Derivatives (Gains Losses Recognized in Income Not Designated or Qualifying) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (40)	$ (7)
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	203	(357)
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	(235)	(390)
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	387	363
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	(3)	(8)
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	(44)	32
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	98	(354)
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Net investment income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	5	(1)
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	4	2
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
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
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
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	1	(3)
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	7	(70)
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	(7)	2
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	2	0
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
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
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	$ 12	$ (72)