Income Taxes - Significant Components of Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Components of Deferred Tax Assets and Liabilities [Abstract]
Accruals and reserves not currently deductible	$ 18,747	$ 16,382
Federal, state and foreign tax credits	25,413	24,183
Other assets	42	269
Equity compensation	7,615	4,447
Net operating loss carryforwards	49,777	73,097
Inventory reserves and valuation	9,847	11,342
Deferred tax assets	111,441	129,720
Depreciation and intangible amortization	(21,200)	(25,850)
Deferred tax liabilities	(21,200)	(25,850)
Valuation allowance	(92,297)	(104,802)
Net deferred tax liability	$ (2,056)	$ (932)