Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Valuation Allowance - Deferred Tax Assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		$ 862	$ 572	$ 807
Increase to costs and expenses		5,260	316	174
Deductions		208	26	409
Balance at end of period		5,914	862	572
Valuation Account - Doubtful Accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		285	367	313
Increase to costs and expenses		10	4	209
Deductions	[1]	86	86	155
Balance at end of period		209	285	367
Reserve for Future Returns and Pricing Adjustments
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period		1,817	1,662	1,770
Increase to costs and expenses		9,946	7,002	6,526
Deductions		9,772	6,847	6,634
Balance at end of period		$ 1,991	$ 1,817	$ 1,662

[1] Uncollectible accounts charged against allowance, net of recoveries