Components of Net Periodic Benefit Cost (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 75	$ 71	$ 151	$ 142
Interest cost	215	247	429	494
Expected return on plan assets	(372)	(351)	(744)	(702)
Amortization of prior service cost	13	12	26	24
Amortization of net loss	215	210	431	420
Settlement cost	191	0	191	0
Net periodic benefit cost	$ 337	$ 189	$ 484	$ 378