Reporting Segments (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information
Life and annuity premiums and contract charges									$ 2,157	$ 2,352	$ 2,241
Net investment income									3,459	3,943	4,010
Restructuring and related charges									(18)	(70)	(34)
Net income available to common shareholders	795	750	614	587	810	310	434	709	2,746	2,263	2,306
Amortization of DAC									4,135	4,002	3,884
Total income tax expense									1,386	1,116	1,000
Property-Liability
Segment Reporting Information
Underwriting income									1,772	2,218	1,200
Net investment income									1,301	1,375	1,326
Income tax (expense) benefit on operations									(1,040)	(1,177)	(779)
Realized capital gains and losses, after-tax									357	339	221
(Loss) gain on disposition of operations, after-tax									37	(1)
Net income available to common shareholders									2,427	2,754	1,968
Amortization of DAC									3,875	3,674	3,483
Total income tax expense									1,211	1,357	893
Allstate Protection
Segment Reporting Information
Underwriting income									1,887	2,361	1,253
Discontinued Lines and Coverages
Segment Reporting Information
Underwriting income									(115)	(143)	(53)
Allstate Financial
Segment Reporting Information
Life and annuity premiums and contract charges									2,157	2,352	2,241
Net investment income									2,131	2,538	2,647
Periodic settlements and accruals on non-hedge derivative instruments									(1)	17	55
Contract benefits and interest credited to contract holder funds									(2,663)	(3,171)	(3,252)
Operating costs and expenses and amortization of deferred policy acquisition costs									(721)	(895)	(926)
Restructuring and related charges									(2)	(7)
Income tax (expense) benefit on operations									(294)	(246)	(236)
Operating income (loss)									607	588	529
Realized capital gains and losses, after-tax									94	46	(8)
Valuation changes on embedded derivatives that are not hedged, after-tax									(15)	(16)	82
DAC and DSI amortization related to realized capital gains and losses and valuation changes on embedded derivatives that are not hedged, after-tax									(3)	(5)	(42)
DAC and DSI unlocking related to realized capital gains and losses, after-tax										7	4
Reclassification of periodic settlements and accruals on non-hedge derivative instruments, after-tax									1	(11)	(36)
(Loss) gain on disposition of operations, after-tax									(53)	(514)	12
Net income available to common shareholders									631	95	541
Amortization of DAC									260	328	401
Total income tax expense									299	87	241
Corporate and Other
Segment Reporting Information
Service fees									5	9	4
Net investment income									27	30	37
Operating costs and expenses									(364)	(627)	(383)
Income tax (expense) benefit on operations									124	220	136
Preferred stock dividends									(104)	(17)
Operating income (loss)									(312)	(385)	(206)
Realized capital gains and losses, after-tax											3
Loss on extinguishment of debt, after-tax										(319)
Postretirement benefits curtailment gain, after-tax										118
Net income available to common shareholders									(312)	(586)	(203)
Total income tax expense									$ (124)	$ (328)	$ (134)