Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 326,561		$ 326,561		$ 299,154
Estimated Fair Value Assets	10,519		10,519		11,866
Estimated Fair Value Liabilities	3,751		3,751		$ 4,229
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	6	$ (8)	$ 5	$ 19
Maximum Length of Time Hedged in Cash Flow Hedge			8 years		8 years
Accumulated Other Comprehensive Income Loss	2,000		$ 2,000		$ 1,900
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	61,847		61,847		60,723
Estimated Fair Value Assets	3,991		3,991		5,432
Estimated Fair Value Liabilities	1,698		1,698		2,222
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,002		6,002		6,228
Estimated Fair Value Assets	2,162		2,162		3,256
Estimated Fair Value Liabilities	86		86		82
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,549		3,549		3,186
Estimated Fair Value Assets	2,154		2,154		3,224
Estimated Fair Value Liabilities	2		2		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	8		8		8
Estimated Fair Value Liabilities	32		32		78
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,545		1,545		1,936
Estimated Fair Value Assets	0		0		24
Estimated Fair Value Liabilities	52		52		0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	52,504		52,504		50,731
Estimated Fair Value Assets	1,697		1,697		2,106
Estimated Fair Value Liabilities	1,612		1,612		2,137
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,429		4,429		4,750
Estimated Fair Value Assets	35		35		44
Estimated Fair Value Liabilities	1		1		0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,874		6,874		7,377
Estimated Fair Value Assets	60		60		513
Estimated Fair Value Liabilities	155		155		120
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	41,201		41,201		38,604
Estimated Fair Value Assets	1,602		1,602		1,549
Estimated Fair Value Liabilities	1,456		1,456		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	132		132		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	18		18		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	114		114		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	264,714		264,714		238,431
Estimated Fair Value Assets	6,528		6,528		6,434
Estimated Fair Value Liabilities	2,053		2,053		2,007
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	41,430		41,430		49,561
Estimated Fair Value Assets	3,793		3,793		3,683
Estimated Fair Value Liabilities	144		144		38
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	367		367		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	8,201		8,201		12,701
Estimated Fair Value Assets	202		202		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	77,814		77,814		40,730
Estimated Fair Value Assets	69		69		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	2,239		2,239		1,498
Estimated Fair Value Assets	3		3		0
Estimated Fair Value Liabilities	1		1		2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	12,508		12,508		17,746
Estimated Fair Value Assets	485		485		502
Estimated Fair Value Liabilities	17		17		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	6		6		0
Estimated Fair Value Liabilities	31		31		59
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	39,365		39,365		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	12,635		12,635		13,265
Estimated Fair Value Assets	690		690		603
Estimated Fair Value Liabilities	664		664		693
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	15,911		15,911		15,643
Estimated Fair Value Assets	99		99		209
Estimated Fair Value Liabilities	563		563		310
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	867		867		914
Estimated Fair Value Assets	1		1		3
Estimated Fair Value Liabilities	0		0		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	3,042		3,042		2,978
Estimated Fair Value Assets	14		14		9
Estimated Fair Value Liabilities	110		110		121
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	8,739		8,739		9,609
Estimated Fair Value Assets	180		180		196
Estimated Fair Value Liabilities	5		5		0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,417		4,417		5,427
Estimated Fair Value Assets	48		48		14
Estimated Fair Value Liabilities	14		14		38
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	31,016		31,016		22,954
Estimated Fair Value Assets	898		898		834
Estimated Fair Value Liabilities	441		441		437
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	733		733		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	3,482		3,482		3,294
Estimated Fair Value Assets	23		23		3
Estimated Fair Value Liabilities	$ 11		$ 11		$ 282