	Indefinite-lived trademarks	22.3				—		22.3
	Total other acquired intangible assets	$	3,090.00			$	930.8	$	2,159.20
	31-Dec-12
	Provider networks	$	703.2			$	458.2	$	245		25-Dec	(1)
	Customer lists	657.4				370.2		287.2			14-May	(1)
	Value of business acquired	149.2				29.2		120			20	(2)
	Technology	116.6				28		88.6			10-May
	Other	6.7				1.5		5.2			15-Feb
	Definite-lived trademarks	65				14.6		50.4			20-Sep
	Indefinite-lived trademarks	22.3				—		22.3
	Total other acquired intangible assets	$	1,720.40			$	901.7	$	818.7
	(1)	The amortization period for our provider networks and customer lists includes an assumption of renewal or extension of these arrangements.  At September 30, 2013 and December 31, 2012, the periods prior to the next renewal or extension for our provider networks primarily ranged from 1 to 3 years and the period prior to the next renewal or extension for our customer lists was less than one year and two years, respectively. Any costs related to the renewal or extension of these contracts are expensed as incurred.
	(2)	VOBA is being amortized over the expected life of the acquired contracts in proportion to estimated premium.
	Refer to Note 3 on page 7 for additional information about other acquired intangible assets in connection with the acquisition of Coventry on the Effective Date.
	We estimate annual pretax amortization for other acquired intangible assets for 2013 and in each of the next five years to be as follows:
	(Millions)
	2013	$	214.6
	2014	238.4
	2015	222.5
	2016	215.5
	2017	201.1
	2018	192.9

Investments

Investments	9 Months Ended
	Sep. 30, 2013
Investments [Abstract]
Investments	7.     Investments
	Total investments at September 30, 2013 and December 31, 2012 were as follows:
		September 30, 2013										December 31, 2012
	(Millions)	Current			Long-term			Total				Current			Long-term		Total
	Debt and equity securities available for sale	$	1,897.80		$	17,361.10		$	19,258.90			$	2,006.80		$	16,821.00	$	18,827.80
	Mortgage loans	136.3			1,419.90			1,556.20				214.4			1,429.20		1,643.60
	Other investments	2.3			1,717.60			1,719.90				0.7			1,448.00		1,448.70
	Total investments	$	2,036.40		$	20,498.60		$	22,535.00			$	2,221.90		$	19,698.20	$	21,920.10
	On the Effective Date, we completed the acquisition of Coventry. As a result, on that date we acquired approximately $2.2 billion of current and long-term investments, primarily consisting of state and municipal bonds and U.S. corporate securities.
	Debt and Equity Securities
	Debt and equity securities available for sale at September 30, 2013 and December 31, 2012 were as follows:
	(Millions)	Amortized			Gross			Gross					Fair
		Cost			Unrealized			Unrealized					Value
					Gains			Losses
	September 30, 2013
	Debt securities:
	U.S. government securities	$	1,424.00		$	83.8		$	(1.0	)			$	1,506.80
	States, municipalities and political subdivisions	3,852.60			138.1			(76.5		)			3,914.20
	U.S. corporate securities	7,272.20			505.6			(122.9		)			7,654.90
	Foreign securities	3,114.30			207.4			(54.2		)			3,267.50
	Residential mortgage-backed securities	951.5			22.6			(11.7		)			962.4
	Commercial mortgage-backed securities	1,321.20			95.6			(4.7		)	(1)		1,412.10
	Other asset-backed securities	379.8			17.9			(2.2		)	(1)		395.5
	Redeemable preferred securities	56.8			8.7			(.4		)			65.1
	Total debt securities	18,372.40			1,079.70			(273.6		)			19,178.50
	Equity securities	46.3			38.3			(4.2		)			80.4
	Total debt and equity securities (2)	$	18,418.70		$	1,118.00		$	(277.8	)			$	19,258.90
	December 31, 2012
	Debt securities:
	U.S. government securities	$	1,413.40		$	147.9		$	(1.8	)			$	1,559.50
	States, municipalities and political subdivisions	2,770.90			267.9			(4.3		)			3,034.50
	U.S. corporate securities	6,926.20			871.7			(7.3		)			7,790.60
	Foreign securities	2,988.10			391.3			(8.8		)			3,370.60
	Residential mortgage-backed securities	929.5			49.9			(.4		)			979
	Commercial mortgage-backed securities	1,268.70			149.7			(1.8		)	(1)		1,416.60
	Other asset-backed securities	517.4			28.3			(3.6		)	(1)		542.1
	Redeemable preferred securities	89.6			12.3			(7.3		)			94.6
	Total debt securities	16,903.80			1,919.00			(35.3		)			18,787.50
	Equity securities	38.3			5.1			(3.1		)			40.3
	Total debt and equity securities (2)	$	16,942.10		$	1,924.10		$	(38.4	)			$	18,827.80
	(1)	At September 30, 2013 and December 31, 2012, we held securities for which we previously recognized $22.9 million and $25.2 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at September 30, 2013 and December 31, 2012 of $8.5 million and $9.6 million, respectively.
	(2)	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 17 beginning on page 36 for additional information on our accounting for discontinued products).  At September 30, 2013, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $320.2 million and gross unrealized capital losses of $63.3 million and, at December 31, 2012, debt and equity securities with a fair value of approximately $4.0 billion, gross unrealized capital gains of $559.4 million and gross unrealized capital losses of $19.4 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 September 30, 2013 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	$	731.9
	One year through five years	5,054.20
	After five years through ten years	5,643.60
	Greater than ten years	4,978.80
	Residential mortgage-backed securities	962.4
	Commercial mortgage-backed securities	1,412.10
	Other asset-backed securities	395.5
	Total	$	19,178.50
	Mortgage-Backed and Other Asset-Backed Securities
	All of our residential mortgage-backed securities at September 30, 2013 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 September 30, 2013, our residential mortgage-backed securities had an average credit quality rating of AAA and a weighted average duration of 4.5 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 probability of default and loss severity.  At September 30, 2013, these securities had an average credit quality rating of AA+ and a weighted average duration of 2.7 years.
	Our other asset-backed securities have a variety of underlying collateral (e.g., automobile loans, credit card receivables and home equity loans).  Significant market observable inputs used to value these securities include the unemployment rate, loss severity and probability of default.  At September 30, 2013, these securities had an average credit quality rating of AA and a weighted average duration of 2.8 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 September 30, 2013 and December 31, 2012 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
September 30, 2013
Debt securities:
U.S. government securities	$	82.1		$	0.6		$	13.7			$	0.4		$	95.8	$	1
States, municipalities and political subdivisions	1,598.90			74.1			31				2.4			1,629.90		76.5
U.S. corporate securities	2,183.70			120.2			15.8				2.7			2,199.50		122.9
Foreign securities	923.9			53			22.6				1.2			946.5		54.2
Residential mortgage-backed securities	333.6			9.5			27.9				2.2			361.5		11.7
Commercial mortgage-backed securities	153.6			4.4			19.3				0.3			172.9		4.7
Other asset-backed securities	92.5			2.2			5.5				—			98		2.2
Redeemable preferred securities	10.1			0.4			—				—			10.1		0.4
Total debt securities	5,378.40			264.4			135.8				9.2			5,514.20		273.6
Equity securities	10.8			1.3			5.2				2.9			16		4.2
Total debt and equity securities (1)	$	5,389.20		$	265.7		$	141			$	12.1		$	5,530.20	$	277.8
December 31, 2012
Debt securities:
U.S. government securities	$	138.3		$	1.4		$	15.1			$	0.4		$	153.4	$	1.8
States, municipalities and political subdivisions	264.6			3			28.5				1.3			293.1		4.3
U.S. corporate securities	598.4			6.1			10.8				1.2			609.2		7.3
Foreign securities	270.4			1.4			35.6				7.4			306		8.8
Residential mortgage-backed securities	51.7			0.3			2.1				0.1			53.8		0.4
Commercial mortgage-backed securities	6.3			0.1			46.1				1.7			52.4		1.8
Other asset-backed securities	44.8			0.1			1.5				3.5			46.3		3.6
Redeemable preferred securities	12.2			0.2			10				7.1			22.2		7.3
Total debt securities	1,386.70			12.6			149.7				22.7			1,536.40		35.3
Equity securities	16.4			2.1			13				1			29.4		3.1
Total debt and equity securities (1)	$	1,403.10		$	14.7		$	162.7			$	23.7		$	1,565.80	$	38.4
(1)	At September 30, 2013 and December 31, 2012, debt and equity securities in an unrealized capital loss position of $63.3 million and $19.4 million, respectively, and with related fair value of $922.4 million and $225.2 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 September 30, 2013, we did not have the intention to sell the debt securities that were in an unrealized capital loss position.
The maturity dates for debt securities in an unrealized capital loss position at September 30, 2013 were as follows:
	Supporting experience-rated						Supporting remaining							Total
	and discontinued products						products
(Millions)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
	Value			Losses			Value				Losses			Value		Losses
Due to mature:
Less than one year	$	—		$	—		$	23.9			$	0.2		$	23.9	$	0.2
One year through five years	72.4			1.5			898.4				13.8			970.8		15.3
After five years through ten years	383			18.8			1,843.20				85.5			2,226.20		104.3
Greater than ten years	421.6			38.2			1,239.30				97			1,660.90		135.2
Residential mortgage-backed securities	6.6			0.1			354.9				11.6			361.5		11.7
Commercial mortgage-backed securities	8.7			0.4			164.2				4.3			172.9		4.7
Other asset-backed securities	14.1			0.3			83.9				1.9			98		2.2
Total	$	906.4		$	59.3		$	4,607.80			$	214.3		$	5,514.20	$	273.6
Net realized capital (losses) gains for the three and nine months ended September 30, 2013 and 2012, excluding amounts related to experience-rated contract holders and discontinued products, were as follows:
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(Millions)	2013			2012			2013				2012
OTTI losses on debt securities	$	(2.4	)	$	(1.8	)	$	(29.6	)		$	(10.4	)
Portion of OTTI losses on debt securities recognized	—			—			—				0.1
in other comprehensive income
Net OTTI losses on debt securities recognized in earnings	(2.4		)	(1.8		)	(29.6		)		(10.3		)
Net realized capital (losses) gains, excluding OTTI losses on debt securities	(10.3		)	19.1			17.4				87.9
Net realized capital (losses) gains	$	(12.7	)	$	17.3		$	(12.2	)		$	77.6
Net realized capital losses for the three months ended September 30, 2013 were primarily attributable to losses from the sales of debt securities and yield-related OTTI on debt securities. Net realized capital losses for the nine months ended September 30, 2013 were primarily attributable to yield-related OTTI on debt securities, primarily on U.S. Treasury securities, which was partially offset by gains from the sale of other debt securities. Net realized capital gains for the three and nine months ended September 30, 2012 were primarily attributable to the sale of debt securities, partially offset by losses from derivative transactions.
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 and nine months ended September 30, 2013 and 2012 were as follows:
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(Millions)	2013			2012			2013				2012
Proceeds on sales	$	1,434.00		$	1,323.30		$	5,216.50			$	4,138.60
Gross realized capital gains	25			30.8			83.9				135.7
Gross realized capital losses	34.9			1.9			78.3				13.2
Mortgage Loans
Our mortgage loans are collateralized by commercial real estate.  During the three and nine months ended September 30, 2013 and 2012 we had the following activity in our mortgage loan portfolio:
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(Millions)	2013			2012			2013				2012
New mortgage loans	$	62.8		$	71.8		$	126.4			$	132.3
Mortgage loans fully repaid	49.1			4.5			168.7				41.8
Mortgage loans foreclosed	—			—			—				16.7
At September 30, 2013 and December 31, 2012, we had no material problem, restructured or potential problem mortgage loans.  We also had no material impairment reserves on these loans at September 30, 2013 or December 31, 2012.
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 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, credit worthiness of the borrower and deal structure.  Based upon our most recent assessments at September 30, 2013 and December 31, 2012, our mortgage loans were given the following credit quality indicators:
(In Millions, except credit ratings indicator)	September 30,			December 31,
	2013			2012
1	$	118.2		$	94
2 to 4	1,346.50			1,451.10
5	32.5			60.2
6 and 7	59			38.3
Total	$	1,556.20		$	1,643.60
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 September 30, 2013 and December 31, 2012 of approximately $212 million and $215 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 $5.9 billion and $5.4 billion at September 30, 2013 and December 31, 2012, respectively.  The hedge fund partnership had total assets of approximately $7.2 billion and $7.0 billion at September 30, 2013 and December 31, 2012, respectively.
Non-controlling (Minority) Interests
At September 30, 2013 and December 31, 2012, continuing business non-controlling interests were approximately $51 million and $23 million, respectively, primarily related to third party interests in our investment holdings as well as third party interests in certain of our operating entities. The non-controlling entities’ share was included in total equity. Net income attributable to non-controlling interests was $.4 million for the three months ended September 30, 2013 and net loss attributable to non-controlling interests was $1.6 million for the nine months ended September 30, 2013, and net income attributable to non-controlling interests was $.4 million and $1.4 million for the three and nine months ended September 30, 2012, respectively.
Net Investment Income
Sources of net investment income for the three and nine months ended September 30, 2013 and 2012 were as follows:
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
(Millions)	2013			2012			2013				2012
Debt securities	$	193.9		$	186		$	573.9			$	574.7
Mortgage loans	27.2			25.3			76.1				90.8
Other investments	(2.2		)	13.1			46.8				39.2
Gross investment income	218.9			224.4			696.8				704.7
Less: investment expenses	(8.9		)	(8.2		)	(26.7		)		(23.1		)
Net investment income (1)	$	210		$	216.2		$	670.1			$	681.6
(1)	Net investment income includes $61.5 million and $210.3 million for the three and nine months ended September 30, 2013, respectively, and $79.8 million and $238.6 million for the three and nine months ended September 30, 2012, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom

