Schedule II - Condensed Financial Information of Registrant - Statement of Financial Position (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Assets
Fixed income securities, at fair value	$ 48,865	$ 42,485
Short-term investments, at fair value	5,144	4,173
Cash	722	736
Total assets	103,362	97,989
Liabilities
Debt	7,942	7,964
Total liabilities	85,732	80,626
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 82.0 thousand and 81.0 thousand shares issued and outstanding, $2,050 and $2,025 aggregate liquidation preference	2,001	1,970
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 262 million and 263 million shares outstanding	9	9
Additional capital paid-in	3,854	3,788
Retained income	49,716	50,970
Treasury stock, at cost (638 million and 637 million shares)	(37,110)	(36,857)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(604)	(2,255)
Unrealized foreign currency translation adjustments	(98)	(165)
Unamortized pension and other postretirement prior service credit	13	29
Discount rate for reserve for future policy benefits	(11)	(1)
Total accumulated other comprehensive loss	(700)	(2,392)
Total Allstate shareholders’ equity	17,770	17,488	$ 24,944
Total liabilities and equity	103,362	97,989
Additional balance sheet disclosures:
Amortized cost, net	49,649	45,370
Other short term Investments, amortized cost	$ 5,145	$ 4,174
Preferred stock, par or stated value per share (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	81,000
Preferred stock, shares outstanding (in shares)	82,000	81,000
Preferred Stock, liquidation preference	$ 2,050	$ 2,025
Common stock, par or stated value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares, issued (in shares)	900,000,000	900,000,000
Common stock, shares, outstanding (in shares)	262,000,000	263,000,000
Treasury stock, shares (in shares)	638,000,000	637,000,000
Allstate Corporation
Assets
Investment in subsidiaries	$ 24,388	$ 23,711
Fixed income securities, at fair value	1,003	2,422
Short-term investments, at fair value	297	291
Cash	0	0
Receivable from subsidiaries	359	341
Deferred income taxes	90	59
Other assets	233	108
Total assets	26,370	26,932
Liabilities
Debt	7,585	7,588
Pension and other postretirement benefit obligations	237	180
Deferred compensation	341	320
Notes due to subsidiaries	0	1,000
Dividends payable to shareholders	270	260
Other liabilities	167	96
Total liabilities	8,600	9,444
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 82.0 thousand and 81.0 thousand shares issued and outstanding, $2,050 and $2,025 aggregate liquidation preference	2,001	1,970
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 262 million and 263 million shares outstanding	9	9
Additional capital paid-in	3,854	3,788
Retained income	49,716	50,970
Treasury stock, at cost (638 million and 637 million shares)	(37,110)	(36,857)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(604)	(2,255)
Unrealized foreign currency translation adjustments	(98)	(165)
Unamortized pension and other postretirement prior service credit	13	29
Discount rate for reserve for future policy benefits	(11)	(1)
Total accumulated other comprehensive loss	(700)	(2,392)
Total Allstate shareholders’ equity	17,770	17,488
Total liabilities and equity	26,370	26,932
Additional balance sheet disclosures:
Amortized cost, net	1,027	2,513
Other short term Investments, amortized cost	$ 297	$ 291
Preferred stock, par or stated value per share (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	81,000
Preferred stock, shares outstanding (in shares)	82,000	81,000
Preferred Stock, liquidation preference	$ 2,050	$ 2,025
Common stock, par or stated value per share (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	2,000,000,000	2,000,000,000
Common stock, shares, issued (in shares)	900,000,000	900,000,000
Common stock, shares, outstanding (in shares)	262,000,000	263,000,000
Treasury stock, shares (in shares)	638,000,000	637,000,000