Components of Net Periodic Benefit Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Service cost	$ 69	$ 37	$ 139	$ 73
Interest cost	256	244	512	487
Expected return on plan assets	(407)	(418)	(815)	(835)
Amortization of net loss	210	136	420	273
Net periodic cost	$ 128	$ (1)	$ 256	$ (2)