Offsetting of Financial Assets (Liabilities) and Derivative Assets (liabilities) (Detail) (Subject to an enforceable master netting arrangement, USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Gross Assets Recognized	$ 6,345	$ 14,467
Gross Liabilities Offset in the Statement of Financial Position	(9,215)	(17,820)
Net Assets (Liabilities) Presented in the Statement of Financial Position	(2,870)	(3,353)
Financial Instruments
Cash Collateral Received
Net Amount	(2,870)	(3,353)
Fair liability and fair asset value of derivative instruments
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Gross Assets Recognized	5,336	7,213
Gross Liabilities Offset in the Statement of Financial Position	(8,253)	(11,212)
Net Assets (Liabilities) Presented in the Statement of Financial Position	(2,917)	(3,999)
Financial Instruments
Cash Collateral Received
Net Amount	(2,917)	(3,999)
Fair asset and fair liability value of derivative instruments
Fair Values Of Financial Assets And Liabilities Including Derivative Financial Instruments [Line Items]
Gross Assets Recognized	1,009	7,254
Gross Liabilities Offset in the Statement of Financial Position	(962)	(6,608)
Net Assets (Liabilities) Presented in the Statement of Financial Position	47	646
Financial Instruments
Cash Collateral Received
Net Amount	$ 47	$ 646