Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income tax benefit	$ 1,947,000	$ 162,000		$ 2,197,000	$ 338,000
Discrete tax benefit under CARES Act	$ 1,800,000			$ 1,800,000
U.S. federal statutory tax rate	21.00%	21.00%	35.00%	21.00%	21.00%
Discrete tax benefits related to stock-based compensation awards	$ 100,000	$ 100,000		$ 300,000	$ 500,000
Unrecognized tax benefits excluding interest and penalties that would impact effective tax rate	2,700,000			2,700,000		$ 2,100,000
Undistributed earnings in foreign subsidiaries	$ 0			$ 0		$ 0

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

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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 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 operation, attributable to nondeductible expense for award under share-based payment arrangement. Includes, but is not limited to, expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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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 other adjustments.

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Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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