Schedule of Net Periodic Benefit Costs (Detail) - Pension Benefits - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Period Benefit Cost Assumptions [Line Items]
Service cost	$ 56	$ 30
Interest cost	932	902
Expected return on plan assets	(563)	(483)
Administrative expenses	10	1
Amortization of net actuarial losses	72
Net periodic pension cost	$ 507	$ 450