Pension plan and 401(k) Program - Changes in Unrecognized Pension Cost (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Changes in Unrecognized pension cost, pre-tax
Unrecognized pension cost, pre-tax, beginning of year	$ (2,561)	$ (4,546)
Amortization during year	(19)	120
Actuarial (losses) gains	(771)	1,129
Asset (losses) gains	(1,140)	472
Changes in Unrecognized pension cost, pre-tax	12	264
Unrecognized pension cost, pre-tax, end of year	$ (4,479)	$ (2,561)

Other Comprehensive Income (Loss), Defined Benefit Plan, Actuarial Gain (Loss) Arising During Period, before Tax

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- Definition

Other Comprehensive Income (Loss), Defined Benefit Plan, Plan Asset Gain (Loss) Arising During Period, before Tax

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- Definition

Other Comprehensive Income (Loss), Defined Benefit Plan, Translation Adjustments, before Tax

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- Definition

Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income [Roll Forward]

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- Definition

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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- Definition

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

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