Investments (Net change in unrealized gains (losses) on investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net change in unrealized gains (losses) on investments	$ (1,119)	$ 1,517	$ (2,556)
Fixed maturity securities [Member]
Net change in unrealized gains (losses) on investments	(1,114)	1,511	(2,541)
Total equity securities available-for-sale [Member]
Net change in unrealized gains (losses) on investments	(6)	6	(15)
Other [Member]
Net change in unrealized gains (losses) on investments	$ 1	$ 0	$ 0