Bank Credit Arrangements - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Debt Disclosure [Abstract]
Credit facility with a commercial bank	$ 30,000
Expiration date of credit facility	Sep. 30, 2015
Credit facility, collateralized	149,000
Borrowings outstanding under credit facility	0	0
Available borrowings under credit facility	30,000	30,000
Cash compensating balance	$ 1,000