Schedule II - Condensed Financial Information of Registrant - Financial Position (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Assets
Fixed income securities	$ 42,485	$ 42,136
Short-term investments	4,173	4,009
Cash	736	763
Total assets	97,957	99,440
Liabilities
Debt	7,964	7,976
Total liabilities	80,607	74,313
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 81.0 thousand shares issued and outstanding, $2,025 aggregate liquidation preference	1,970	1,970
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 263 million and 281 million shares outstanding	9	9
Additional capital paid-in	3,788	3,722
Retained income	50,954	53,294
Treasury stock, at cost (637 million and 619 million shares)	(36,857)	(34,471)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(2,253)	598
Unrealized foreign currency translation adjustments	(165)	(15)
Unamortized pension and other postretirement prior service credit	29	72
Total accumulated other comprehensive (loss) income	(2,389)	655
Total Allstate shareholders’ equity	17,475	25,179	$ 30,217
Total liabilities and equity	97,957	99,440
Additional balance sheet disclosures:
Amortized cost, net	45,370	41,376
Other short term Investments, amortized cost	$ 4,174	$ 4,009
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)	81,000	81,000
Preferred stock, shares outstanding (in shares)	81,000	81,000
Preferred Stock, liquidation preference	$ 2,025	$ 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)	263,000,000	281,000,000
Treasury stock, shares (in shares)	637,000,000	619,000,000
Allstate Corporation
Assets
Investment in subsidiaries	$ 23,698	$ 32,058
Fixed income securities	2,422	1,718
Short-term investments	291	297
Cash	0	1
Receivable from subsidiaries	341	504
Deferred income taxes	59	22
Other assets	108	222
Total assets	26,919	34,822
Liabilities
Debt	7,588	7,581
Pension and other postretirement benefit obligations	180	211
Deferred compensation	320	383
Notes due to subsidiaries	1,000	1,000
Dividends payable to shareholders	260	269
Other liabilities	96	199
Total liabilities	9,444	9,643
Shareholders’ equity
Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 81.0 thousand shares issued and outstanding, $2,025 aggregate liquidation preference	1,970	1,970
Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 263 million and 281 million shares outstanding	9	9
Additional capital paid-in	3,788	3,722
Retained income	50,954	53,294
Treasury stock, at cost (637 million and 619 million shares)	(36,857)	(34,471)
Accumulated other comprehensive income:
Unrealized net capital gains and losses	(2,253)	598
Unrealized foreign currency translation adjustments	(165)	(15)
Unamortized pension and other postretirement prior service credit	29	72
Total accumulated other comprehensive (loss) income	(2,389)	655
Total Allstate shareholders’ equity	17,475	25,179
Total liabilities and equity	26,919	34,822
Additional balance sheet disclosures:
Amortized cost, net	2,513	1,708
Other short term Investments, amortized cost	$ 291	$ 297
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)	81,000	81,000
Preferred stock, shares outstanding (in shares)	81,000	81,000
Preferred Stock, liquidation preference	$ 2,025	$ 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)	263,000,000	281,000,000
Treasury stock, shares (in shares)	637,000,000	619,000,000