Derivatives (Credit Derivatives) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	$ 147,000,000	$ 165,000,000
Maximum Amount of Future Payments under Credit Default Swaps	10,929,000,000	9,055,000,000
Weighted Average Years to Maturity	3 years 3 months	3 years 5 months
Aaa/Aa/A [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	16,000,000	36,000,000
Maximum Amount of Future Payments under Credit Default Swaps	3,567,000,000	3,284,000,000
Weighted Average Years to Maturity	1 year 9 months	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	690,000,000	545,000,000
Weighted Average Years to Maturity	2 years 4 months 20 days	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	7,000,000	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 8 months	1 year 6 months
Baa [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	108,000,000	97,000,000
Maximum Amount of Future Payments under Credit Default Swaps	6,706,000,000	5,391,000,000
Weighted Average Years to Maturity	4 years 1 month	4 years 4 months
Baa [Member] | Single name credit default swaps (corporate) [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	24,000,000	24,000,000
Maximum Amount of Future Payments under Credit Default Swaps	1,632,000,000	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	84,000,000	73,000,000
Maximum Amount of Future Payments under Credit Default Swaps	5,074,000,000	4,071,000,000
Weighted Average Years to Maturity	4 years 6 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	155,000,000	5,000,000
Weighted Average Years to Maturity	2 years 8 months	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	55,000,000	5,000,000
Weighted Average Years to Maturity	3 years 0 months	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	100,000,000	0
Weighted Average Years to Maturity	2 years 6 months	0 years
B [Member]
Credit Derivatives [Line Items]
Estimated Fair Value of Credit Default Swaps	23,000,000	32,000,000
Maximum Amount of Future Payments under Credit Default Swaps	501,000,000	375,000,000
Weighted Average Years to Maturity	4 years 1 month	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	23,000,000	32,000,000
Maximum Amount of Future Payments under Credit Default Swaps	$ 501,000,000	$ 375,000,000
Weighted Average Years to Maturity	4 years 1 month	4 years 11 months