Employee Benefit Plans - Changes in Benefit Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Changes in benefit obligation
Benefit obligation at beginning of year	$ 2,496,600	$ 2,278,043
Service cost	12,105	9,558	$ 10,410
Interest cost	83,732	97,441	88,247
Plan participants’ contributions	1,864	2,246
Actuarial loss	218,534	246,352
Foreign currency exchange rate changes	9,394	9,073
Gross benefits paid	(144,508)	(119,789)
Plan amendments	0	3,327
Curtailments	(472)	(6,569)
Settlements	0	(67,831)
Special termination costs	0	42,757
Acquired plans	1,717	1,992
Benefit obligation at end of year	$ 2,678,966	$ 2,496,600	$ 2,278,043

Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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Amount of increase in benefit obligation of defined benefit plan from business combination.

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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.

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No definition available.

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Amount of (increase) decrease in benefit obligation of defined benefit plan from event reducing expected years of future service of present employees or eliminating accrual of benefits for some or all future services of present employees.

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

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of increase (decrease) in benefit obligation of defined benefit plan from change in terms of existing plan or initiation of new plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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- Definition

Amount of (increase) decrease to benefit obligation of defined benefit plan from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk for obligation and assets used to effect settlement. Includes, but is not limited to, lump-sum cash payment to participant in exchange for right to receive specified benefits, purchase of nonparticipating annuity contract and change from remeasurement.

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Amount of increase in benefit obligation for benefits provided to employees payable from defined benefit plan or payable upon retirement.

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