Reporting Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information
Property-liability insurance premiums	$ 7,204	$ 6,862	$ 14,268	$ 13,632
Life and annuity premiums and contract charges	518	579	1,125	1,158
Net investment income	898	984	1,857	1,967
Realized capital gains and losses	240	362	294	493
Consolidated revenues	8,860	8,787	17,544	17,250
Property-Liability
Segment Reporting Information
Property-liability insurance premiums	7,204	6,862	14,268	13,632
Net investment income	351	343	663	684
Realized capital gains and losses	250	305	303	417
Consolidated revenues	7,805	7,510	15,234	14,733
Property-Liability | Auto
Segment Reporting Information
Property-liability insurance premiums	4,824	4,599	9,536	9,129
Property-Liability | Homeowners
Segment Reporting Information
Property-liability insurance premiums	1,714	1,630	3,411	3,246
Property-Liability | Other personal lines
Segment Reporting Information
Property-liability insurance premiums	414	405	826	809
Property-Liability | Commercial lines
Segment Reporting Information
Property-liability insurance premiums	121	113	231	227
Property-Liability | Other business lines
Segment Reporting Information
Property-liability insurance premiums	131	115	264	221
Allstate Protection
Segment Reporting Information
Property-liability insurance premiums	7,204	6,862	14,268	13,632
Allstate Financial
Segment Reporting Information
Life and annuity premiums and contract charges	518	579	1,125	1,158
Net investment income	538	633	1,178	1,268
Realized capital gains and losses	(10)	57	(9)	76
Consolidated revenues	1,046	1,269	2,294	2,502
Allstate Financial | Total life and annuity premiums
Segment Reporting Information
Life and annuity premiums and contract charges	312	307	639	610
Allstate Financial | Traditional life insurance
Segment Reporting Information
Life and annuity premiums and contract charges	125	119	252	235
Allstate Financial | Immediate annuities with life contingencies
Segment Reporting Information
Life and annuity premiums and contract charges		9	5	16
Allstate Financial | Accident and health insurance
Segment Reporting Information
Life and annuity premiums and contract charges	187	179	382	359
Allstate Financial | Total contract charges
Segment Reporting Information
Life and annuity premiums and contract charges	206	272	486	548
Allstate Financial | Interest-sensitive life insurance
Segment Reporting Information
Life and annuity premiums and contract charges	202	268	476	541
Allstate Financial | Fixed annuities
Segment Reporting Information
Life and annuity premiums and contract charges	4	4	10	7
Corporate and Other
Segment Reporting Information
Service fees	1	2	3	3
Net investment income	9	8	16	15
Total Corporate and Other before reclassification of service fees	10	10	19	18
Reclassification of service fees	(1)	(2)	(3)	(3)
Consolidated revenues	$ 9	$ 8	$ 16	$ 15