Income Taxes - Components of Income Tax Benefit (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Dec. 31, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Provision For Income Taxes [Line Items]
Income tax expense (benefit)	$ 0	$ 0	$ 0	$ (155)
U.S. Operations [Member]
Provision For Income Taxes [Line Items]
Current income tax expense (benefit)	0	0	0	4
Deferred income tax benefit	0	0	0	0
Income tax expense (benefit)	0	0	0	4
Non-U.S. Operations [Member]
Provision For Income Taxes [Line Items]
Current income tax expense (benefit)	0	0	0	(159)
Deferred income tax benefit	0	0	0	0
Income tax expense (benefit)	$ 0	$ 0	$ 0	$ (159)

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

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Name:	us-gaap_DeferredIncomeTaxExpenseBenefit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration