Postretirement Benefits - Additional Information (Detail) $ in Thousands	12 Months Ended
	Sep. 30, 2016 USD ($) Plan	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial losses	$ (165)	$ (722)
Defined Benefit Pension Plan, Number of Plans | Plan	2
Accumulated benefit obligation	$ 6,300	6,900
Curtailment gain	852	0
Amortization of net loss	(227)	0	$ 0
Settlement loss	0	(232)	0
Curtailment gain including foreign currency	1,100
Fair value of plan assets	4,734	4,838	6,131
Expected contribution to the Plan to meet minimum funding targets	200
Employer contributions	3,600	3,000	$ 3,500
Market Related Valuation of Assets
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial losses	$ (900)	(800)
Investment gains or losses recognition period	5 years
Other actuarial losses
Defined Benefit Plan Disclosure [Line Items]
Unrecognized net actuarial losses	$ (300)	$ (200)
Nexus Plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,200
Taiwan Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 500
Worldwide Defined Contribution Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.50%