Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2012	Sep. 30, 2012
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Notional Amount of Interest Rate Derivatives	$ 625
Derivative, Average Remaining Maturity	4 months
Derivative, Number of Instruments Held	3,100,000	4,100,000