Benefit Plans (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit Plans
Principal balance of note from ESOP	$ 15
Interest rate on note from ESOP (as a percent)	7.90%
Company's contribution to the Allstate Plan	75	54	52
ESOP benefit computed
Interest expense recognized by ESOP	1	2	2
Less: dividends accrued on ESOP shares	(4)	(3)	(2)
Cost of shares allocated	8	7	2
Compensation expense	5	6	2
Reduction of defined contribution due to ESOP	71	46	10
ESOP benefit	(66)	(40)	(8)
Contributions to ESOP	3	2	0
ESOP shares committed to be released	1.0
Allocated ESOP shares	35
Unallocated ESOP shares	3
Defined contribution plan expense for eligible employees of Canadian insurance subsidiaries and Sterling	$ 11	$ 11	$ 7

This element represents the defined contribution plans expenses for eligible employees of certain subsidiaries.

No definition available.

Name:	all_DefinedContributionPlanExpenseForEligibleEmployeesOfCertainSubsidiaries
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	all_EmployeeStockOwnershipPlanESOPAbstract
Namespace Prefix:	all_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The element represents the aggregate amount of ESOP benefit.

+ References

No definition available.

+ Details

Name:	all_EmployeeStockOwnershipPlanESOPBenefit
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the cost of the shares allocated to an employee stock ownership plan during the period.

+ References

No definition available.

+ Details

Name:	all_EmployeeStockOwnershipPlanESOPCostOfSharesAllocatedToESOP
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The stated interest rate on a loan made by a third-party lender directly to the ESOP.

+ References

No definition available.

+ Details

Name:	all_EmployeeStockOwnershipPlanESOPDebtStructureDirectLoanInterestRate
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Dividends accrued during the period on stock held by an employee stock ownership plan.

+ References

No definition available.

+ Details

Name:	all_EmployeeStockOwnershipPlanESOPDividendsAccruedToESOP
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents the reduction in the entity's cost recognized during the period for defined contribution plans due to use of the ESOP for pre-funding anticipated contributions.

+ References

No definition available.

+ Details

Name:	all_EmployeeStockOwnershipPlanESOPReductionInDefinedContribution
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the amount of cash contributions during the period made by the entity to the Employee Stock Ownership Plan (ESOP).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPCashContributionsToESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of plan compensation cost recognized during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount reported as a liability as of the balance sheet date by the entity (the employer) of the loan made by a third-party lender directly to the ESOP.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Direct Loan

-URI http://asc.fasb.org/extlink&oid=6510849

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 9

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16545-113920

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPDebtStructureDirectLoanAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

An entity often discloses the amount of interest paid by the ESOP to a lender.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 9

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16545-113920

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPInterestPaymentsFromESOP
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The shares or units in an ESOP trust that have been assigned to individual participant accounts based on a known formula. IRS rules require allocations to be nondiscriminatory generally based on compensation, length of service, or a combination of both. For any particular participant such shares or units may be vested, unvested, or partially vested.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The shares that, although not legally released, will be released by a future scheduled and committed debt service payment and will be allocated to employees for service rendered in the current accounting period. The ESOP documents typically define the period of service to which the shares relate. ESOP shares are released to compensate employees directly, to settle employer liabilities for other employee benefits, and to replace dividends on allocated shares that are used for debt service.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPNumberOfCommittedToBeReleasedShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Shares contributed to the ESOP that have not yet been released, committed to be released, or allocated to participant accounts. Suspense shares generally collateralize ESOP debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

Name:	us-gaap_EmployeeStockOwnershipPlanESOPNumberOfSuspenseShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant