Reinsurance (Reinsurance on premiums - short-duration contracts) (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Premiums Earned, Net, by Business [Abstract]
Total net earned premiums	$ 1,455	$ 1,385	$ 1,282
Property and casualty [Member]
Premiums Written, Net [Abstract]
Direct premiums written	1,093	1,025	900
Ceded premiums written	(19)	(17)	(16)
Total net written premiums	1,074	1,008	884
Premiums Earned, Net, by Business [Abstract]
Direct premiums earned	1,068	979	868
Ceded premiums earned	(19)	(17)	(16)
Total net earned premiums	$ 1,049	$ 962	$ 852