Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 106,224	$ 92,676
Derivative Asset, Fair Value, Gross Asset	4,798	2,993
Derivative Liability, Fair Value, Gross Liability	6,909	4,628
Embedded Derivative, Fair Value of Embedded Derivative Asset	303	228
Embedded Derivative, Fair Value of Embedded Derivative Liability	4,673	2,516
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,134	2,461
Derivative Asset, Fair Value, Gross Asset	355	200
Derivative Liability, Fair Value, Gross Liability	16	30
Derivatives Designated as Hedging Instruments: | Cash flow hedges: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	460	0
Derivative Asset, Fair Value, Gross Asset	51	0
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	2,674	2,461
Derivative Asset, Fair Value, Gross Asset	304	200
Derivative Liability, Fair Value, Gross Liability	16	30
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	103,090	90,215
Derivative Asset, Fair Value, Gross Asset	4,140	2,565
Derivative Liability, Fair Value, Gross Liability	2,220	2,082
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,730	10,747
Derivative Asset, Fair Value, Gross Asset	1,049	528
Derivative Liability, Fair Value, Gross Liability	32	558
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	2	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]
Derivative, 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]
Derivative, Notional Amount	27,250	17,168
Derivative Asset, Fair Value, Gross Asset	1,771	168
Derivative Liability, Fair Value, Gross Liability	375	61
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,143	0
Derivative Asset, Fair Value, Gross Asset	241	0
Derivative Liability, Fair Value, Gross Liability	15	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,066	1,398
Derivative Asset, Fair Value, Gross Asset	143	99
Derivative Liability, Fair Value, Gross Liability	13	18
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	118	125
Derivative Asset, Fair Value, Gross Asset	2	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Derivative, 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]
Derivative, Notional Amount	1,712	1,798
Derivative Asset, Fair Value, Gross Asset	30	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]
Derivative, 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]
Derivative, Notional Amount	46,098	45,815
Derivative Asset, Fair Value, Gross Asset	766	1,372
Derivative Liability, Fair Value, Gross Liability	1,503	1,207
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	5,574	5,574
Derivative Asset, Fair Value, Gross Asset	95	80
Derivative Liability, Fair Value, Gross Liability	249	232
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	5,037	3,920
Derivative Asset, Fair Value, Gross Asset	41	280
Derivative Liability, Fair Value, Gross Liability	33	3
Ceded Guaranteed Minimum Benefit
Derivatives, Fair Value [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	303	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	2,250	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	541	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	1,566	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	$ 316	$ 96