Derivative Financial Instruments - Additional Information (Detail) (USD $)	Sep. 30, 2012 Contract	Sep. 30, 2011 Contract
Derivative [Line Items]
Termination value of derivatives in a net liability position	$ 10,567,000
Derivative collateral posted	9,337,000
Cash Flow Hedging | Interest Rate Swap
Derivative [Line Items]
Number of interest rate derivatives held	2	1
Notional amount of interest rate derivatives	26,000,000	13,000,000
Cash Flow Hedging | Interest Rate Cap
Derivative [Line Items]
Number of interest rate derivatives held	1	1
Notional amount of interest rate derivatives	13,000,000	13,000,000
Not Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Notional amount of interest rate derivatives	$ 152,667,000