Reserve for Property-Liability Insurance Claims and Claims Expense (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	$ 81	$ (84)	$ (121)
Total auto
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	30	(238)	(237)
Catastrophes
Increase (decrease) in claims and claims expense
Losses from catastrophes, net of recoveries	1,720	1,990	1,250
Reserve reestimates | Other personal lines
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	22	13	(21)
Reserve reestimates | Discontinued Lines and Coverages
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	53	112	142
Catastrophe loss reestimates
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	15	43	(88)
Catastrophe loss reestimates | Homeowners
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves			$ (5)
Non-catastrophes loss reestimates | Homeowners
Increase (decrease) in claims and claims expense
Net increase (decrease) to reserves	$ (24)	$ 29