Analysis of Cost or Amortized Cost, Gross Unrealized Gains and Losses and Fair Value for Investments (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 10,311	$ 10,174
Gross Unrealized Gains	1,267	1,299
Gross Unrealized Losses	115	49
Fair Value	11,463	11,424
OTTI in AOCI
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	8,179	7,888
Gross Unrealized Gains	693	515
Gross Unrealized Losses	18	20
Fair Value	8,854	8,383
OTTI in AOCI
Debt Securities \| US States and Political Subdivisions Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3,020	3,043
Gross Unrealized Gains	220	110
Gross Unrealized Losses	1	10
Fair Value	3,239	3,143
OTTI in AOCI
Debt Securities \| Convertibles and Bonds with Warrants Attached
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	69	69
Fair Value	69	69
OTTI in AOCI
Debt Securities \| US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	6	4
Gross Unrealized Gains	1	1
Fair Value	7	5
OTTI in AOCI
Debt Securities \| US Government-sponsored Enterprises Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	217	201
Gross Unrealized Losses		1
Fair Value	217	200
OTTI in AOCI
Debt Securities \| Foreign Government
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	3	3
Fair Value	3	3
OTTI in AOCI
Debt Securities \| Corporate Bond Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	4,864	4,568
Gross Unrealized Gains	472	404
Gross Unrealized Losses	17	9
Fair Value	5,319	4,963
OTTI in AOCI
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,132	2,286
Gross Unrealized Gains	574	784
Gross Unrealized Losses	97	29
Fair Value	2,609	3,041
OTTI in AOCI
Equity Securities \| Common Stock
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	2,057	2,211
Gross Unrealized Gains	548	757
Gross Unrealized Losses	96	28
Fair Value	2,509	2,940
OTTI in AOCI
Equity Securities \| Preferred Stock
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	75	75
Gross Unrealized Gains	26	27
Gross Unrealized Losses	1	1
Fair Value	100	101
OTTI in AOCI

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

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

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

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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.

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

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

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

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+ Details