Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Gross Notional Amount	$ 401,246	$ 404,844
Estimated Fair Value Assets	18,747	14,406
Estimated Fair Value Liabilities	8,122	7,049
Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Gross Notional Amount	49,399	46,808
Estimated Fair Value Assets	4,883	4,358
Estimated Fair Value Liabilities	1,929	2,074
Derivatives Designated as Hedging Instruments | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	9,111	9,367
Estimated Fair Value Assets	2,724	2,277
Estimated Fair Value Liabilities	159	223
Derivatives Designated as Hedging Instruments | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,491	5,528
Estimated Fair Value Assets	2,596	2,215
Estimated Fair Value Liabilities	17	12
Derivatives Designated as Hedging Instruments | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,135	2,154
Estimated Fair Value Assets	66	62
Estimated Fair Value Liabilities	142	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	62	0
Estimated Fair Value Liabilities	0	52
Derivatives Designated as Hedging Instruments | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	27,101	25,956
Estimated Fair Value Assets	2,116	1,813
Estimated Fair Value Liabilities	1,511	1,803
Derivatives Designated as Hedging Instruments | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,945	2,190
Estimated Fair Value Assets	643	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	35	105
Estimated Fair Value Assets	12	23
Estimated Fair Value Liabilities	0	0
Derivatives Designated as Hedging Instruments | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	25,121	23,661
Estimated Fair Value Assets	1,461	1,303
Estimated Fair Value Liabilities	1,511	1,803
Derivatives Designated as Hedging Instruments | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	13,187	11,485
Estimated Fair Value Assets	43	268
Estimated Fair Value Liabilities	259	48
Derivatives Designated as Hedging Instruments | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,043	3,916
Estimated Fair Value Assets	2	63
Estimated Fair Value Liabilities	179	12
Derivatives Designated as Hedging Instruments | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,144	7,569
Estimated Fair Value Assets	41	205
Estimated Fair Value Liabilities	80	36
Derivatives Not Designated or Not Qualifying as Hedging Instruments
Derivatives, Fair Value [Line Items]
Gross Notional Amount	351,847	358,036
Estimated Fair Value Assets	13,864	10,048
Estimated Fair Value Liabilities	6,193	4,975
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	80,829	89,336
Estimated Fair Value Assets	7,277	5,111
Estimated Fair Value Liabilities	3,215	2,247
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Interest rate forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	43	43
Estimated Fair Value Assets	5	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	20,837	23,837
Estimated Fair Value Assets	386	311
Estimated Fair Value Liabilities	53	48
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Interest rate caps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	70,928	68,928
Estimated Fair Value Assets	70	105
Estimated Fair Value Liabilities	3	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Interest rate futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	6,652	5,808
Estimated Fair Value Assets	21	4
Estimated Fair Value Liabilities	7	7
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Interest rate options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	27,590	30,234
Estimated Fair Value Assets	2,316	1,177
Estimated Fair Value Liabilities	2	30
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Synthetic GICs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	3,980	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	11,512	11,081
Estimated Fair Value Assets	768	766
Estimated Fair Value Liabilities	459	431
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	14,539	11,724
Estimated Fair Value Assets	388	154
Estimated Fair Value Liabilities	187	220
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Currency futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	985	930
Estimated Fair Value Assets	1	0
Estimated Fair Value Liabilities	1	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Currency options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,016	9,590
Estimated Fair Value Assets	337	466
Estimated Fair Value Liabilities	66	189
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,079	1,870
Estimated Fair Value Assets	22	28
Estimated Fair Value Liabilities	22	34
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Gross Notional Amount	10,729	10,311
Estimated Fair Value Assets	105	78
Estimated Fair Value Liabilities	11	13
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Equity futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	11,768	7,206
Estimated Fair Value Assets	28	63
Estimated Fair Value Liabilities	15	18
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Equity index options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	53,981	55,682
Estimated Fair Value Assets	1,924	1,542
Estimated Fair Value Liabilities	1,241	1,041
Derivatives Not Designated or Not Qualifying as Hedging Instruments | Equity variance swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	23,466	23,437
Estimated Fair Value Assets	208	195
Estimated Fair Value Liabilities	682	636
Derivatives Not Designated or Not Qualifying as Hedging Instruments | TRRs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	3,913	3,803
Estimated Fair Value Assets	8	47
Estimated Fair Value Liabilities	$ 229	$ 58