Investments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Available for sale fixed maturities and equity securities
Gross Unrealized, Losses	$ (66)
U.S. Government and government agencies [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	373	363
Fair Value	388	382
Gross Unrealized, Gains	15	19
Gross Unrealized, Losses
States, municipalities and political subdivisions [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	4,144	3,613
Fair Value	4,468	3,877
Gross Unrealized, Gains	329	267
Gross Unrealized, Losses	(5)	(3)
Foreign government [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	242	236
Fair Value	260	254
Gross Unrealized, Gains	18	18
Residential Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	3,921	3,858
Fair Value	4,204	3,848
Gross Unrealized, Gains	337	170
Gross Unrealized, Losses	(54)	(180)
Commercial Mortgage Backed Securities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	2,583	2,628
Fair Value	2,918	2,840
Gross Unrealized, Gains	335	218
Gross Unrealized, Losses		(6)
All other corporate [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	10,820	9,864
Fair Value	11,880	10,606
Gross Unrealized, Gains	1,067	802
Gross Unrealized, Losses	(7)	(60)
Fixed maturities [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	22,083	20,562
Fair Value	24,118	21,807
Gross Unrealized, Gains	2,101	1,494
Gross Unrealized, Losses	(66)	(249)
Common stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	600	610
Fair Value	749	797
Gross Unrealized, Gains	157	207
Gross Unrealized, Losses	(8)	(20)
Perpetual preferred stocks [Member]
Available for sale fixed maturities and equity securities
Amortized Cost	178	134
Fair Value	190	131
Gross Unrealized, Gains	13	5
Gross Unrealized, Losses	$ (1)	$ (8)

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 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 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 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 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 Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 7: 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 8: 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 9: 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 10: 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.

+ 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