SCHEDULE III - SUPPLEMENTARY INSURANCE INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplementary Insurance Information
Deferred policy acquisition costs	$ 3,954	$ 3,861	$ 3,525
Reserves for claims and claims expense, contract benefits and contractholder funds	57,749	57,411	57,832
Unearned premiums	12,583	12,202	11,655
Premium revenue and contract charges	33,582	32,467	31,086
Net investment income	3,042	3,156	3,459
Claims and claims expense, contract benefits and interest credited to contractholders	24,804	23,598	22,112
Amortization of deferred policy acquisition costs	4,550	4,364	4,135
Other operating costs and expenses	4,431	4,412	4,682
Premiums written (excluding life)	32,455	31,648	30,360
Allstate Protection
Supplementary Insurance Information
Deferred policy acquisition costs	2,188	2,029	1,820
Reserves for claims and claims expense, contract benefits and contractholder funds	23,297	21,807	20,709
Unearned premiums	12,571	12,189	11,640
Premium revenue and contract charges	31,307	30,309	28,928
Claims and claims expense, contract benefits and interest credited to contractholders	22,116	20,981	19,315
Amortization of deferred policy acquisition costs	4,267	4,102	3,875
Other operating costs and expenses	3,607	3,612	3,851
Premiums written (excluding life)	31,597	30,871	29,613
Discontinued Lines and Coverages
Supplementary Insurance Information
Deferred policy acquisition costs	0	0	0
Reserves for claims and claims expense, contract benefits and contractholder funds	1,953	2,062	2,214
Unearned premiums	0	0	0
Premium revenue and contract charges	0	0	1
Claims and claims expense, contract benefits and interest credited to contractholders	105	53	113
Amortization of deferred policy acquisition costs	0	0	0
Other operating costs and expenses	2	2	3
Premiums written (excluding life)	3	0	1
Property-Liability
Supplementary Insurance Information
Deferred policy acquisition costs	2,188	2,029	1,820
Reserves for claims and claims expense, contract benefits and contractholder funds	25,250	23,869	22,923
Unearned premiums	12,571	12,189	11,640
Premium revenue and contract charges	31,307	30,309	28,929
Net investment income	1,266	1,237	1,301
Claims and claims expense, contract benefits and interest credited to contractholders	22,221	21,034	19,428
Amortization of deferred policy acquisition costs	4,267	4,102	3,875
Other operating costs and expenses	3,609	3,614	3,854
Premiums written (excluding life)	31,600	30,871	29,614
Allstate Financial operations
Supplementary Insurance Information
Deferred policy acquisition costs	1,766	1,832	1,705
Reserves for claims and claims expense, contract benefits and contractholder funds	32,499	33,542	34,909
Unearned premiums	12	13	15
Premium revenue and contract charges	2,275	2,158	2,157
Net investment income	1,734	1,884	2,131
Claims and claims expense, contract benefits and interest credited to contractholders	2,583	2,564	2,684
Amortization of deferred policy acquisition costs	283	262	260
Other operating costs and expenses	498	472	468
Premiums written (excluding life)	855	777	746
Corporate and Other
Supplementary Insurance Information
Deferred policy acquisition costs	0	0	0
Reserves for claims and claims expense, contract benefits and contractholder funds	0	0	0
Unearned premiums	0	0	0
Premium revenue and contract charges	0	0	0
Net investment income	42	35	27
Claims and claims expense, contract benefits and interest credited to contractholders	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Other operating costs and expenses	324	326	360
Premiums written (excluding life)	$ 0	$ 0	$ 0