Reporting Segments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	4
Period within which an unusual or infrequent item is unlikely to recur	2 years
Prior period with no similar unusual or infrequent item	2 years
Outside United States
Segment Reporting Information
Revenues from external customers generated outside the United States	$ 0	$ 0	$ 0
Allstate Protection
Segment Reporting Information
Revenues from external customers generated outside the United States	$ 1,030	$ 1,080	$ 1,060