Benefit Plans - Schedule of Fair Values of Pension Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Free-standing derivatives, liabilities \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value		$ (3)
Free-standing derivatives, liabilities \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value		(9)
Free-standing derivatives, liabilities \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value		0
Pension benefits
Components of net periodic cost
Total plan assets at fair value	$ 2,942	$ 2,915
Total plan assets at fair value, allocation (as a percent)	100.00%	100.00%
Investments measured using the net asset value practical expedient	$ 1,559	$ 1,570
Securities lending obligation	(124)	(158)
Derivatives counterparty and cash collateral netting	(1)	(8)
Other net plan assets	38	49
Total reported plan assets	4,414	4,368	$ 4,440
Pension benefits \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	$ 1,586	$ 1,582
Total plan assets at fair value, allocation (as a percent)	53.90%	54.20%
Pension benefits \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	$ 1,278	$ 1,252
Total plan assets at fair value, allocation (as a percent)	43.40%	43.00%
Pension benefits \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	$ 78	$ 81
Total plan assets at fair value, allocation (as a percent)	2.70%	2.80%
Total reported plan assets	$ 78	$ 81	0
Pension benefits \| Equity securities
Components of net periodic cost
Total plan assets at fair value	133	107
Pension benefits \| Equity securities \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	128	106
Pension benefits \| Equity securities \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	5	1
Pension benefits \| Equity securities \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Government bonds
Components of net periodic cost
Total plan assets at fair value	1,424	1,525
Pension benefits \| Government bonds \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	1,296	1,401
Pension benefits \| Government bonds \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	128	124
Pension benefits \| Government bonds \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Corporate bonds
Components of net periodic cost
Total plan assets at fair value	1,079	985
Pension benefits \| Corporate bonds \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Corporate bonds \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	1,079	985
Pension benefits \| Corporate bonds \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Short-term investments
Components of net periodic cost
Total plan assets at fair value	235	220
Pension benefits \| Short-term investments \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	166	78
Pension benefits \| Short-term investments \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	69	142
Pension benefits \| Short-term investments \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Free-standing derivatives, assets
Components of net periodic cost
Total plan assets at fair value	3	9
Pension benefits \| Free-standing derivatives, assets \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Free-standing derivatives, assets \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	3	9
Pension benefits \| Free-standing derivatives, assets \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Free-standing derivatives, liabilities
Components of net periodic cost
Total plan assets at fair value	(10)	(12)
Pension benefits \| Free-standing derivatives, liabilities \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	(4)
Pension benefits \| Free-standing derivatives, liabilities \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	(6)
Pension benefits \| Free-standing derivatives, liabilities \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	0
Pension benefits \| Bank loans
Components of net periodic cost
Total plan assets at fair value	78	81
Pension benefits \| Bank loans \| Quoted prices in active markets for identical assets (Level 1)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Bank loans \| Significant other observable inputs (Level 2)
Components of net periodic cost
Total plan assets at fair value	0	0
Pension benefits \| Bank loans \| Significant unobservable inputs (Level 3)
Components of net periodic cost
Total plan assets at fair value	78	81
Total reported plan assets	$ 78	$ 81	$ 0

ALLSTATE CORP 10-K