Derivatives (Gains Losses Recognized in Income Not Designated or Qualifying) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (125)	$ 71	$ (165)	$ 64
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(271)	(667)	(68)	(1,024)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses) | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(75)	72	(310)	(318)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses) | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	(544)	386	(181)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses) | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	14	(7)	11	(15)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses) | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(35)	44	(79)	76
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net derivative gains (losses) | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(174)	(232)	(76)	(586)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(3)	5	(4)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(2)	4	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(1)	1	(4)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(43)	(56)	(36)	(126)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(5)	(15)	(12)	(13)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(5)	2	(3)	2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Policyholder benefits and claims | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (33)	$ (43)	$ (21)	$ (115)