Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Long Duration Contracts [Abstract]
Beginning balance	$ 5,940
Deferred policy acquisition costs	6,112	$ 5,607
Ending balance	6,112	5,607
Allstate Health and Benefits
Long Duration Contracts [Abstract]
Beginning balance	511	502
Acquisition costs deferred	87	45
Amortization charged to income	(57)	(30)
Experience adjustment	(11)	(14)
Deferred policy acquisition costs	530	503
Short-duration contracts	32	27
Ending balance	530	503
Accident and health insurance
Long Duration Contracts [Abstract]
Beginning balance	321	322
Acquisition costs deferred	51	25
Amortization charged to income	(40)	(16)
Experience adjustment	(9)	(13)
Deferred policy acquisition costs	323	318
Ending balance	323	318
Traditional life
Long Duration Contracts [Abstract]
Beginning balance	90	79
Acquisition costs deferred	27	13
Amortization charged to income	(10)	(7)
Experience adjustment	(1)	0
Deferred policy acquisition costs	106	85
Ending balance	106	85
Interest-sensitive life insurance
Long Duration Contracts [Abstract]
Beginning balance	100	101
Acquisition costs deferred	9	7
Amortization charged to income	(7)	(7)
Experience adjustment	(1)	(1)
Deferred policy acquisition costs	101	100
Ending balance	101	100
Allstate Protection
Long Duration Contracts [Abstract]
Deferred policy acquisition costs	2,478	2,203
Ending balance	2,478	2,203
Protection Services
Long Duration Contracts [Abstract]
Deferred policy acquisition costs	3,072	2,874
Ending balance	$ 3,072	$ 2,874