Reporting Segments (Details 2) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Property-Liability
Net investment income	$ 731	$ 850
Allstate Financial
Life and annuity premiums and contract charges	566	537
Corporate and Other
Net income applicable to common shareholders	217	648
Income tax expense	109	404
Allstate Protection
Property-Liability
Underwriting income	127	469
Discontinued Lines and Coverages
Property-Liability
Underwriting income	(2)	(2)
Property-Liability
Property-Liability
Underwriting income	125	467
Net investment income	302	358
Income tax (expense) benefit on operations	(141)	(305)
Realized capital gains and losses, after-tax	(64)	18
Allstate Financial
Realized capital gains and losses, after-tax	(64)	18
Corporate and Other
Realized capital gains and losses, after-tax	(64)	18
Net income applicable to common shareholders	222	538
Allstate Financial
Property-Liability
Net investment income	419	484
Income tax (expense) benefit on operations	(48)	(62)
Realized capital gains and losses, after-tax	(32)	72
Allstate Financial
Life and annuity premiums and contract charges	566	537
Contract benefits and interest credited to contractholder funds	(639)	(633)
Operating costs and expenses and amortization of deferred policy acquisition costs	(194)	(192)
Operating income (loss)	104	134
Realized capital gains and losses, after-tax	(32)	72
Valuation changes on embedded derivatives that are not hedged, after-tax	(4)	(5)
DAC and DSI amortization related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax	(1)	0
Gain (loss) on disposition of operations, after-tax	1	(1)
Change in accounting for investments in qualified affordable housing projects, after-tax	0	(17)
Corporate and Other
Operating income (loss)	104	134
Realized capital gains and losses, after-tax	(32)	72
Net income applicable to common shareholders	68	183
Corporate and Other
Segment Reporting Information
Fees and Commissions	1	1
Property-Liability
Net investment income	10	8
Income tax (expense) benefit on operations	25	26
Realized capital gains and losses, after-tax	0	0
Allstate Financial
Operating income (loss)	(73)	(73)
Realized capital gains and losses, after-tax	0	0
Corporate and Other
Operating costs and expenses	(80)	(79)
Preferred stock dividends	(29)	(29)
Operating income (loss)	(73)	(73)
Realized capital gains and losses, after-tax	0	0
Net income applicable to common shareholders	$ (73)	(73)
Accounting Standards Update 2014-01 \| Property-Liability
Corporate and Other
Income tax expense		$ 28

Contract benefits and interest credited to contract holder funds.

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The amount of deferred policy acquisition costs and sales inducement costs (amortization) accretion related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, net of tax effect.

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The amount of operating costs and expenses and amortization of deferred policy acquisition costs.

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The gain (loss) resulting from the sale of a disposal group that is not a discontinued operation, net of tax effect.

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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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The operating income (loss), net of tax effect, as measured by the entity for segment reporting purposes.

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A measure that is not based on GAAP, which is calculated as premiums earned, less claims and claims expense ("losses"), amortization of deferred policy acquisition costs ("DAC"), operating costs and expenses and restructuring and related charges, as determined using GAAP.

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The amount of valuation changes on embedded derivatives that are not hedged, net of tax effect.

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Amount of paid and unpaid preferred stock dividends declared with the form of settlement in cash.

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-Publisher FASB
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Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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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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