Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 329,791		$ 329,791		$ 299,154
Estimated Fair Value Assets	10,361		10,361		11,866
Estimated Fair Value Liabilities	4,028		4,028		$ 4,229
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	1	$ 32	$ (1)	$ 27
Maximum Length of Time Hedged in Cash Flow Hedge			8 years		8 years
Accumulated Other Comprehensive Income Loss	1,400		$ 1,400		$ 1,900
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	62,252		62,252		60,723
Estimated Fair Value Assets	3,750		3,750		5,432
Estimated Fair Value Liabilities	2,034		2,034		2,222
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,225		6,225		6,228
Estimated Fair Value Assets	2,171		2,171		3,256
Estimated Fair Value Liabilities	139		139		82
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,581		3,581		3,186
Estimated Fair Value Assets	2,165		2,165		3,224
Estimated Fair Value Liabilities	3		3		4
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	908		908		1,106
Estimated Fair Value Assets	6		6		8
Estimated Fair Value Liabilities	59		59		78
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,736		1,736		1,936
Estimated Fair Value Assets	0		0		24
Estimated Fair Value Liabilities	77		77		0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	52,686		52,686		50,731
Estimated Fair Value Assets	1,458		1,458		2,106
Estimated Fair Value Liabilities	1,895		1,895		2,137
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,480		4,480		4,750
Estimated Fair Value Assets	25		25		44
Estimated Fair Value Liabilities	0		0		0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	7,234		7,234		7,377
Estimated Fair Value Assets	75		75		513
Estimated Fair Value Liabilities	183		183		120
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	40,972		40,972		38,604
Estimated Fair Value Assets	1,358		1,358		1,549
Estimated Fair Value Liabilities	1,712		1,712		2,017
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,341		3,341		3,764
Estimated Fair Value Assets	121		121		70
Estimated Fair Value Liabilities	0		0		3
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	341		341		164
Estimated Fair Value Assets	8		8		0
Estimated Fair Value Liabilities	0		0		3
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,000		3,000		3,600
Estimated Fair Value Assets	113		113		70
Estimated Fair Value Liabilities	0		0		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	267,539		267,539		238,431
Estimated Fair Value Assets	6,611		6,611		6,434
Estimated Fair Value Liabilities	1,994		1,994		2,007
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	43,920		43,920		49,561
Estimated Fair Value Assets	3,923		3,923		3,683
Estimated Fair Value Liabilities	64		64		38
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	309		309		351
Estimated Fair Value Assets	0		0		0
Estimated Fair Value Liabilities	37		37		10
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate floors
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	12,201		12,201		12,701
Estimated Fair Value Assets	241		241		350
Estimated Fair Value Liabilities	0		0		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate caps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	76,614		76,614		40,730
Estimated Fair Value Assets	63		63		13
Estimated Fair Value Liabilities	0		0		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,427		2,427		1,498
Estimated Fair Value Assets	0		0		0
Estimated Fair Value Liabilities	4		4		2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	13,342		13,342		17,746
Estimated Fair Value Assets	541		541		502
Estimated Fair Value Liabilities	25		25		5
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		1,048
Estimated Fair Value Assets	15		15		0
Estimated Fair Value Liabilities	22		22		59
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	37,773		37,773		38,646
Estimated Fair Value Assets	0		0		0
Estimated Fair Value Liabilities	0		0		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	12,667		12,667		13,265
Estimated Fair Value Assets	624		624		603
Estimated Fair Value Liabilities	591		591		693
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	14,810		14,810		15,643
Estimated Fair Value Assets	119		119		209
Estimated Fair Value Liabilities	569		569		310
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	869		869		914
Estimated Fair Value Assets	0		0		3
Estimated Fair Value Liabilities	4		4		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	900		900		1,350
Estimated Fair Value Assets	0		0		0
Estimated Fair Value Liabilities	0		0		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,999		2,999		2,978
Estimated Fair Value Assets	12		12		9
Estimated Fair Value Liabilities	115		115		121
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	9,216		9,216		9,609
Estimated Fair Value Assets	192		192		196
Estimated Fair Value Liabilities	6		6		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,227		4,227		5,427
Estimated Fair Value Assets	9		9		14
Estimated Fair Value Liabilities	9		9		38
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	30,947		30,947		22,954
Estimated Fair Value Assets	853		853		834
Estimated Fair Value Liabilities	478		478		437
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	716		716		716
Estimated Fair Value Assets	17		17		15
Estimated Fair Value Liabilities	15		15		12
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,554		2,554		3,294
Estimated Fair Value Assets	2		2		3
Estimated Fair Value Liabilities	$ 55		$ 55		$ 282