Derivatives (Primary Risks Managed by Derivatives) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 271,246	$ 277,286
Derivative assets	4,146	4,118
Derivative liabilities	5,286	5,248
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,246	4,278
Derivative assets	421	439
Derivative liabilities	27	25
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	267,000	273,008
Derivative assets	3,725	3,679
Derivative liabilities	5,259	5,223
Interest rate swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	43,020	69,303
Derivative assets	169	131
Derivative liabilities	267	444
Interest rate floors | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,500	8,000
Derivative assets	4	1
Derivative liabilities	12	30
Interest rate caps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	7,850	7,850
Derivative assets	4	14
Derivative liabilities	8	14
Interest rate futures | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	0	171
Derivative assets	0	0
Derivative liabilities	0	0
Interest rate options | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	28,300	23,060
Derivative assets	29	11
Derivative liabilities	359	371
Interest rate forwards | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	13,499	16,352
Derivative assets	52	121
Derivative liabilities	1,423	1,876
Interest rate forwards | Cash flow hedges: | Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	500	500
Derivative assets	2	9
Derivative liabilities	0	0
Foreign currency swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	665	674
Derivative assets	103	111
Derivative liabilities	1	0
Foreign currency swaps | Cash flow hedges: | Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,746	3,778
Derivative assets	419	430
Derivative liabilities	27	25
Foreign currency forwards | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	305	304
Derivative assets	2	6
Derivative liabilities	0	0
Credit default swaps — written | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	780	780
Derivative assets	16	19
Derivative liabilities	0	0
Equity futures | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	172	316
Derivative assets	1	0
Derivative liabilities	0	1
Equity index options | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	60,308	39,897
Derivative assets	1,660	1,722
Derivative liabilities	1,201	1,041
Equity total return swaps | Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	103,601	106,301
Derivative assets	1,685	1,543
Derivative liabilities	$ 1,988	$ 1,446