Other Comprehensive (Loss) Income	9 Months Ended
	Sep. 30, 2013
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive (Loss) Income	8.    Other Comprehensive (Loss) Income
	Shareholders’ equity included the following activity in accumulated other comprehensive loss for the nine months ended September 30, 2013 and 2012:
		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					Cost
	Nine months ended September 30, 2013
	Balance at December 31, 2012	$	57.3				$	825.2				$	(29.5	)			$	(1,909.4	)			$	23				$	(1,033.4	)
	Other comprehensive (loss) income
	before reclassifications	(40.8		)			(481.1		)			22.9					—					—					(499.0		)
	Amounts reclassified from accumulated
	other comprehensive income	20.6			(2	)	17.2			(2	)	2.6			(3	)	37.9			(4	)	(2.0		)	(4	)	76.3
	Other comprehensive (loss) income	(20.2		)			(463.9		)			25.5					37.9					(2.0		)			(422.7		)
	Balance at September 30, 2013	$	37.1				$	361.3				$	(4.0	)			$	(1,871.5	)			$	21				$	(1,456.1	)
	Nine months ended September 30, 2012
	Balance at December 31, 2011	$	58.2				$	595.2				$	(33.7	)			$	(1,834.6	)			$	25.7				$	(1,189.2	)
	Other comprehensive (loss) income	2.4					258.5					5					36.4					(2.0		)			300.3
	Balance at September 30, 2012	$	60.6				$	853.7				$	(28.7	)			$	(1,798.2	)			$	23.7				$	(888.9	)
	(1)	Represents unrealized losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.
	(2)	Reclassifications out of accumulated other comprehensive income for previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statement 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 Statement of Income, except for derivatives related to interest rate swaps which are reflected in interest expense and were not material during the nine months ended September 30, 2013.
	(4)	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statement of Income (Refer to Note 10 of Condensed Notes to Consolidated Financial Statements beginning on page 27 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	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Financial Instruments	9.    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 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 as 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 as 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.  If Level 1 valuations are not available, the fair value is determined 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 obtained one price for each of our Level 2 debt securities and did not adjust any of these prices at September 30, 2013 or December 31, 2012.
	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 September 30, 2013 or December 31, 2012.  The total fair value of our broker quoted securities was approximately $99 million at September 30, 2013 and $117 million at December 31, 2012.  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 as 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 as 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 of the fair value hierarchy.  Certain of our derivative instruments are valued using models that primarily use market observable inputs and therefore are classified as 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 September 30, 2013 and December 31, 2012 were as follows:
	(Millions)	Level 1				Level 2				Level 3				Total
	September 30, 2013
	Assets:
	Debt securities:
	U.S. government securities	$	1,272.90			$	233.9			$	—			$	1,506.80
	States, municipalities and political subdivisions	—				3,912.90				1.3				3,914.20
	U.S. corporate securities	—				7,618.40				36.5				7,654.90
	Foreign securities	—				3,226.00				41.5				3,267.50
	Residential mortgage-backed securities	—				962.4				—				962.4
	Commercial mortgage-backed securities	—				1,404.70				7.4				1,412.10
	Other asset-backed securities	—				362.7				32.8				395.5
	Redeemable preferred securities	—				61				4.1				65.1
	Total debt securities	1,272.90				17,782.00				123.6				19,178.50
	Equity securities	17.8				0.3				62.3				80.4
	Derivatives	—				41.8				—				41.8
	Total	$	1,290.70			$	17,824.10			$	185.9			$	19,300.70
	Liabilities:
	Derivatives	$	—			$	2.2			$	—			$	2.2
	December 31, 2012
	Assets:
	Debt securities:
	U.S. government securities	$	1,311.40			$	248.1			$	—			$	1,559.50
	States, municipalities and political subdivisions	—				3,031.80				2.7				3,034.50
	U.S. corporate securities	—				7,736.00				54.6				7,790.60
	Foreign securities	—				3,317.90				52.7				3,370.60
	Residential mortgage-backed securities	—				979				—				979
	Commercial mortgage-backed securities	—				1,396.50				20.1				1,416.60
	Other asset-backed securities	—				512.6				29.5				542.1
	Redeemable preferred securities	—				80.5				14.1				94.6
	Total debt securities	1,311.40				17,302.40				173.7				18,787.50
	Equity securities	18.2				—				22.1				40.3
	Derivatives	—				8.9				—				8.9
	Total	$	1,329.60			$	17,311.30			$	195.8			$	18,836.70
	Liabilities:
	Derivatives	$	—			$	0.3			$	—			$	0.3
	There were no transfers between Levels 1 and 2 during the three or nine months ended September 30, 2013 and 2012.
	The gross transfers into (out of) Level 3 during the three and nine months ended September 30, 2013 and 2012 are as follows:
		Three Months Ended							Nine Months Ended
		September 30,							September 30,
	(Millions)	2013			2012				2013			2012
	Gross transfers into Level 3	$	3.8		$	—			$	3.8		$	1.8
	Gross transfers out of Level 3	(21.7		)	(7.4		)		(48.9		)	(30.1		)
	Net transfers (out of) Level 3	$	(17.9	)	$	(7.4	)		$	(45.1	)	$	(28.3	)
	Gross transfers out of Level 3 during the three and nine months ended September 30, 2013 primarily related to securities of States, municipalities and political subdivisions; U.S. corporate securities; and Foreign securities. The fair value of securities transferred out of Level 3 had been based on broker quotes and effective in the third quarter of 2013 is based primarily on a matrix pricing model, which uses quoted market prices of debt securities with similar characteristics. Gross transfers into Level 3 during the three and nine months ended September 30, 2013 primarily were due to quoted prices for certain securities no longer being available in active markets.
	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 as Level 2 because they are traded in markets where quoted market prices of identical bank loans are not readily available. For bank loans classified as Level 3, fair value is determined by outside brokers using an internal analysis through a combination of their knowledge of the current pricing environment and market flows.
	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 September 30, 2013 and December 31, 2012 were as follows:
	Carrying				Estimated Fair Value
(Millions)	Value				Level 1			Level 2			Level 3			Total
September 30, 2013
Assets:
Mortgage loans	$	1,556.20			$	—		$	—		$	1,598.60		$	1,598.60
Bank loans	142.2				—			130.1			10.5			140.6
Liabilities:
Investment contract liabilities:
With a fixed maturity	9.2				—			—			9.2			9.2
Without a fixed maturity	578.5				—			—			547.4			547.4
Long-term debt	8,266.30				—			8,716.00			—			8,716.00
December 31, 2012
Assets:
Mortgage loans	$	1,643.60			$	—		$	—		$	1,698.60		$	1,698.60
Liabilities:
Investment contract liabilities:
With a fixed maturity	18.5				—			—			18.5			18.5
Without a fixed maturity	590.2				—			—			611.1			611.1
Long-term debt	6,481.30				—			7,408.70			—			7,408.70
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 21.  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 as 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 September 30, 2013 and December 31, 2012 were as follows:
	September 30, 2013															December 31, 2012
(Millions)	Level 1				Level 2				Level 3				Total			Level 1		Level 2			Level 3		Total
Debt securities	$	685.7			$	2,163.90			$	0.6			$	2,850.20		$	721.7	$	2,343.90		$	0.4	$	3,066.00
Equity securities	209.4				1.6				—				211			194.9		1			—		195.9
Derivatives	—				0.2				—				0.2			—		(1.8		)	—		(1.8		)
Common/collective trusts	—				692.7				—				692.7			—		749			—		749
Total (1)	$	895.1			$	2,858.40			$	0.6			$	3,754.10		$	916.6	$	3,092.10		$	0.4	$	4,009.10
(1)	Excludes $179.5 million and $238.0 million of cash and cash equivalents and other receivables at September 30, 2013 and December 31, 2012, respectively.
Gross transfers of Separate Accounts financial assets out of Level 3 during the nine months ended September 30, 2013 and 2012 were $4.6 million and $.6 million, respectively. For the three and nine months ended September 30, 2013 and 2012, there were no transfers of Separate Accounts financial assets between Levels 1 and 2 and no transfers of Separate Accounts financial assets into or out of Level 3 except as previously stated.
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 September 30, 2013 and December 31, 2012 were as follows:
	Gross Amounts of Recognized Assets (1)			Gross Amounts Not Offset
				In the Balance Sheets
				Financial Instruments			Cash Collateral Received
(Millions)										Net Amount
30-Sep-13
Derivatives	$	41.8		$	—		$	(40.4	)	$	1.4
Total	$	41.8		$	—		$	(40.4	)	$	1.4
31-Dec-12
Derivatives	$	9.4		$	12.5		$	(7.5	)	$	14.4
Total	$	9.4		$	12.5		$	(7.5	)	$	14.4
(1) There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.
Financial liabilities, including derivative liabilities, subject to offsetting and enforceable master netting arrangements as of September 30, 2013 and December 31, 2012 were as follows:
	Gross Amounts of Recognized Liabilities (1)			Gross Amounts Not Offset
				In the Balance Sheets
				Financial Instruments			Cash Collateral Paid
(Millions)										Net Amount
30-Sep-13
Derivatives	$	6.1		$	(10.7	)	$	(.9	)	$	(5.5	)
Securities lending	550.2			(550.2		)	—			—
Total	$	556.3		$	(560.9	)	$	(.9	)	$	(5.5	)
31-Dec-12
Derivatives	$	0.3		$	—		$	—		$	0.3
Securities lending	47.1			(47.1		)	—			—
Total	$	47.4		$	(47.1	)	$	—		$	0.3
(1) There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.

Pension_and_Other_Postretireme

Pension and Other Postretirement Plans	9 Months Ended
	Sep. 30, 2013
Compensation and Retirement Disclosure [Abstract]
Pension and Other Postretirement Plans	10.    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 benefit (“OPEB”) plans for the three and nine months ended September 30, 2013 and 2012 were as follows:
		Pension Plans												OPEB Plans
		Three Months Ended						Nine Months Ended						Three Months Ended						Nine Months Ended
		September 30,						September 30,						September 30,						September 30,
	(Millions)	2013			2012			2013			2012			2013			2012			2013			2012
	Service cost	$	—		$	—		$	—		$	—		$	—		$	—		$	—		$	0.1
	Amortization of prior service cost	(.1		)	(.1		)	(.3		)	(.3		)	(1.0		)	(.9		)	(2.7		)	(2.7		)
	Interest cost	67.9			74.6			203.6			223.8			2.8			3.6			8.3			10.8
	Expected return on plan assets	(99.1		)	(96.8		)	(297.3		)	(290.5		)	(.6		)	(.6		)	(1.8		)	(2.0		)
	Recognized net actuarial losses	19			17.5			56.6			52.7			0.6			1.1			1.7			3.3
	Net periodic benefit (income) cost	$	(12.3	)	$	(4.8	)	$	(37.4	)	$	(14.3	)	$	1.8		$	3.2		$	5.5		$	9.5
	During each of the third quarters of 2013 and 2012, we made $60 million in voluntary cash contributions to our tax-qualified noncontributory defined benefit pension plan.

Debt

Debt	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Debt Disclosure	11.    Debt
	The carrying value of our long-term debt at September 30, 2013 and December 31, 2012 was as follows:
	(Millions)	September 30,		December 31,
		2013		2012
	Senior notes, 6.3%, due 2014	$	392.2	$	—
	Senior notes, 6.125%, due 2015	243.4		—
	Senior notes, 6.0%, due 2016	748.8		748.5
	Senior notes, 5.95%, due 2017	438.2		—
	Senior notes, 1.75%, due 2017	248.8		248.6
	Senior notes, 1.5%, due 2017	498		497.7
	Senior notes, 6.5%, due 2018	494.9		494.8
	Senior notes, 3.95%, due 2020	744.1		743.4
	Senior notes, 5.45%, due 2021	705.8		—
	Senior notes, 4.125%, due 2021	494.7		494.1
	Senior notes, 2.75%, due 2022	984.6		983.4
	Senior notes, 6.625%, due 2036	769.8		769.7
	Senior notes, 6.75%, due 2037	530.6		529.5
	Senior notes, 4.5%, due 2042	479.9		479.3
	Senior notes, 4.125%, due 2042	492.5		492.3
	Total long-term debt	8,266.30		6,481.30
	Less current portion of long-term debt (1)	392.2		—
	Total long-term debt, less current portion	$	7,874.10	$	6,481.30
	(1) At September 30, 2013, our 6.3% senior notes due August 2014 are classified as current in the accompanying consolidated balance sheet.
	As discussed in Note 3 beginning on page 7, our total long-term debt outstanding increased by $1.8 billion as a result of the acquisition of Coventry, which includes $216.6 million to adjust the Coventry long-term debt to its estimated fair value at the Effective Date. The principal amounts of the outstanding Coventry notes are $375 million of 6.3% senior notes due 2014, $229 million of 6.125% senior notes due 2015, $383 million of 5.95% senior notes due 2017 and $600 million of 5.45% senior notes due 2021.
	We issued approximately $700 million of commercial paper in 2013 to finance a portion of the cash purchase price for the acquisition of Coventry. At both September 30, 2013 and December 31, 2012, we did not have any commercial paper outstanding.
	Interest Rate Swaps
	During June and July of 2012, we entered into two interest rate swaps with an aggregate notional value of $375 million. We designated these swaps as cash flow hedges against interest rate exposure related to the forecasted future issuance of fixed-rate debt to refinance long-term debt maturing in June 2016. At September 30, 2013, these interest rate swaps had a pretax fair value gain of $39.9 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, and 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”, and together with the First Amendment 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. On March 27, 2013, the maturity date of the Facility was extended by one year to March 27, 2018.
	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 .070% to .150% per annum, depending upon our long-term senior unsecured debt rating.  The facility fee was .100% at September 30, 2013.  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 September 30, 2013.  There were no amounts outstanding under the Facility at any time during the nine months ended September 30, 2013.

Capital_Stock

Capital Stock	9 Months Ended
	Sep. 30, 2013
Class of Stock Disclosures [Abstract]
Capital Stock	12.    Capital Stock
	On September 27, 2013, February 19, 2013 and July 27, 2012, our Board of Directors (our “Board”) authorized three separate share repurchase programs. Each repurchase program authorized us to repurchase up to $750 million of our common stock.  During the nine months ended September 30, 2013, we repurchased approximately 16 million shares of common stock at a cost of approximately $958 million.  At September 30, 2013, we had remaining authorization to repurchase an aggregate of up to approximately $1 billion of common stock under the September 27, 2013 and February 19, 2013 programs.
	During the nine months ended September 30, 2013 our Board declared the following cash dividends:
	Date Declared	Dividend Amount			Stockholders of	Date Paid/	Total Dividends
		Per Share			Record Date	To be Paid	(Millions)
	February 19, 2013		$	0.2	April 11, 2013	April 26, 2013		$	65.2
	May 17, 2013		0.2		July 11, 2013	July 26, 2013		74.4
	September 27, 2013		0.2		October 10, 2013	October 25, 2013		73.6
	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 the Effective Date, we issued approximately 52.2 million Aetna common shares, with a fair value of approximately $3.1 billion and paid approximately $3.8 billion in cash in exchange for all the outstanding shares of Coventry common stock and outstanding awards.
	On May 24, 2013, approximately .5 million restricted stock units (“RSUs”) were granted to certain employees.
	On February 1, 2013, approximately .5 million performance stock units (“PSUs”), 1.1 million market stock units (“MSUs”) and 1.1 million RSUs 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 performance goals during the performance periods as determined by our Board’s Committee on Compensation and Organization.  The PSUs have two separate performance periods which relate to the Company's operating performance during the years ending December 31, 2013 and December 31, 2014. The vesting period for the PSUs ends on February 1, 2015. The number of vested MSUs (which could range from zero to 150% of the original number of units granted) is based on the percentage change between the closing price of our common stock on the grant date and the weighted average closing price of our common stock for the thirty trading days prior to and including the vesting dates.  Certain MSUs contain a performance condition that relates to the Company's cumulative performance during the years ending December 31, 2013 and December 31, 2014. The vesting period for the MSUs ends February 1, 2016. Each vested PSU, MSU 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 will become 100% vested approximately three years from the grant date, with one-third vesting each December.

