Investments (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	$ 41,703	$ 43,481
Fair value	45,455	45,428
U.S. government and agencies
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	2,027	2,502
Gross unrealized gains	259	241
Fair value	2,286	2,743
Municipal
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	4,267	4,380
Gross unrealized gains	604	426
Gross unrealized losses	(74)	(114)
Fair value	4,797	4,692
Corporate
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	29,052	28,496
Gross unrealized gains	3,041	2,234
Gross unrealized losses	(130)	(326)
Fair value	31,963	30,404
Foreign government
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	883	927
Gross unrealized gains	167	142
Gross unrealized losses		(1)
Fair value	1,050	1,068
Residential mortgage-backed securities ("RMBS")
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	2,017	2,954
Gross unrealized gains	87	74
Gross unrealized losses	(96)	(314)
Fair value	2,008	2,714
Commercial mortgage-backed securities ("CMBS")
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	1,465	1,862
Gross unrealized gains	61	45
Gross unrealized losses	(91)	(224)
Fair value	1,435	1,683
Asset-backed securities ("ABS")
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	1,977	2,345
Gross unrealized gains	58	44
Gross unrealized losses	(137)	(281)
Fair value	1,898	2,108
Redeemable preferred stock
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	15	15
Gross unrealized gains	3	1
Fair value	18	16
Fixed income securities
Amortized cost, gross unrealized gains and losses and fair value for fixed income securities
Amortized cost	41,703	43,481
Gross unrealized gains	4,280	3,207
Gross unrealized losses	(528)	(1,260)
Fair value	$ 45,455	$ 45,428

Amount of debt 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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

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

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

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-Name Accounting Standards Codification

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

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

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+ 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