Derivative Financial Instruments (Details 10) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	$ 58	$ 62
Maximum Amount of Future Payments under Credit Default Swaps	6,490	5,089
Weighted Average Years to Maturity	4.1	4.1
Aaa/Aa/A [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	49	50
Maximum Amount of Future Payments under Credit Default Swaps	3,553	3,398
Weighted Average Years to Maturity	3.6	3.7
Aaa/Aa/A [Member] | Single name credit default swaps (corporate) [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	7	5
Maximum Amount of Future Payments under Credit Default Swaps	740	470
Weighted Average Years to Maturity	3.9	3.8
Aaa/Aa/A [Member] | Credit default swaps referencing indices [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	42	45
Maximum Amount of Future Payments under Credit Default Swaps	2,813	2,928
Weighted Average Years to Maturity	3.5	3.7
Single name credit default swaps (corporate) [Member] | Baa [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	2	5
Maximum Amount of Future Payments under Credit Default Swaps	1,155	735
Weighted Average Years to Maturity	4.3	4.3
Credit default swaps referencing indices [Member] | Baa [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	7	7
Maximum Amount of Future Payments under Credit Default Swaps	1,752	931
Weighted Average Years to Maturity	5.0	5.0
Baa [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	9	12
Maximum Amount of Future Payments under Credit Default Swaps	2,907	1,666
Weighted Average Years to Maturity	4.8	4.7
Ba [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	0	0
Maximum Amount of Future Payments under Credit Default Swaps	30	25
Weighted Average Years to Maturity	4.2	4.4
Ba [Member] | Single name credit default swaps (corporate) [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	0	0
Maximum Amount of Future Payments under Credit Default Swaps	30	25
Weighted Average Years to Maturity	4.2	4.4
Ba [Member] | Credit default swaps referencing indices [Member]
Schedule of estimated fair value, maximum amount of future payments and weighted average years to maturity of written credit default swaps
Estimated Fair Value of Credit Default Swaps	0	0
Maximum Amount of Future Payments under Credit Default Swaps	$ 0	$ 0
Weighted Average Years to Maturity	0	0