The gross amount of life insurance in force as of the balance sheet date.

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the carrying amount of the investments held by trust.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The percentage of morbidity risk ceded to reinsurers on term life insurance policies prior to October 2009.

+ References

No definition available.

+ Details

Name:	all_MorbidityRiskCededTermLifeInsurancePercent
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of reinsurance ceded under various contracts.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents reinsurance agreements entered with non associated reinsurers to limit the risk of mortality and morbidity losses.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

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+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of life insurance issued and outstanding ceded to other entities. Includes, but not limited to, dividends and adjustments to face value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-17)
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+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

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Balance Type:	debit
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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.

+ References

No definition available.

+ Details

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- Details

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- Details

Name:	us-gaap_CededCreditRiskAxis=all_PrudentialMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=all_CitigroupAndScottishReMember
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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- Details

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- Details

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- Details

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Reinsurance - Asbestos, environmental and other, Allstate Financial (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) reinsurer	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables, net	$ 8,921	$ 8,745
Life insurance in force ceded to unaffiliated reinsurers	86,642	90,011	$ 93,326
Lloyds of London
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables, net	167	174
Allstate Financial
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables, net	$ 2,354	2,468
Percent of morbidity risk ceded for term-life insurance policies	90.00%
Number of unaffiliated reinsurers \| reinsurer	14
Gross life insurance in force	$ 447,860
Life insurance in force ceded to unaffiliated reinsurers	86,640
Allstate Financial \| Prudential
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables, net	1,350	1,410
Allstate Financial \| Citigroup Subsidiaries and Scottish Re
Reinsurance Retention Policy [Line Items]
Reinsurance recoverables, net	139	144
Life and annuity premiums and contract charges \| Allstate Financial \| Prudential
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	76	78	94
Life and annuity contract benefits
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	179	208	219
Life and annuity contract benefits \| Allstate Financial \| Prudential
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	7	21	40
Interest credited to contractholder funds
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	25	26	25
Interest credited to contractholder funds \| Allstate Financial \| Prudential
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	20	20	21
Operating costs and expenses \| Allstate Financial \| Prudential
Reinsurance Retention Policy [Line Items]
Ceded losses incurred	15	$ 15	$ 18
LBL
Reinsurance Retention Policy [Line Items]
Investments held by trust	$ 5,890
Reinsurer Concentration Risk \| A- \| Allstate Financial
Reinsurance Retention Policy [Line Items]
Concentration risk, percentage	92.00%	92.00%