Pension and Postretirement Benefits - Summary of Funded Status of the Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Domestic Plans
Change in plan assets:
Fair value of plan assets at beginning of year	$ 10,416
Fair value of plan assets at end of year	11,590	$ 10,416
Foreign Pension Plans
Change in benefit obligation:
Service cost	530	488	$ 503
Interest cost	492	488	505
Actuarial adjustments	(106)	158	182
Change in plan assets:
Fair value of plan assets at beginning of year	10,576
Fair value of plan assets at end of year	9,493	10,576
Foreign Pension Plans \| Funded Plans
Change in benefit obligation:
Benefit obligation at beginning of year	10,488	9,744
Service cost	530	488
Interest cost	406	400
Actuarial adjustments	658	395
Benefits paid	(3,231)	(818)
Translation adjustment	670	279
Benefit obligation at end of year	9,521	10,488	9,744
Change in plan assets:
Fair value of plan assets at beginning of year	10,576	9,705
Actual return on plan assets	764	617
Company contributions	710	795
Benefits paid	(3,231)	(818)
Translation adjustment	674	277
Fair value of plan assets at end of year	9,493	10,576	9,705
Funded status at end of year	(28)	88
Foreign Pension Plans \| Unfunded Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	2,486	2,470
Interest cost	87	87
Actuarial adjustments	(54)	105
Benefits paid	(182)	(177)
Translation adjustment	245	1
Benefit obligation at end of year	2,582	2,486	2,470
Change in plan assets:
Company contributions	182	177
Benefits paid	(182)	(177)
Funded status at end of year	(2,582)	(2,486)
Pension Plans \| Domestic Plans
Change in benefit obligation:
Service cost	64	98	101
Interest cost	803	1,032	1,018
Actuarial adjustments	114	1	(963)
Pension Plans \| Domestic Plans \| Funded Plans
Change in benefit obligation:
Benefit obligation at beginning of year	15,027	14,906
Interest cost	492	629
Actuarial adjustments	618	240
Benefits paid	(697)	(748)
Benefit obligation at end of year	15,440	15,027	14,906
Change in plan assets:
Fair value of plan assets at beginning of year	10,416	10,479
Actual return on plan assets	855	273
Company contributions	1,016	412
Benefits paid	(697)	(748)
Fair value of plan assets at end of year	11,590	10,416	10,479
Funded status at end of year	(3,850)	(4,611)
Pension Plans \| Domestic Plans \| Unfunded Pension Plans
Change in benefit obligation:
Benefit obligation at beginning of year	9,825	10,049
Service cost	64	97
Interest cost	311	403
Actuarial adjustments	175	(221)
Benefits paid	(518)	(503)
Benefit obligation at end of year	9,857	9,825	10,049
Change in plan assets:
Company contributions	518	503
Benefits paid	(518)	(503)
Funded status at end of year	(9,857)	(9,825)
Postretirement Benefit Plans \| Domestic Plans
Change in benefit obligation:
Benefit obligation at beginning of year	13,619	14,573
Service cost	92	99	152
Interest cost	413	573	619
Actuarial adjustments	237	(790)	(1,248)
Plan amendments	816	73
Benefits paid	(1,370)	(909)
Benefit obligation at end of year	13,807	13,619	$ 14,573
Change in plan assets:
Company contributions	1,370	909
Benefits paid	(1,370)	(909)
Funded status at end of year	$ (13,807)	$ (13,619)

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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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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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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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and 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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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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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 payment to participant under defined benefit plan which decreases plan assets. 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 cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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