Derivative Financial Instruments (Details 2) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Notional Amount	$ 295,022	$ 290,021
Estimated Fair Value Assets	16,602	16,200
Estimated Fair Value Liabilities	4,353	4,011
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	269,192	268,117
Estimated Fair Value Assets	12,533	12,248
Estimated Fair Value Liabilities	3,833	3,493
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	86,665	71,923
Estimated Fair Value Assets	6,080	5,410
Estimated Fair Value Liabilities	2,221	2,107
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate floors [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	23,866	23,866
Estimated Fair Value Assets	1,291	1,246
Estimated Fair Value Liabilities	172	165
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	46,045	49,665
Estimated Fair Value Assets	54	102
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	14,350	14,965
Estimated Fair Value Assets	16	25
Estimated Fair Value Liabilities	51	19
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	16,002	16,988
Estimated Fair Value Assets	927	896
Estimated Fair Value Liabilities	5	6
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Interest rate forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	82	13,068
Estimated Fair Value Assets	0	76
Estimated Fair Value Liabilities	0	91
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Synthetic GICs [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	4,506	4,454
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	7,210	6,871
Estimated Fair Value Assets	287	320
Estimated Fair Value Liabilities	635	656
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Foreign currency forwards [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	5,573	6,630
Estimated Fair Value Assets	140	145
Estimated Fair Value Liabilities	35	38
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Currency futures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	934	633
Estimated Fair Value Assets	2	0
Estimated Fair Value Liabilities	1	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Currency options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	401	1,321
Estimated Fair Value Assets	2	6
Estimated Fair Value Liabilities	0	0
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Credit default swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	13,803	13,136
Estimated Fair Value Assets	168	326
Estimated Fair Value Liabilities	80	113
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity futures [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	7,682	7,053
Estimated Fair Value Assets	1	26
Estimated Fair Value Liabilities	236	10
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Equity Options [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	20,315	17,099
Estimated Fair Value Assets	3,315	3,263
Estimated Fair Value Liabilities	209	179
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Variance swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	19,833	18,801
Estimated Fair Value Assets	216	397
Estimated Fair Value Liabilities	144	75
Derivatives Not Designated or Not Qualifying as Hedging Instruments [Member] | Total rate of return swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	2,007	1,644
Estimated Fair Value Assets	34	10
Estimated Fair Value Liabilities	$ 44	$ 34