Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 14, 2019
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	1-11840
Entity Registrant Name	ALLSTATE CORP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-3871531
Entity Address, Address Line One	2775 Sanders Road
Entity Address, City or Town	Northbrook
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60062
City Area Code	847
Local Phone Number	402-5000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		323,956,116
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000899051
NEW YORK STOCK EXCHANGE, INC. | Common stock par value
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	ALL
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | Subordinated Debentures Due 2053 at 5.10 Percent
Document Information [Line Items]
Title of 12(b) Security	5.100% Fixed-to-Floating Rate Subordinated Debentures due 2053
Trading Symbol	ALL.PR.B
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | Series A Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares represent 1/1,000th of a share of 5.625% Noncumulative Preferred Stock, Series A
Trading Symbol	ALL PR A
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | Series G Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares represent 1/1,000th of a share of 5.625% Noncumulative Preferred Stock, Series G
Trading Symbol	ALL PR G
Security Exchange Name	NYSE
NEW YORK STOCK EXCHANGE, INC. | Series H Preferred Stock
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares represent 1/1,000th of a share of 5.100% Noncumulative Preferred Stock, Series H
Trading Symbol	ALL PR H
Security Exchange Name	NYSE
CHICAGO STOCK EXCHANGE, INC | Common stock par value
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	ALL
Security Exchange Name	CHX