Pension and other Post-Employment Benefits - Summary of Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Covia Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 126	$ 551
Interest cost	971	2,084
Expected return on plan assets	(1,263)	(2,308)
Amortization of prior service cost	27	82
Amortization of net actuarial loss	476	522
Settlement loss	2,011	1,679
Net periodic benefit cost	2,348	2,610
Postretirement Medical Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	79	73
Interest cost	35	120
Amortization of net actuarial loss	15	40
Net periodic benefit cost	$ 129	$ 233