Schedule II - Condensed Financial Information of Registrant - Statement of Cash Flows (Details) - USD ($) $ in Millions		12 Months Ended
	Apr. 17, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net (loss) income		$ (188)	$ (1,289)	$ 1,614
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net (gains) losses on investments and derivatives		300	1,072	(1,279)
Pension and other postretirement remeasurement (gains) losses		9	116	(644)
Changes in:
Net cash provided by operating activities		4,228	5,121	5,116
Cash flows from investing activities
Change in short-term investments, net		(617)	792	4,017
Acquisition of subsidiaries		0	0	(3,593)
Net cash (used in) provided by investing activities		(2,999)	(1,728)	510
Cash flows from financing activities
Proceeds from issuance of debt		743	0	0
Redemption of preferred stock	$ (575)
Redemption and repayment of debt		(750)	0	(436)
Proceeds from issuance of preferred stock		587	0	0
Dividends paid on common stock		(925)	(926)	(885)
Dividends paid on preferred stock		(107)	(105)	(114)
Treasury stock purchases		(335)	(2,520)	(3,120)
Shares reissued under equity incentive plans, net		73	82	114
Other		(49)	(35)	(35)
Net cash used in financing activities		(1,243)	(3,420)	(5,240)
Net (decrease) increase in cash		(14)	(27)	386
Cash from continuing operations at beginning of period		736	763	311
Cash from continuing operations at end of period		722	736	763
Allstate Corporation
Cash flows from operating activities
Net (loss) income		(188)	(1,289)	1,614
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Equity in net (loss) income of subsidiaries		(257)	929	(1,252)
Dividends received from subsidiaries		250	3,396	5,112
Net (gains) losses on investments and derivatives		28	34	(12)
Pension and other postretirement remeasurement (gains) losses		12	179	(611)
Changes in:
Pension and other postretirement benefits		55	(98)	(218)
Income taxes		(78)	(14)	177
Operating assets and liabilities		43	76	158
Net cash provided by operating activities		(135)	3,213	4,968
Cash flows from investing activities
Proceeds from sales of investments		1,427	2,572	1,743
Investment purchases		(50)	(2,507)	(2,673)
Investment collections		85	39	38
Capital contribution or return of capital from subsidiaries		975	145	383
Change in short-term investments, net		(7)	6	4,182
Acquisition of subsidiaries		0	0	(4,144)
Net cash (used in) provided by investing activities		2,430	255	(471)
Cash flows from financing activities
Proceeds from borrowings from subsidiaries		0	1,000	2,200
Repayment of notes due to subsidiaries		(1,000)	(1,000)	(2,450)
Proceeds from issuance of debt		743	0	0
Redemption of preferred stock		(575)	0	0
Redemption and repayment of debt		(750)	0	(250)
Proceeds from issuance of preferred stock		587	0	0
Dividends paid on common stock		(925)	(926)	(885)
Dividends paid on preferred stock		(107)	(105)	(105)
Treasury stock purchases		(335)	(2,520)	(3,120)
Shares reissued under equity incentive plans, net		73	82	114
Other		(6)	0	0
Net cash used in financing activities		(2,295)	(3,469)	(4,496)
Net (decrease) increase in cash		0	(1)	1
Cash from continuing operations at beginning of period		0	1	0
Cash from continuing operations at end of period		$ 0	$ 0	$ 1