Statutory Financial Information and Dividend Limitations - Allstates domestic insurance subsidiaries (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Amount per statutory accounting practices
Net income (loss)	$ 6,246	$ 4,411	$ 3,404
Capital and surplus	21,383	20,400
Property and casualty
Amount per statutory accounting practices
Net income (loss)	6,232	3,989	2,939
Capital and surplus	17,128	16,192
Allstate Annuities
Amount per statutory accounting practices
Net income (loss)	14	422	$ 465
Capital and surplus	$ 4,255	$ 4,208