Pension and Other Postretirement Benefits - Level 3 Asset Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets at Beginning of Year	$ 136,041
Fair Value of Plan Assets at End of Year		$ 136,041
Fair Value Inputs Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets at Beginning of Year	74,819
Purchases	2,350	2,584
Settlements	(1,661)	(1,350)
Unrealized Gains	(1,237)	12,061
Translation Difference	10,249	(3,273)
Fair Value of Plan Assets at End of Year	84,520	74,819
Insurance Contract [Member] \| Fair Value Inputs Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Purchases	2,350	2,584
Settlements	(1,661)	(1,350)
Unrealized Gains	(1,425)	12,005
Translation Difference	10,050	(2,870)
Real Estate Fund [Member] \| Fair Value Inputs Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets at Beginning of Year	2,041
Purchases	0	0
Settlements	0	0
Unrealized Gains	188	56
Translation Difference	$ 199	(403)
Fair Value of Plan Assets at End of Year		$ 2,041

The amount of decrease in plan assets attributable to the payment of benefits or the payment of plan expenses.

No definition available.

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- Definition

The amount of increase in the plan assets attributable to the purchase of plan assets.

+ References

No definition available.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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