SCHEDULE II - CONDENSED FINANCIAL INFORMATION OF REGISTRANT (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income	$ 1,877	$ 2,171	$ 2,850
Adjustments to reconcile net income to net cash provided by operating activities:
Realized capital gains and losses	90	(30)	(694)
Loss on extinguishment of debt	0	0	1
Changes in:
Net cash provided by operating activities	3,993	3,616	3,236
Cash flows from investing activities
Change in short-term investments, net	(2,446)	385	272
Net cash (used in) provided by investing activities	(2,526)	742	1,621
Cash flows from financing activities
Proceeds from issuance of long-term debt	1,236	0	0
Repayments of long-term debt	(17)	(20)	(1,006)
Proceeds from issuance of preferred stock	0	0	965
Dividends paid on common stock	(486)	(483)	(477)
Dividends paid on preferred stock	(116)	(116)	(87)
Treasury stock purchases	(1,337)	(2,808)	(2,301)
Shares reissued under equity incentive plans, net	164	130	266
Excess tax benefits on share-based payment arrangements	32	45	41
Other	36	7	(14)
Net cash used in financing activities	(1,526)	(4,520)	(4,875)
Net decrease in cash	(59)	(162)	(18)
Cash at beginning of year	495	657	675
Cash at end of year	436	495	657
Supplemental disclosures of non-cash investing activity and cash flow information
Interest paid on debt	287	289	332
Allstate Corporation
Cash flows from operating activities
Net income	1,877	2,171	2,850
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in net income of subsidiaries	(2,027)	(2,300)	(3,039)
Dividends received from subsidiaries	1,874	2,300	2,497
Realized capital gains and losses	(2)	0	0
Loss on extinguishment of debt	0	0	1
Changes in:
Pension and other postretirement benefits	10	(15)	41
Income taxes	13	77	(158)
Operating assets and liabilities	43	26	(29)
Net cash provided by operating activities	1,788	2,259	2,163
Cash flows from investing activities
Proceeds from sales of investments	389	399	351
Investment purchases	(243)	(4)	(1,174)
Investment collections	60	0	155
Return of capital from subsidiaries	(1,500)	50	1,200
Transfers to subsidiaries through intercompany loan agreement	(30)	0	0
Change in short-term investments, net	58	397	(88)
Net cash (used in) provided by investing activities	(1,266)	842	444
Cash flows from financing activities
Proceeds from issuance of long-term debt	1,236	0	0
Repayments of long-term debt	(17)	(20)	(962)
Proceeds from issuance of preferred stock	0	0	965
Dividends paid on common stock	(486)	(483)	(477)
Dividends paid on preferred stock	(116)	(116)	(87)
Treasury stock purchases	(1,337)	(2,808)	(2,301)
Shares reissued under equity incentive plans, net	164	130	266
Excess tax benefits on share-based payment arrangements	32	45	41
Other	0	0	(2)
Net cash used in financing activities	(524)	(3,252)	(2,557)
Net decrease in cash	(2)	(151)	50
Cash at beginning of year	4	155	105
Cash at end of year	2	4	155
Supplemental disclosures of non-cash investing activity and cash flow information
Interest paid on debt	$ 287	$ 289	$ 332