Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Gross Notional Amount	$ 98,841	$ 92,676
Derivative Asset, Fair Value, Gross Asset	3,093	2,993
Derivative Liability, Fair Value, Gross Liability	5,871	4,628
Embedded Derivative, Fair Value of Embedded Derivative Asset	253	228
Embedded Derivative, Fair Value of Embedded Derivative Liability	3,703	2,516
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,634	2,461
Derivative Asset, Fair Value, Gross Asset	220	200
Derivative Liability, Fair Value, Gross Liability	38	30
Derivatives Designated as Hedging Instruments: | Cash flow hedges: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,634	2,461
Derivative Asset, Fair Value, Gross Asset	220	200
Derivative Liability, Fair Value, Gross Liability	38	30
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	96,207	90,215
Derivative Asset, Fair Value, Gross Asset	2,620	2,565
Derivative Liability, Fair Value, Gross Liability	2,130	2,082
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	7,960	10,747
Derivative Asset, Fair Value, Gross Asset	873	528
Derivative Liability, Fair Value, Gross Liability	37	558
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate caps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	3,350	3,350
Derivative Asset, Fair Value, Gross Asset	4	21
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	0	53
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	25,445	17,168
Derivative Asset, Fair Value, Gross Asset	753	168
Derivative Liability, Fair Value, Gross Liability	111	61
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forward
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,237	0
Derivative Asset, Fair Value, Gross Asset	16	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,097	1,398
Derivative Asset, Fair Value, Gross Asset	112	99
Derivative Liability, Fair Value, Gross Liability	15	18
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	138	125
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Gross Notional Amount	12	98
Derivative Asset, Fair Value, Gross Asset	0	3
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,883	1,798
Derivative Asset, Fair Value, Gross Asset	32	14
Derivative Liability, Fair Value, Gross Liability	0	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	0	169
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	43,450	45,815
Derivative Asset, Fair Value, Gross Asset	731	1,372
Derivative Liability, Fair Value, Gross Liability	1,627	1,207
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,574	5,574
Derivative Asset, Fair Value, Gross Asset	95	80
Derivative Liability, Fair Value, Gross Liability	247	232
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,061	3,920
Derivative Asset, Fair Value, Gross Asset	4	280
Derivative Liability, Fair Value, Gross Liability	92	3
Ceded Guaranteed Minimum Benefit
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	253	228
Embedded Derivative, Fair Value of Embedded Derivative Liability	0	0
Direct Guaranteed Minimum Benefit
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Embedded Derivative, Fair Value of Embedded Derivative Liability	1,563	1,546
Assumed Guaranteed Minimum Benefit
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Embedded Derivative, Fair Value of Embedded Derivative Liability	436	386
Direct index-linked annuities
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Embedded Derivative, Fair Value of Embedded Derivative Liability	1,516	488
Direct index-linked annuities | Assumed
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	0	0
Embedded Derivative, Fair Value of Embedded Derivative Liability	$ 188	$ 96