Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Federal tax rate	21.00%		35.00%
Taxes paid on the deemed mandatory repatriation	$ 386
Income tax (benefit) expense	3,129	$ (8,381)
(Loss) income from operations before income taxes	10,608	9,572
Excess tax benefits on stock-based compensation	$ 1,649	7,873
Federal statutory rate, blended rate for next fiscal year	28.00%
Discrete tax benefit from net operating loss carryforwards		$ 4,075
Deferred tax assets, effect of Tax Cuts and Jobs Act, tax expense (benefit)	$ 1,711

Tax Cuts And Jobs Act Of 2017 Change In Tax Rate Deferred Tax Asset Income Tax Expense Benefit

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Tax Cuts And Jobs Act Of 2017, Federal Statutory Rate, Blended Rate For Next Fiscal Year

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

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Amount of cash outflow for realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes.

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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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 tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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