Derivatives (Primary Risks) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Gross Notional Amount	$ 414,040	$ 404,844
Estimated Fair Value Assets	21,788	14,406
Estimated Fair Value Liabilities	8,352	7,049
Derivatives Designated as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	49,873	46,808
Estimated Fair Value Assets	6,005	4,358
Estimated Fair Value Liabilities	2,143	2,074
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,089	9,367
Estimated Fair Value Assets	3,048	2,277
Estimated Fair Value Liabilities	170	223
Derivatives Designated as Hedging Instruments: | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,383	5,528
Estimated Fair Value Assets	2,824	2,215
Estimated Fair Value Liabilities	14	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	28	62
Estimated Fair Value Liabilities	156	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	196	0
Estimated Fair Value Liabilities	0	52
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	31,485	25,956
Estimated Fair Value Assets	2,933	1,813
Estimated Fair Value Liabilities	1,694	1,803
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,251	2,190
Estimated Fair Value Assets	672	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	2,032	105
Estimated Fair Value Assets	49	23
Estimated Fair Value Liabilities	10	0
Derivatives Designated as Hedging Instruments: | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	27,202	23,661
Estimated Fair Value Assets	2,212	1,303
Estimated Fair Value Liabilities	1,684	1,803
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	10,299	11,485
Estimated Fair Value Assets	24	268
Estimated Fair Value Liabilities	279	48
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,087	3,916
Estimated Fair Value Assets	6	63
Estimated Fair Value Liabilities	53	12
Derivatives Designated as Hedging Instruments: | Foreign Operations Hedges [Member] | Currency options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	9,212	7,569
Estimated Fair Value Assets	18	205
Estimated Fair Value Liabilities	226	36
Derivatives Not Designated or Not Qualifying as Hedging Instruments:
Derivatives, Fair Value [Line Items]
Gross Notional Amount	364,167	358,036
Estimated Fair Value Assets	15,783	10,048
Estimated Fair Value Liabilities	6,209	4,975
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	82,791	89,336
Estimated Fair Value Assets	9,586	5,111
Estimated Fair Value Liabilities	3,033	2,247
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	171	43
Estimated Fair Value Assets	16	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	350	311
Estimated Fair Value Liabilities	34	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	35	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	9,110	5,808
Estimated Fair Value Assets	4	4
Estimated Fair Value Liabilities	41	7
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Interest rate options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	21,383	30,234
Estimated Fair Value Assets	1,790	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	5,925	0
Estimated Fair Value Assets	106	0
Estimated Fair Value Liabilities	36	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Synthetic GICs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,328	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	12,790	11,081
Estimated Fair Value Assets	1,183	766
Estimated Fair Value Liabilities	467	431
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	17,371	11,724
Estimated Fair Value Assets	584	154
Estimated Fair Value Liabilities	250	220
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Currency futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	1,060	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	4,780	9,590
Estimated Fair Value Assets	204	466
Estimated Fair Value Liabilities	11	189
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,038	1,870
Estimated Fair Value Assets	10	28
Estimated Fair Value Liabilities	44	34
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Gross Notional Amount	11,664	10,311
Estimated Fair Value Assets	150	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	12,886	7,206
Estimated Fair Value Assets	13	63
Estimated Fair Value Liabilities	68	18
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity index options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	53,911	55,682
Estimated Fair Value Assets	1,519	1,542
Estimated Fair Value Liabilities	1,362	1,041
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity variance swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	23,658	23,437
Estimated Fair Value Assets	228	195
Estimated Fair Value Liabilities	745	636
Derivatives Not Designated or Not Qualifying as Hedging Instruments: | Equity total return swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,070	3,803
Estimated Fair Value Assets	5	47
Estimated Fair Value Liabilities	$ 102	$ 58