Guarantees and Contingent Liabilities (Details)			6 Months Ended	12 Months Ended	18 Months Ended
	May 20, 2016 Plaintiff	Jun. 17, 2015 Plaintiff	Jun. 30, 2016 USD ($) claim employee defense	Dec. 31, 2001 employee	Jun. 30, 2016 USD ($) Plaintiff	Dec. 31, 2015 USD ($)	Aug. 19, 2015 opinion
Guarantees:
Limitations or indemnifications of reinsurance agreements			$ 0		$ 0
Proceedings:
Number of class action cases | claim			2
Opinions, number | opinion							3
Number of former employee agents plaintiffs seek benefits for | employee				6,300
Loss contingency, number of plaintiffs	499	10	32		459
Number of defenses | defense			2
Reserves for asbestos claims			$ 890,000,000		$ 890,000,000	$ 960,000,000
Reinsurance recoverables for asbestos claims			443,000,000		443,000,000	458,000,000
Reserves for environmental claims			173,000,000		173,000,000	179,000,000
Reinsurance recoverables for environmental claims			$ 42,000,000		$ 42,000,000	$ 43,000,000
Percentage of net asbestos and environmental reserves that were for incurred but not reported estimated losses			55.00%		55.00%	57.00%
Minimum
Proceedings:
Loss contingencies, reasonably possible pretax loss exposure in excess of the amount accrued			$ 0
Maximum
Proceedings:
Loss contingencies, reasonably possible pretax loss exposure in excess of the amount accrued			875,000,000
Residual guarantee
Guarantees:
Potential leased automobiles residual value			$ 46,000,000		$ 46,000,000
Guarantee obligations term, low end of range			1 year
Guarantee obligations term, high end of range			4 years
Against Allstate
Proceedings:
Opinions, number | opinion							2
In Favor of Allstate
Proceedings:
Opinions, number | opinion							1
Signed Releases Knowingly and Voluntarily | Judicial Ruling
Proceedings:
Loss contingency, number of plaintiffs | Plaintiff		2
Did Not Sign Releases Knowingly and Voluntarily | Judicial Ruling
Proceedings:
Loss contingency, number of plaintiffs | Plaintiff		8