Dividend_Restrictions_and_Stat

Dividend Restrictions and Statutory Surplus	9 Months Ended
	Sep. 30, 2013
Dividend Restrictions and Statutory Surplus [Abstract]
Dividend Restrictions and Statutory Surplus	13.    Dividend Restrictions and Statutory Surplus
	Under regulatory requirements at September 30, 2013, the amount of dividends that may be paid through the end of 2013 by our insurance and HMO subsidiaries without prior approval by regulatory authorities is approximately $900 million in the aggregate. There are no such regulatory restrictions on distributions from Aetna to its shareholders. In the third quarter of 2013, our insurance and HMO subsidiaries paid approximately $637 million of dividends to the Company.
	The combined statutory capital and surplus of our insurance and HMO subsidiaries was $8.8 billion and $6.4 billion at September 30, 2013 and December 31, 2012, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14.    Commitments and Contingencies
	Guaranty Fund Assessments, Market Stabilization and Other Non-Voluntary Risk Sharing Pools
	Under guaranty fund laws existing in all states, insurers doing business in those states can be assessed (up to prescribed limits) for certain obligations of insolvent insurance companies to policyholders and claimants. The health insurance guaranty associations in which we participate that operate under these laws respond to insolvencies of long-term care insurers as well as health insurers.  Our assessments generally are based on a formula relating to our premiums in the state compared to the premiums of other insurers. Certain states allow assessments to be recovered as offsets to premium taxes.  Some states have similar laws relating to HMOs.  The Pennsylvania Insurance Commissioner (the “Commissioner”) has placed long-term care insurer Penn Treaty Network America Insurance Company and one of its subsidiaries (collectively, “Penn Treaty”) in rehabilitation, an intermediate action before insolvency, and subsequently petitioned a state court to convert the rehabilitation into a liquidation. In May 2012, the state court denied the request and ordered the Commissioner to propose a rehabilitation plan. In September 2012, the state court finalized its opinion that Penn Treaty is not insolvent and remains in rehabilitation. The Commissioner has appealed the state court's decision and has filed a proposed rehabilitation plan with the state court. If the rehabilitation is not successful and Penn Treaty ultimately is placed in liquidation, we and other insurers likely would be assessed over a period of years by guaranty associations for the payments the guaranty associations are required to make to Penn Treaty policyholders.  We are currently unable to predict the ultimate outcome of, or reasonably estimate the loss or range of losses resulting from, this potential insolvency because we cannot predict whether rehabilitation efforts will succeed, the amount of the insolvency, if any, the amount and timing of associated guaranty association assessments or the amount or availability of potential offsets, such as premium tax offsets.  It is reasonably possible that in future reporting periods we may record a liability and expense relating to Penn Treaty or other insolvencies which could have a material adverse effect on our operating results, financial position and cash flows.  While we have historically recovered more than half of guaranty fund assessments through statutorily permitted premium tax offsets, significant increases in assessments could lead to legislative and/or regulatory actions that may limit future offsets.
	HMOs in certain states in which we do business are subject to assessments, including market stabilization and other risk-sharing pools, for which we are assessed charges based on incurred claims, demographic membership mix and other factors. We establish liabilities for these assessments based on applicable laws and regulations. In certain states, the ultimate assessments we pay are dependent upon our experience relative to other entities subject to the assessment and the ultimate liability is not known at the balance sheet date. While the ultimate amount of the assessment is dependent upon the experience of all pool participants, we believe we have adequate reserves to cover such assessments.
	Litigation and Regulatory Proceedings
	Out-of-Network Benefit Proceedings
	We are named as a defendant in several purported class actions and individual lawsuits arising out of our practices related to the payment of claims for services rendered to our members by health care providers with whom we do not have a contract (“out-of-network providers”).   Among other things, these lawsuits allege that we paid too little to our health plan members and/or providers for these services, among other reasons, because of our use of data provided by Ingenix, Inc., a subsidiary of one of our competitors (“Ingenix”). Other major health insurers are the subject of similar litigation or have settled similar litigation.
	Various plaintiffs who are health care providers or medical associations seek to represent nationwide classes of out-of-network providers who provided services to our members during the period from 2001 to the present.  Various plaintiffs who are members in our health plans seek to represent nationwide classes of our members who received services from out-of-network providers during the period from 2001 to the present.  Taken together, these lawsuits allege that we violated state law, the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), the Racketeer Influenced and Corrupt Organizations Act 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 No. 2020. Under the terms of the proposed nationwide settlement, we will be 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 class period for health plan members begins on March 1, 2001, and the settlement class period for health care providers begins on June 3, 2003. The agreement contains no admission of wrongdoing. The medical associations are not parties to the settlement agreement.
	Under the settlement agreement, we will pay $60 million, the substantial majority of which will be payable upon final court approval of the settlement, and pay up to an additional $60 million at the end of a claim submission and validation period that commences upon final court approval of the settlement. These payments will fund claims submitted by health plan members who are members of the plaintiff class and health care providers who are members of the plaintiff class. These payments also will fund the legal fees of plaintiffs' counsel and the costs of administering the settlement, in each case in amounts to be determined by the New Jersey District Court.
	The New Jersey District Court preliminarily approved the settlement on August 30, 2013. The proposed settlement remains subject to final court approval, and a final approval hearing is scheduled for March 2014. Final court approval of the settlement could be delayed by appeals or other proceedings. In addition, the Company has the right to terminate the settlement agreement if more than certain percentages of class members, or class members collectively holding specified dollar amounts of claims, elect to opt-out of the settlement. In connection with the proposed settlement, the Company recorded an after-tax charge to net income of approximately $78 million in the fourth quarter of 2012. The Company will pay for the settlement with available resources and expects the settlement payments to occur over the next twelve to twenty-four months.  We intend to continue to vigorously defend ourselves against the claims brought in these cases by non-settling plaintiffs.
	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 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 practices.
	CMS Actions
	In June 2011, the Centers for Medicare & Medicaid Services (“CMS”) lifted the intermediate sanctions it had previously imposed on us in April 2010 that required us to suspend the enrollment of and marketing to new members of all Aetna Medicare Advantage and Standalone Prescription Drug Plan (“PDP”) contracts.  The sanctions related to our compliance with certain Medicare Part D requirements.  On September 27, 2012, CMS notified us that we were again eligible to receive assignments of low-income subsidy PDP members from CMS.
	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 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 and document their medical records.  CMS pays increased premiums to Medicare Advantage plans and PDPs for members who have certain medical conditions identified with specific diagnosis codes.  Federal regulators review and audit the providers’ medical records and 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. 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.
	In February 2012, CMS published a Notice of Final Payment Error Calculation Methodology for Part C Medicare Advantage Risk Adjustment Data Validation Contract-Level Audits (the “Notice”). The Notice outlines the methodology that CMS will use to determine RADV audit premium refunds payable by Medicare Advantage plans for contract years 2011 and forward. Under that methodology, the RADV audit premium refund calculation will include an adjustment for the differences in documentation standards between the RADV audits and the risk adjustment model; however, the Notice provides limited information about that adjustment. In addition, CMS will project the error rate identified in the audit sample to all risk adjusted premium payments made under the contract being audited. Historically, CMS did not make an adjustment for differences in documentation standards or project sample error rates to the entire contract. During 2013, CMS is expected to select 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 financial impact of the documentation standard adjustment, 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 bid submissions to CMS for the current or future contract years or compromise premium assumptions made in our bids for prior contract years or the current contract year. Any premium refunds or adjustments resulting from regulatory audits, whether as a result of RADV or other audits by CMS, the OIG or otherwise, 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 employment litigation and claims of bad faith, medical malpractice, non-compliance with state and federal regulatory regimes, marketing misconduct, failure to timely or appropriately pay medical and/or group insurance claims (including post-payment audit and collection practices), rescission of insurance coverage, improper disclosure of personal information, patent infringement and other intellectual property litigation and other litigation in our Health Care and Group Insurance businesses.  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.
	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, 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.”
	Over 35 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.  We may incur a liability as a result of these investigations and/or audits, whether as a result of 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 heightened review by regulatory authorities of and increased litigation regarding 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 the use of performance-based networks and termination of provider contracts), delegated arrangements, rescission of insurance coverage, limited benefit health products, student health products, pharmacy benefit management practices, sales 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, assessments of damages, civil or criminal fines or penalties, or other sanctions, including the possible loss of licensure or suspension or exclusion from participation in government programs, such as the intermediate sanctions previously imposed on us by CMS that are described above under “CMS Actions.”
	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 “Out-of-Network Benefit 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	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Segment Information	15.    Segment Information
	Our operations are conducted in three business segments:  Health Care, Group Insurance and Large Case Pensions.  The acquired Coventry operations are reflected in our Health Care segment for the three and nine months ended September 30, 2013. 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).
	Summarized financial information of our segments for the three and nine months ended September 30, 2013 and 2012 was as follows:
	(Millions)	Health			Group			Large Case			Corporate			Total Company
		Care			Insurance			Pensions (2)			Financing
	Three Months Ended September 30, 2013
	Revenue from external customers	$	12,228.70		$	510.7		$	98.9		$	—		$	12,838.30
	Operating earnings (loss) (1)	585.8			19.7			6.2			(49.9		)	561.8
	Three Months Ended September 30, 2012
	Revenue from external customers	$	8,172.70		$	465.8		$	45.3		$	—		$	8,683.80
	Operating earnings (loss) (1)	531.8			29.3			3.7			(41.6		)	523.2
	Nine Months Ended September 30, 2013
	Revenue from external customers	$	31,743.00		$	1,536.80		$	174.2		$	—		$	33,454.00
	Operating earnings (loss) (1)	1,637.80			80.8			16.2			(128.6		)	1,606.20
	Nine Months Ended September 30, 2012
	Revenue from external customers	$	24,398.40		$	1,378.10		$	134.5		$	—		$	25,911.00
	Operating earnings (loss) (1)	1,444.20			116.2			13.4			(121.2		)	1,452.60
	(1)	Operating earnings (loss) excludes net realized capital gains or losses and the other items described in the reconciliation below.
	(2)	In the third quarter of 2013, an existing group annuity contract converted from a participating to a non-participating contract. Upon conversion, we recorded $54.1 million of non-cash group annuity conversion premium for this contract and a corresponding $54.1 million non-cash benefit expense on group annuity conversion for this contract.
	A reconciliation of operating earnings (1) to net income attributable to Aetna for the three and nine months ended September 30, 2013 and 2012 was as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013			2012
	Operating earnings (1)	$	561.8		$	523.2		$	1,606.20		$	1,452.60
	Transaction and integration-related costs, net of tax	(34.6		)	(12.5		)	(140.6		)	(12.5		)
	Reduction of reserve for anticipated future losses on discontinued products, net of tax	—			—			55.9			—
	Reversal of allowance and gain on sale of reinsurance recoverable, net of tax	—			—			32.1			—
	Loss on early extinguishment of long-term debt, net of tax	—			(23.0		)	—			(23.0		)
	Net realized capital (losses) gains, net of tax	(8.6		)	11.5			(8.9		)	50.7
	Net income attributable to Aetna	$	518.6		$	499.2		$	1,544.70		$	1,467.80
	(1)	In addition to net realized capital gains (losses), the following 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 related to the acquisition of Coventry of $34.6 million ($51.2 million pretax) and $140.6 million ($189.6 million pretax) during the three and nine months ended September 30, 2013, respectively, and $12.5 million ($13.8 million pretax) during the three and nine months ended September 30, 2012. 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, as well as the cost of the bridge credit agreement that was in effect prior to the Coventry acquisition, which is reflected in the GAAP Consolidated Statements of Income in interest expense. Transaction costs also include transaction-related payments as well as expenses related to the negative cost of carry associated with the permanent financing that we obtained in November 2012 for the Coventry acquisition. Prior to the Effective Date, the negative cost of carry was excluded from operating earnings. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense, net investment income, and general and administrative expenses. On and after the Effective Date, the interest expense and general and administrative expenses associated with the permanent financing are no longer excluded from operating earnings.
	•	We reduced the reserve for anticipated future losses on discontinued products by $55.9 million ($86.0 million pretax) in the second quarter of 2013. We believe excluding any changes in the reserve for anticipated future losses on discontinued products from operating earnings provides more useful information as to our continuing products and is consistent with the treatment of the operating results of these discontinued products, which are credited or charged to the reserve and do not affect our operating results. Refer to Note 17 beginning on page 36 for additional information on the reduction of the reserve for anticipated future losses on discontinued products.
	•	In 2008, as a result of the liquidation proceedings of Lehman Re, a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re of $27.4 million ($42.2 million pretax). This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $27.4 million ($42.2 million pretax) and recognized a $4.7 million ($7.2 million pretax) gain on the sale in fees and other revenue.
	•	In the third quarter of 2012, we incurred a loss on the early extinguishment of long-term debt of $23.0 million ($35.4 million pretax) related to repurchases of certain of our outstanding senior notes.

Reinsurance

Reinsurance	9 Months Ended
	Sep. 30, 2013
Reinsurance Disclosures [Abstract]
Reinsurance	16.     Reinsurance
	In January 2013, we entered into four-year reinsurance agreements with Vitality Re IV Limited, an unrelated insurer. The agreements allow us to reduce our required capital and provide $150 million of collateralized excess of loss reinsurance coverage on a portion of Aetna's group Commercial Insured Health Care business.
	In May 2013, we entered into two agreements with unrelated reinsurers to reinsure a portion of our Medicare Advantage business and a portion of our group Commercial Insured Health Care business, respectively. These contracts did not qualify for reinsurance accounting under GAAP, and consequently are accounted for using deposit accounting.
	In 2008, as a result of the liquidation proceedings of Lehman Re, a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re of $27.4 million ($42.2 million pretax). This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In September 2008, we took possession of assets supporting the reinsurance recoverable, which previously were held as collateral in a trust. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $27.4 million ($42.2 million pretax) and recognized a $4.7 million ($7.2 million pretax) gain on the sale in fees and other revenue.

Discontinued_Products

Discontinued Products	9 Months Ended
	Sep. 30, 2013
Discontinued Products [Abstract]
Discontinued Products
	17	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.  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. As of September 30, 2013, our remaining GIC liability was not material.
	Key assumptions in setting the reserve for anticipated losses include future investment results, payments to retirees, mortality and retirement rates and the cost of asset management and customer service.  In 2012, we modified the mortality tables used in order to reflect a more up-to-date 2000 Retired Pensioner’s Mortality table. The mortality tables were previously modified in 1995, in order to reflect a 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.  If actual or expected future losses are greater than we currently estimate, we may increase the reserve, which could adversely impact net income.  If actual or expected future losses are less than we currently estimate, we may decrease the reserve, which could favorably impact net income.  As a result of this review, $55.9 million ($86.0 million pretax) of the reserve was released in the nine months ended September 30, 2013. This reserve release was primarily due to favorable investment performance as well as favorable retirement experience compared to assumptions we previously made in estimating the reserve. The reserve at each of September 30, 2013 and December 31, 2012 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 nine months ended September 30, 2013 and 2012 (pretax) was as follows:
	(Millions)	2013			2012
	Reserve, beginning of period	$	978.5		$	896.3
	Operating loss	(8.5		)	(5.1		)
	Net realized capital gains	73.7			55.2
	Reserve reduction	(86.0		)	—
	Reserve, end of period	$	957.7		$	946.4
	During the nine months ended September 30, 2013, our discontinued products reflected net realized capital gains, primarily attributable to gains from other invested assets and from the sale of debt securities. We evaluated these results against expectations of future cash flows assumed in estimating the reserve and do not believe that an adjustment to the reserve was required at September 30, 2013.
	Assets and liabilities supporting discontinued products at September 30, 2013 and December 31, 2012 were as
	follows: (1)
	(Millions)	2013			2012
	Assets:
	Debt and equity securities available for sale	$	2,326.90		$	2,515.30
	Mortgage loans	407.2			448.6
	Other investments	690.9			711.6
	Total investments	3,425.00			3,675.50
	Other assets	101			79.2
	Collateral received under securities loan agreements	151			3.8
	Current and deferred income taxes	25.2			19.3
	Receivable from continuing products (2)	525.1			556
	Total assets	$	4,227.30		$	4,333.80
	Liabilities:
	Future policy benefits	$	2,795.30		$	2,857.60
	Policyholders' funds	—			6.6
	Reserve for anticipated future losses on discontinued products	957.7			978.5
	Collateral payable under securities loan agreements	151.1			3.8
	Other liabilities (3)	323.2			487.3
	Total liabilities	$	4,227.30		$	4,333.80
	(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 $98 million and $296 million for the three and nine months ended September 30, 2013, respectively, and $99 million and $300 million for the three and nine months ended September 30, 2012, respectively. Participant-directed withdrawals from our discontinued products were not significant during the three or nine months ended September 30, 2013 or 2012.  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)	9 Months Ended
	Sep. 30, 2013
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 2012 Annual Report on Form 10-K (our “2012 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 2012 Annual Report, unless the information contained in those disclosures materially changed and is required by GAAP.  We evaluated subsequent events that occurred after September 30, 2013 through the date the financials were issued and determined there were no other items to disclose.
Principles of Consolidation	Principles of Consolidation
	These 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.
Reclassifications	Reclassifications
	Certain reclassifications were made to 2012 financial information to conform with 2013 presentation.

Completed_Acquisition_Complete

Completed Acquisition; Completed Disposition Completed Acquisition, Completed Disposition (Tables)	9 Months Ended
	Sep. 30, 2013
Business Acquisition [Line Items]
Schedule of Purchase Price Allocation	The components of consideration transferred for the acquisition of Coventry were as follows:
	(Certain amounts may reflect rounding adjustments)
		Conversion						Form of
	(Millions, except per common share data)	Calculation			Fair Value			Consideration
	Consideration Transferred:
	Number of shares of Coventry common stock outstanding at May 7, 2013:	133.7
	Multiplied by Aetna's share price at May 7, 2013, multiplied by the							Aetna
	exchange ratio ($58.69*0.3885)	$	22.8		$	3,047.40		Common Shares
	Multiplied by the per common share cash consideration	$	27.3		$	3,648.70		Cash
	Number of shares underlying in-the-money Coventry stock options vested and unvested
	outstanding as of May 7, 2013, canceled and exchanged for cash	4.9
	Multiplied by the excess, if any, of (1) the sum of (x) the per
	common share cash consideration plus (y) the Aetna closing share price (1)
	multiplied by the exchange ratio ($57.93*0.3885) over
	(2) the weighted-average exercise price of such
	in-the-money stock options	$	15.94		$	78.1		Cash
	Number of Coventry performance share units and restricted stock
	units outstanding at May 7, 2013, canceled and paid in cash	1.6
	Multiplied by the equity award cash consideration	$	49.8		$	58.5		Cash (2)
	Number of Coventry restricted shares outstanding at May 7, 2013:	1.1
	Less: employee tax withholdings	(.4		)	$	18.8		Cash
	Net restricted shares outstanding at May 7, 2013	0.7
	Multiplied by Aetna's share price at May 7, 2013, multiplied by							Aetna
	the exchange ratio ($58.69*0.3885)	$	22.8		$	17.2		Common Shares
	Multiplied by the per common share cash consideration	$	27.3		$	20.5		Cash
	Other consideration transferred  (3)				6.9
	Total consideration transferred				$	6,896.10
	(1)	Based on the average of the volume weighted averages of the trading prices of Aetna common shares on the New York Stock Exchange for each of the five consecutive trading days ending on the trading day that was two trading days prior to the Effective Date.
	(2)	Pursuant to the terms of certain employment agreements, an aggregate of approximately .5 million performance share units and restricted stock units did not automatically vest upon the change of control of Coventry. In the absence of such automatic vesting upon a change in control, pursuant to GAAP, Aetna estimated the fair value of these awards at the Effective Date and attributed that fair value to pre-Merger and post-Merger services. Accordingly, $6.9 million of the fair value of these awards was attributed to pre-Merger services and is included in the estimated consideration transferred, and approximately $19.0 million will be accounted for in Aetna's post-Merger financial statements as transaction-related costs and reflected as a selling, general and administrative expense in Aetna's statements of income.
	(3)	Certain of Coventry's named executive officers received payments pursuant to employment agreements entered into prior to the Coventry acquisition. The total compensation paid in cash pursuant to such agreements in connection with the Merger was $6.5 million. Other consideration transferred also includes the portion of the fair value of the Rollover Units that was attributed to pre-Merger services. The fair value attributable to post-Merger services will be recorded as selling, general and administrative expense in Aetna's post-Merger financial statements.
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following table summarizes the estimated fair values of major classes of assets acquired and liabilities assumed as part of the Merger, reconciled to the total consideration transferred:
			At May 7,
	(Millions)		2013
	Cash and cash equivalents		$	2,195.60
	Investments		2,156.40
	Premiums and other receivables, net		1,141.10
	Intangible assets acquired		1,490.00
	Property and equipment		174.8
	Other assets		97.5
	Total assets acquired		7,255.40
	Health care costs payable		1,440.10
	Long-term debt		1,803.80
	Net deferred tax liabilities (1)		257
	Other liabilities		854.9
	Total liabilities assumed		4,355.80
	Total identifiable net assets		2,899.60
	Goodwill acquired		3,996.50
	Total consideration transferred		$	6,896.10
	(1)	Includes $521.5 million of deferred tax liabilities on identifiable intangible assets acquired and $75.8 million of deferred tax assets on the fair value adjustment to Coventry's outstanding debt.
Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination	The fair value and weighted-average useful lives for all intangible assets acquired are as follows:
		Fair Value (Millions)			Useful Life (Years)
	Customer lists	$	810		10
	Provider networks	550			17
	Trademarks/tradenames	100			10
	Technology	30			4
	Total	$	1,490.00
Actual Impacts of Acquisition	Actual and Pro Forma Impact of Acquisition
	The results of Coventry have been included in our results from the Effective Date through September 30, 2013. The following table presents revenue and net income of Coventry included in our results for the three and nine months ended September 30, 2013:
		Three Months Ended				Nine Months Ended
	(Millions)	30-Sep-13				30-Sep-13
	Revenue	$	3,531.30			$	5,599.80
	Net Income	112.8				169
Business Acquisition, Pro Forma Information	The following table presents supplemental pro forma information as if the Merger had occurred on January 1, 2012 for the nine months ended September 30, 2013 and for the three and nine months ended September 30, 2012. The pro forma consolidated results are not necessarily indicative of what our consolidated results would have been had the Merger been completed on January 1, 2012. In addition, the pro forma consolidated results do not purport to project the future results of the combined company nor do they reflect the expected realization of any cost savings associated with the Merger.
		Three Months Ended				Nine Months Ended September 30,
	(Millions, except per common share data)	30-Sep-12				2013			2012
	Total revenue	$	12,253.30			$	38,906.60		$	37,031.80
	Net income	600				1,775.30			1,810.10
	Earnings per share:
	Basic	$	1.55			$	4.73		$	4.59
	Diluted	1.54				4.68			4.53

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	9 Months Ended
	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Share	The computations of basic and diluted EPS for the three and nine months ended September 30, 2013 and 2012 were as follows:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(Millions, except per common share data)	2013		2012		2013		2012
	Net income attributable to Aetna	$	518.6	$	499.2	$	1,544.70	$	1,467.80
	Weighted average shares used to compute basic EPS	371.1		334.8		351.8		342.2
	Dilutive effect of outstanding stock-based compensation awards (1)	4.1		3.8		3.7		5
	Weighted average shares used to compute diluted EPS	375.2		338.6		355.5		347.2
	Basic EPS	$	1.4	$	1.49	$	4.39	$	4.29
	Diluted EPS	$	1.38	$	1.47	$	4.35	$	4.23
	(1)	Stock-based compensation awards are not included in 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).  Approximately 2.2 million stock appreciation rights were not included in the calculation of diluted EPS for the nine months ended September 30, 2013 and 11.0 million and 8.6 million stock appreciation rights were not included in the calculation of diluted EPS for the three and nine months ended September 30, 2012, respectively, because they were anti-dilutive. All stock options were included in the calculation of diluted EPS for the three and nine months ended September 30, 2013 and 2012.

