Derivatives (Credit Derivatives) (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 173,000,000	$ 165,000,000
Maximum Amount of Future Payments under Credit Default Swaps	9,982,000,000	9,055,000,000
Weighted Average Years to Maturity	3 years 6 months	3 years 5 months
Aaa/Aa/A [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	24,000,000	36,000,000
Maximum Amount of Future Payments under Credit Default Swaps	3,482,000,000	3,284,000,000
Weighted Average Years to Maturity	2 years	1 year 7 months
Aaa/Aa/A [Member] | Single name credit default swaps (corporate) [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	9,000,000	10,000,000
Maximum Amount of Future Payments under Credit Default Swaps	605,000,000	545,000,000
Weighted Average Years to Maturity	2 years 5 months	2 years 7 months
Aaa/Aa/A [Member] | Credit default swaps referencing indices [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	15,000,000	26,000,000
Maximum Amount of Future Payments under Credit Default Swaps	2,877,000,000	2,739,000,000
Weighted Average Years to Maturity	1 year 11 months	1 year 6 months
Baa [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	116,000,000	97,000,000
Maximum Amount of Future Payments under Credit Default Swaps	6,113,000,000	5,391,000,000
Weighted Average Years to Maturity	4 years 4 months	4 years 4 months
Baa [Member] | Single name credit default swaps (corporate) [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	27,000,000	24,000,000
Maximum Amount of Future Payments under Credit Default Swaps	1,478,000,000	1,320,000,000
Weighted Average Years to Maturity	2 years 11 months	3 years 1 month
Baa [Member] | Credit default swaps referencing indices [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	89,000,000	73,000,000
Maximum Amount of Future Payments under Credit Default Swaps	4,635,000,000	4,071,000,000
Weighted Average Years to Maturity	4 years 8 months	4 years 8 months
Ba [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	0	0
Maximum Amount of Future Payments under Credit Default Swaps	15,000,000	5,000,000
Weighted Average Years to Maturity	3 years 1 month	3 years 9 months
Ba [Member] | Single name credit default swaps (corporate) [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	0	0
Maximum Amount of Future Payments under Credit Default Swaps	15,000,000	5,000,000
Weighted Average Years to Maturity	3 years 1 month	3 years 9 months
Ba [Member] | Credit default swaps referencing indices [Member]
Credit Derivatives [Line Items]
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 years	0 years
B [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	33,000,000	32,000,000
Maximum Amount of Future Payments under Credit Default Swaps	372,000,000	375,000,000
Weighted Average Years to Maturity	4 years 11 months	4 years 11 months
B [Member] | Single name credit default swaps (corporate) [Member]
Credit Derivatives [Line Items]
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 years	0 years
B [Member] | Credit default swaps referencing indices [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	33,000,000	32,000,000
Maximum Amount of Future Payments under Credit Default Swaps	$ 372,000,000	$ 375,000,000
Weighted Average Years to Maturity	4 years 11 months	4 years 11 months