Fair Value and Investment Securities Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Fair Value By Balance Sheet Grouping [Line Items]
Investment income	$ 11	$ 9	$ 30	$ 27
Percentage of fair value of investments using discounted cash flow pricing model	10.00%		10.00%		10.00%
Minimum [Member]
Fair Value By Balance Sheet Grouping [Line Items]
Collateral Requirements Minimum Percentage Collateral To Fair Value Of Securities Loaned Under Security Lending Transactions	95.00%		95.00%
Maximum [Member]
Fair Value By Balance Sheet Grouping [Line Items]
Collateral Requirements Minimum Percentage Collateral To Fair Value Of Securities Loaned Under Security Lending Transactions	98.00%		98.00%