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Retirement Plans (Details 11) - USD ($) $ in Thousands | 12 Months Ended
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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 + Details
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