Pensions and Postretirement Benefits Other than Pensions - Details of Activity in Investment in European Infrastructure and Property Funds (Detail) - United Kingdom plan - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plans’ assets at beginning of year	$ 377,536
Fair value of plans’ assets at end of year	407,336	$ 377,536
Significant Unobservable Inputs Level (3)
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation [Roll Forward]
Fair value of plans’ assets at beginning of year	30,180	28,938	$ 38,070
Change in fair value	(2,172)	97	(7,294)
Foreign currency translation effect	805	1,145	(1,838)
Fair value of plans’ assets at end of year	$ 28,813	$ 30,180	$ 28,938

Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) plan assets of defined benefit plan.

+ References

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