Operating_Expenses_Tables

Operating Expenses (Tables)	9 Months Ended
	Sep. 30, 2013
Operating Expenses [Abstract]
Operating Expenses	For the three and nine months ended September 30, 2013 and 2012, 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:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
	(Millions)	2013		2012		2013		2012
	Selling expenses	$	353.9	$	272.8	$	983.3	$	820.5
	General and administrative expenses:
	Salaries and related benefits	1,119.40		780.4		2,914.50		2,336.70
	Other general and administrative expenses  (1) (2)	831.2		586.4		2,240.30		1,794.80
	Total general and administrative expenses	1,950.60		1,366.80		5,154.80		4,131.50
	Total operating expenses	$	2,304.50	$	1,639.60	$	6,138.10	$	4,952.00
	(1)	Includes $51.2 million and $171.4 million of transaction and integration-related costs related to the acquisition of Coventry, including advisory, legal and other professional services fees and transaction-related payments as well as integration costs incurred in the three and nine months ended September 30, 2013, respectively and $10.0 million during the three and nine months ended September 30, 2012.
	(2)	In 2008, as a result of the liquidation proceedings of Lehman Re Ltd. (“Lehman Re”), a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re. This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $42.2 million pretax

Goodwill_and_Other_Acquired_In1

Goodwill and Other Acquired Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The change in goodwill for the nine months ended September 30, 2013 was as follows:
	(Millions)	2013
	Balance, beginning of the period	$	6,214.40
	Goodwill acquired:
	Coventry (1)	3,996.50
	Other	(5.2		)
	Balance, end of the period (2)	$	10,205.70
	(1)	Goodwill related to the acquisition of Coventry is considered preliminary, pending the final allocation of the applicable purchase price.
	(2)	At September 30, 2013, approximately $113 million was assigned to the Group Insurance segment, with the remainder assigned to the Health Care segment.
Schedule Of Intangible Assets	Other acquired intangible assets at September 30, 2013 and December 31, 2012 were comprised of the following:
	(Millions)	Cost			Accumulated			Net Balance		Amortization
					Amortization					Period (Years)
	30-Sep-13
	Provider networks	$	1,253.20			$	493.4	$	759.8		25-Dec	(1)
	Customer lists	1,347.00				326.7		1,020.30			14-May	(1)
	Value of business acquired (“VOBA”)	149.2				43.7		105.5			20	(2)
	Technology	146.6				43.4		103.2			10-Apr
	Other	6.7				1.8		4.9			15-Feb
	Definite-lived trademarks	165				21.8		143.2			20-Sep
	Indefinite-lived trademarks	22.3				—		22.3
	Total other acquired intangible assets	$	3,090.00			$	930.8	$	2,159.20
	31-Dec-12
	Provider networks	$	703.2			$	458.2	$	245		25-Dec	(1)
	Customer lists	657.4				370.2		287.2			14-May	(1)
	Value of business acquired	149.2				29.2		120			20	(2)
	Technology	116.6				28		88.6			10-May
	Other	6.7				1.5		5.2			15-Feb
	Definite-lived trademarks	65				14.6		50.4			20-Sep
	Indefinite-lived trademarks	22.3				—		22.3
	Total other acquired intangible assets	$	1,720.40			$	901.7	$	818.7
	(1)	The amortization period for our provider networks and customer lists includes an assumption of renewal or extension of these arrangements.  At September 30, 2013 and December 31, 2012, the periods prior to the next renewal or extension for our provider networks primarily ranged from 1 to 3 years and the period prior to the next renewal or extension for our customer lists was less than one year and two years, respectively. Any costs related to the renewal or extension of these contracts are expensed as incurred.
	(2)	VOBA is being amortized over the expected life of the acquired contracts in proportion to estimated premium.
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	We estimate annual pretax amortization for other acquired intangible assets for 2013 and in each of the next five years to be as follows:
	(Millions)
	2013	$	214.6
	2014	238.4
	2015	222.5
	2016	215.5
	2017	201.1
	2018	192.9

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2013
Investments [Abstract]
Total investments	Total investments at September 30, 2013 and December 31, 2012 were as follows:
		September 30, 2013										December 31, 2012
	(Millions)	Current			Long-term			Total				Current			Long-term		Total
	Debt and equity securities available for sale	$	1,897.80		$	17,361.10		$	19,258.90			$	2,006.80		$	16,821.00	$	18,827.80
	Mortgage loans	136.3			1,419.90			1,556.20				214.4			1,429.20		1,643.60
	Other investments	2.3			1,717.60			1,719.90				0.7			1,448.00		1,448.70
	Total investments	$	2,036.40		$	20,498.60		$	22,535.00			$	2,221.90		$	19,698.20	$	21,920.10
Debt and equity securities available for sale	Debt and equity securities available for sale at September 30, 2013 and December 31, 2012 were as follows:
	(Millions)	Amortized			Gross			Gross					Fair
		Cost			Unrealized			Unrealized					Value
					Gains			Losses
	September 30, 2013
	Debt securities:
	U.S. government securities	$	1,424.00		$	83.8		$	(1.0	)			$	1,506.80
	States, municipalities and political subdivisions	3,852.60			138.1			(76.5		)			3,914.20
	U.S. corporate securities	7,272.20			505.6			(122.9		)			7,654.90
	Foreign securities	3,114.30			207.4			(54.2		)			3,267.50
	Residential mortgage-backed securities	951.5			22.6			(11.7		)			962.4
	Commercial mortgage-backed securities	1,321.20			95.6			(4.7		)	(1)		1,412.10
	Other asset-backed securities	379.8			17.9			(2.2		)	(1)		395.5
	Redeemable preferred securities	56.8			8.7			(.4		)			65.1
	Total debt securities	18,372.40			1,079.70			(273.6		)			19,178.50
	Equity securities	46.3			38.3			(4.2		)			80.4
	Total debt and equity securities (2)	$	18,418.70		$	1,118.00		$	(277.8	)			$	19,258.90
	December 31, 2012
	Debt securities:
	U.S. government securities	$	1,413.40		$	147.9		$	(1.8	)			$	1,559.50
	States, municipalities and political subdivisions	2,770.90			267.9			(4.3		)			3,034.50
	U.S. corporate securities	6,926.20			871.7			(7.3		)			7,790.60
	Foreign securities	2,988.10			391.3			(8.8		)			3,370.60
	Residential mortgage-backed securities	929.5			49.9			(.4		)			979
	Commercial mortgage-backed securities	1,268.70			149.7			(1.8		)	(1)		1,416.60
	Other asset-backed securities	517.4			28.3			(3.6		)	(1)		542.1
	Redeemable preferred securities	89.6			12.3			(7.3		)			94.6
	Total debt securities	16,903.80			1,919.00			(35.3		)			18,787.50
	Equity securities	38.3			5.1			(3.1		)			40.3
	Total debt and equity securities (2)	$	16,942.10		$	1,924.10		$	(38.4	)			$	18,827.80
	(1)	At September 30, 2013 and December 31, 2012, we held securities for which we previously recognized $22.9 million and $25.2 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at September 30, 2013 and December 31, 2012 of $8.5 million and $9.6 million, respectively.
	(2)	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 17 beginning on page 36 for additional information on our accounting for discontinued products).  At September 30, 2013, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $320.2 million and gross unrealized capital losses of $63.3 million and, at December 31, 2012, debt and equity securities with a fair value of approximately $4.0 billion, gross unrealized capital gains of $559.4 million and gross unrealized capital losses of $19.4 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 September 30, 2013 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	$	731.9
	One year through five years	5,054.20
	After five years through ten years	5,643.60
	Greater than ten years	4,978.80
	Residential mortgage-backed securities	962.4
	Commercial mortgage-backed securities	1,412.10
	Other asset-backed securities	395.5
	Total	$	19,178.50
Debt and Equity Securities in an Unrealized Capital Loss Position	Summarized below are the debt and equity securities we held at September 30, 2013 and December 31, 2012 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
	September 30, 2013
	Debt securities:
	U.S. government securities	$	82.1		$	0.6		$	13.7			$	0.4		$	95.8	$	1
	States, municipalities and political subdivisions	1,598.90			74.1			31				2.4			1,629.90		76.5
	U.S. corporate securities	2,183.70			120.2			15.8				2.7			2,199.50		122.9
	Foreign securities	923.9			53			22.6				1.2			946.5		54.2
	Residential mortgage-backed securities	333.6			9.5			27.9				2.2			361.5		11.7
	Commercial mortgage-backed securities	153.6			4.4			19.3				0.3			172.9		4.7
	Other asset-backed securities	92.5			2.2			5.5				—			98		2.2
	Redeemable preferred securities	10.1			0.4			—				—			10.1		0.4
	Total debt securities	5,378.40			264.4			135.8				9.2			5,514.20		273.6
	Equity securities	10.8			1.3			5.2				2.9			16		4.2
	Total debt and equity securities (1)	$	5,389.20		$	265.7		$	141			$	12.1		$	5,530.20	$	277.8
	December 31, 2012
	Debt securities:
	U.S. government securities	$	138.3		$	1.4		$	15.1			$	0.4		$	153.4	$	1.8
	States, municipalities and political subdivisions	264.6			3			28.5				1.3			293.1		4.3
	U.S. corporate securities	598.4			6.1			10.8				1.2			609.2		7.3
	Foreign securities	270.4			1.4			35.6				7.4			306		8.8
	Residential mortgage-backed securities	51.7			0.3			2.1				0.1			53.8		0.4
	Commercial mortgage-backed securities	6.3			0.1			46.1				1.7			52.4		1.8
	Other asset-backed securities	44.8			0.1			1.5				3.5			46.3		3.6
	Redeemable preferred securities	12.2			0.2			10				7.1			22.2		7.3
	Total debt securities	1,386.70			12.6			149.7				22.7			1,536.40		35.3
	Equity securities	16.4			2.1			13				1			29.4		3.1
	Total debt and equity securities (1)	$	1,403.10		$	14.7		$	162.7			$	23.7		$	1,565.80	$	38.4
	(1)	At September 30, 2013 and December 31, 2012, debt and equity securities in an unrealized capital loss position of $63.3 million and $19.4 million, respectively, and with related fair value of $922.4 million and $225.2 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 September 30, 2013 were as follows:
		Supporting experience-rated						Supporting remaining							Total
		and discontinued products						products
	(Millions)	Fair			Unrealized			Fair				Unrealized			Fair		Unrealized
		Value			Losses			Value				Losses			Value		Losses
	Due to mature:
	Less than one year	$	—		$	—		$	23.9			$	0.2		$	23.9	$	0.2
	One year through five years	72.4			1.5			898.4				13.8			970.8		15.3
	After five years through ten years	383			18.8			1,843.20				85.5			2,226.20		104.3
	Greater than ten years	421.6			38.2			1,239.30				97			1,660.90		135.2
	Residential mortgage-backed securities	6.6			0.1			354.9				11.6			361.5		11.7
	Commercial mortgage-backed securities	8.7			0.4			164.2				4.3			172.9		4.7
	Other asset-backed securities	14.1			0.3			83.9				1.9			98		2.2
	Total	$	906.4		$	59.3		$	4,607.80			$	214.3		$	5,514.20	$	273.6
Net realized capital gains (losses)	Net realized capital (losses) gains for the three and nine months ended September 30, 2013 and 2012, excluding amounts related to experience-rated contract holders and discontinued products, were as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013				2012
	OTTI losses on debt securities	$	(2.4	)	$	(1.8	)	$	(29.6	)		$	(10.4	)
	Portion of OTTI losses on debt securities recognized	—			—			—				0.1
	in other comprehensive income
	Net OTTI losses on debt securities recognized in earnings	(2.4		)	(1.8		)	(29.6		)		(10.3		)
	Net realized capital (losses) gains, excluding OTTI losses on debt securities	(10.3		)	19.1			17.4				87.9
	Net realized capital (losses) gains	$	(12.7	)	$	17.3		$	(12.2	)		$	77.6
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 and nine months ended September 30, 2013 and 2012 were as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013				2012
	Proceeds on sales	$	1,434.00		$	1,323.30		$	5,216.50			$	4,138.60
	Gross realized capital gains	25			30.8			83.9				135.7
	Gross realized capital losses	34.9			1.9			78.3				13.2
Activity in mortgage loan portfolio	During the three and nine months ended September 30, 2013 and 2012 we had the following activity in our mortgage loan portfolio:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013				2012
	New mortgage loans	$	62.8		$	71.8		$	126.4			$	132.3
	Mortgage loans fully repaid	49.1			4.5			168.7				41.8
	Mortgage loans foreclosed	—			—			—				16.7
Mortgage loan internal credit rating	Based upon our most recent assessments at September 30, 2013 and December 31, 2012, our mortgage loans were given the following credit quality indicators:
	(In Millions, except credit ratings indicator)	September 30,			December 31,
		2013			2012
	1	$	118.2		$	94
	2 to 4	1,346.50			1,451.10
	5	32.5			60.2
	6 and 7	59			38.3
	Total	$	1,556.20		$	1,643.60
Net Investment Income	Sources of net investment income for the three and nine months ended September 30, 2013 and 2012 were as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013				2012
	Debt securities	$	193.9		$	186		$	573.9			$	574.7
	Mortgage loans	27.2			25.3			76.1				90.8
	Other investments	(2.2		)	13.1			46.8				39.2
	Gross investment income	218.9			224.4			696.8				704.7
	Less: investment expenses	(8.9		)	(8.2		)	(26.7		)		(23.1		)
	Net investment income (1)	$	210		$	216.2		$	670.1			$	681.6
	(1)	Net investment income includes $61.5 million and $210.3 million for the three and nine months ended September 30, 2013, respectively, and $79.8 million and $238.6 million for the three and nine months ended September 30, 2012, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom1

Other Comprehensive (Loss) Income (Tables)	9 Months Ended
	Sep. 30, 2013
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 nine months ended September 30, 2013 and 2012:
		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					Cost
	Nine months ended September 30, 2013
	Balance at December 31, 2012	$	57.3				$	825.2				$	(29.5	)			$	(1,909.4	)			$	23				$	(1,033.4	)
	Other comprehensive (loss) income
	before reclassifications	(40.8		)			(481.1		)			22.9					—					—					(499.0		)
	Amounts reclassified from accumulated
	other comprehensive income	20.6			(2	)	17.2			(2	)	2.6			(3	)	37.9			(4	)	(2.0		)	(4	)	76.3
	Other comprehensive (loss) income	(20.2		)			(463.9		)			25.5					37.9					(2.0		)			(422.7		)
	Balance at September 30, 2013	$	37.1				$	361.3				$	(4.0	)			$	(1,871.5	)			$	21				$	(1,456.1	)
	Nine months ended September 30, 2012
	Balance at December 31, 2011	$	58.2				$	595.2				$	(33.7	)			$	(1,834.6	)			$	25.7				$	(1,189.2	)
	Other comprehensive (loss) income	2.4					258.5					5					36.4					(2.0		)			300.3
	Balance at September 30, 2012	$	60.6				$	853.7				$	(28.7	)			$	(1,798.2	)			$	23.7				$	(888.9	)
	(1)	Represents unrealized losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.
	(2)	Reclassifications out of accumulated other comprehensive income for previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statement 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 Statement of Income, except for derivatives related to interest rate swaps which are reflected in interest expense and were not material during the nine months ended September 30, 2013.
	(4)	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statement of Income (Refer to Note 10 of Condensed Notes to Consolidated Financial Statements beginning on page 27 for additional information).

