Investments (Investment Income (Loss), Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Gains on sales and exchanges of investments, net	$ 13	$ 4	$ 15	$ 4
Investment impairment losses	(1)	(16)	(21)	(31)
Unrealized gains (losses) on securities underlying prepaid forward sale agreements	0	0	0	42
Mark to market adjustments on derivative component of prepaid forward sale agreements and indexed debt instruments	1	1	1	(37)
Interest and dividend income	31	28	60	56
Other, net	14	0	33	16
Investment income (loss), net	$ 58	$ 17	$ 88	$ 50