Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 107,791	$ 113,375
Derivative Asset, Fair Value, Gross Asset	9,776	3,222
Derivative Liability, Fair Value, Gross Liability	7,706	7,119
Embedded Derivative, Fair Value of Embedded Derivative Asset	316	217
Embedded Derivative, Fair Value of Embedded Derivative Liability	5,063	4,582
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,151	3,121
Derivative Asset, Fair Value, Gross Asset	725	198
Derivative Liability, Fair Value, Gross Liability	2	27
Derivatives Designated as Hedging Instruments: | Cash flow hedges: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	390	420
Derivative Asset, Fair Value, Gross Asset	114	22
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Designated as Hedging Instruments: | Cash flow hedges: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,761	2,701
Derivative Asset, Fair Value, Gross Asset	611	176
Derivative Liability, Fair Value, Gross Liability	2	27
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	104,640	110,254
Derivative Asset, Fair Value, Gross Asset	8,735	2,807
Derivative Liability, Fair Value, Gross Liability	2,641	2,510
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,060	7,559
Derivative Asset, Fair Value, Gross Asset	739	878
Derivative Liability, Fair Value, Gross Liability	7	29
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate caps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,350	3,350
Derivative Asset, Fair Value, Gross Asset	1	2
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]
Derivative, Notional Amount	27,650	29,750
Derivative Asset, Fair Value, Gross Asset	3,657	782
Derivative Liability, Fair Value, Gross Liability	833	187
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,656	5,418
Derivative Asset, Fair Value, Gross Asset	1,439	94
Derivative Liability, Fair Value, Gross Liability	0	114
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,027	1,040
Derivative Asset, Fair Value, Gross Asset	215	94
Derivative Liability, Fair Value, Gross Liability	13	15
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	142	138
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	1	1
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	18	18
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: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,876	1,613
Derivative Asset, Fair Value, Gross Asset	7	36
Derivative Liability, Fair Value, Gross Liability	13	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	51,247	51,509
Derivative Asset, Fair Value, Gross Asset	1,243	850
Derivative Liability, Fair Value, Gross Liability	1,655	1,728
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,098	2,136
Derivative Asset, Fair Value, Gross Asset	11	69
Derivative Liability, Fair Value, Gross Liability	30	69
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,516	7,723
Derivative Asset, Fair Value, Gross Asset	1,423	2
Derivative Liability, Fair Value, Gross Liability	89	367
Ceded Guaranteed Minimum Benefit
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	316	217
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	4,190	1,548
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	709	442
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	(116)	2,253
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	$ 280	$ 339