Business Segments (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Segment Reporting Information
Net investment income	$ 1,026	$ 1,020	$ 2,037	$ 2,002
Net income (loss)	423	(624)	1,189	(100)
Life and annuity premiums and contract charges	559	547	1,112	1,116
Restructuring and related charges	10	11	16	20
Property-Liability
Segment Reporting Information
Underwriting income (loss)	134	(1,502)	657	(1,174)
Net investment income	352	310	665	594
Income tax benefit (expense) on operations	(144)	461	(409)	279
Realized capital gains and losses, after-tax	12	(6)	136	32
Net income (loss)	354	(737)	1,049	(269)
Allstate Protection
Segment Reporting Information
Underwriting income (loss)	138	(1,498)	664	(1,164)
Discontinued Lines and Coverages
Segment Reporting Information
Underwriting income (loss)	(4)	(4)	(7)	(10)
Allstate Financial
Segment Reporting Information
Net investment income	663	694	1,350	1,378
Income tax benefit (expense) on operations	(64)	(69)	(134)	(122)
Realized capital gains and losses, after-tax	5	40	(9)	65
Net income (loss)	132	161	244	263
Life and annuity premiums and contract charges	559	547	1,112	1,116
Periodic settlements and accruals on non-hedge derivative instruments	15	19	30	36
Contract benefits and interest credited to contract holder funds	(824)	(834)	(1,631)	(1,713)
Operating costs and expenses and amortization of deferred policy acquisition costs	(211)	(222)	(439)	(449)
Restructuring and related charges				2
Operating income (loss)	138	135	288	248
Valuation changes on embedded derivatives that are not hedged, after-tax	(3)	(3)	(9)	5
DAC and DSI (amortization) accretion related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax		(5)	(10)	(27)
DAC and DSI unlocking related to realized capital gains and losses, after-tax				3
Reclassification of periodic settlements and accruals on non-hedge derivative instruments, after-tax	(10)	(11)	(20)	(23)
Gain (loss) on disposition of operations, after-tax	2	5	4	(8)
Corporate and Other
Segment Reporting Information
Net investment income	11	16	22	30
Income tax benefit (expense) on operations	33	32	67	63
Realized capital gains and losses, after-tax		2		2
Net income (loss)	(63)	(48)	(104)	(94)
Operating income (loss)	(63)	(50)	(104)	(96)
Service fees	1	2	2	4
Operating costs and expenses	$ (108)	$ (100)	$ (195)	$ (193)