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Retirement Plans (Details 11) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of defined benefit plan assets, beginning balance	$ 219,355
Fair value of defined benefit plan assets, ending balance	257,488	$ 219,355
Bank and Insurance Investment Contracts [Member] | Significant Unobservable Inputs (Level 3)
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of defined benefit plan assets, beginning balance	45,093	38,943
Net purchases (sales) and appreciation (depreciation) of defined benefit plan assets	6,870	6,150
Fair value of defined benefit plan assets, ending balance	51,963	45,093
U.S. Pension Plans
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of defined benefit plan assets, beginning balance	144,665	136,128
Fair value of defined benefit plan assets, ending balance	171,373	144,665
Non-U.S. Pension Plans
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of defined benefit plan assets, beginning balance	65,548	60,441
Fair value of defined benefit plan assets, ending balance	$ 74,990	$ 65,548

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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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 increase (decrease) in plan assets of defined benefit plan.

+ References

No definition available.

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