Derivatives (Gains Losses Recognized in Income Not Designated or Qualifying) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (14)	$ (56)	$ (300)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(2,216)	(758)	(254)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses) | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(549)	(990)	(354)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses) | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(742)	882	502
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses) | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(24)	(40)	7
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses) | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	145	71	(69)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net derivative gains (losses) | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1,046)	(681)	(340)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(8)	(16)	(13)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	1	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	(3)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Net Investment Income | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(9)	(16)	(10)
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(248)	(110)	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims | Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	46	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims | Foreign currency exchange rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	5	(18)	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims | Credit derivatives — purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims | Credit derivatives — written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Policyholder benefits and claims | Equity derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (252)	$ (138)	$ 0