Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Gross Notional Amount	$ 400,821	$ 404,844
Estimated Fair Value Assets	23,563	14,406
Estimated Fair Value Liabilities	8,704	7,049
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	48,051	46,808
Estimated Fair Value Assets	6,140	4,358
Estimated Fair Value Liabilities	2,204	2,074
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,141	9,367
Estimated Fair Value Assets	3,043	2,277
Estimated Fair Value Liabilities	175	223
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,435	5,528
Estimated Fair Value Assets	2,831	2,215
Estimated Fair Value Liabilities	20	12
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,221	2,154
Estimated Fair Value Assets	26	62
Estimated Fair Value Liabilities	155	159
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,485	1,685
Estimated Fair Value Assets	186	0
Estimated Fair Value Liabilities	0	52
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	30,198	25,956
Estimated Fair Value Assets	3,077	1,813
Estimated Fair Value Liabilities	1,769	1,803
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,332	2,190
Estimated Fair Value Assets	695	487
Estimated Fair Value Liabilities	0	0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,610	105
Estimated Fair Value Assets	56	23
Estimated Fair Value Liabilities	2	0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	26,256	23,661
Estimated Fair Value Assets	2,326	1,303
Estimated Fair Value Liabilities	1,767	1,803
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	9,712	11,485
Estimated Fair Value Assets	20	268
Estimated Fair Value Liabilities	260	48
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,466	3,916
Estimated Fair Value Assets	4	63
Estimated Fair Value Liabilities	61	12
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,246	7,569
Estimated Fair Value Assets	16	205
Estimated Fair Value Liabilities	199	36
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	352,770	358,036
Estimated Fair Value Assets	17,423	10,048
Estimated Fair Value Liabilities	6,500	4,975
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	74,587	89,336
Estimated Fair Value Assets	9,659	5,111
Estimated Fair Value Liabilities	3,472	2,247
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	128	43
Estimated Fair Value Assets	11	1
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate floors
Derivatives, Fair Value [Line Items]
Gross Notional Amount	15,201	23,837
Estimated Fair Value Assets	407	311
Estimated Fair Value Liabilities	47	48
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate caps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	79,030	68,928
Estimated Fair Value Assets	36	105
Estimated Fair Value Liabilities	2	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	7,969	5,808
Estimated Fair Value Assets	2	4
Estimated Fair Value Liabilities	12	7
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	23,156	30,234
Estimated Fair Value Assets	2,417	1,177
Estimated Fair Value Liabilities	1	30
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,775	0
Estimated Fair Value Assets	172	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	3,962	4,216
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]
Gross Notional Amount	12,655	11,081
Estimated Fair Value Assets	1,120	766
Estimated Fair Value Liabilities	522	431
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	17,822	11,724
Estimated Fair Value Assets	1,083	154
Estimated Fair Value Liabilities	260	220
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,009	930
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	2	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	6,137	9,590
Estimated Fair Value Assets	218	466
Estimated Fair Value Liabilities	6	189
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,823	1,870
Estimated Fair Value Assets	16	28
Estimated Fair Value Liabilities	37	34
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Gross Notional Amount	11,183	10,311
Estimated Fair Value Assets	106	78
Estimated Fair Value Liabilities	10	13
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	12,649	7,206
Estimated Fair Value Assets	2	63
Estimated Fair Value Liabilities	194	18
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	55,075	55,682
Estimated Fair Value Assets	1,906	1,542
Estimated Fair Value Liabilities	1,218	1,041
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	23,608	23,437
Estimated Fair Value Assets	209	195
Estimated Fair Value Liabilities	682	636
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	4,001	3,803
Estimated Fair Value Assets	59	47
Estimated Fair Value Liabilities	$ 35	$ 58