Income Taxes [Line Items]

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- Definition

Tax credits, net capital and operating loss carryforwards to expire within 20 years of balance sheet date.

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- Definition

Tax credit net capital and operating loss carryforwards expiration dates.

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The sum of tax credits, net capital and operating loss carryforwards available to reduce future tax liabilities.

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Amount of expense (benefit) for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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No definition available.

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- Definition

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

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- Definition

Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

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The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

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Amount of unrecognized tax benefits.

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- Definition

Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
Net increase (decrease) in valuation allowances	$ (27,194)	$ 18,154
Tax credits, net capital and operating loss carryforwards	797,091	894,997
Tax credits, net capital and operating loss carryforwards having expiration date	$ 244,711	$ 322,816
Tax credits, net capital and operating loss carryforwards expiration date	Through 2039 for $244,711 in net operating losses	Through 2038 for $322,816 in net operating losses
Gross unrecognized tax benefits	$ 169,322	$ 187,646	$ 193,024	$ 196,668
Accrued income taxes payable for interest and penalties relating to unrecognized tax benefits	31,108	30,807
Accrued income taxes payable for interest and penalties relating to unrecognized tax benefits, tax expense (benefit) recognized in the statements of income, net of interest and penalty reversals	4,679	$ 2,579
Maximum [Member]
Income Taxes [Line Items]
Expected decrease in unrecognized tax benefits within next 12 months	$ 12,763
GUERNSEY
Income Taxes [Line Items]
Statutory Guernsey tax rate	0.00%	0.00%	0.00%
Prepaid Expenses and Other Current Assets [Member]
Income Taxes [Line Items]
Tax receivable balance	$ 53,143	$ 55,198