Derivatives (Net Derivative Gains Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components of Net Derivatives Gains (Losses)
Derivatives and hedging gains (losses)	$ 1,001	$ (1,389)	$ (509)
Embedded derivative gains (losses)	(150)	799	(181)
Total net derivative gains (losses)	$ 851	$ (590)	$ (690)