Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 322,137	$ 307,459
Estimated Fair Value Assets	12,945	8,969
Estimated Fair Value Liabilities	3,680	3,930
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	56,617	54,384
Estimated Fair Value Assets	5,868	4,225
Estimated Fair Value Liabilities	1,792	2,297
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	5,856	5,819
Estimated Fair Value Assets	2,932	2,279
Estimated Fair Value Liabilities	19	20
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,305	2,446
Estimated Fair Value Assets	2,847	2,197
Estimated Fair Value Liabilities	3	2
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,155	1,233
Estimated Fair Value Assets	72	54
Estimated Fair Value Liabilities	0	0
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,396	2,140
Estimated Fair Value Assets	13	28
Estimated Fair Value Liabilities	16	18
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	46,375	42,468
Estimated Fair Value Assets	2,891	1,939
Estimated Fair Value Liabilities	1,682	2,048
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,724	3,515
Estimated Fair Value Assets	200	143
Estimated Fair Value Liabilities	0	1
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	6,983	3,022
Estimated Fair Value Assets	242	0
Estimated Fair Value Liabilities	16	216
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	35,668	35,931
Estimated Fair Value Assets	2,449	1,796
Estimated Fair Value Liabilities	1,666	1,831
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,386	6,097
Estimated Fair Value Assets	45	7
Estimated Fair Value Liabilities	91	229
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	436	960
Estimated Fair Value Assets	18	4
Estimated Fair Value Liabilities	1	27
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	3,950	5,137
Estimated Fair Value Assets	27	3
Estimated Fair Value Liabilities	90	202
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	265,520	253,075
Estimated Fair Value Assets	7,077	4,744
Estimated Fair Value Liabilities	1,888	1,633
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	56,457	54,891
Estimated Fair Value Assets	3,160	1,796
Estimated Fair Value Liabilities	194	175
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	235	234
Estimated Fair Value Assets	15	1
Estimated Fair Value Liabilities	0	15
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate floors
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	12,701	12,701
Estimated Fair Value Assets	212	102
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	55,638	54,575
Estimated Fair Value Assets	14	154
Estimated Fair Value Liabilities	6	1
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,967	2,353
Estimated Fair Value Assets	4	1
Estimated Fair Value Liabilities	1	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	29,919	26,690
Estimated Fair Value Assets	1,542	416
Estimated Fair Value Liabilities	0	0
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
Estimated Fair Value Assets	48	33
Estimated Fair Value Liabilities	8	2
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	28,098	25,700
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	13,235	11,388
Estimated Fair Value Assets	920	884
Estimated Fair Value Liabilities	498	458
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	13,213	13,417
Estimated Fair Value Assets	111	198
Estimated Fair Value Liabilities	296	213
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	891	847
Estimated Fair Value Assets	0	4
Estimated Fair Value Liabilities	3	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	1,861	2,040
Estimated Fair Value Assets	1	7
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	2,635	1,903
Estimated Fair Value Assets	9	25
Estimated Fair Value Liabilities	84	39
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	11,583	11,391
Estimated Fair Value Assets	231	95
Estimated Fair Value Liabilities	2	13
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	4,128	2,992
Estimated Fair Value Assets	7	13
Estimated Fair Value Liabilities	16	77
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	28,783	27,707
Estimated Fair Value Assets	759	884
Estimated Fair Value Liabilities	684	550
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	2,292	2,269
Estimated Fair Value Assets	41	40
Estimated Fair Value Liabilities	94	87
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	836	929
Estimated Fair Value Assets	3	91
Estimated Fair Value Liabilities	$ 2	$ 0