Financial_Instruments_Tables

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2013
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 September 30, 2013 and December 31, 2012 were as follows:
	(Millions)	Level 1				Level 2				Level 3				Total
	September 30, 2013
	Assets:
	Debt securities:
	U.S. government securities	$	1,272.90			$	233.9			$	—			$	1,506.80
	States, municipalities and political subdivisions	—				3,912.90				1.3				3,914.20
	U.S. corporate securities	—				7,618.40				36.5				7,654.90
	Foreign securities	—				3,226.00				41.5				3,267.50
	Residential mortgage-backed securities	—				962.4				—				962.4
	Commercial mortgage-backed securities	—				1,404.70				7.4				1,412.10
	Other asset-backed securities	—				362.7				32.8				395.5
	Redeemable preferred securities	—				61				4.1				65.1
	Total debt securities	1,272.90				17,782.00				123.6				19,178.50
	Equity securities	17.8				0.3				62.3				80.4
	Derivatives	—				41.8				—				41.8
	Total	$	1,290.70			$	17,824.10			$	185.9			$	19,300.70
	Liabilities:
	Derivatives	$	—			$	2.2			$	—			$	2.2
	December 31, 2012
	Assets:
	Debt securities:
	U.S. government securities	$	1,311.40			$	248.1			$	—			$	1,559.50
	States, municipalities and political subdivisions	—				3,031.80				2.7				3,034.50
	U.S. corporate securities	—				7,736.00				54.6				7,790.60
	Foreign securities	—				3,317.90				52.7				3,370.60
	Residential mortgage-backed securities	—				979				—				979
	Commercial mortgage-backed securities	—				1,396.50				20.1				1,416.60
	Other asset-backed securities	—				512.6				29.5				542.1
	Redeemable preferred securities	—				80.5				14.1				94.6
	Total debt securities	1,311.40				17,302.40				173.7				18,787.50
	Equity securities	18.2				—				22.1				40.3
	Derivatives	—				8.9				—				8.9
	Total	$	1,329.60			$	17,311.30			$	195.8			$	18,836.70
	Liabilities:
	Derivatives	$	—			$	0.3			$	—			$	0.3
Gross Transfers into (out of) Level 3	The gross transfers into (out of) Level 3 during the three and nine months ended September 30, 2013 and 2012 are as follows:
		Three Months Ended							Nine Months Ended
		September 30,							September 30,
	(Millions)	2013			2012				2013			2012
	Gross transfers into Level 3	$	3.8		$	—			$	3.8		$	1.8
	Gross transfers out of Level 3	(21.7		)	(7.4		)		(48.9		)	(30.1		)
	Net transfers (out of) Level 3	$	(17.9	)	$	(7.4	)		$	(45.1	)	$	(28.3	)
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 September 30, 2013 and December 31, 2012 were as follows:
		Carrying				Estimated Fair Value
	(Millions)	Value				Level 1			Level 2			Level 3			Total
	September 30, 2013
	Assets:
	Mortgage loans	$	1,556.20			$	—		$	—		$	1,598.60		$	1,598.60
	Bank loans	142.2				—			130.1			10.5			140.6
	Liabilities:
	Investment contract liabilities:
	With a fixed maturity	9.2				—			—			9.2			9.2
	Without a fixed maturity	578.5				—			—			547.4			547.4
	Long-term debt	8,266.30				—			8,716.00			—			8,716.00
	December 31, 2012
	Assets:
	Mortgage loans	$	1,643.60			$	—		$	—		$	1,698.60		$	1,698.60
	Liabilities:
	Investment contract liabilities:
	With a fixed maturity	18.5				—			—			18.5			18.5
	Without a fixed maturity	590.2				—			—			611.1			611.1
	Long-term debt	6,481.30				—			7,408.70			—			7,408.70
Separate Account Financial Assets	Separate Accounts financial assets at September 30, 2013 and December 31, 2012 were as follows:
		September 30, 2013															December 31, 2012
	(Millions)	Level 1				Level 2				Level 3				Total			Level 1		Level 2			Level 3		Total
	Debt securities	$	685.7			$	2,163.90			$	0.6			$	2,850.20		$	721.7	$	2,343.90		$	0.4	$	3,066.00
	Equity securities	209.4				1.6				—				211			194.9		1			—		195.9
	Derivatives	—				0.2				—				0.2			—		(1.8		)	—		(1.8		)
	Common/collective trusts	—				692.7				—				692.7			—		749			—		749
	Total (1)	$	895.1			$	2,858.40			$	0.6			$	3,754.10		$	916.6	$	3,092.10		$	0.4	$	4,009.10
	(1)	Excludes $179.5 million and $238.0 million of cash and cash equivalents and other receivables at September 30, 2013 and December 31, 2012, respectively.
Balance Sheet Offsetting Assets	Financial assets, including derivative assets, subject to offsetting and enforceable master netting arrangements as of September 30, 2013 and December 31, 2012 were as follows:
		Gross Amounts of Recognized Assets (1)			Gross Amounts Not Offset
					In the Balance Sheets
					Financial Instruments			Cash Collateral Received
	(Millions)										Net Amount
	30-Sep-13
	Derivatives	$	41.8		$	—		$	(40.4	)	$	1.4
	Total	$	41.8		$	—		$	(40.4	)	$	1.4
	31-Dec-12
	Derivatives	$	9.4		$	12.5		$	(7.5	)	$	14.4
	Total	$	9.4		$	12.5		$	(7.5	)	$	14.4
	(1) There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.
Balance Sheet Offsetting Liabilities	Financial liabilities, including derivative liabilities, subject to offsetting and enforceable master netting arrangements as of September 30, 2013 and December 31, 2012 were as follows:
		Gross Amounts of Recognized Liabilities (1)			Gross Amounts Not Offset
					In the Balance Sheets
					Financial Instruments			Cash Collateral Paid
	(Millions)										Net Amount
	30-Sep-13
	Derivatives	$	6.1		$	(10.7	)	$	(.9	)	$	(5.5	)
	Securities lending	550.2			(550.2		)	—			—
	Total	$	556.3		$	(560.9	)	$	(.9	)	$	(5.5	)
	31-Dec-12
	Derivatives	$	0.3		$	—		$	—		$	0.3
	Securities lending	47.1			(47.1		)	—			—
	Total	$	47.4		$	(47.1	)	$	—		$	0.3
	(1) There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.

Pension_and_Other_Postretireme1

Pension and Other Postretirement Plans (Tables)	9 Months Ended
	Sep. 30, 2013
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 benefit (“OPEB”) plans for the three and nine months ended September 30, 2013 and 2012 were as follows:
		Pension Plans												OPEB Plans
		Three Months Ended						Nine Months Ended						Three Months Ended						Nine Months Ended
		September 30,						September 30,						September 30,						September 30,
	(Millions)	2013			2012			2013			2012			2013			2012			2013			2012
	Service cost	$	—		$	—		$	—		$	—		$	—		$	—		$	—		$	0.1
	Amortization of prior service cost	(.1		)	(.1		)	(.3		)	(.3		)	(1.0		)	(.9		)	(2.7		)	(2.7		)
	Interest cost	67.9			74.6			203.6			223.8			2.8			3.6			8.3			10.8
	Expected return on plan assets	(99.1		)	(96.8		)	(297.3		)	(290.5		)	(.6		)	(.6		)	(1.8		)	(2.0		)
	Recognized net actuarial losses	19			17.5			56.6			52.7			0.6			1.1			1.7			3.3
	Net periodic benefit (income) cost	$	(12.3	)	$	(4.8	)	$	(37.4	)	$	(14.3	)	$	1.8		$	3.2		$	5.5		$	9.5

Debt_Tables

Debt (Tables)	9 Months Ended
	Sep. 30, 2013
Debt Disclosure [Abstract]
Carrying Value of Long-Term Debt	The carrying value of our long-term debt at September 30, 2013 and December 31, 2012 was as follows:
	(Millions)	September 30,		December 31,
		2013		2012
	Senior notes, 6.3%, due 2014	$	392.2	$	—
	Senior notes, 6.125%, due 2015	243.4		—
	Senior notes, 6.0%, due 2016	748.8		748.5
	Senior notes, 5.95%, due 2017	438.2		—
	Senior notes, 1.75%, due 2017	248.8		248.6
	Senior notes, 1.5%, due 2017	498		497.7
	Senior notes, 6.5%, due 2018	494.9		494.8
	Senior notes, 3.95%, due 2020	744.1		743.4
	Senior notes, 5.45%, due 2021	705.8		—
	Senior notes, 4.125%, due 2021	494.7		494.1
	Senior notes, 2.75%, due 2022	984.6		983.4
	Senior notes, 6.625%, due 2036	769.8		769.7
	Senior notes, 6.75%, due 2037	530.6		529.5
	Senior notes, 4.5%, due 2042	479.9		479.3
	Senior notes, 4.125%, due 2042	492.5		492.3
	Total long-term debt	8,266.30		6,481.30
	Less current portion of long-term debt (1)	392.2		—
	Total long-term debt, less current portion	$	7,874.10	$	6,481.30
	(1) At September 30, 2013, our 6.3% senior notes due August 2014 are classified as current in the accompanying consolidated balance sheet.

Capital_Stock_Tables

Capital Stock (Tables)	9 Months Ended
	Sep. 30, 2013
Class of Stock Disclosures [Abstract]
Dividends declared	During the nine months ended September 30, 2013 our Board declared the following cash dividends:
	Date Declared	Dividend Amount			Stockholders of	Date Paid/	Total Dividends
		Per Share			Record Date	To be Paid	(Millions)
	February 19, 2013		$	0.2	April 11, 2013	April 26, 2013		$	65.2
	May 17, 2013		0.2		July 11, 2013	July 26, 2013		74.4
	September 27, 2013		0.2		October 10, 2013	October 25, 2013		73.6

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2013
Segment Reporting [Abstract]
Summarized financial information of segments	Summarized financial information of our segments for the three and nine months ended September 30, 2013 and 2012 was as follows:
	(Millions)	Health			Group			Large Case			Corporate			Total Company
		Care			Insurance			Pensions (2)			Financing
	Three Months Ended September 30, 2013
	Revenue from external customers	$	12,228.70		$	510.7		$	98.9		$	—		$	12,838.30
	Operating earnings (loss) (1)	585.8			19.7			6.2			(49.9		)	561.8
	Three Months Ended September 30, 2012
	Revenue from external customers	$	8,172.70		$	465.8		$	45.3		$	—		$	8,683.80
	Operating earnings (loss) (1)	531.8			29.3			3.7			(41.6		)	523.2
	Nine Months Ended September 30, 2013
	Revenue from external customers	$	31,743.00		$	1,536.80		$	174.2		$	—		$	33,454.00
	Operating earnings (loss) (1)	1,637.80			80.8			16.2			(128.6		)	1,606.20
	Nine Months Ended September 30, 2012
	Revenue from external customers	$	24,398.40		$	1,378.10		$	134.5		$	—		$	25,911.00
	Operating earnings (loss) (1)	1,444.20			116.2			13.4			(121.2		)	1,452.60
	(1)	Operating earnings (loss) excludes net realized capital gains or losses and the other items described in the reconciliation below.
	(2)	In the third quarter of 2013, an existing group annuity contract converted from a participating to a non-participating contract. Upon conversion, we recorded $54.1 million of non-cash group annuity conversion premium for this contract and a corresponding $54.1 million non-cash benefit expense on group annuity conversion for this contract.
Reconciliation of Operating Earnings to Net Income	A reconciliation of operating earnings (1) to net income attributable to Aetna for the three and nine months ended September 30, 2013 and 2012 was as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
	(Millions)	2013			2012			2013			2012
	Operating earnings (1)	$	561.8		$	523.2		$	1,606.20		$	1,452.60
	Transaction and integration-related costs, net of tax	(34.6		)	(12.5		)	(140.6		)	(12.5		)
	Reduction of reserve for anticipated future losses on discontinued products, net of tax	—			—			55.9			—
	Reversal of allowance and gain on sale of reinsurance recoverable, net of tax	—			—			32.1			—
	Loss on early extinguishment of long-term debt, net of tax	—			(23.0		)	—			(23.0		)
	Net realized capital (losses) gains, net of tax	(8.6		)	11.5			(8.9		)	50.7
	Net income attributable to Aetna	$	518.6		$	499.2		$	1,544.70		$	1,467.80
	(1)	In addition to net realized capital gains (losses), the following 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 related to the acquisition of Coventry of $34.6 million ($51.2 million pretax) and $140.6 million ($189.6 million pretax) during the three and nine months ended September 30, 2013, respectively, and $12.5 million ($13.8 million pretax) during the three and nine months ended September 30, 2012. 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, as well as the cost of the bridge credit agreement that was in effect prior to the Coventry acquisition, which is reflected in the GAAP Consolidated Statements of Income in interest expense. Transaction costs also include transaction-related payments as well as expenses related to the negative cost of carry associated with the permanent financing that we obtained in November 2012 for the Coventry acquisition. Prior to the Effective Date, the negative cost of carry was excluded from operating earnings. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense, net investment income, and general and administrative expenses. On and after the Effective Date, the interest expense and general and administrative expenses associated with the permanent financing are no longer excluded from operating earnings.
	•	We reduced the reserve for anticipated future losses on discontinued products by $55.9 million ($86.0 million pretax) in the second quarter of 2013. We believe excluding any changes in the reserve for anticipated future losses on discontinued products from operating earnings provides more useful information as to our continuing products and is consistent with the treatment of the operating results of these discontinued products, which are credited or charged to the reserve and do not affect our operating results. Refer to Note 17 beginning on page 36 for additional information on the reduction of the reserve for anticipated future losses on discontinued products.
	•	In 2008, as a result of the liquidation proceedings of Lehman Re, a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re of $27.4 million ($42.2 million pretax). This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $27.4 million ($42.2 million pretax) and recognized a $4.7 million ($7.2 million pretax) gain on the sale in fees and other revenue.
	•	In the third quarter of 2012, we incurred a loss on the early extinguishment of long-term debt of $23.0 million ($35.4 million pretax) related to repurchases of certain of our outstanding senior notes.

Discontinued_Products_Tables

Discontinued Products (Tables)	9 Months Ended
	Sep. 30, 2013
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 nine months ended September 30, 2013 and 2012 (pretax) was as follows:
	(Millions)	2013			2012
	Reserve, beginning of period	$	978.5		$	896.3
	Operating loss	(8.5		)	(5.1		)
	Net realized capital gains	73.7			55.2
	Reserve reduction	(86.0		)	—
	Reserve, end of period	$	957.7		$	946.4
Assets and Liabilities Supporting Discontinued Products	Assets and liabilities supporting discontinued products at September 30, 2013 and December 31, 2012 were as
	follows: (1)
	(Millions)	2013			2012
	Assets:
	Debt and equity securities available for sale	$	2,326.90		$	2,515.30
	Mortgage loans	407.2			448.6
	Other investments	690.9			711.6
	Total investments	3,425.00			3,675.50
	Other assets	101			79.2
	Collateral received under securities loan agreements	151			3.8
	Current and deferred income taxes	25.2			19.3
	Receivable from continuing products (2)	525.1			556
	Total assets	$	4,227.30		$	4,333.80
	Liabilities:
	Future policy benefits	$	2,795.30		$	2,857.60
	Policyholders' funds	—			6.6
	Reserve for anticipated future losses on discontinued products	957.7			978.5
	Collateral payable under securities loan agreements	151.1			3.8
	Other liabilities (3)	323.2			487.3
	Total liabilities	$	4,227.30		$	4,333.80
	(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.

Organization_Organization_Deta

Organization Organization (Details) (USD $)	7-May-13
In Billions, unless otherwise specified
Organization [Line Items]
Total purchase price for an acquisition	$8.70

Completed_Acquisition_Complete1

Completed Acquisition, Completed Disposition (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	7-May-13	Apr. 30, 2013	Dec. 31, 2012	Aug. 19, 2012
Business Acquisition [Line Items]
Share Price							$58.69
Total purchase price for an acquisition							$8,700,000,000
Goodwill	10,205,700,000	[1]		10,205,700,000	[1]				6,214,400,000
Transaction and integration-related costs, after-tax	34,600,000		12,500,000	140,600,000		12,500,000
Transaction and integration-related costs, pretax	51,200,000		13,800,000	189,600,000
Number of shares not automatically vested							500,000
Common Stock, Shares, Issued	367,500,000			367,500,000			133,700,000		327,600,000
Other consideration per share							22.8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options							4,900,000
In-the-money consideration per share							15.94
Acquired Finite-lived Intangible Asset, Amount				1,490,000,000
Long-term debt acquired				1,803,800,000
Cash to be Received by Shareholders Upon Acquisition, per share							27.3			27.3
Exchange ratio used in calculation of merger consideration							0.3885
Total number of shares issued in a business acquisition				52,200,000
Total value of equity consideration transferred							3,100,000,000
Cash consideration transferred				3,800,000,000
Net restricted shares outstanding							700,000
Restricted shares outstanding							1,100,000
Employee tax withholdings							-400,000
Performance share units and restricted stock units							1,600,000
Equity cash consideration							49.8
Other consideration transferred				6,900,000	[2]
Debt fair value adjustment							216,600,000
Tax deductible goodwill							267,000,000
Fair value of awards attributed to pre-merger services				6,900,000
Fair value attributed to post-merger services				19,000,000
Cash compensation pursuant to employee agreements				6,500,000
Total consideration transferred				6,896,100,000
Cash per share and closing price								57.93
Customer Lists [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount				810,000,000
Finite-Lived Intangible Asset, Useful Life	10 years
Provider networks [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount				550,000,000
Finite-Lived Intangible Asset, Useful Life	17 years
Trademarks [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount				100,000,000
Finite-Lived Intangible Asset, Useful Life	10 years
Developed Technology Rights [Member]
Business Acquisition [Line Items]
Acquired Finite-lived Intangible Asset, Amount				30,000,000
Finite-Lived Intangible Asset, Useful Life	4 years
Premiums Receivable [Member]
Business Acquisition [Line Items]
Gross Contractual Receivable Amount							485,500,000
Allowance for Uncollectible Premiums Receivable [Member]
Business Acquisition [Line Items]
Allowance for Doubtful Accounts Receivable							12,500,000
Common Stock [Member]
Business Acquisition [Line Items]
Cash consideration transferred				3,648,700,000
Value of common shares issued				3,047,400,000
Stock Options [Member]
Business Acquisition [Line Items]
Cash consideration transferred				78,100,000
Performance share units and restricted stock units [Member]
Business Acquisition [Line Items]
Cash consideration transferred				58,500,000
Restricted Stock [Member]
Business Acquisition [Line Items]
Cash consideration transferred				20,500,000
Cash paid for employee tax withholdings				18,800,000
Value of common shares issued				$17,200,000
[1]	At September 30, 2013, approximately $113 million was assigned to the Group Insurance segment, with the remainder assigned to the Health Care segment.
[2]	Certain of Coventry's named executive officers received payments pursuant to employment agreements entered into prior to the Coventry acquisition. The total compensation paid in cash pursuant to such agreements in connection with the Merger was $6.5 million. Other consideration transferred also includes the portion of the fair value of the Rollover Units that was attributed to pre-Merger services. The fair value attributable to post-Merger services will be recorded as selling, general and administrative expense in Aetna's post-Merger financial statements.

