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Derivatives (Primary Risks) (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2023
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | $ 297,041 |  | $ 301,234
Estimated Fair Value Assets | 8,291 |  | 8,737
Estimated Fair Value Liabilities | 6,985 |  | $ 6,298
Derivative, Gain (Loss) on Derivative, Net | 181 | $ 312 |
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net | $ (10) | 1 |
Maximum Length of Time Hedged in Cash Flow Hedge | 5 years |  | 5 years
Accumulated Other Comprehensive Income Loss | $ 182 |  | $ 166
Cash Flow Hedges [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | 0 | 0 |
Not Designated as Hedging Instrument, Economic Hedge | Derivative Contract [Domain] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Gain (Loss) on Derivative, Net | (295) | 153 |
Derivatives Designated as Hedging Instruments: |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 66,909 |  | 64,155
Estimated Fair Value Assets | 4,205 |  | 4,215
Estimated Fair Value Liabilities | 3,590 |  | 3,320
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 6,728 |  | 6,475
Estimated Fair Value Assets | 1,152 |  | 1,312
Estimated Fair Value Liabilities | 703 |  | 600
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 4,878 |  | 4,550
Estimated Fair Value Assets | 1,112 |  | 1,257
Estimated Fair Value Liabilities | 610 |  | 535
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 1,400 |  | 1,475
Estimated Fair Value Assets | 40 |  | 55
Estimated Fair Value Liabilities | 6 |  | 0
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 450 |  | 450
Estimated Fair Value Assets | 0 |  | 0
Estimated Fair Value Liabilities | 87 |  | 65
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 56,767 |  | 54,177
Estimated Fair Value Assets | 2,516 |  | 2,509
Estimated Fair Value Liabilities | 2,887 |  | 2,712
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 4,655 |  | 4,156
Estimated Fair Value Assets | 0 |  | 1
Estimated Fair Value Liabilities | 304 |  | 265
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 5,815 |  | 6,115
Estimated Fair Value Assets | 27 |  | 51
Estimated Fair Value Liabilities | 897 |  | 938
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 46,297 |  | 43,906
Estimated Fair Value Assets | 2,489 |  | 2,457
Estimated Fair Value Liabilities | 1,686 |  | 1,509
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 3,414 |  | 3,503
Estimated Fair Value Assets | 537 |  | 394
Estimated Fair Value Liabilities | 0 |  | 8
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 414 |  | 503
Estimated Fair Value Assets | 24 |  | 0
Estimated Fair Value Liabilities | 0 |  | 8
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 3,000 |  | 3,000
Estimated Fair Value Assets | 513 |  | 394
Estimated Fair Value Liabilities | 0 |  | 0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 230,132 |  | 237,079
Estimated Fair Value Assets | 4,086 |  | 4,522
Estimated Fair Value Liabilities | 3,395 |  | 2,978
Derivative, Gain (Loss) on Derivative, Net | (1,211) | $ (403) |
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 30,308 |  | 29,801
Estimated Fair Value Assets | 1,525 |  | 1,497
Estimated Fair Value Liabilities | 1,127 |  | 1,102
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 2,671 |  | 2,383
Estimated Fair Value Assets | 25 |  | 69
Estimated Fair Value Liabilities | 75 |  | 36
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate floors |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 13,171 |  | 15,321
Estimated Fair Value Assets | 34 |  | 41
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 | 30,322 |  | 30,016
Estimated Fair Value Assets | 313 |  | 373
Estimated Fair Value Liabilities | 0 |  | 0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 1,696 |  | 1,243
Estimated Fair Value Assets | 1 |  | 1
Estimated Fair Value Liabilities | 1 |  | 5
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 42,262 |  | 43,926
Estimated Fair Value Assets | 225 |  | 385
Estimated Fair Value Liabilities | 150 |  | 103
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 48,100 |  | 49,066
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 | 12,072 |  | 11,891
Estimated Fair Value Assets | 1,321 |  | 1,200
Estimated Fair Value Liabilities | 393 |  | 356
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 14,526 |  | 14,128
Estimated Fair Value Assets | 40 |  | 310
Estimated Fair Value Liabilities | 1,163 |  | 806
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 309 |  | 314
Estimated Fair Value Assets | 0 |  | 2
Estimated Fair Value Liabilities | 0 |  | 0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency options |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 95 |  | 50
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 | 2,837 |  | 2,877
Estimated Fair Value Assets | 0 |  | 3
Estimated Fair Value Liabilities | 83 |  | 79
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 13,901 |  | 12,468
Estimated Fair Value Assets | 271 |  | 233
Estimated Fair Value Liabilities | 7 |  | 5
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 1,988 |  | 2,163
Estimated Fair Value Assets | 5 |  | 8
Estimated Fair Value Liabilities | 6 |  | 11
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 13,738 |  | 19,421
Estimated Fair Value Assets | 326 |  | 399
Estimated Fair Value Liabilities | 249 |  | 255
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 116 |  | 99
Estimated Fair Value Assets | 0 |  | 0
Estimated Fair Value Liabilities | 3 |  | 2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 2,020 |  | 1,912
Estimated Fair Value Assets | 0 |  | 1
Estimated Fair Value Liabilities | 138 |  | 218
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Derivatives hedging MRBs |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 14,840 |  | 15,001
Estimated Fair Value Assets | 148 |  | 112
Estimated Fair Value Liabilities | 994 |  | 1,038
Not Designated as Hedging Instrument, Economic Hedge | Interest Rate Contract |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 9,106 |  | 9,096
Estimated Fair Value Assets | 6 |  | 13
Estimated Fair Value Liabilities | 724 |  | 663
Not Designated as Hedging Instrument, Economic Hedge | Foreign currency exchange rate |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 747 |  | 716
Estimated Fair Value Assets | 3 |  | 22
Estimated Fair Value Liabilities | 15 |  | 2
Not Designated as Hedging Instrument, Economic Hedge | Equity |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, Notional Amount | 4,987 |  | 5,189
Estimated Fair Value Assets | 139 |  | 77
Estimated Fair Value Liabilities | $ 255 |  | $ 373

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