Components of Net Pension Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 149	$ 29	$ 300	$ 57
Interest cost	248	192	497	385
Amortization of losses	116	116	231	232
Expected return on assets	(235)	(188)	(470)	(375)
Net periodic pension cost	$ 278	$ 149	$ 558	$ 299