Business Segments (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information
Net investment income	$ 983,000,000	$ 1,011,000,000
Net income	709,000,000	766,000,000
Life and annuity premiums and contract charges	579,000,000	553,000,000
Restructuring and related charges	(26,000,000)	(6,000,000)
Property-Liability
Segment Reporting Information
Underwriting income (loss)	458,000,000	523,000,000
Net investment income	341,000,000	313,000,000
Income tax benefit (expense) on operations	(256,000,000)	(265,000,000)
Realized capital gains and losses, after-tax	73,000,000	124,000,000
Net income	616,000,000	695,000,000
Allstate Protection
Segment Reporting Information
Underwriting income (loss)	462,000,000	526,000,000
Discontinued Lines and Coverages
Segment Reporting Information
Underwriting income (loss)	(4,000,000)	(3,000,000)
Allstate Financial
Segment Reporting Information
Net investment income	635,000,000	687,000,000
Income tax benefit (expense) on operations	(60,000,000)	(70,000,000)
Realized capital gains and losses, after-tax	12,000,000	(14,000,000)
Net income	146,000,000	112,000,000
Life and annuity premiums and contract charges	579,000,000	553,000,000
Periodic settlements and accruals on non-hedge derivative instruments	10,000,000	15,000,000
Contract benefits and interest credited to contract holder funds	(794,000,000)	(807,000,000)
Operating costs and expenses and amortization of deferred policy acquisition costs	(224,000,000)	(228,000,000)
Restructuring and related charges	(2,000,000)
Operating income (loss)	144,000,000	150,000,000
Valuation changes on embedded derivatives that are not hedged, after-tax	(6,000,000)	(6,000,000)
DAC and DSI amortization related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax	1,000,000	(10,000,000)
Reclassification of periodic settlements and accruals on non-hedge derivative instruments, after-tax	(6,000,000)	(10,000,000)
Gain (loss) on disposition of operations, after-tax	1,000,000	2,000,000
Corporate and Other
Segment Reporting Information
Net investment income	7,000,000	11,000,000
Income tax benefit (expense) on operations	35,000,000	34,000,000
Net income	(53,000,000)	(41,000,000)
Operating income (loss)	(53,000,000)	(41,000,000)
Service fees	1,000,000	1,000,000
Operating costs and expenses	$ (96,000,000)	$ (87,000,000)