Retirement Plans and Other Post-Retirement Benefits - Schedule of Net Periodic Costs of Pension and Post Retirement Medical Benefit Plans Included in Continuing Operations (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 44	$ 484
Interest cost	301	3,450
Expected return on plan assets		(3,696)
Amortization of prior service cost/(credit)	12	34
Amortization of unrecognized/actuarial loss (gain)	160	775
Total net periodic benefit cost/(credit)	517	1,047
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7	9
Interest cost	46	84
Amortization of prior service cost/(credit)	(116)	(2)
Amortization of unrecognized/actuarial loss (gain)	(209)	(173)
Total net periodic benefit cost/(credit)	$ (272)	$ (82)