Postretirement Benefit Plans - Schedule of Amounts Recognized in Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
United States [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Current liability	$ (302)	$ (302)
Non-current liability	(24,094)	(23,148)
Net amount recognized	(24,396)	(23,450)
United Kingdom [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Non-current asset	570	120
Net amount recognized	$ 570	$ 120

Pension plans postretirement and other employee benefits.

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Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans.

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- Definition

Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as current.

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Amount of liability, recognized in statement of financial position, for defined benefit pension and other postretirement plans, classified as noncurrent.

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