Insurance (Details 2) - Property and casualty insurance [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effects of Reinsurance [Line Items]
Direct premiums written	$ 5,713	$ 5,387	$ 4,744
Reinsurance assumed	119	90	61
Reinsurance ceded	(1,505)	(1,457)	(1,464)
Net written premiums	4,327	4,020	3,341
Direct premiums earned	5,613	5,195	4,684
Reinsurance assumed	105	75	45
Reinsurance ceded	(1,494)	(1,392)	(1,525)
Net earned premiums	4,224	3,878	3,204
Reinsurance recoveries	$ 936	$ 895	$ 1,255