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Pensions and Other Post-retirement Benefits - Schedule of Reconciliation of Level Three Assets (Detail) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Insurance contracts |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at January 1 | $ 14,948 | $ 13,681
Net realized and unrealized gains included in earnings | 2,741 | 975
Net purchases, issuances and settlements | 145 | 292
Transfers out of Level 3 | 0 | 0
Fair value of plan assets at December 31 | 17,834 | 14,948
Other |  |
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] |  |
Fair value of plan assets at January 1 | 0 | 0
Net realized and unrealized gains included in earnings | 0 | 0
Net purchases, issuances and settlements | 0 | 0
Transfers out of Level 3 | 0 | 0
Fair value of plan assets at December 31 | $ 0 | $ 0

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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, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from purchases, sales and settlements. + 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)(B) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs. + 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)(C) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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