Business Segments (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information
Property-liability insurance premiums	$ 6,432	$ 6,499	$ 19,337	$ 19,515
Life and annuity premiums and contract charges	552	548	1,668	1,637
Net investment income	994	1,005	2,996	3,104
Realized capital gains and losses	264	(144)	417	(943)
Consolidated revenues	8,242	7,908	24,418	23,313
Property-Liability
Segment Reporting Information
Net investment income	298	284	892	898
Realized capital gains and losses	24	(107)	73	(403)
Consolidated revenues	6,754	6,676	20,302	20,010
Property-Liability \| Total auto
Segment Reporting Information
Property-liability insurance premiums	4,266	4,358	12,864	13,113
Property-Liability \| Standard auto
Segment Reporting Information
Property-liability insurance premiums	4,070	4,134	12,251	12,425
Property-Liability \| Non-standard auto
Segment Reporting Information
Property-liability insurance premiums	196	224	613	688
Property-Liability \| Homeowners
Segment Reporting Information
Property-liability insurance premiums	1,553	1,526	4,640	4,554
Property-Liability \| Other personal lines
Segment Reporting Information
Property-liability insurance premiums	613	614	1,834	1,847
Allstate Protection
Segment Reporting Information
Property-liability insurance premiums	6,432	6,498	19,338	19,514
Discontinued Lines and Coverages
Segment Reporting Information
Property-liability insurance premiums		1	(1)	1
Allstate Financial
Segment Reporting Information
Life and annuity premiums and contract charges	552	548	1,668	1,637
Net investment income	682	707	2,060	2,161
Realized capital gains and losses	219	(38)	320	(553)
Consolidated revenues	1,453	1,217	4,048	3,245
Allstate Financial \| Total life and annuity premiums
Segment Reporting Information
Life and annuity premiums and contract charges	287	290	885	865
Allstate Financial \| Traditional life insurance
Segment Reporting Information
Life and annuity premiums and contract charges	111	107	328	317
Allstate Financial \| Immediate annuities with life contingencies
Segment Reporting Information
Life and annuity premiums and contract charges	16	26	74	84
Allstate Financial \| Accident and health insurance:
Segment Reporting Information
Life and annuity premiums and contract charges	160	157	483	464
Allstate Financial \| Total contract charges
Segment Reporting Information
Life and annuity premiums and contract charges	265	258	783	772
Allstate Financial \| Interest-sensitive life insurance
Segment Reporting Information
Life and annuity premiums and contract charges	258	249	759	740
Allstate Financial \| Fixed annuities
Segment Reporting Information
Life and annuity premiums and contract charges	7	9	24	32
Corporate and Other
Segment Reporting Information
Service fees	1	2	5	8
Net investment income	14	14	44	45
Realized capital gains and losses	21	1	24	13
Total Corporate and Other before reclassification of service fees	36	17	73	66
Reclassification of service fees	(1)	(2)	(5)	(8)
Consolidated revenues	$ 35	$ 15	$ 68	$ 58

Premiums recognized as revenue in the period on all life insurance and reinsurance contracts, as well as accident and health insurance and reinsurance contracts, after subtracting any amounts ceded to another insurer. Also includes an amount that an insurer adds to a policy's premium, or deducts from a policy's cash value or contract holder's account, as compensation for services rendered (may include fees), after subtracting any amounts ceded to another insurer.

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Represents the reclassification of service fees.

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Total fees and commissions earned from providing services such as leasing of space or maintaining: (1) depositor accounts; (2) transfer agent; (3) fiduciary and trust; (4) brokerage and underwriting; (5) mortgage; (6) credit cards; (7) correspondent clearing; and (8) other such services and activities performed for others.

+ References

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Paragraph 13

-Subsection II

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It 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

-Section 04

-Paragraph 13

-Article 9

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

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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

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-Publisher SEC

-Name Regulation S-X (SX)

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

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Premiums recognized as revenue in the period earned on all property and casualty insurance and reinsurance contracts after subtracting any amounts ceded to another insurer.

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-Publisher FASB

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 27

-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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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

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-Publisher SEC

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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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