Fair Value and Investment Securities Narrative Investment Securities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Investment Identifier [Line Items]
Estimated discount to the par value of the ARS portfolio	10.00%	10.00%
Pre-tax impairment available accumulated other comprehensive income	$ 1	$ 3
Impact of a 100 Basis Points Hypothetical Increase in the Discount Rate Used to Value Auction Rate Securities	$ 1	$ 2
Minimum
Investment Identifier [Line Items]
ARS, collateralized by student loans with guarantees of principal and interest by the U.S. government via the Department of Education	95.00%
Maximum
Investment Identifier [Line Items]
ARS, collateralized by student loans with guarantees of principal and interest by the U.S. government via the Department of Education	98.00%