Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk - Derivatives Volume (Details) (USD $)	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Financial Instruments with Off-Balance Sheet Risk and Concentrations of Credit Risk [Abstract]
Derivative, Collateral, Obligation to Return Cash	$ 9,200,000	$ 0
Derivative, Collateral, Right to Reclaim Cash	0	53,500,000
Notional Amount of Interest Rate Derivatives	$ 765,000,000	$ 1,100,000,000
Derivative, Average Remaining Maturity	6 months	14 months
Derivative, Number of Instruments Held	4,100,000	3,900,000