Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 322,231	$ 311,853
Estimated Fair Value Assets	15,871	10,084
Estimated Fair Value Liabilities	4,001	3,737
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	60,412	59,290
Estimated Fair Value Assets	7,708	4,572
Estimated Fair Value Liabilities	2,118	1,761
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,329	6,009
Estimated Fair Value Assets	3,456	2,684
Estimated Fair Value Liabilities	42	59
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,220	2,369
Estimated Fair Value Assets	3,401	2,667
Estimated Fair Value Liabilities	13	2
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,073	1,304
Estimated Fair Value Assets	45	16
Estimated Fair Value Liabilities	1	17
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,036	2,336
Estimated Fair Value Assets	10	1
Estimated Fair Value Liabilities	28	40
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	50,288	48,022
Estimated Fair Value Assets	4,160	1,855
Estimated Fair Value Liabilities	2,070	1,601
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,972	3,675
Estimated Fair Value Assets	124	145
Estimated Fair Value Liabilities	35	27
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,038	7,364
Estimated Fair Value Assets	871	83
Estimated Fair Value Liabilities	64	144
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	37,278	36,983
Estimated Fair Value Assets	3,165	1,627
Estimated Fair Value Liabilities	1,971	1,430
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,795	5,259
Estimated Fair Value Assets	92	33
Estimated Fair Value Liabilities	6	101
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	595	1,059
Estimated Fair Value Assets	24	0
Estimated Fair Value Liabilities	6	10
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,200	4,200
Estimated Fair Value Assets	68	33
Estimated Fair Value Liabilities	0	91
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	261,819	252,563
Estimated Fair Value Assets	8,163	5,512
Estimated Fair Value Liabilities	1,883	1,976
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	51,032	58,083
Estimated Fair Value Assets	4,269	2,867
Estimated Fair Value Liabilities	83	185
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	130	129
Estimated Fair Value Assets	3	1
Estimated Fair Value Liabilities	1	2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate floors
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	12,701	12,701
Estimated Fair Value Assets	436	155
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate caps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	55,631	42,622
Estimated Fair Value Assets	21	18
Estimated Fair Value Liabilities	0	5
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,779	2,423
Estimated Fair Value Assets	2	2
Estimated Fair Value Liabilities	0	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	27,650	27,344
Estimated Fair Value Assets	1,007	764
Estimated Fair Value Liabilities	0	1
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,048	1,048
Estimated Fair Value Assets	79	5
Estimated Fair Value Liabilities	6	49
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	34,921	30,341
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	14,238	13,699
Estimated Fair Value Assets	1,130	644
Estimated Fair Value Liabilities	635	461
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	13,674	13,507
Estimated Fair Value Assets	60	50
Estimated Fair Value Liabilities	443	393
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	883	880
Estimated Fair Value Assets	0	7
Estimated Fair Value Liabilities	6	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,800	1,801
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,031	2,944
Estimated Fair Value Assets	25	4
Estimated Fair Value Liabilities	105	102
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	10,780	11,520
Estimated Fair Value Assets	120	272
Estimated Fair Value Liabilities	13	1
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,461	4,540
Estimated Fair Value Assets	3	6
Estimated Fair Value Liabilities	45	8
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	24,873	27,105
Estimated Fair Value Assets	975	694
Estimated Fair Value Liabilities	409	677
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	937	1,115
Estimated Fair Value Assets	33	23
Estimated Fair Value Liabilities	12	19
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,250	761
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	$ 125	$ 70