Completed_Acquisition_Complete2

Completed Acquisition; Completed Disposition Pro Forma Financials (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pro Forma Financial Information [Abstract]
Revenue of Acquiree since Acquisition Date, Actual	$3,531.30		$5,599.80
Earnings or Loss of Acquiree since Acquisition Date, Actual	112.8		169
Pro Forma Revenue		12,253.30	38,906.60	37,031.80
Pro Forma Net Income (Loss)		$600	$1,775.30	$1,810.10
Pro Forma Earnings Per Share, Basic		$1.55	$4.73	$4.59
Pro Forma Earnings Per Share, Diluted		$1.54	$4.68	$4.53

Completed_Acquisition_Complete3

Completed Acquisition; Completed Disposition Fair Value of Major Classes of Assets and Liabilities (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		7-May-13
Business Acquisition [Line Items]
Cash and cash equivalents			$2,195.60
Investments			2,156.40
Premiums and other receivables, net			1,141.10
Intangible assets acquired			1,490
Property and equipment			174.8
Other assets			97.5
Total assets acquired			7,255.40
Health care costs payable			1,440.10
Long-term debt			1,803.80
Net deferred tax liabilities			257	[1]
Other liabilities			854.9
Total liabilities assumed			4,355.80
Total identifiable net assets			2,899.60
Total consideration transferred	6,896.10
Deferred tax liabilities on intangible assets			521.5
Deferred tax asset on debt fair market value adjustment			75.8
Coventry [Member]
Business Acquisition [Line Items]
Goodwill acquired	3,996.50	[2]
Allowance for Doubtful Accounts [Member]
Business Acquisition [Line Items]
Allowance for Doubtful Accounts Receivable			14.1
Allowance for Uncollectible Premiums Receivable [Member]
Business Acquisition [Line Items]
Allowance for Doubtful Accounts Receivable			12.5
Premiums Receivable [Member]
Business Acquisition [Line Items]
Gross Contractual Receivable Amount			485.5
Other Assets [Member]
Business Acquisition [Line Items]
Gross Contractual Receivable Amount			$682.20
[1]	Includes $521.5 million of deferred tax liabilities on identifiable intangible assets acquired and $75.8 million of deferred tax assets on the fair value adjustment to Coventry's outstanding debt.
[2]	Goodwill related to the acquisition of Coventry is considered preliminary, pending the final allocation of the applicable purchase price.

Earnings_Per_Common_Share_Deta

Earnings Per Common Share (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$518.60		$499.20		$1,544.70		$1,467.80
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares used to compute basic EPS (in shares)	371.1		334.8		351.8		342.2
Dilutive effect of outstanding stock-based compensation awards (in shares)	4.1	[1]	3.8	[1]	3.7	[1]	5	[1]
Weighted average shares used to compute diluted EPS (in shares)	375.2		338.6		355.5		347.2
Basic EPS (in dollars per share)	$1.40		$1.49		$4.39		$4.29
Diluted EPS (in dollars per share)	$1.38		$1.47		$4.35		$4.23
Stock Appreciation Rights [Member]
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)			11		2.2		8.6
[1]	Stock-based compensation awards are not included in 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). Approximately 2.2 million stock appreciation rights were not included in the calculation of diluted EPS for the nine months ended SeptemberB 30, 2013 and 11.0 million and 8.6 million stock appreciation rights were not included in the calculation of diluted EPS for the three and nine months ended SeptemberB 30, 2012, respectively, because they were anti-dilutive. All stock options were included in the calculation of diluted EPS for the three and nine months ended SeptemberB 30, 2013 and 2012.

Operating_Expenses_Details

Operating Expenses (Details) (USD $)	3 Months Ended					9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Jun. 30, 2013	Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
General and administrative transaction and integration-related costs	$51.20					$171.40		$10
Selling expenses	353.9			272.8		983.3		820.5
General and administrative expenses:
Salaries and related benefits	1,119.40			780.4		2,914.50		2,336.70
Other general and administrative expenses	831.2	[1],[2]		586.4	[1],[2]	2,240.30	[1],[2]	1,794.80	[1],[2]
Total general and administrative expenses	1,950.60			1,366.80		5,154.80		4,131.50
Total operating expenses	2,304.50			1,639.60		6,138.10		4,952
Reversal of allowance reinsurance recoverable, pretax			$42.20
[1]	Includes $51.2 million and $171.4 million of transaction and integration-related costs related to the acquisition of Coventry, including advisory, legal and other professional services fees and transaction-related payments as well as integration costs incurred in the three and nine months ended September 30, 2013, respectively and $10.0 million during the three and nine months ended September 30, 2012.
[2]	In 2008, as a result of the liquidation proceedings of Lehman Re Ltd. (bLehman Reb), a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re. This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $42.2 million pretax

Goodwill_and_Other_Acquired_In2

Goodwill and Other Acquired Intangible Assets (Details) (USD $)

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

In Millions, unless otherwise specified

Group Insurance [Member]

Coventry [Member]

Goodwill [Member]

Trademarks Indefinite Lived [Member]

Trademarks Indefinite Lived [Member]

Customer Lists [Member]

Customer Lists [Member]

Value Of Business Acquired [Member]

Value Of Business Acquired [Member]

Trademarks Definite Lived [Member]

Trademarks Definite Lived [Member]

Developed Technology Rights [Member]

Developed Technology Rights [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Provider networks [Member]

Provider networks [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Minimum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Maximum [Member]

Customer Lists [Member]

Customer Lists [Member]

Trademarks Definite Lived [Member]

Trademarks Definite Lived [Member]

Developed Technology Rights [Member]

Developed Technology Rights [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Provider networks [Member]

Provider networks [Member]

Customer Lists [Member]

Customer Lists [Member]

Value Of Business Acquired [Member]

Value Of Business Acquired [Member]

Trademarks Definite Lived [Member]

Trademarks Definite Lived [Member]

Developed Technology Rights [Member]

Developed Technology Rights [Member]

Other Intangible Assets [Member]

Other Intangible Assets [Member]

Provider networks [Member]

Provider networks [Member]

Goodwill [Line Items]

Goodwill

$10,205.70

[1]

$6,214.40

$113

Goodwill, Acquired During Period

3,996.50

[2]

-5.2

Finite-Lived Intangible Assets, Gross

1,347

657.4

149.2

149.2

165

65

146.6

116.6

6.7

6.7

1,253.20

703.2

Finite-Lived Intangible Assets, Accumulated Amortization

930.8

901.7

326.7

370.2

43.7

29.2

21.8

14.6

43.4

28

1.8

1.5

493.4

458.2

Finite-Lived Intangible Assets, Net

1,020.30

287.2

105.5

120

143.2

50.4

103.2

88.6

4.9

5.2

759.8

245

Other Acquired Intangible Assets Gross

3,090

1,720.40

Other acquired intangible assets, net

2,159.20

818.7

Indefinite-Lived Trademarks

22.3

22.3

Indefinite-lived intangible asset, accumulated amortization

0

0

Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year

214.6

Finite-Lived Intangible Assets, Amortization Expense, Year Two

238.4

Finite-Lived Intangible Assets, Amortization Expense, Year Three

222.5

Finite-Lived Intangible Assets, Amortization Expense, Year Four

215.5

Finite-Lived Intangible Assets, Amortization Expense, Year Five

201.1

Finite-Lived Intangible Assets, Amortization Expense, Year Six

$192.90

Useful Life

5 years

[3]

5 years

[3]

9 years

9 years

4 years

5 years

2 years

2 years

12 years

[3]

12 years

[3]

14 years

[3]

14 years

[3]

20 years

[4]

20 years

[4]

20 years

20 years

10 years

10 years

15 years

15 years

25 years

[3]

25 years

[3]

[1]

At September 30, 2013, approximately $113 million was assigned to the Group Insurance segment, with the remainder assigned to the Health Care segment.

[2]

Goodwill related to the acquisition of Coventry is considered preliminary, pending the final allocation of the applicable purchase price.

[3]

The amortization period for our provider networks and customer lists includes an assumption of renewal or extension of these arrangements. At September 30, 2013 and December 31, 2012, the periods prior to the next renewal or extension for our provider networks primarily ranged from 1 to 3 years and the period prior to the next renewal or extension for our customer lists was less than one year and two years, respectively. Any costs related to the renewal or extension of these contracts are expensed as incurred.

[4]

VOBA is being amortized over the expected life of the acquired contracts in proportion to estimated premium.

Investments_Details

Investments (Details) (USD $)	Sep. 30, 2013	7-May-13	Dec. 31, 2012
In Millions, unless otherwise specified
Total Investments [Line Items]
Investments acquired		$2,156.40
Current	2,036.40		2,221.90
Long-term investments	20,498.60		19,698.20
Total investments	22,535		21,920.10
Debt And Equity Securities Available For Sale [Member]
Total Investments [Line Items]
Current	1,897.80		2,006.80
Long-term investments	17,361.10		16,821
Total investments	19,258.90		18,827.80
Mortgage Loans [Member]
Total Investments [Line Items]
Current	136.3		214.4
Long-term investments	1,419.90		1,429.20
Total investments	1,556.20		1,643.60
Other Investments [Member]
Total Investments [Line Items]
Current	2.3		0.7
Long-term investments	1,717.60		1,448
Total investments	$1,719.90		$1,448.70

Investments_Debt_and_Equity_Se

Investments - Debt and Equity Securities (Details) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Non-credit related impairments previously recognized in other comprehensive income	$22.90		$25.20
Available-for-sale Securities, Amortized Cost Basis	18,418.70	[1]	16,942.10	[1]
Available-for-sale Securities, Gross Unrealized Gains	1,118	[1]	1,924.10	[1]
Available-for-sale Securities, Gross Unrealized Losses	-277.8	[1]	-38.4	[1]
Available-for-sale Securities, Fair Value Disclosure	19,258.90	[1]	18,827.80	[1]
Net Unrealized Capital (Loss) Gains	8.5		9.6
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Unrealized Gains	320.2		559.4
Available-for-sale Securities, Gross Unrealized Losses	-63.3		-19.4
Available-for-sale Securities, Fair Value Disclosure	3,700		4,000
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	18,372.40		16,903.80
Available-for-sale Securities, Gross Unrealized Gains	1,079.70		1,919
Available-for-sale Securities, Gross Unrealized Losses	-273.6		-35.3
Available-for-sale Securities, Fair Value Disclosure	19,178.50		18,787.50
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,424		1,413.40
Available-for-sale Securities, Gross Unrealized Gains	83.8		147.9
Available-for-sale Securities, Gross Unrealized Losses	-1		-1.8
Available-for-sale Securities, Fair Value Disclosure	1,506.80		1,559.50
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,852.60		2,770.90
Available-for-sale Securities, Gross Unrealized Gains	138.1		267.9
Available-for-sale Securities, Gross Unrealized Losses	-76.5		-4.3
Available-for-sale Securities, Fair Value Disclosure	3,914.20		3,034.50
Domestic Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	7,272.20		6,926.20
Available-for-sale Securities, Gross Unrealized Gains	505.6		871.7
Available-for-sale Securities, Gross Unrealized Losses	-122.9		-7.3
Available-for-sale Securities, Fair Value Disclosure	7,654.90		7,790.60
Foreign Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,114.30		2,988.10
Available-for-sale Securities, Gross Unrealized Gains	207.4		391.3
Available-for-sale Securities, Gross Unrealized Losses	-54.2		-8.8
Available-for-sale Securities, Fair Value Disclosure	3,267.50		3,370.60
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	951.5		929.5
Available-for-sale Securities, Gross Unrealized Gains	22.6		49.9
Available-for-sale Securities, Gross Unrealized Losses	-11.7		-0.4
Available-for-sale Securities, Fair Value Disclosure	962.4		979
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,321.20		1,268.70
Available-for-sale Securities, Gross Unrealized Gains	95.6		149.7
Available-for-sale Securities, Gross Unrealized Losses	-4.7	[2]	-1.8	[2]
Available-for-sale Securities, Fair Value Disclosure	1,412.10		1,416.60
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	379.8		517.4
Available-for-sale Securities, Gross Unrealized Gains	17.9		28.3
Available-for-sale Securities, Gross Unrealized Losses	-2.2	[2]	-3.6	[2]
Available-for-sale Securities, Fair Value Disclosure	395.5		542.1
Redeemable Preferred Stock [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	56.8		89.6
Available-for-sale Securities, Gross Unrealized Gains	8.7		12.3
Available-for-sale Securities, Gross Unrealized Losses	-0.4		-7.3
Available-for-sale Securities, Fair Value Disclosure	65.1		94.6
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	46.3		38.3
Available-for-sale Securities, Gross Unrealized Gains	38.3		5.1
Available-for-sale Securities, Gross Unrealized Losses	-4.2		-3.1
Available-for-sale Securities, Fair Value Disclosure	$80.40		$40.30
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 17 beginning on page 36 for additional information on our accounting for discontinued products). At SeptemberB 30, 2013, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $320.2 million and gross unrealized capital losses of $63.3 million and, at DecemberB 31, 2012, debt and equity securities with a fair value of approximately $4.0 billion, gross unrealized capital gains of $559.4 million and gross unrealized capital losses of $19.4 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 SeptemberB 30, 2013 and DecemberB 31, 2012, we held securities for which we previously recognized $22.9 million and $25.2 million, respectively, of non-credit related impairments in accumulated other comprehensive loss. These securities had a net unrealized capital gain at SeptemberB 30, 2013 and December 31, 2012 of $8.5 million and $9.6 million, respectively.

Investments_Debt_Securities_by

Investments - Debt Securities by Maturity (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	$19,258.90	[1]	$18,827.80	[1]
Debt Securities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	19,178.50		18,787.50
Available-for-sale Securities With Established Maturities [Member]
Available-for-sale Securities, Debt Maturities [Abstract]
Due To Mature Less Than One Year	731.9
Available-for-sale Securities, Debt Maturities, Year Two Through Five, Fair Value	5,054.20
Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Fair Value	5,643.60
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	4,978.80
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	4 years 6 months 0 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	962.4		979
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	2 years 8 months 0 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,412.10		1,416.60
Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities, Weighted Average Duration Of Securities	2 years 10 months 0 days
Available-for-sale Securities, Debt Maturities [Abstract]
Available-for-sale Securities, Fair Value Disclosure	$395.50		$542.10
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 17 beginning on page 36 for additional information on our accounting for discontinued products). At SeptemberB 30, 2013, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $320.2 million and gross unrealized capital losses of $63.3 million and, at DecemberB 31, 2012, debt and equity securities with a fair value of approximately $4.0 billion, gross unrealized capital gains of $559.4 million and gross unrealized capital losses of $19.4 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 $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$5,389.20	[1]	$1,403.10	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	265.7	[1]	14.7	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	141	[1]	162.7	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	12.1	[1]	23.7	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,530.20	[1]	1,565.80	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	277.8	[1]	38.4	[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	922.4		225.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	63.3		19.4
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	5,378.40		1,386.70
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	264.4		12.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	135.8		149.7
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	9.2		22.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,514.20	[1]	1,536.40	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	273.6	[1]	35.3	[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	906.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	59.3
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	4,607.80
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	214.3
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	82.1		138.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0.6		1.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	13.7		15.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0.4		0.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	95.8	[1]	153.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	1	[1]	1.8	[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	1,598.90		264.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	74.1		3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	31		28.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2.4		1.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,629.90	[1]	293.1	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	76.5	[1]	4.3	[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	2,183.70		598.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	120.2		6.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	15.8		10.8
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2.7		1.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,199.50	[1]	609.2	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	122.9	[1]	7.3	[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	923.9		270.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	53		1.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	22.6		35.6
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	1.2		7.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	946.5	[1]	306	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	54.2	[1]	8.8	[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	333.6		51.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	9.5		0.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	27.9		2.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2.2		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	361.5	[1]	53.8	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	11.7	[1]	0.4	[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	153.6		6.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	4.4		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	19.3		46.1
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0.3		1.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	172.9	[1]	52.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	4.7	[1]	1.8	[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	92.5		44.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	2.2		0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5.5		1.5
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0		3.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	98	[1]	46.3	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	2.2	[1]	3.6	[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	10.1		12.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	0.4		0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0		10
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	0		7.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	10.1	[1]	22.2	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	0.4	[1]	7.3	[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	10.8		16.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses	1.3		2.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	5.2		13
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	2.9		1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	16	[1]	29.4	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$4.20	[1]	$3.10	[1]
[1]	At SeptemberB 30, 2013 and DecemberB 31, 2012, debt and equity securities in an unrealized capital loss position of $63.3 million and $19.4 million, respectively, and with related fair value of $922.4 million and $225.2 million, respectively, related to experience-rated and discontinued products.

