Derivative and Hedging Activities Derivative Instruments, Gain/Loss In Statement Of Financial Performance Table (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
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts	$ 3	$ 2	$ (51)	$ 4
Fair Value Hedging | Interest rate contract | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Interest rate contracts	$ 1	$ 2	$ 4	$ 6