Reporting Segments (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Property-Liability
Net investment income	$ 789	$ 898	$ 1,639	$ 1,857
Allstate Financial
Life and annuity premiums and contract charges	536	518	1,073	1,125
Restructuring and related charges	(19)	(4)	(23)	(10)
Corporate and Other
Net income available to common shareholders	326	614	974	1,201
Property-Liability
Property-Liability
Underwriting income	(10)	189	457	561
Net investment income	292	351	650	663
Realized capital gains and losses, after-tax	31	161	49	195
Allstate Financial
Realized capital gains and losses, after-tax	31	161	49	195
Loss on disposition of operations, after-tax	1	38	1	38
Income tax (expense) benefit on operations	(92)	(185)	(397)	(410)
Corporate and Other
Realized capital gains and losses, after-tax	31	161	49	195
Net income available to common shareholders	222	554	760	1,047
Allstate Protection
Property-Liability
Underwriting income	(8)	192	461	567
Discontinued Lines and Coverages
Property-Liability
Underwriting income	(2)	(3)	(4)	(6)
Allstate Financial
Property-Liability
Net investment income	489	538	973	1,178
Realized capital gains and losses, after-tax	38	(6)	110	(6)
Allstate Financial
Life and annuity premiums and contract charges	536	518	1,073	1,125
Periodic Settlements and Accruals on Non Hedge Derivative Financial Instruments	0	(1)	0	(1)
Contract benefits and interest credited to contractholder funds	(637)	(621)	(1,270)	(1,400)
Operating costs and expenses and amortization of deferred policy acquisition costs	(180)	(177)	(372)	(369)
Restructuring and related charges	(2)	(1)	(2)	(3)
Operating income (loss)	139	165	273	354
Realized capital gains and losses, after-tax	38	(6)	110	(6)
Valuation changes on embedded derivatives that are not hedged, after-tax	4	(3)	(1)	(14)
DAC and DSI amortization related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax	(2)	0	(2)	0
Reclassification of periodic settlements and accruals on non-hedge derivative instruments, after-tax	0	1	0	1
Loss on disposition of operations, after-tax	0	(12)	(1)	(28)
Change in accounting for investments in qualified affordable housing projects, after-tax	0	0	(17)	0
Income tax (expense) benefit on operations	(67)	(91)	(129)	(176)
Corporate and Other
Operating income (loss)	139	165	273	354
Realized capital gains and losses, after-tax	38	(6)	110	(6)
Net income available to common shareholders	179	145	362	307
Corporate and Other
Segment Reporting Information
Fees and Commissions	1	1	2	3
Property-Liability
Net investment income	8	9	16	16
Realized capital gains and losses, after-tax	0	(1)	0	0
Allstate Financial
Operating income (loss)	(75)	(84)	(148)	(153)
Realized capital gains and losses, after-tax	0	(1)	0	0
Income tax (expense) benefit on operations	28	32	54	64
Corporate and Other
Operating income (loss)	(75)	(84)	(148)	(153)
Operating costs and expenses	(83)	(95)	(162)	(192)
Preferred stock dividends	(29)	(31)	(58)	(44)
Realized capital gains and losses, after-tax	0	(1)	0	0
Net income available to common shareholders	$ (75)	$ (85)	$ (148)	$ (153)