Supplementary Balance Sheet Information - Allowance for Doubtful Accounts Activity (Detail) - Allowance for doubtful accounts - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 1,019	$ 1,031	$ 863
Provisions	202	0	438
Reversals of Bad Debt Expense	0	0	(315)
Write-offs and Adjustments	1,020	(12)	45
Balance at End of Period	$ 2,241	$ 1,019	$ 1,031