Comprehensive Income (Loss) - Changes in accumulated comprehensive loss (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Comprehensive Income (Loss)
Foreign Currency Translation Adjustments, Beginning balance	$ (6,050)
Foreign Currency Translation Adjustments, Other comprehensive loss before reclassifications	(143)
Foreign Currency Translation Adjustments, Amounts reclassified from accumulated other comprehensive loss	0
Foreign Currency Translation Adjustments, Net current period other comprehensive (loss) income	(143)
Foreign Currency Translation Adjustments, Ending balance	(6,193)
Defined Benefit Pension Items, Beginning balance	(21,955)
Defined Benefit Pension Items, Other comprehensive loss before reclassifications	0
Defined Benefit Pension Items, Amounts reclassified from accumulated other comprehensive loss	183	$ 138
Defined Benefit Pension Items, Net current period other comprehensive (loss) income	183
Defined Benefit Pension Items, Ending balance	(21,772)
Beginning balance	(28,005)
Other comprehensive loss before reclassifications	(143)
Amounts reclassified from accumulated other comprehensive loss	183
Net current period other comprehensive (loss) income	40
Ending balance	$ (27,965)

Amount, after 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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Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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The increase (decrease) in cumulative translation adjustment before transfers included in determining net income.

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Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for translation gain (loss) realized upon the sale or liquidation of an investment in a foreign entity and foreign currency hedges that are designated and qualified as hedging instruments for hedges of the foreign currency exposure of a net investment in a foreign operation.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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