Investments (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Investments
Amortized Cost	$ 22,669	$ 23,060
Gross Unrealized Gains	1,956	2,978
Gross Unrealized Losses	(209)	(102)
Fair Value	24,416	25,936
Noncredit OTTI	(16)	(23)
Corporate debt securities
Investments
Amortized Cost	14,654	14,881
Gross Unrealized Gains	1,431	2,167
Gross Unrealized Losses	(80)	(7)
Fair Value	16,005	17,041
Noncredit OTTI	2
Residential mortgage backed securities
Investments
Amortized Cost	3,529	3,446
Gross Unrealized Gains	158	233
Gross Unrealized Losses	(82)	(58)
Fair Value	3,605	3,621
Noncredit OTTI	(20)	(24)
Commercial mortgage backed securities
Investments
Amortized Cost	2,453	2,717
Gross Unrealized Gains	177	287
Gross Unrealized Losses	(9)
Fair Value	2,621	3,004
State and municipal obligations
Investments
Amortized Cost	942	976
Gross Unrealized Gains	109	180
Gross Unrealized Losses	(29)	(34)
Fair Value	1,022	1,122
Asset backed securities
Investments
Amortized Cost	808	808
Gross Unrealized Gains	54	66
Gross Unrealized Losses	(4)	(3)
Fair Value	858	871
Foreign government bonds and obligations
Investments
Amortized Cost	241	188
Gross Unrealized Gains	18	36
Gross Unrealized Losses	(5)
Fair Value	254	224
U.S. government and agencies obligations
Investments
Amortized Cost	40	42
Gross Unrealized Gains	6	7
Fair Value	46	49
Total fixed maturities
Investments
Amortized Cost	22,667	23,058
Gross Unrealized Gains	1,953	2,976
Gross Unrealized Losses	(209)	(102)
Fair Value	24,411	25,932
Noncredit OTTI	(18)	(24)
Common stocks
Investments
Amortized Cost	2	2
Gross Unrealized Gains	3	2
Fair Value	5	4
Noncredit OTTI	$ 2	$ 1

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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