Postretirement Benefits - Funded Status and Amounts Recognized in Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 7,107	$ 10,181
Service cost	406	604	787
Interest cost	154	148	984
Actuarial loss (gain)	968	(670)
Benefits paid	(141)	(1,421)
Settlements paid	0	(1,383)
Curtailment gain	0	(500)
Foreign currency translation	(281)	148
Benefit obligation at end of year	8,213	7,107	10,181
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of assets at beginning of year	5,996	8,015
Actual return on plan assets	98	304
Disbursements	(264)	(1,573)
Employer contributions	302	292
Employee contributions	200	194
Settlements paid	0	(1,383)
Foreign currency translation	(201)	147
Fair value of assets at end of year	6,131	5,996	8,015
Accrued benefit liability	$ 2,082	$ 1,111