Derivatives (Earned Income On Derivatives) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	$ 785	$ 965	$ 886
Derivatives Designated as Hedging Instruments [Member] | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	299	267	206
Derivatives Designated as Hedging Instruments [Member] | Interest credited to policyholder account balances
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	(64)	(1)	27
Derivatives Designated as Hedging Instruments [Member] | Other expenses
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	(10)	(12)	(6)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	0	(1)	(6)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	551	705	663
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Total earned income	$ 9	$ 7	$ 2