Derivatives (Primary Risks Managed by Derivatives) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 181,765	$ 173,236
Derivative assets	3,845	3,714
Derivative liabilities	5,373	5,088
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,423	3,939
Derivative assets	386	348
Derivative liabilities	31	45
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	177,342	169,297
Derivative assets	3,459	3,366
Derivative liabilities	5,342	5,043
Interest rate swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	31,565	31,252
Derivative assets	115	140
Derivative liabilities	144	103
Interest rate floors | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,500	3,500
Derivative assets	3	7
Derivative liabilities	0	1
Interest rate caps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	7,050	7,050
Derivative assets	20	19
Derivative liabilities	0	1
Interest rate options | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	23,580	33,680
Derivative assets	20	47
Derivative liabilities	269	167
Interest rate forwards | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	19,649	17,017
Derivative assets	92	32
Derivative liabilities	2,325	1,937
Interest rate forwards | Cash flow hedges: | Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	500	0
Derivative assets	9	0
Derivative liabilities	0	0
Foreign currency swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	737	747
Derivative assets	105	101
Derivative liabilities	0	1
Foreign currency swaps | Cash flow hedges: | Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,923	3,939
Derivative assets	377	348
Derivative liabilities	31	45
Foreign currency forwards | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	479	535
Derivative assets	2	0
Derivative liabilities	0	9
Credit default swaps — written | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,405	1,405
Derivative assets	29	27
Derivative liabilities	0	0
Credit default swaptions | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	300	0
Derivative assets	0	0
Derivative liabilities	1	0
Equity index options | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	23,490	20,099
Derivative assets	1,132	757
Derivative liabilities	884	687
Equity total return swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	65,287	53,742
Derivative assets	1,940	2,236
Derivative liabilities	1,719	2,137
Hybrid options | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	300	270
Derivative assets	1	0
Derivative liabilities	$ 0	$ 0