Investment Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Schedule of Investments [Line Items]
Residential mortgage-backed securities and collateralized mortgage obligations, term (years)	15
U.S. Treasury And Sponsored Entities Callable Notes [Member]
Schedule of Investments [Line Items]
Available-for-sale securities	$ 193
U.S. Treasury And Sponsored Entities Discount Notes [Member]
Schedule of Investments [Line Items]
Maturity period of U.S. treasury and sponsored entities callable notes	30 D
Available-for-sale securities	$ 30
Minimum [Member]
Schedule of Investments [Line Items]
Maturity period of U.S. treasury and sponsored entities callable notes	7Y
Maximum [Member]
Schedule of Investments [Line Items]
Maturity period of U.S. treasury and sponsored entities callable notes	11Y