Investments_Unrealized_Loss_Po1

Investments - Unrealized Loss Position Maturities (Details) (USD $)	9 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	$277.80	[1]	$38.40	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,530.20	[1]	1,565.80	[1]
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses	273.6	[1]	35.3	[1]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	5,514.20	[1]	1,536.40	[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	214.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,607.80
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	63.3		19.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	922.4		225.2
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	59.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	906.4
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	0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	23.9
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	0.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	23.9
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	15.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	970.8
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	13.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	898.4
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	1.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	72.4
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	104.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,226.20
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	85.5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,843.20
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	18.8
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	383
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	135.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,660.90
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	97
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,239.30
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	38.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	421.6
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	11.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	361.5
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	11.6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	354.9
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	0.1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	6.6
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	4.7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	172.9
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	4.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	164.2
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	0.4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	8.7
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	2.2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	98
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	1.9
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	83.9
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	0.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$14.10
[1]	At SeptemberB 30, 2013 and DecemberB 31, 2012, debt and equity securities in an unrealized capital loss position of $63.3 million and $19.4 million, respectively, and with related fair value of $922.4 million and $225.2 million, respectively, related to experience-rated and discontinued products.

Investments_Realized_Gains_Det

Investments - Realized Gains (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
OTTI losses on securities	($2.40)	($1.80)	($29.60)	($10.40)
Portion of OTTI losses recognized in other comprehensive income	0	0	0	0.1
Net OTTI losses on securities recognized in earnings	-2.4	-1.8	-29.6	-10.3
Net realized capital gains losses excluding OTTI losses on securities	-10.3	19.1	17.4	87.9
Net realized capital (losses) gains	-12.7	17.3	-12.2	77.6
Debt Securities [Member]
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Proceeds On Sales	1,434	1,323.30	5,216.50	4,138.60
Gross Realized Capital Gains	25	30.8	83.9	135.7
Gross Realized Capital Losses	$34.90	$1.90	$78.30	$13.20

Investments_Mortgage_Loans_Det

Investments - Mortgage Loans (Details) (Commercial Real Estate [Member], USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Movement in Mortgage Loans on Real Estate [Roll Forward]
New Mortgage Loans	$62.80	$71.80	$126.40	$132.30
Mortgage loans fully repaid	49.1	4.5	168.7	41.8
Mortgage loans foreclosed	0	0	0	16.7
Mortgage Loans on Real Estate	1,556.20		1,556.20		1,643.60
Category 1 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	118.2		118.2		94
Category 2 to 4 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	1,346.50		1,346.50		1,451.10
Category 5 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	32.5		32.5		60.2
Categories 6 and 7 [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate	$59		$59		$38.30

Investments_Investments_Variab

Investments Investments - Variable Interest Entities and Noncontrolling Interests (Details) (USD $)

3 Months Ended

9 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2012

Dec. 31, 2012

Dec. 31, 2011

Variable Interest Entity, Not Primary Beneficiary [Member]

Variable Interest Entity, Not Primary Beneficiary [Member]

Real Estate Partnerships [Member]

Real Estate Partnerships [Member]

Hedge Fund Partnerships [Member]

Hedge Fund Partnerships [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]

Long-term investments

$20,498,600,000

$20,498,600,000

$19,698,200,000

$212,000,000

$215,000,000

Variable Interest Entity Assets

5,900,000,000

5,400,000,000

7,200,000,000

7,000,000,000

Stockholders' Equity Attributable to Noncontrolling Interest

51,300,000

23,100,000

23,400,000

24,400,000

Noncontrolling Interest [Abstract]

Net (Loss) Income Attributable to Non-controlling Interest

$400,000

$400,000

($1,600,000)

$1,400,000

($1,600,000)

$1,400,000

Investments_Investment_Income_

Investments - Investment Income (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$218.90		$224.40		$696.80		$704.70
Less: investment expenses	-8.9		-8.2		-26.7		-23.1
Net Investment Income	210	[1]	216.2	[1]	670.1	[1]	681.6	[1]
Supporting Discontinued And Experience Rated Products [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net Investment Income	61.5		79.8		210.3		238.6
Debt Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	193.9		186		573.9		574.7
Mortgage Loans [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	27.2		25.3		76.1		90.8
Other Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	($2.20)		$13.10		$46.80		$39.20
[1]	Net investment income includes $61.5 million and $210.3 million for the three and nine months ended SeptemberB 30, 2013, respectively, and $79.8 million and $238.6 million for the three and nine months ended SeptemberB 30, 2012, respectively, related to investments supporting our experience-rated and discontinued products.

Other_Comprehensive_Loss_Incom2

Other Comprehensive (Loss) Income (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					($1,033.40)
Other comprehensive (loss) income	18.9		166		-422.7		300.3
Balance at end of period	-1,456.10				-1,456.10
Net Unrealized Gains (Losses) Previously Impaired Securities [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)					-40.8	[1]
Net unrealized gains (losses) on securities, reclassification of gains to earnings					20.6	[1],[2]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					57.3	[1]	58.2	[1]
Other comprehensive (loss) income					-20.2	[1]	2.4	[1]
Balance at end of period	37.1	[1]	60.6	[1]	37.1	[1]	60.6	[1]
Net Unrealized Gains (Losses) All Other Securities [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)					-481.1
Net unrealized gains (losses) on securities, reclassification of gains to earnings					17.2	[2]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					825.2		595.2
Other comprehensive (loss) income					-463.9		258.5
Balance at end of period	361.3		853.7		361.3		853.7
Net Unrealized Gains (Losses) Foreign Currency And Derivatives [Member]
Comprehensive Income Loss [Line Items]
Net unrealized gains (losses)					22.9
Foreign currency and derivatives reclassification of losses to earnings					2.6	[3]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					-29.5		-33.7
Other comprehensive (loss) income					25.5		5
Balance at end of period	-4		-28.7		-4		-28.7
Pension And OPEB Plans Unrecognized Net Actuarial (Losses) [Member]
Comprehensive Income Loss [Line Items]
Amortization of net actuarial losses					37.9	[4]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					-1,909.40		-1,834.60
Other comprehensive (loss) income					37.9		36.4
Balance at end of period	-1,871.50		-1,798.20		-1,871.50		-1,798.20
Pension And OPEB Plans Unrecognized Prior Service Cost [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Amortization, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost Recognized in Net Periodic Pension Cost, Net of Tax					-2	[4]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					23		25.7
Other comprehensive (loss) income					-2		-2
Balance at end of period	21		23.7		21		23.7
Accumulated Other Comprehensive Loss [Member]
Comprehensive Income Loss [Line Items]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent					-499
Other Comprehensive Income Loss Net Of Tax Reclassification To Earnings					76.3
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period					-1,033.40		-1,189.20
Other comprehensive (loss) income					-422.7		300.3
Balance at end of period	($1,456.10)		($888.90)		($1,456.10)		($888.90)
[1]	Represents unrealized losses on the non-credit related component of impaired debt securities that we do not intend to sell and subsequent changes in the fair value of any previously impaired security.
[2]	Reclassifications out of accumulated other comprehensive income for previously impaired debt securities and all other securities are reflected in net realized capital gains (losses) within the Consolidated Statement 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 Statement of Income, except for derivatives related to interest rate swaps which are reflected in interest expense and were not material during the nine months ended SeptemberB 30, 2013.
[4]	Reclassifications out of accumulated other comprehensive income for pension and OPEB plan expenses are reflected in general and administrative expenses within the Consolidated Statement of Income (Refer to Note 10 of Condensed Notes to Consolidated Financial Statements beginning on pageB 27 for additional information).

Financial_Instruments_Fair_Val

Financial Instruments - Fair Value Measurements (Details) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	$19,258,900,000	[1]		$19,258,900,000	[1]		$18,827,800,000	[1]
Gross transfers out of level 3	-21,700,000		-7,400,000	-48,900,000		-30,100,000
Gross transfers into Level 3, Separate Accounts	0		0	0		0
Gross transfers out of separate accounts				4,600,000		600,000
Transfers between Level 1 and 2, Separate Accounts	0		0	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	-17,900,000		-7,400,000	-45,100,000		-28,300,000
Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	19,178,500,000			19,178,500,000			18,787,500,000
US Government Agencies Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,506,800,000			1,506,800,000			1,559,500,000
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	3,914,200,000			3,914,200,000			3,034,500,000
Domestic Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	7,654,900,000			7,654,900,000			7,790,600,000
Foreign Corporate Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	3,267,500,000			3,267,500,000			3,370,600,000
Residential Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	962,400,000			962,400,000			979,000,000
Commercial Mortgage Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,412,100,000			1,412,100,000			1,416,600,000
Other Asset-Backed Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	395,500,000			395,500,000			542,100,000
Redeemable Preferred Stock [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	65,100,000			65,100,000			94,600,000
Equity Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	80,400,000			80,400,000			40,300,000
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			0
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	0			0			0
Assets, Fair Value Disclosure	1,290,700,000			1,290,700,000			1,329,600,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	2,200,000			2,200,000			300,000
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	41,800,000			41,800,000			8,900,000
Assets, Fair Value Disclosure	17,824,100,000			17,824,100,000			17,311,300,000
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			0
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	0			0			0
Assets, Fair Value Disclosure	185,900,000			185,900,000			195,800,000
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	0		0
Derivative Liabilities	2,200,000			2,200,000			300,000
Assets, Fair Value Disclosure [Abstract]
Derivative Assets	41,800,000			41,800,000			8,900,000
Assets, Fair Value Disclosure	19,300,700,000			19,300,700,000			18,836,700,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	3,800,000		0	3,800,000		1,800,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	1,272,900,000			1,272,900,000			1,311,400,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	17,782,000,000			17,782,000,000			17,302,400,000
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	123,600,000			123,600,000			173,700,000
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	19,178,500,000			19,178,500,000			18,787,500,000
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	1,272,900,000			1,272,900,000			1,311,400,000
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	233,900,000			233,900,000			248,100,000
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			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	1,506,800,000			1,506,800,000			1,559,500,000
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			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	3,912,900,000			3,912,900,000			3,031,800,000
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	1,300,000			1,300,000			2,700,000
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	3,914,200,000			3,914,200,000			3,034,500,000
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			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	7,618,400,000			7,618,400,000			7,736,000,000
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	36,500,000			36,500,000			54,600,000
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	7,654,900,000			7,654,900,000			7,790,600,000
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			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	3,226,000,000			3,226,000,000			3,317,900,000
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	41,500,000			41,500,000			52,700,000
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	3,267,500,000			3,267,500,000			3,370,600,000
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			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	962,400,000			962,400,000			979,000,000
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			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	962,400,000			962,400,000			979,000,000
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			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	1,404,700,000			1,404,700,000			1,396,500,000
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	7,400,000			7,400,000			20,100,000
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	1,412,100,000			1,412,100,000			1,416,600,000
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			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	362,700,000			362,700,000			512,600,000
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	32,800,000			32,800,000			29,500,000
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	395,500,000			395,500,000			542,100,000
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			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	61,000,000			61,000,000			80,500,000
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			14,100,000
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	65,100,000			65,100,000			94,600,000
Fair Value, Measurements, Recurring [Member] | Brokered Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	99,000,000			99,000,000			117,000,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	17,800,000			17,800,000			18,200,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	300,000			300,000			0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Fair Value Disclosure	62,300,000			62,300,000			22,100,000
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	80,400,000			80,400,000			40,300,000
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			0
Bank loans	0			0
Investment contracts with a fixed maturity	0			0			0
Investment contracts without a fixed maturity	0			0			0
Long-term debt	0			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			0
Bank loans	130,100,000			130,100,000
Investment contracts with a fixed maturity	0			0			0
Investment contracts without a fixed maturity	0			0			0
Long-term debt	8,716,000,000			8,716,000,000			7,408,700,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans	1,598,600,000			1,598,600,000			1,698,600,000
Bank loans	10,500,000			10,500,000
Investment contracts with a fixed maturity	9,200,000			9,200,000			18,500,000
Investment contracts without a fixed maturity	547,400,000			547,400,000			611,100,000
Long-term debt	0			0			0
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	1,556,200,000			1,556,200,000			1,643,600,000
Bank loans	142,200,000			142,200,000
Investment contracts with a fixed maturity	9,200,000			9,200,000			18,500,000
Investment contracts without a fixed maturity	578,500,000			578,500,000			590,200,000
Long-term debt	8,266,300,000			8,266,300,000			6,481,300,000
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	1,598,600,000			1,598,600,000			1,698,600,000
Bank loans	140,600,000			140,600,000
Investment contracts with a fixed maturity	9,200,000			9,200,000			18,500,000
Investment contracts without a fixed maturity	547,400,000			547,400,000			611,100,000
Long-term debt	$8,716,000,000			$8,716,000,000			$7,408,700,000
[1]	Investment risks associated with our experience-rated and discontinued products generally do not impact our operating results (refer to Note 17 beginning on page 36 for additional information on our accounting for discontinued products). At SeptemberB 30, 2013, debt and equity securities with a fair value of approximately $3.7 billion, gross unrealized capital gains of $320.2 million and gross unrealized capital losses of $63.3 million and, at DecemberB 31, 2012, debt and equity securities with a fair value of approximately $4.0 billion, gross unrealized capital gains of $559.4 million and gross unrealized capital losses of $19.4 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.

Financial_Instruments_Separate

Financial Instruments - Separate Accounts Fair Value (Details) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	$3,933.60			$3,933.60			$4,247.10
Gross transfers out of separate accounts				4.6		0.6
Transfers between Level 1 and 2, Separate Accounts	0		0	0		0
Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Derivative Asset, Fair Value, Gross Asset	41.8	[1]		41.8	[1]		9.4	[1]
Separate Account Assets	3,754.10	[2]		3,754.10	[2]		4,009.10	[2]
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	895.1	[2]		895.1	[2]		916.6	[2]
Derivative Assets	0			0			0
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	2,858.40	[2]		2,858.40	[2]		3,092.10	[2]
Derivative Assets	41.8			41.8			8.9
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	0.6	[2]		0.6	[2]		0.4	[2]
Derivative Assets	0			0			0
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]
Derivative Assets	41.8			41.8			8.9
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	685.7			685.7			721.7
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	2,163.90			2,163.90			2,343.90
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	0.6			0.6			0.4
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	2,850.20			2,850.20			3,066
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	209.4			209.4			194.9
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	1.6			1.6			1
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			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	211			211			195.9
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			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	0.2			0.2			-1.8
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			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	0.2			0.2			-1.8
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			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	692.7			692.7			749
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			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	692.7			692.7			749
Cash and Cash Equivalents [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Assets	179.5			179.5			238
Financial Instruments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Collateral Already Posted, Aggregate Fair Value	-560.9			-560.9			-47.1
Cash [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Collateral Already Posted, Aggregate Fair Value	-0.9			-0.9			0
Derivative [Member] | Fair Value, Measurements, Recurring [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Derivative Asset, Fair Value, Gross Asset	41.8	[1]		41.8	[1]		9.4	[1]
Derivative [Member] | Financial Instruments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Collateral Already Posted, Aggregate Fair Value	-10.7			-10.7			0
Derivative [Member] | Cash [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Collateral Already Posted, Aggregate Fair Value	($0.90)			($0.90)			$0
[1]	There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.
[2]	Excludes $179.5 million and $238.0 million of cash and cash equivalents and other receivables at SeptemberB 30, 2013 and DecemberB 31, 2012, respectively.

Financial_Instruments_Financia

Financial Instruments Financial Instruments - Balance Sheet Offsetting (Details) (USD $)	Sep. 30, 2013		Dec. 31, 2012
In Millions, unless otherwise specified
Derivatives, Fair Value [Line Items]
Cash Collateral for Borrowed Securities	$550.20		$47.10
Collateral Payable Under Securities Loan Agreements	-550.2		-47.1
Total Gross Liabilities Recognized Subject to Offsetting	556.3	[1]	47.4	[1]
Derivative liabilities, net	-5.5		0.3
Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	41.8	[1]	9.4	[1]
Derivative Assets	1.4		14.4
Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value	0		12.5
Collateral Already Posted, Aggregate Fair Value	-560.9		-47.1
Cash [Member]
Derivatives, Fair Value [Line Items]
Cash collateral received	-40.4		-7.5
Collateral Already Posted, Aggregate Fair Value	-0.9		0
Securities Loaned or Sold under Agreements to Repurchase [Member]
Derivatives, Fair Value [Line Items]
Cash Collateral for Borrowed Securities	550.2	[1]	47.1	[1]
Securities loaned agreements, net amount	0		0
Securities Loaned or Sold under Agreements to Repurchase [Member] | Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Payable Under Securities Loan Agreements	-550.2		-47.1
Securities Loaned or Sold under Agreements to Repurchase [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value	0		0
Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities	-5.5		0.3
Derivative Liability, Fair Value, Gross Liability	6.1	[1]	0.3	[1]
Derivative [Member] | Fair Value, Measurements, Recurring [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	41.8	[1]	9.4	[1]
Derivative Assets	1.4		14.4
Derivative [Member] | Financial Instruments [Member]
Derivatives, Fair Value [Line Items]
Collateral Already Posted, Aggregate Fair Value	0		12.5
Collateral Already Posted, Aggregate Fair Value	-10.7		0
Derivative [Member] | Cash [Member]
Derivatives, Fair Value [Line Items]
Cash collateral received	-40.4		-7.5
Collateral Already Posted, Aggregate Fair Value	($0.90)		$0
[1]	There were no amounts offset in our balance sheets at September 30, 2013 or December 31, 2012.

