Derivative Financial Instruments (Summary Of CDS Contracts) (Details) (USD $) In Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
Credit Derivatives [Line Items]
Fair Value of Credit Default Swaps	$ (4)	$ 1
Maximum Amount of Future Payments under Credit Default Swaps	50	8
Weighted Average Years To Maturity	4.5	2.1
A-Rated [Member]
Credit Derivatives [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	5
Weighted Average Years To Maturity	5.0
BBB-Rated [Member]
Credit Derivatives [Line Items]
Fair Value of Credit Default Swaps	(2)
Maximum Amount of Future Payments under Credit Default Swaps	15
Weighted Average Years To Maturity	5.1
BB-Rated [Member]
Credit Derivatives [Line Items]
Fair Value of Credit Default Swaps	(1)	1
Maximum Amount of Future Payments under Credit Default Swaps	22	5
Weighted Average Years To Maturity	4.3	2.5
B-Rated [Member]
Credit Derivatives [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	3	3
Weighted Average Years To Maturity	0.7	1.5
CCC-Rated [Member]
Credit Derivatives [Line Items]
Fair Value of Credit Default Swaps	(1)
Maximum Amount of Future Payments under Credit Default Swaps	$ 5
Weighted Average Years To Maturity	5.0