Employee Benefit Plans - Changes in Benefit Obligation (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Changes in benefit obligation
Benefit obligation at beginning of year	$ 2,435,765	$ 2,306,859
Service cost	10,410	8,459	$ 7,746
Interest cost	88,247	96,651	104,485
Plan participants’ contributions	2,466	2,454
Actuarial (gain) loss	(122,556)	94,546
Foreign currency exchange rate changes	(18,416)	15,073
Gross benefits paid	(118,643)	(106,885)
Plan amendments	0	4,768
Acquired plans	770	13,840
Benefit obligation at end of year	$ 2,278,043	$ 2,435,765	$ 2,306,859

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

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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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