Derivatives (Earned Income On Derivatives) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	$ 73	$ 133	$ 277	$ 344
Derivatives Designated as Hedging Instruments: | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	5	5	16	13
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	67	124	253	320
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	$ 1	$ 4	$ 8	$ 11