Derivatives (Primary Risks) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Notional Amount	$ 378,723	$ 334,351
Estimated Fair Value Assets	10,434	13,777
Estimated Fair Value Liabilities	4,945	5,536
Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	33,750	28,866
Estimated Fair Value Assets	2,761	3,402
Estimated Fair Value Liabilities	694	594
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	8,438	8,584
Estimated Fair Value Assets	1,680	2,253
Estimated Fair Value Liabilities	225	175
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	5,434	5,397
Estimated Fair Value Assets	1,469	1,921
Estimated Fair Value Liabilities	58	90
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member] | Foreign currency swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	3,004	3,187
Estimated Fair Value Assets	211	332
Estimated Fair Value Liabilities	167	85
Derivatives Designated as Hedging Instruments [Member] | Fair Value Hedges [Member] | Foreign currency forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	0	0
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	16,143	13,355
Estimated Fair Value Assets	718	1,063
Estimated Fair Value Liabilities	461	355
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	3,382	3,642
Estimated Fair Value Assets	273	705
Estimated Fair Value Liabilities	48	0
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Interest rate forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,035	675
Estimated Fair Value Assets	79	139
Estimated Fair Value Liabilities	0	0
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Foreign currency swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	11,666	9,038
Estimated Fair Value Assets	366	219
Estimated Fair Value Liabilities	410	355
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedges [Member] | Credit forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	60	0
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	3	0
Derivatives Designated as Hedging Instruments [Member] | Foreign Operations Hedges [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	9,169	6,927
Estimated Fair Value Assets	363	86
Estimated Fair Value Liabilities	8	64
Derivatives Designated as Hedging Instruments [Member] | Foreign Operations Hedges [Member] | Foreign currency forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	4,015	2,552
Estimated Fair Value Assets	91	43
Estimated Fair Value Liabilities	6	61
Derivatives Designated as Hedging Instruments [Member] | Foreign Operations Hedges [Member] | Currency options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	5,154	4,375
Estimated Fair Value Assets	272	43
Estimated Fair Value Liabilities	2	3
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	344,973	305,485
Estimated Fair Value Assets	7,673	10,375
Estimated Fair Value Liabilities	4,251	4,942
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	104,030	83,250
Estimated Fair Value Assets	3,606	5,201
Estimated Fair Value Liabilities	1,684	2,043
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	0	0
Estimated Fair Value Assets	0	0
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate floors [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	63,064	56,246
Estimated Fair Value Assets	646	1,174
Estimated Fair Value Liabilities	515	837
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	34,960	49,465
Estimated Fair Value Assets	193	74
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate futures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	6,836	11,684
Estimated Fair Value Assets	11	1
Estimated Fair Value Liabilities	13	38
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	34,585	16,328
Estimated Fair Value Assets	352	640
Estimated Fair Value Liabilities	181	60
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Synthetic GICs [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	4,309	4,162
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 [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	8,671	8,208
Estimated Fair Value Assets	296	199
Estimated Fair Value Liabilities	485	736
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Foreign currency forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	11,340	9,202
Estimated Fair Value Assets	148	26
Estimated Fair Value Liabilities	171	288
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Currency futures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,238	1,408
Estimated Fair Value Assets	0	4
Estimated Fair Value Liabilities	2	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Currency options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	1,010	129
Estimated Fair Value Assets	65	1
Estimated Fair Value Liabilities	9	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Credit default swaps - purchased [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	3,299	3,674
Estimated Fair Value Assets	13	11
Estimated Fair Value Liabilities	32	34
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Credit default swaps - written [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	9,644	8,879
Estimated Fair Value Assets	92	79
Estimated Fair Value Liabilities	10	5
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity futures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	5,982	7,008
Estimated Fair Value Assets	11	14
Estimated Fair Value Liabilities	54	132
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity Options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	30,381	22,920
Estimated Fair Value Assets	2,044	2,825
Estimated Fair Value Liabilities	610	356
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Variance swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	21,888	19,830
Estimated Fair Value Assets	114	122
Estimated Fair Value Liabilities	441	310
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Total rate of return swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	3,736	3,092
Estimated Fair Value Assets	82	4
Estimated Fair Value Liabilities	$ 44	$ 103