Long Term Debt Maturing Next Twelve Months Years Through Five

No definition available.

Name:	all_LongTermDebtMaturingNextTwelveMonthsYearsThroughFive
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long Term Debt Maturing Years Five Through Ten

+ References

No definition available.

+ Details

Name:	all_LongTermDebtMaturingYearsFiveThroughTen
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Long-Term Debt, Maturities, Repayments Of Principal In Rolling After Year Ten

+ References

No definition available.

+ Details

Name:	all_LongTermDebtMaturitiesRepaymentsOfPrincipalInRollingAfterYearTen
Namespace Prefix:	all_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage of the principal amount plus accrued and unpaid interest at which the debt instrument is subject to redemption at the entity's option.

+ References

No definition available.

+ Details

Name:	all_LongTermDebtRedemptionPrice
Namespace Prefix:	all_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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

- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorDebenturesDue2018At6.75PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2019At7.45PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2023At3.15PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2026at3.28PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2032At6.125PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2033At5.35PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2035At5.55PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2036At5.95PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorDebenturesDue2038At6.90PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2042At5.20PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2043At4.50PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SeniorNotesDue2046at4.20PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SubordinatedDebenturesDue2053At5.10PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_SubordinatedDebenturesDue2053At5.75PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_JuniorSubordinatedDebenturesDue2067At6.125PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=all_JuniorSubordinatedDebenturesDue2067At6.50PercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Capital Structure - Total debt outstanding (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 08, 2016
Debt Instrument [Line Items]
Due after one year through five years	$ 493	$ 493
Due after five years through ten years	1,050	1,050
Due after ten years	4,865	4,865
Total long-term debt principal	6,408	6,408
Debt issuance costs	(58)	(61)
Total long-term debt	6,350	6,347
Short-term debt	0	0
Total debt	$ 6,350	6,347
Redemption price as percentage of principal amount plus accrued and unpaid interest	100.00%
6.75% Senior Debentures, due 2018
Debt Instrument [Line Items]
Due after one year through five years	$ 176	176
Note stated interest rate (as a percent)	6.75%
7.45% Senior Notes, due 2019
Debt Instrument [Line Items]
Due after one year through five years	$ 317	317
Note stated interest rate (as a percent)	7.45%
3.15% Senior Notes, due 2023
Debt Instrument [Line Items]
Due after five years through ten years	$ 500	500
Note stated interest rate (as a percent)	3.15%
3.28% Senior Notes, due 2026
Debt Instrument [Line Items]
Due after five years through ten years	$ 550	550
Note stated interest rate (as a percent)	3.28%		3.28%
6.125% Senior Notes, due 2032
Debt Instrument [Line Items]
Due after ten years	$ 159	159
Note stated interest rate (as a percent)	6.125%
5.35% Senior Notes due 2033
Debt Instrument [Line Items]
Due after ten years	$ 323	323
Note stated interest rate (as a percent)	5.35%
5.55% Senior Notes due 2035
Debt Instrument [Line Items]
Due after ten years	$ 546	546
Note stated interest rate (as a percent)	5.55%
5.95% Senior Notes, due 2036
Debt Instrument [Line Items]
Due after ten years	$ 386	386
Note stated interest rate (as a percent)	5.95%
6.90% Senior Debentures, due 2038
Debt Instrument [Line Items]
Due after ten years	$ 165	165
Note stated interest rate (as a percent)	6.90%
5.20% Senior Notes due 2042
Debt Instrument [Line Items]
Due after ten years	$ 62	62
Note stated interest rate (as a percent)	5.20%
4.50% Senior Notes, due 2043
Debt Instrument [Line Items]
Due after ten years	$ 500	500
Note stated interest rate (as a percent)	4.50%
4.20% Senior Notes, due 2046
Debt Instrument [Line Items]
Due after ten years	$ 700	700
Note stated interest rate (as a percent)	4.20%		4.20%
5.10% Subordinated Debentures, due 2053
Debt Instrument [Line Items]
Due after ten years	$ 500	500
Note stated interest rate (as a percent)	5.10%
5.75% Subordinated Debentures, due 2053
Debt Instrument [Line Items]
Due after ten years	$ 800	800
Note stated interest rate (as a percent)	5.75%
6.125% Junior Subordinated Debentures, due 2067
Debt Instrument [Line Items]
Due after ten years	$ 224	224
Total long-term debt	$ 224
Note stated interest rate (as a percent)	6.125%
6.50% Junior Subordinated Debentures, due 2067
Debt Instrument [Line Items]
Due after ten years	$ 500	$ 500
Total long-term debt	$ 500
Note stated interest rate (as a percent)	6.50%