Fair Values of Financial Instruments (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Short term investments	$ 2,012	$ 1,893
Tax exempt, Fair value	20,260	20,211
Taxable, Fair value	17,253	16,973
Total fixed maturities, Fair Value	37,513	37,184
Equity securities	1,583	1,512
Long term debt	3,575	3,575
Fair Value [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Short term investments	2,012	1,893
Total fixed maturities, Fair Value	37,513	37,184
Equity securities	1,583	1,512
Total fixed maturities and equity securities, Fair value	41,108	40,589
Long term debt	4,281	4,085
U.S. Government and government agency and authority obligations [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,076	868
Corporate bonds [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	7,084	6,465
Foreign government and government agency obligations [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,660	6,823
Residential mortgage-backed securities [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	610	855
Commercial mortgage-backed securities [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,823	1,962
Level 1 [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Short term investments	115	117
Equity securities	1,575	1,504
Total fixed maturities and equity securities, Fair value	1,690	1,621
Long term debt
Level 2 [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Short term investments	1,897	1,776
Tax exempt, Fair value	20,254	20,203
Taxable, Fair value	17,094	16,808
Total fixed maturities, Fair Value	37,348	37,011
Total fixed maturities and equity securities, Fair value	39,245	38,787
Long term debt	4,281	4,085
Level 2 [Member] \| U.S. Government and government agency and authority obligations [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,076	868
Level 2 [Member] \| Corporate bonds [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,935	6,313
Level 2 [Member] \| Foreign government and government agency obligations [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,660	6,820
Level 2 [Member] \| Residential mortgage-backed securities [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	600	845
Level 2 [Member] \| Commercial mortgage-backed securities [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,823	1,962
Level 3 [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Tax exempt, Fair value	6	8
Taxable, Fair value	159	165
Total fixed maturities, Fair Value	165	173
Equity securities	8	8
Total fixed maturities and equity securities, Fair value	173	181
Long term debt
Level 3 [Member] \| Corporate bonds [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	149	152
Level 3 [Member] \| Foreign government and government agency obligations [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value		3
Level 3 [Member] \| Residential mortgage-backed securities [Member]
Fair values of financial instruments categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	$ 10	$ 10

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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+ Details

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References+ Details

- Definition

Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale.

+ References+ Details

- Definition

Other investments not otherwise specified in the taxonomy that will be realized in a short period of time, usually less than one year or the normal operating cycle, whichever is longer.

+ References+ Details