Derivative Instruments and Hedging Activities - Fair Value Hedge (Detail) (Other Income Expense [Member], Fair Value Hedging [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2010
Swap [Member]
Derivatives And Hedging Activities [Line Items]
Gain/(Loss) on the hedged fixed rate debt attributable to changes in the market interest rates	$ (3,607)	[1]	$ (2,650)	[1]	$ 6,638	[1]
Borrowings [Member]
Derivatives And Hedging Activities [Line Items]
Gain/(Loss) on the hedged fixed rate debt attributable to changes in the market interest rates	$ 3,607	[1]	$ 2,650	[1]	$ (6,638)	[1]

[1] Changes in the fair value of the interest rate swap offset changes in the fair value of the fixed rate debt due to changes in market interest rates. There was no hedge ineffectiveness relating to this interest rate swap.