Investment Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011 years
Schedule of Investments [Line Items]
Residential mortgage-backed securities and collateralized mortgage obligations, term (years)	15
Minimum [Member]
Schedule of Investments [Line Items]
Maturity period of U.S. Treasury and sponsored entities callable notes	7
Maximum [Member]
Schedule of Investments [Line Items]
Maturity period of U.S. Treasury and sponsored entities callable notes	11
U.S. Treasury And Sponsored Entities Callable Notes [Member]
Schedule of Investments [Line Items]
Available-for-sale securities	278
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	2
Available-for-sale securities	30