Income Tax Expense - Schedule Of Actual Income Tax Expense (Benefit) From Continuing Operations (Details)	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Income Tax Expense
Federal corporate statutory rate	21.00%	24.50%	35.00%
State and local, net of Federal benefits	3.30%	3.00%	2.40%
Foreign	0.70%	0.60%	(0.10%)
Research credit	(0.90%)	(1.60%)	(1.10%)
Domestic production deduction	0.00%	(1.10%)	(2.70%)
Change in uncertain tax positions	(0.10%)	(0.10%)	0.00%
Executive compensation	0.30%	(0.10%)	(0.10%)
Valuation allowance	(2.40%)	3.00%	(0.30%)
GILTI and FDII	(0.80%)	0.00%	0.00%
Tax reform - impact on U.S. deferred tax assets and liabilities	(0.30%)	(37.20%)	0.00%
Tax reform - transition tax	(0.10%)	1.50%	0.00%
Tax reform - taxes related to foreign unremitted earnings	0.00%	2.80%	0.00%
Other, net	0.00%	0.00%	(0.10%)
Effective income tax rate	20.70%	(4.70%)	33.00%

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

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage 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 changes in the valuation allowance for deferred tax assets.

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Percentage 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 applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to nondeductible expense for share-based payment arrangement.

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Percentage 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 income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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