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Pension and Other Postretirement Benefits - Fair Values of Pension Plan Assets by Asset Category (Detail) - USD ($) $ in Thousands | Dec. 31, 2015 | Dec. 31, 2014
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Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | $ 204,372 | $ 216,754
Large-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 77,618 | 82,816
Mid-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 14,427 | 15,276
Small-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 19,260 | 19,952
Government Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 26,827 | 29,121
Corporate Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 24,975 | 27,485
Fixed Income Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 40,989 | 41,975
Cash & Equivalents [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 276 | 129
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 9,541 | 10,362
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Large-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 3,266 | 3,414
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mid-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 957 | 1,448
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Small-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 461 | 312
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Government Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 1,387 | 1,244
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 3,194 | 3,815
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Cash & Equivalents [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 276 | 129
Significant Observable Inputs (Level 2) [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 194,831 | 206,392
Significant Observable Inputs (Level 2) [Member] | Large-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 74,352 | 79,402
Significant Observable Inputs (Level 2) [Member] | Mid-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 13,470 | 13,828
Significant Observable Inputs (Level 2) [Member] | Small-Cap Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 18,799 | 19,640
Significant Observable Inputs (Level 2) [Member] | Government Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 25,440 | 27,877
Significant Observable Inputs (Level 2) [Member] | Corporate Bond Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | 21,781 | 23,670
Significant Observable Inputs (Level 2) [Member] | Fixed Income Fund [Member] |  |
Pension And Other Employee Benefit Plans [Line Items] |  |
Fair values of pension plan assets by asset category | $ 40,989 | $ 41,975

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- Definition Pension And Other Employee Benefit Plans [Line Items] + References No definition available. + Details
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- Definition Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=49178875&loc=d3e12355-114930 Reference 2: 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=58740216&loc=d3e1928-114920 + Details
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