Components of Net Periodic Benefit Cost (Benefit Cost (Increase) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	$ 0	$ 0
Interest cost	250	300
Expected return on plan assets	(737)	(641)
Amortization of prior service cost	0	0
Amortization of the net loss (gain)	174	254
Net periodic (decrease) increase in benefit cost	(313)	(87)
Other post-retirement benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Service cost	20	20
Interest cost	178	210
Expected return on plan assets	0	0
Amortization of prior service cost	0	0
Amortization of the net loss (gain)	(62)	(207)
Net periodic (decrease) increase in benefit cost	$ 136	$ 23