Derivatives (Primary Risks) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Gross Notional Amount	$ 206,302	$ 179,075
Estimated Fair Value Assets	7,104	4,141
Estimated Fair Value Liabilities	2,732	2,322
Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	25,497	21,880
Estimated Fair Value Assets	3,062	1,983
Estimated Fair Value Liabilities	733	802
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,341	8,531
Estimated Fair Value Assets	2,096	1,529
Estimated Fair Value Liabilities	119	190
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,632	5,940
Estimated Fair Value Assets	2,031	1,277
Estimated Fair Value Liabilities	18	68
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,709	2,591
Estimated Fair Value Assets	65	252
Estimated Fair Value Liabilities	101	122
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	17,156	13,349
Estimated Fair Value Assets	966	454
Estimated Fair Value Liabilities	614	612
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	2,191	2,584
Estimated Fair Value Assets	447	77
Estimated Fair Value Liabilities	0	109
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest rate forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	70	205
Estimated Fair Value Assets	18	3
Estimated Fair Value Liabilities	0	3
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	14,895	10,560
Estimated Fair Value Assets	501	374
Estimated Fair Value Liabilities	614	500
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Gross Notional Amount	180,805	157,195
Estimated Fair Value Assets	4,042	2,158
Estimated Fair Value Liabilities	1,999	1,520
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	56,394	59,022
Estimated Fair Value Assets	2,213	1,320
Estimated Fair Value Liabilities	1,072	732
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate floors
Derivatives, Fair Value [Line Items]
Gross Notional Amount	36,141	38,220
Estimated Fair Value Assets	319	323
Estimated Fair Value Liabilities	108	234
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate caps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	41,227	29,809
Estimated Fair Value Assets	134	141
Estimated Fair Value Liabilities	1	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	70	105
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	6,399	4,849
Estimated Fair Value Assets	379	120
Estimated Fair Value Liabilities	15	8
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Synthetic GICs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	4,298	4,409
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Foreign currency swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	8,774	7,267
Estimated Fair Value Assets	359	79
Estimated Fair Value Liabilities	176	492
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Gross Notional Amount	3,985	4,261
Estimated Fair Value Assets	92	44
Estimated Fair Value Liabilities	80	32
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Credit default swaps — purchased
Derivatives, Fair Value [Line Items]
Gross Notional Amount	857	1,506
Estimated Fair Value Assets	8	7
Estimated Fair Value Liabilities	11	21
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Credit default swaps — written
Derivatives, Fair Value [Line Items]
Gross Notional Amount	7,419	6,600
Estimated Fair Value Assets	130	124
Estimated Fair Value Liabilities	5	1
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity futures
Derivatives, Fair Value [Line Items]
Gross Notional Amount	954	0
Estimated Fair Value Assets	10	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity index options
Derivatives, Fair Value [Line Items]
Gross Notional Amount	7,698	1,147
Estimated Fair Value Assets	328	0
Estimated Fair Value Liabilities	352	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity variance swaps
Derivatives, Fair Value [Line Items]
Gross Notional Amount	5,678	0
Estimated Fair Value Assets	60	0
Estimated Fair Value Liabilities	146	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | TRRs
Derivatives, Fair Value [Line Items]
Gross Notional Amount	911	0
Estimated Fair Value Assets	10	0
Estimated Fair Value Liabilities	$ 33	$ 0