Fair Values of Financial Instruments (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Tax exempt, Fair value	$ 20,211	$ 19,774
Taxable, Fair value	16,973	16,745
Total fixed maturities, Fair value	37,184	36,519
Equity securities	1,512	1,550
Total fixed maturities and equity securities, Fair value	38,696	38,069
U.S. Government and government agency and authority obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	868	829
Corporate bonds [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,465	6,410
Foreign government and government agency obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,823	6,399
Residential Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	855	1,350
Commercial Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,962	1,757
Level 1 [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Tax exempt, Fair value	0	0
Taxable, Fair value	0	0
Total fixed maturities, Fair value	0	0
Equity securities	1,504	1,537
Total fixed maturities and equity securities, Fair value	1,504	1,537
Level 1 [Member] \| U.S. Government and government agency and authority obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 1 [Member] \| Corporate bonds [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 1 [Member] \| Foreign government and government agency obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 1 [Member] \| Residential Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 1 [Member] \| Commercial Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 2 [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Tax exempt, Fair value	20,203	19,765
Taxable, Fair value	16,808	16,533
Total fixed maturities, Fair value	37,011	36,298
Equity securities	0	0
Total fixed maturities and equity securities, Fair value	37,011	36,298
Level 2 [Member] \| U.S. Government and government agency and authority obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	868	829
Level 2 [Member] \| Corporate bonds [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,313	6,245
Level 2 [Member] \| Foreign government and government agency obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	6,820	6,373
Level 2 [Member] \| Residential Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	845	1,329
Level 2 [Member] \| Commercial Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	1,962	1,757
Level 3 [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Tax exempt, Fair value	8	9
Taxable, Fair value	165	212
Total fixed maturities, Fair value	173	221
Equity securities	8	13
Total fixed maturities and equity securities, Fair value	181	234
Level 3 [Member] \| U.S. Government and government agency and authority obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	0	0
Level 3 [Member] \| Corporate bonds [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	152	165
Level 3 [Member] \| Foreign government and government agency obligations [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	3	26
Level 3 [Member] \| Residential Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	10	21
Level 3 [Member] \| Commercial Mortgage-Backed Securities [Member]
Fair values of fixed maturities and equity securities categorized based upon the lowest level of input [Abstract]
Taxable, Fair value	$ 0	$ 0

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

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-Paragraph 2

-Subparagraph (b)-(g)

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 3

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 86-40

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ 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