Investments (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at January 1	$ 170	$ 194	$ 192
Additional credit impairments on:
Previously impaired securities	1	0	0
Securities without prior impairments	2	0	3
Reductions due to:
Sales or redemptions	(9)	(24)	(1)
Sale of subsidiaries	(4)	0	0
Balance at December 31	$ 160	$ 170	$ 194