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Retirement Plans (Details 4) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
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Funded Status of Plan [Abstract] |  |  |
Fair value of defined benefit plan assets | $ 257,488 | $ 219,355 |
U.S. Pension Plans |  |  |
Funded Status of Plan [Abstract] |  |  |
Projected benefit obligation | (168,064) | (159,416) | $ (155,003)
Fair value of defined benefit plan assets | 171,373 | 144,665 | 136,128
Funded status of defined benefit plan | 3,309 | (14,751) |
U.S. Retiree Healthcare Plan |  |  |
Funded Status of Plan [Abstract] |  |  |
Projected benefit obligation | (17,121) | (14,921) | (12,963)
Fair value of defined benefit plan assets | 11,125 | 9,142 | 8,001
Funded status of defined benefit plan | (5,996) | (5,779) |
Non-U.S. Pension Plans |  |  |
Funded Status of Plan [Abstract] |  |  |
Projected benefit obligation | (96,378) | (85,311) | (75,677)
Fair value of defined benefit plan assets | 74,990 | 65,548 | $ 60,441
Funded status of defined benefit plan | $ (21,388) | $ (19,763) |

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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for 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 (a) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + 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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- Definition Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status. + 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 (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919 + Details
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