Income Taxes - Differences Between Income Tax Provision (Benefit) and Income Taxes Computed using Applicable U.S. Statutory Federal Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Differences between the income tax provision (benefit) and income taxes computed using the applicable U.S. statutory federal tax rate
Income tax provision computed at federal statutory rate	$ 5,014	$ 4,923	$ (6,722)
State income taxes, net of federal benefit	692	137	(374)
Foreign income taxed at different rates	920	(1,644)	(690)
Impact of investments in subsidiaries	(729)	(965)	(971)
Change in deferred tax asset valuation allowance	(75,918)	319	76,486
Net increase (reduction) in uncertain tax positions	220	731	(1,543)
Impact of U.S. federal tax rate change	15,287
Compensation	(701)	579	743
Tax credits	(1,633)	(1,151)	(1,555)
Merger costs	1,405		503
Transition Tax	8,027
Other	165	451	373
Income tax provision (benefit)	$ (47,251)	$ 3,380	$ 66,250

Effective Income Tax Rate Reconciliation, Merger Costs, Amount

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Amount of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to increase (decrease) from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act of 2017.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in the valuation allowance for deferred tax assets.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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