Reporting Segments - Performance data and tax items (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information
Amortization of DAC	$ 5,533	$ 5,222	$ 4,784
Income tax expense	1,242	468	995
Allstate Protection
Segment Reporting Information
Amortization of DAC	4,649	4,475	4,205
Service Businesses
Segment Reporting Information
Amortization of DAC	543	463	296
Income tax expense	(18)	(19)	(194)
Allstate Life
Segment Reporting Information
Amortization of DAC	173	132	134
Income tax expense	53	75	(226)
Allstate Benefits
Segment Reporting Information
Amortization of DAC	161	145	142
Income tax expense	35	32	1
Allstate Annuities
Segment Reporting Information
Amortization of DAC	7	7	7
Income tax expense	73	(66)	(58)
Property-Liability
Segment Reporting Information
Income tax expense	1,196	613	1,285
Corporate and Other
Segment Reporting Information
Income tax expense	$ (97)	$ (167)	$ 187