Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
U.S. Government and government agencies [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	$ 363	$ 453
Fair Value	382	467
Gross Unrealized, Gains	19	15
Gross Unrealized, Losses	0	(1)
States, municipalities and political subdivisions [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	3,613	2,927
Fair Value	3,877	2,939
Gross Unrealized, Gains	267	53
Gross Unrealized, Losses	(3)	(41)
Foreign government [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	236	269
Fair Value	254	278
Gross Unrealized, Gains	18	9
Gross Unrealized, Losses	0	0
Residential Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	3,858	3,781
Fair Value	3,848	3,875
Gross Unrealized, Gains	170	222
Gross Unrealized, Losses	(180)	(128)
Commercial Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	2,628	1,972
Fair Value	2,840	2,123
Gross Unrealized, Gains	218	153
Gross Unrealized, Losses	(6)	(2)
All Other Corporate [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	9,864	9,088
Fair Value	10,606	9,646
Gross Unrealized, Gains	802	602
Gross Unrealized, Losses	(60)	(44)
Fixed Maturity Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	20,562	18,490
Fair Value	21,807	19,328
Gross Unrealized, Gains	1,494	1,054
Gross Unrealized, Losses	(249)	(216)
Common Stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	610	312
Fair Value	797	543
Gross Unrealized, Gains	207	232
Gross Unrealized, Losses	(20)	(1)
Perpetual preferred stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	134	146
Fair Value	131	147
Gross Unrealized, Gains	5	6
Gross Unrealized, Losses	$ (8)	$ (5)

For an unclassified balance sheet, this item represents investments in debt and equity securities which are 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

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

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-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 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 15D

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-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

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.

+ References+ Details

- 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.

+ References+ Details