Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Accruals of interest and penalties	$ 0		$ 0
Recognized interest or penalties	$ 0	$ 0
Tax benefit resulting in remeasurement of deferred tax balances		$ (1,300,000)

Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)

No definition available.

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- References

No definition available.

+ Details

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- Definition

The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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- Definition

The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations.

+ References

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