Investments (Details 4) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Investment income from portfolios
Investment income, net of expenses	$ 108	$ 110	$ 326	$ 322
Indemnity
Investment income from portfolios
Total investment income	4	10	13	29
Less: Investment expenses	0	0	1	1
Investment income, net of expenses	4	10	12	28
Indemnity \| Fixed maturities
Investment income from portfolios
Total investment income	3	8	10	25
Indemnity \| Equity securities
Investment income from portfolios
Total investment income	1	1	2	3
Indemnity \| Cash equivalents and other
Investment income from portfolios
Total investment income	0	1	1	1
Exchange
Investment income from portfolios
Total investment income	112	107	338	314
Less: Investment expenses	8	7	24	20
Investment income, net of expenses	104	100	314	294
Exchange \| Fixed maturities
Investment income from portfolios
Total investment income	91	88	275	261
Exchange \| Equity securities
Investment income from portfolios
Total investment income	21	18	63	52
Exchange \| Cash equivalents and other
Investment income from portfolios
Total investment income	$ 0	$ 1	$ 0	$ 1

Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein.

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

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Chapter 4

-Paragraph 9, 51, 54

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 04

-Paragraph 1, 2 , 3, 4, 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.1-5)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

Total expenses related to the generation of investment income in debt and equity securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.9)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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- Definition

The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It does not include realized gains and losses on investments.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.2)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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