Derivatives (Net Derivative Gains Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Components of Net Derivatives Gains (Losses)
Derivatives and hedging gains (losses)	$ (424)	$ (820)	$ (1,084)	$ 2,918
Embedded derivatives gains (losses)	234	277	421	(1,480)
Total net derivative gains (losses)	$ (190)	$ (543)	$ (663)	$ 1,438