Schedule II - Condensed Financial Information of Registrant - Statement of Financial Position (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Assets
Fixed income securities, at fair value	$ 52,747	$ 48,865
Equity securities	4,463	2,411
Short-term investments, at fair value	4,537	5,144
Cash	704	722
Total assets	111,617	103,362
Liabilities
Debt	8,085	7,942
Total liabilities	90,250	85,732
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 82.0 thousand shares issued and outstanding, $2,050 aggregate liquidation preference	2,001	2,001
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 265 million and 262 million shares outstanding	9	9
Additional capital paid-in	4,029	3,854
Retained income	53,288	49,716
Treasury stock, at cost (635 million and 638 million shares)	(36,996)	(37,110)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(771)	(604)
Unrealized foreign currency translation adjustments	(145)	(98)
Unamortized pension and other postretirement prior service credit	11	13
Discount rate for reserve for future policy benefits	16	(11)
Total accumulated other comprehensive loss	(889)	(700)
Total Allstate shareholders’ equity	21,442	17,770
Total liabilities and equity	111,617	103,362
Additional balance sheet disclosures:
Fixed income securities, at fair value, amortized cost	53,616	49,649
Equity securities, at fair value, cost	4,329	2,244
Other short term Investments, amortized cost	$ 4,539	$ 5,145
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	82,000	82,000
Preferred stock, shares outstanding (in shares)	82,000	82,000
Preferred stock, value aggregate liquidation preference	$ 2,050	$ 2,050
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	2,000,000,000.0	2,000,000,000.0
Common stock, shares, issued (in shares)	900,000,000	900,000,000
Common stock, shares, outstanding (in shares)	265,000,000	262,000,000
Treasury stock, shares (in shares)	635,000,000	638,000,000
Allstate Corporation
Assets
Investments in subsidiaries	$ 28,684	$ 24,388
Fixed income securities, at fair value	635	1,003
Equity securities	1	0
Short-term investments, at fair value	507	297
Cash	1	0
Receivable from subsidiaries	748	359
Deferred income taxes	48	90
Other assets	149	233
Total assets	30,773	26,370
Liabilities
Debt	8,085	7,585
Pension and other postretirement benefit obligations	170	237
Deferred compensation	360	341
Notes due to subsidiaries	350	0
Dividends payable to shareholders	281	270
Other liabilities	85	167
Total liabilities	9,331	8,600
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 82.0 thousand shares issued and outstanding, $2,050 aggregate liquidation preference	2,001	2,001
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 265 million and 262 million shares outstanding	9	9
Additional capital paid-in	4,029	3,854
Retained income	53,288	49,716
Treasury stock, at cost (635 million and 638 million shares)	(36,996)	(37,110)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(771)	(604)
Unrealized foreign currency translation adjustments	(145)	(98)
Unamortized pension and other postretirement prior service credit	11	13
Discount rate for reserve for future policy benefits	16	(11)
Total accumulated other comprehensive loss	(889)	(700)
Total Allstate shareholders’ equity	21,442	17,770
Total liabilities and equity	30,773	26,370
Additional balance sheet disclosures:
Fixed income securities, at fair value, amortized cost	639	1,027
Equity securities, at fair value, cost	1	0
Other short term Investments, amortized cost	$ 507	$ 297
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	82,000
Preferred stock, shares outstanding (in shares)	82,000
Preferred stock, value aggregate liquidation preference	$ 2,050
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	2,000,000,000.0	2,000,000,000.0
Common stock, shares, issued (in shares)	900,000,000	900,000,000
Common stock, shares, outstanding (in shares)	265,000,000	262,000,000
Treasury stock, shares (in shares)	635,000,000	638,000,000