Reporting Segments (Details 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Property-Liability
Net investment income	$ 807	$ 823	$ 2,446	$ 2,680
Allstate Financial
Life and annuity premiums and contract charges	538	512	1,611	1,637
Restructuring and related charges	(9)	(3)	(32)	(13)
Corporate and Other
Net income available to common shareholders	621	750	1,595	1,951
Property-Liability
Property-Liability
Underwriting income	491	474	948	1,035
Net investment income	307	344	957	1,007
Realized capital gains and losses, after-tax	(104)	173	(55)	368
Allstate Financial
Realized capital gains and losses, after-tax	(104)	173	(55)	368
Gain (loss) on disposition of operations, after-tax	(1)	(1)	0	37
Income tax (expense) benefit on operations	(256)	(276)	(653)	(686)
Corporate and Other
Realized capital gains and losses, after-tax	(104)	173	(55)	368
Net income available to common shareholders	437	714	1,197	1,761
Allstate Protection
Property-Liability
Underwriting income	540	579	1,001	1,146
Discontinued Lines and Coverages
Property-Liability
Underwriting income	(49)	(105)	(53)	(111)
Allstate Financial
Property-Liability
Net investment income	491	473	1,464	1,651
Realized capital gains and losses, after-tax	125	19	235	13
Allstate Financial
Life and annuity premiums and contract charges	538	512	1,611	1,637
Periodic Settlements and Accruals on Non Hedge Derivative Financial Instruments	0	0	0	(1)
Contract benefits and interest credited to contractholder funds	(651)	(633)	(1,921)	(2,033)
Operating costs and expenses and amortization of deferred policy acquisition costs	(173)	(171)	(545)	(540)
Restructuring and related charges	(1)	1	(3)	(2)
Operating income (loss)	138	125	411	479
Realized capital gains and losses, after-tax	125	19	235	13
Valuation changes on embedded derivatives that are not hedged, after-tax	(2)	2	(3)	(12)
DAC and DSI amortization related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax	(1)	(3)	(3)	(3)
Reclassification of periodic settlements and accruals on non-hedge derivative instruments, after-tax	0	0	0	1
Gain (loss) on disposition of operations, after-tax	2	(27)	1	(55)
Change in accounting for investments in qualified affordable housing projects, after-tax	0	0	(17)	0
Income tax (expense) benefit on operations	(66)	(57)	(195)	(233)
Corporate and Other
Operating income (loss)	138	125	411	479
Realized capital gains and losses, after-tax	125	19	235	13
Net income available to common shareholders	262	116	624	423
Corporate and Other
Segment Reporting Information
Fees and Commissions	0	1	2	4
Property-Liability
Net investment income	9	6	25	22
Realized capital gains and losses, after-tax	0	0	0	0
Allstate Financial
Operating income (loss)	(78)	(80)	(226)	(233)
Realized capital gains and losses, after-tax	0	0	0	0
Income tax (expense) benefit on operations	28	28	82	92
Corporate and Other
Operating income (loss)	(78)	(80)	(226)	(233)
Operating costs and expenses	(86)	(84)	(248)	(276)
Preferred stock dividends	(29)	(31)	(87)	(75)
Realized capital gains and losses, after-tax	0	0	0	0
Net income available to common shareholders	$ (78)	$ (80)	$ (226)	$ (233)