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Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance			$ (5,336)
Accumulated other comprehensive income, tax, beginning balance			(970)
Accumulated Other Comprehensive Income Beginning Balance			(4,366)
Cumulative effect of new accounting principle in period of adoption					$ 274
Other comprehensive income (loss), net of tax	$ (1,761)	$ 1,118	(1,974)	$ 1,823
AOCI before tax, ending balance	(7,289)		(7,289)
Accumulated other comprehensive income, tax, ending balance	(949)		(949)
Accumulated Other Comprehensive Income Ending Balance	(6,340)		(6,340)
Accumulated Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance			(2,698)
Other comprehensive income adjustments			(1,677)
Other comprehensive income (loss), net of tax			(1,677)
AOCI before tax, ending balance	(4,375)		(4,375)
Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive income adjustments			74
Other comprehensive income (loss), tax			21
Other comprehensive income (loss), net of tax			53
Minimum Pension Liability Adjustment | Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance			171
Other comprehensive income adjustments			(14)
AOCI before tax, ending balance	172		172
Postretirement Health Coverage | Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance			(2,809)
Other comprehensive income adjustments			88
AOCI before tax, ending balance	$ (3,086)		$ (3,086)
Accounting Standards Update 2014-09
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle in period of adoption					(350)
Accounting Standards Update 2014-09 | Minimum Pension Liability Adjustment | Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle in period of adoption					15
Accounting Standards Update 2014-09 | Postretirement Health Coverage | Accumulated Defined Benefit Plans Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect of new accounting principle in period of adoption					$ (365)

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Accumulated Other Comprehensive Income (Loss), Tax

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Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, including portion attributable to noncontrolling interest. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).

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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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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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

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

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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