Post-Retirement Benefits - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Compensation And Retirement Disclosure [Abstract]
Contributions to the Compensation Plan by the employer	$ 0.8	$ 0.9
Contributions to the Compensation Plan by the employer in remainder of fiscal year 2018	$ 2.5

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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