Reinsurance (Reinsurance on premiums - short-duration contracts) (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums Earned, Net, by Business [Abstract]
Total net earned premiums	$ 1,491	$ 1,455	$ 1,385
Property and casualty [Member]
Premiums Written, Net [Abstract]
Direct premiums written	1,085	1,093	1,025
Ceded premiums written	(20)	(19)	(17)
Total net written premiums	1,065	1,074	1,008
Premiums Earned, Net, by Business [Abstract]
Direct premiums earned	1,094	1,068	979
Ceded premiums earned	(20)	(19)	(17)
Total net earned premiums	$ 1,074	$ 1,049	$ 962