Supplementary Balance Sheet Information - Product Warranty and Retrofit Activity on Gross Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance at beginning of year	$ 6,089	$ 6,499	$ 7,260
Adjustments for acquisitions and divestitures	0	81	364
Accruals for warranties during the year	9,975	9,917	9,969
Costs incurred	(9,740)	(10,408)	(11,094)
Balance at end of year	$ 6,324	$ 6,089	$ 6,499