Schedule II - Condensed Financial Information of Registrant - Statement of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues
Investment income, less investment expense									$ 3,092	$ 2,478	$ 2,403
Net gains (losses) on investments and derivatives									(225)	(300)	(1,072)
Total revenues	$ 16,506	$ 16,627	$ 15,714	$ 15,259	$ 14,832	$ 14,497	$ 13,979	$ 13,786	64,106	57,094	51,411
Expenses
Pension and other postretirement remeasurement (gains) losses									(37)	9	116
Other operating expenses									8,626	7,137	7,446
Total costs and expenses									58,345	57,442	53,241
Income tax benefit									1,162	(135)	(488)
Net income (loss) attributable to Allstate									4,667	(188)	(1,289)
Preferred stock dividends									117	128	105
Net income (loss) applicable to common shareholders, basic	1,899	1,161	301	1,189	1,460	(41)	(1,389)	(346)	4,550	(316)	(1,394)
Net income (loss) applicable to common shareholders, diluted	$ 1,899	$ 1,161	$ 301	$ 1,189	$ 1,460	$ (41)	$ (1,389)	$ (346)	4,550	(316)	(1,394)
Other comprehensive income (loss), after-tax
Unrealized foreign currency translation adjustments									(47)	67	(150)
Unamortized pension and other postretirement prior service credit									(2)	(16)	(43)
Discount rate for reserve for future policy benefits									27	(10)	228
Less: change in unrealized net capital gains and losses related to noncontrolling interest									(167)	1,651	(2,853)
Comprehensive income (loss) attributable to Allstate									4,468	1,494	(4,087)
Allstate Corporation
Revenues
Investment income, less investment expense									49	45	59
Net gains (losses) on investments and derivatives									(9)	(28)	(34)
Total revenues									40	17	25
Expenses
Interest expense									411	396	351
Pension and other postretirement remeasurement (gains) losses									(21)	12	179
Pension and other postretirement (benefit) expense									(36)	55	(98)
Other operating expenses									70	142	56
Total costs and expenses									424	605	488
Loss from operations before income tax benefit and equity in net income of subsidiaries									(384)	(588)	(463)
Income tax benefit									(97)	(143)	(103)
Loss before equity in net income of subsidiaries									(287)	(445)	(360)
Equity in net income (loss) of subsidiaries									4,954	257	(929)
Net income (loss) attributable to Allstate									4,667	(188)	(1,289)
Preferred stock dividends									117	128	105
Net income (loss) applicable to common shareholders, basic									4,550	(316)	(1,394)
Net income (loss) applicable to common shareholders, diluted									4,550	(316)	(1,394)
Other comprehensive income (loss), after-tax
Unrealized net capital gains and losses									(167)	1,651	(2,853)
Unrealized foreign currency translation adjustments									(47)	67	(150)
Unamortized pension and other postretirement prior service credit									(2)	(16)	(43)
Discount rate for reserve for future policy benefits									27	(10)	228
Other comprehensive (loss) income, after-tax									(189)	1,692	(2,818)
Less: change in unrealized net capital gains and losses related to noncontrolling interest									10	10	(20)
Comprehensive income (loss) attributable to Allstate									$ 4,468	$ 1,494	$ (4,087)