Pensions and Other Post-retirement Benefits - Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis by Fair Value Hierarchy (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 433,262	$ 419,088
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	304,460	280,619
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	87,776	100,067
Pooled investment funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	20,156	19,345
Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	14,948	13,681
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	5,922	5,376
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	273,192	260,470
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	242,161	225,191
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	25,109	29,903
Quoted Prices in Active Markets for Identical Assets (Level 1) | Pooled investment funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	5,922	5,376
Significant Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	145,122	144,937
Significant Observable Inputs (Level 2) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	62,299	55,428
Significant Observable Inputs (Level 2) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	62,667	70,164
Significant Observable Inputs (Level 2) | Pooled investment funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	20,156	19,345
Significant Observable Inputs (Level 2) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Significant Observable Inputs (Level 2) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	14,948	13,681
Significant Unobservable Inputs (Level 3) | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Significant Unobservable Inputs (Level 3) | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Significant Unobservable Inputs (Level 3) | Pooled investment funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Significant Unobservable Inputs (Level 3) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	14,948	13,681	$ 15,069
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 0	$ 0