Pension Plans - Additional Information (Detail) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Compensation And Retirement Disclosure [Abstract]
Contribution to pension plan	$ 0.5
Pension plan contributions to be made during the second half of 2018	$ 0.1

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