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