Pensions and Other Post-retirement Benefits - Summary of Pension Plan Assets Measured at Fair Value on Recurring Basis by Fair Value Hierarchy (Detail) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 515,858	$ 443,112	$ 492,677
Fair Value, Measurements, Recurring
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	515,858	443,112
Plan assets at NAV	159,614	118,109
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	253,976	226,406
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	80,766	81,564
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	21,502	17,033
Fair Value, Measurements, Recurring | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	235,491	259,014
Plan assets at NAV	56,449	62,027
Fair Value, Measurements, Recurring | Equity securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	179,042	196,987
Fair Value, Measurements, Recurring | Equity securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Equity securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	154,640	109,876
Fair Value, Measurements, Recurring | Fixed income securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	73,874	28,312
Fair Value, Measurements, Recurring | Fixed income securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	80,766	81,564
Fair Value, Measurements, Recurring | Fixed income securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Pooled investment funds
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	97,373	49,823
Plan assets at NAV	97,373	49,823
Fair Value, Measurements, Recurring | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	21,502	17,033
Fair Value, Measurements, Recurring | Insurance contracts | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Insurance contracts | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Insurance contracts | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	21,502	17,033
Fair Value, Measurements, Recurring | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	6,852	7,366
Plan assets at NAV	5,792	6,259
Fair Value, Measurements, Recurring | Cash and cash equivalents | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	1,060	1,107
Fair Value, Measurements, Recurring | Cash and cash equivalents | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	0	0
Fair Value, Measurements, Recurring | Cash and cash equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Total pension plan assets measured at fair value	$ 0	$ 0