Pension_and_Other_Postretireme2

Pension and Other Postretirement Plans (Details) (USD $)	3 Months Ended		9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Contributions by Employer	$60	$60
Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0	0
Amortization of prior service cost	-0.1	-0.1	-0.3	-0.3
Interest cost	67.9	74.6	203.6	223.8
Expected Return on Plan Assets	-99.1	-96.8	-297.3	-290.5
Amortization of net actuarial losses	19	17.5	56.6	52.7
Net periodic benefit (income) cost	-12.3	-4.8	-37.4	-14.3
OPEB Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	0	0	0	0.1
Amortization of prior service cost	-1	-0.9	-2.7	-2.7
Interest cost	2.8	3.6	8.3	10.8
Expected Return on Plan Assets	-0.6	-0.6	-1.8	-2
Amortization of net actuarial losses	0.6	1.1	1.7	3.3
Net periodic benefit (income) cost	$1.80	$3.20	$5.50	$9.50

Debt_Details

Debt (Details) (USD $)	Sep. 30, 2013		7-May-13	Dec. 31, 2012		Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013
In Millions, unless otherwise specified						Senior Notes, 6.3%, due 2014 [Member]	Senior Notes, 6.3%, due 2014 [Member]	Senior Notes, 6.125%, Due 2015 [Member]	Senior Notes, 6.125%, Due 2015 [Member]	Senior Notes, 6.0%, Due 2016 [Member]	Senior Notes, 6.0%, Due 2016 [Member]	Senior Notes, 5.95%, Due 2017 [Member]	Senior Notes, 5.95%, Due 2017 [Member]	Senior Notes, 1.75%, Due 2017 [Member]	Senior Notes, 1.75%, Due 2017 [Member]	Senior Notes, 1.5%, Due 2017 [Member]	Senior Notes, 1.5%, Due 2017 [Member]	Senior Notes, 6.5%, Due 2018 [Member]	Senior Notes, 6.5%, Due 2018 [Member]	Senior Notes, 3.95%, Due 2020 [Member]	Senior Notes, 3.95%, Due 2020 [Member]	Senior Notes, 5.45%, Due 2021 [Member]	Senior Notes, 5.45%, Due 2021 [Member]	Senior Notes, 4.125%, Due 2021 [Member]	Senior Notes, 4.125%, Due 2021 [Member]	Senior Notes, 2.75%, Due 2022 [Member]	Senior Notes, 2.75%, Due 2022 [Member]	Senior Notes, 6.625%, Due 2036 [Member]	Senior Notes, 6.625%, Due 2036 [Member]	Senior Notes, 6.75%, Due 2037 [Member]	Senior Notes, 6.75%, Due 2037 [Member]	Senior Notes, 4.5%, Due 2042 [Member]	Senior Notes, 4.5%, Due 2042 [Member]	Senior Notes, 4.125%, Due 2042 [Member]	Senior Notes, 4.125%, Due 2042 [Member]	Debt refinance [Domain]
																																				Derivatives_and_swaps
Debt Instrument [Line Items]
Derivative, Notional Amount																																				$375
Debt fair value adjustment			216.6
Long-term debt, amount of outstanding principal						375		229				383										600
Long-term Debt	8,266.30			6,481.30				243.4	0	748.8	748.5	438.2	0	248.8	248.6	498	497.7	494.9	494.8	744.1	743.4	705.8	0	494.7	494.1	984.6	983.4	769.8	769.7	530.6	529.5	479.9	479.3	492.5	492.3
Current portion of long-term debt	392.2	[1]		0	[1]	392.2	0
Debt Instrument, Interest Rate, Stated Percentage						6.30%	6.30%	6.13%	6.13%	6.00%	6.00%	5.95%	5.95%	1.75%	1.75%	1.50%	1.50%	6.50%	6.50%	3.95%	3.95%	5.45%	5.45%	4.13%	4.13%	2.75%	2.75%	6.63%	6.63%	6.75%	6.75%	4.50%	4.50%	4.13%	4.13%
Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss)																																				39.9
Number of Interest Rate Derivatives Held																																				2
Long-term debt, less current portion	$7,874.10			$6,481.30
[1]	At September 30, 2013, our 6.3% senior notes due August 2014 are classified as current in the accompanying consolidated balance sheet.

Debt_Shortterm_Debt_Details

Debt - Short-term Debt (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Jun. 30, 2013
In Millions, unless otherwise specified			Completed Acquisition [Member]
Short-term Debt [Line Items]
Commercial Paper	$0	$0
Issuance of short-term debt			$700

Debt_Line_of_Credit_Details

Debt - Line of Credit (Details) (USD $)	9 Months Ended
	Sep. 30, 2013
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)	0.07%
Maximum [Member] | Line of Credit [Member]
Line of Credit Facility [Line Items]
Facility fee (in hundredths)	0.15%
Maximum [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			9 Months Ended
Share data in Millions, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Equity, Class of Treasury Stock [Line Items]
Commercial Paper	$0			$0		$0
Stock Repurchase Program, Authorized Amount	750,000,000	750,000,000	750,000,000
Stock Repurchased During Period, Shares				16
Stock Repurchased During Period, Value				957,700,000	924,500,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount				1,000,000,000
Treasury Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased During Period, Value				$958,000,000

Capital_Stock_Dividends_Detail

Capital Stock - Dividends (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013
Class of Stock Disclosures [Abstract]
Dividends Amount Per Share	$0.20	$0.20	$0.20
Dividends	$73.60	$74.40	$65.20

Capital_Stock_Stock_Units_Deta

Capital Stock - Stock Units (Details) (USD $)	9 Months Ended		3 Months Ended
Share data in Millions, unless otherwise specified	Sep. 30, 2013	7-May-13	Mar. 31, 2013	Mar. 31, 2013	Jun. 30, 2013	Mar. 31, 2013
			Performance Stock Units [Member]	Market Stock Units [Member]	Restricted Stock Units (RSUs) [Member]	Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares issued in a business acquisition	52.2
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			0.5	1.1	0.5	1.1
Minimum Vesting Percentage During Performance Period For Performance Stock Units	0.00%
Maximum Vesting Percentage During Performance Period For Performance Stock Units	200.00%
Vesting Percentage For Market Stock Units Range Minimum	0.00%
Vesting Percentage For Market Stock Units Range Maximum	150.00%
Percentage Restricted Stock Units Vested In Three Years	100.00%
Total value of equity consideration transferred		$3,100,000,000
Cash consideration transferred	$3,800,000,000

Dividend_Restrictions_and_Stat1

Dividend Restrictions and Statutory Surplus (Details) (Insurance and HMO [Member], USD $)	3 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Insurance and HMO [Member]
Dividend Restrictions and Statutory Surplus [Line Items]
Dividends available	$900,000,000
Proceeds from dividends received	637,000,000
Statutory capital and surplus	$8,800,000,000	$6,400,000,000

Commitments_and_Contingencies_

Commitments and Contingencies Commitments and Contingencies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2012
Loss Contingencies [Line Items]
Settlement payment upon final court approval	$60
Settlement payment upon validation	60
Settlement of class action litigation, after-tax	$78

Segment_Information_Details

Segment Information (Details) (USD $)	3 Months Ended				9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	$12,838.30		$8,683.80		$33,454		$25,911
Operating Earnings	561.8	[1],[2]	523.2	[1],[2]	1,606.20	[1],[2]	1,452.60	[1],[2]
Health Care [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	12,228.70		8,172.70		31,743		24,398.40
Operating Earnings	585.8	[1]	531.8	[1]	1,637.80	[1]	1,444.20	[1]
Group Insurance [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	510.7		465.8		1,536.80		1,378.10
Operating Earnings	19.7	[1]	29.3	[1]	80.8	[1]	116.2	[1]
Large Case Pension [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	98.9	[3]	45.3	[3]	174.2	[3]	134.5	[3]
Operating Earnings	6.2	[1],[3]	3.7	[1],[3]	16.2	[1],[3]	13.4	[1],[3]
Corporate Financing [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue from external customers	0		0		0		0
Operating Earnings	($49.90)	[1]	($41.60)	[1]	($128.60)	[1]	($121.20)	[1]
[1]	Operating earnings (loss) excludes net realized capital gains or losses and the other items described in the reconciliation below.
[2]	In addition to net realized capital gains (losses), the following 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 related to the acquisition of Coventry of $34.6 million ($51.2 million pretax) and $140.6 million ($189.6 million pretax) during the three and nine months ended September 30, 2013, respectively, and $12.5 millionB ($13.8 million pretax) during the three and nine months ended September 30, 2012. 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, as well as the cost of the bridge credit agreement that was in effect prior to the Coventry acquisition, which is reflected in the GAAP Consolidated Statements of Income in interest expense. Transaction costs also include transaction-related payments as well as expenses related to the negative cost of carry associated with the permanent financing that we obtained in November 2012 for the Coventry acquisition. Prior to the Effective Date, the negative cost of carry was excluded from operating earnings. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense, net investment income, and general and administrative expenses. On and after the Effective Date, the interest expense and general and administrative expenses associated with the permanent financing are no longer excluded from operating earnings.b"We reduced the reserve for anticipated future losses on discontinued products by $55.9 million ($86.0 million pretax) in the second quarter of 2013. We believe excluding any changes in the reserve for anticipated future losses on discontinued products from operating earnings provides more useful information as to our continuing products and is consistent with the treatment of the operating results of these discontinued products, which are credited or charged to the reserve and do not affect our operating results. Refer to Note 17 beginning on page 36 for additional information on the reduction of the reserve for anticipated future losses on discontinued products.b"In 2008, as a result of the liquidation proceedings of Lehman Re, a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re of $27.4 million ($42.2 million pretax). This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $27.4 million ($42.2 million pretax) and recognized a $4.7 million ($7.2 million pretax) gain on the sale in fees and other revenue.b"In the third quarter of 2012, we incurred a loss on the early extinguishment of long-term debt of $23.0 million ($35.4 million pretax) related to repurchases of certain of our outstanding senior notes.
[3]	In the third quarter of 2013, an existing group annuity contract converted from a participating to a non-participating contract. Upon conversion, we recorded $54.1 million of non-cash group annuity conversion premium for this contract and a corresponding $54.1 million non-cash benefit expense on group annuity conversion for this contract.

Segment_Information_Reconcilia

Segment Information - Reconciliation of Operating Earnings (Details) (USD $)	3 Months Ended						9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Jun. 30, 2013	Sep. 30, 2012		Sep. 30, 2008	Sep. 30, 2013		Sep. 30, 2012
Segment Reconciliation [Abstract]
Operating Earnings	$561.80	[1],[2]		$523.20	[1],[2]		$1,606.20	[1],[2]	$1,452.60	[1],[2]
Transaction and integration-related costs, after-tax	-34.6			-12.5			-140.6		-12.5
Net realized capital (losses) gains, net of tax	-8.6			11.5			-8.9		50.7
Net income	518.6			499.2			1,544.70		1,467.80
Transaction and integration-related costs, pretax	51.2			13.8			189.6
Reduction of reserve for anticipated future losses on discontinued products, after tax	0			0			55.9		0
Reversal of allowance and gain on sale of reinsurance recoverable, net of tax	0			0			32.1		0
Extinguishment of Debt, Gain (Loss), Net of Tax	0			-23			0		-23
Reduction of reserve for anticipated future losses on discontinued products	0			0			86		0
Establishment of allowance on reinsurance recoverable net of tax						27.4
Establishment of allowance on reinsurance recoverable pretax						42.2
Reversal of allowance on reinsurance recoverable, net of tax			27.4
Reversal of allowance reinsurance recoverable, pretax			42.2
Gain on sale of reinsurance recoverable, net of tax			4.7
Gain on sale of reinsurance recoverable, pretax			7.2
Loss on early extinguishment of long-term debt	$0			$35.40			$0		$35.40
[1]	Operating earnings (loss) excludes net realized capital gains or losses and the other items described in the reconciliation below.
[2]	In addition to net realized capital gains (losses), the following 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 related to the acquisition of Coventry of $34.6 million ($51.2 million pretax) and $140.6 million ($189.6 million pretax) during the three and nine months ended September 30, 2013, respectively, and $12.5 millionB ($13.8 million pretax) during the three and nine months ended September 30, 2012. 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, as well as the cost of the bridge credit agreement that was in effect prior to the Coventry acquisition, which is reflected in the GAAP Consolidated Statements of Income in interest expense. Transaction costs also include transaction-related payments as well as expenses related to the negative cost of carry associated with the permanent financing that we obtained in November 2012 for the Coventry acquisition. Prior to the Effective Date, the negative cost of carry was excluded from operating earnings. The components of the negative cost of carry are reflected in our GAAP Consolidated Statements of Income in interest expense, net investment income, and general and administrative expenses. On and after the Effective Date, the interest expense and general and administrative expenses associated with the permanent financing are no longer excluded from operating earnings.b"We reduced the reserve for anticipated future losses on discontinued products by $55.9 million ($86.0 million pretax) in the second quarter of 2013. We believe excluding any changes in the reserve for anticipated future losses on discontinued products from operating earnings provides more useful information as to our continuing products and is consistent with the treatment of the operating results of these discontinued products, which are credited or charged to the reserve and do not affect our operating results. Refer to Note 17 beginning on page 36 for additional information on the reduction of the reserve for anticipated future losses on discontinued products.b"In 2008, as a result of the liquidation proceedings of Lehman Re, a subsidiary of Lehman Brothers Holdings Inc., we recorded an allowance against our reinsurance recoverable from Lehman Re of $27.4 million ($42.2 million pretax). This reinsurance was placed in 1999 and was on a closed book of paid-up group whole life insurance business. In the second quarter of 2013, we sold our claim against Lehman Re to an unrelated third party including the reinsurance recoverable and terminated the reinsurance arrangement. Upon the sale of the claim and termination of the arrangement, we released the related allowance thereby reducing other general and administrative expenses by $27.4 million ($42.2 million pretax) and recognized a $4.7 million ($7.2 million pretax) gain on the sale in fees and other revenue.b"In the third quarter of 2012, we incurred a loss on the early extinguishment of long-term debt of $23.0 million ($35.4 million pretax) related to repurchases of certain of our outstanding senior notes.

Reinsurance_Details

Reinsurance (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2013	Sep. 30, 2008	Mar. 31, 2013
Reinsurance Disclosures [Abstract]
Collateralized excess of loss on resinsurance coverage			$150
Establishment of allowance on reinsurance recoverable net of tax		27.4
Establishment of allowance on reinsurance recoverable pretax		42.2
Statement [Line Items]
Reversal of allowance on reinsurance recoverable, net of tax	27.4
Reversal of allowance reinsurance recoverable, pretax	42.2
Gain on sale of reinsurance recoverable, net of tax	4.7
Gain on sale of reinsurance recoverable, pretax	$7.20

Discontinued_Products_Details

Discontinued Products (Details) (USD $)	3 Months Ended			9 Months Ended
In Millions, unless otherwise specified	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
Reduction of reserve for anticipated future losses on discontinued products, after tax	$0		$0	$55.90		$0
Reserve For Discontinued Products [Roll Forward]
Operating income (loss)	806.7		774.7	2,405.10		2,255.70
Reduction of reserve for anticipated future losses on discontinued products	0		0	-86		0
Assets:
Investments	22,535			22,535			21,920.10
Cash Collateral for Borrowed Securities	550.2			550.2			47.1
Total assets	49,252.90			49,252.90			41,494.50
Liabilities:
Policyholders' funds	1,231.20			1,231.20			1,364
Collateral payable under securities loan agreements	550.2			550.2			47.1
Total liabilities	35,583.40			35,583.40			31,065.30
Discontinued Products [Member]
Reserve For Discontinued Products [Roll Forward]
Reserve, beginning of period				978.5	[1]	896.3
Operating income				-8.5		-5.1
Net realized capital gains				73.7		55.2
Reduction of reserve for anticipated future losses on discontinued products				-86		0
Reserve, end of period	957.7	[1]	946.4	957.7	[1]	946.4
Assets:
Investments	3,425	[1]		3,425	[1]		3,675.50	[1]
Other Assets	101	[1]		101	[1]		79.2	[1]
Cash Collateral for Borrowed Securities	151	[1]		151	[1]		3.8	[1]
Current and deferred income taxes	25.2	[1]		25.2	[1]		19.3	[1]
Receivable from continuing products	525.1	[1],[2]		525.1	[1],[2]		556	[1],[2]
Total assets	4,227.30	[1]		4,227.30	[1]		4,333.80	[1]
Liabilities:
Future Policy Benefits	2,795.30	[1]		2,795.30	[1]		2,857.60	[1]
Policyholders' funds	0	[1]		0	[1]		6.6	[1]
Reserve for anticipated future losses on discontinued products	957.7	[1]	946.4	957.7	[1]	946.4
Collateral payable under securities loan agreements	151.1	[1]		151.1	[1]		3.8	[1]
Other Liabilities	323.2	[1],[3]		323.2	[1],[3]		487.3	[1],[3]
Total liabilities	4,227.30	[1]		4,227.30	[1]		4,333.80	[1]
Scheduled Contract Maturities, Settlements And Benefit Payments	98		99	296		300
Debt And Equity Securities Available For Sale [Member]
Assets:
Investments	19,258.90			19,258.90			18,827.80
Debt And Equity Securities Available For Sale [Member] | Discontinued Products [Member]
Assets:
Investments	2,326.90	[1]		2,326.90	[1]		2,515.30	[1]
Mortgage Loans [Member]
Assets:
Investments	1,556.20			1,556.20			1,643.60
Mortgage Loans [Member] | Discontinued Products [Member]
Assets:
Investments	407.2	[1]		407.2	[1]		448.6	[1]
Other Investments [Member]
Assets:
Investments	1,719.90			1,719.90			1,448.70
Other Investments [Member] | Discontinued Products [Member]
Assets:
Investments	$690.90	[1]		$690.90	[1]		$711.60	[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 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 shareholdersb equity.